diff --git a/Documentation/x86/intel_mpx.rst b/Documentation/x86/intel_mpx.rst deleted file mode 100644 index 387a640..0000000 --- a/Documentation/x86/intel_mpx.rst +++ /dev/null @@ -1,252 +0,0 @@ -.. SPDX-License-Identifier: GPL-2.0 - -=========================================== -Intel(R) Memory Protection Extensions (MPX) -=========================================== - -Intel(R) MPX Overview -===================== - -Intel(R) Memory Protection Extensions (Intel(R) MPX) is a new capability -introduced into Intel Architecture. Intel MPX provides hardware features -that can be used in conjunction with compiler changes to check memory -references, for those references whose compile-time normal intentions are -usurped at runtime due to buffer overflow or underflow. - -You can tell if your CPU supports MPX by looking in /proc/cpuinfo:: - - cat /proc/cpuinfo | grep ' mpx ' - -For more information, please refer to Intel(R) Architecture Instruction -Set Extensions Programming Reference, Chapter 9: Intel(R) Memory Protection -Extensions. - -Note: As of December 2014, no hardware with MPX is available but it is -possible to use SDE (Intel(R) Software Development Emulator) instead, which -can be downloaded from -http://software.intel.com/en-us/articles/intel-software-development-emulator - - -How to get the advantage of MPX -=============================== - -For MPX to work, changes are required in the kernel, binutils and compiler. -No source changes are required for applications, just a recompile. - -There are a lot of moving parts of this to all work right. The following -is how we expect the compiler, application and kernel to work together. - -1) Application developer compiles with -fmpx. The compiler will add the - instrumentation as well as some setup code called early after the app - starts. New instruction prefixes are noops for old CPUs. -2) That setup code allocates (virtual) space for the "bounds directory", - points the "bndcfgu" register to the directory (must also set the valid - bit) and notifies the kernel (via the new prctl(PR_MPX_ENABLE_MANAGEMENT)) - that the app will be using MPX. The app must be careful not to access - the bounds tables between the time when it populates "bndcfgu" and - when it calls the prctl(). This might be hard to guarantee if the app - is compiled with MPX. You can add "__attribute__((bnd_legacy))" to - the function to disable MPX instrumentation to help guarantee this. - Also be careful not to call out to any other code which might be - MPX-instrumented. -3) The kernel detects that the CPU has MPX, allows the new prctl() to - succeed, and notes the location of the bounds directory. Userspace is - expected to keep the bounds directory at that location. We note it - instead of reading it each time because the 'xsave' operation needed - to access the bounds directory register is an expensive operation. -4) If the application needs to spill bounds out of the 4 registers, it - issues a bndstx instruction. Since the bounds directory is empty at - this point, a bounds fault (#BR) is raised, the kernel allocates a - bounds table (in the user address space) and makes the relevant entry - in the bounds directory point to the new table. -5) If the application violates the bounds specified in the bounds registers, - a separate kind of #BR is raised which will deliver a signal with - information about the violation in the 'struct siginfo'. -6) Whenever memory is freed, we know that it can no longer contain valid - pointers, and we attempt to free the associated space in the bounds - tables. If an entire table becomes unused, we will attempt to free - the table and remove the entry in the directory. - -To summarize, there are essentially three things interacting here: - -GCC with -fmpx: - * enables annotation of code with MPX instructions and prefixes - * inserts code early in the application to call in to the "gcc runtime" -GCC MPX Runtime: - * Checks for hardware MPX support in cpuid leaf - * allocates virtual space for the bounds directory (malloc() essentially) - * points the hardware BNDCFGU register at the directory - * calls a new prctl(PR_MPX_ENABLE_MANAGEMENT) to notify the kernel to - start managing the bounds directories -Kernel MPX Code: - * Checks for hardware MPX support in cpuid leaf - * Handles #BR exceptions and sends SIGSEGV to the app when it violates - bounds, like during a buffer overflow. - * When bounds are spilled in to an unallocated bounds table, the kernel - notices in the #BR exception, allocates the virtual space, then - updates the bounds directory to point to the new table. It keeps - special track of the memory with a VM_MPX flag. - * Frees unused bounds tables at the time that the memory they described - is unmapped. - - -How does MPX kernel code work -============================= - -Handling #BR faults caused by MPX ---------------------------------- - -When MPX is enabled, there are 2 new situations that can generate -#BR faults. - - * new bounds tables (BT) need to be allocated to save bounds. - * bounds violation caused by MPX instructions. - -We hook #BR handler to handle these two new situations. - -On-demand kernel allocation of bounds tables --------------------------------------------- - -MPX only has 4 hardware registers for storing bounds information. If -MPX-enabled code needs more than these 4 registers, it needs to spill -them somewhere. It has two special instructions for this which allow -the bounds to be moved between the bounds registers and some new "bounds -tables". - -#BR exceptions are a new class of exceptions just for MPX. They are -similar conceptually to a page fault and will be raised by the MPX -hardware during both bounds violations or when the tables are not -present. The kernel handles those #BR exceptions for not-present tables -by carving the space out of the normal processes address space and then -pointing the bounds-directory over to it. - -The tables need to be accessed and controlled by userspace because -the instructions for moving bounds in and out of them are extremely -frequent. They potentially happen every time a register points to -memory. Any direct kernel involvement (like a syscall) to access the -tables would obviously destroy performance. - -Why not do this in userspace? MPX does not strictly require anything in -the kernel. It can theoretically be done completely from userspace. Here -are a few ways this could be done. We don't think any of them are practical -in the real-world, but here they are. - -:Q: Can virtual space simply be reserved for the bounds tables so that we - never have to allocate them? -:A: MPX-enabled application will possibly create a lot of bounds tables in - process address space to save bounds information. These tables can take - up huge swaths of memory (as much as 80% of the memory on the system) - even if we clean them up aggressively. In the worst-case scenario, the - tables can be 4x the size of the data structure being tracked. IOW, a - 1-page structure can require 4 bounds-table pages. An X-GB virtual - area needs 4*X GB of virtual space, plus 2GB for the bounds directory. - If we were to preallocate them for the 128TB of user virtual address - space, we would need to reserve 512TB+2GB, which is larger than the - entire virtual address space today. This means they can not be reserved - ahead of time. Also, a single process's pre-populated bounds directory - consumes 2GB of virtual *AND* physical memory. IOW, it's completely - infeasible to prepopulate bounds directories. - -:Q: Can we preallocate bounds table space at the same time memory is - allocated which might contain pointers that might eventually need - bounds tables? -:A: This would work if we could hook the site of each and every memory - allocation syscall. This can be done for small, constrained applications. - But, it isn't practical at a larger scale since a given app has no - way of controlling how all the parts of the app might allocate memory - (think libraries). The kernel is really the only place to intercept - these calls. - -:Q: Could a bounds fault be handed to userspace and the tables allocated - there in a signal handler instead of in the kernel? -:A: mmap() is not on the list of safe async handler functions and even - if mmap() would work it still requires locking or nasty tricks to - keep track of the allocation state there. - -Having ruled out all of the userspace-only approaches for managing -bounds tables that we could think of, we create them on demand in -the kernel. - -Decoding MPX instructions -------------------------- - -If a #BR is generated due to a bounds violation caused by MPX. -We need to decode MPX instructions to get violation address and -set this address into extended struct siginfo. - -The _sigfault field of struct siginfo is extended as follow:: - - 87 /* SIGILL, SIGFPE, SIGSEGV, SIGBUS */ - 88 struct { - 89 void __user *_addr; /* faulting insn/memory ref. */ - 90 #ifdef __ARCH_SI_TRAPNO - 91 int _trapno; /* TRAP # which caused the signal */ - 92 #endif - 93 short _addr_lsb; /* LSB of the reported address */ - 94 struct { - 95 void __user *_lower; - 96 void __user *_upper; - 97 } _addr_bnd; - 98 } _sigfault; - -The '_addr' field refers to violation address, and new '_addr_and' -field refers to the upper/lower bounds when a #BR is caused. - -Glibc will be also updated to support this new siginfo. So user -can get violation address and bounds when bounds violations occur. - -Cleanup unused bounds tables ----------------------------- - -When a BNDSTX instruction attempts to save bounds to a bounds directory -entry marked as invalid, a #BR is generated. This is an indication that -no bounds table exists for this entry. In this case the fault handler -will allocate a new bounds table on demand. - -Since the kernel allocated those tables on-demand without userspace -knowledge, it is also responsible for freeing them when the associated -mappings go away. - -Here, the solution for this issue is to hook do_munmap() to check -whether one process is MPX enabled. If yes, those bounds tables covered -in the virtual address region which is being unmapped will be freed also. - -Adding new prctl commands -------------------------- - -Two new prctl commands are added to enable and disable MPX bounds tables -management in kernel. -:: - - 155 #define PR_MPX_ENABLE_MANAGEMENT 43 - 156 #define PR_MPX_DISABLE_MANAGEMENT 44 - -Runtime library in userspace is responsible for allocation of bounds -directory. So kernel have to use XSAVE instruction to get the base -of bounds directory from BNDCFG register. - -But XSAVE is expected to be very expensive. In order to do performance -optimization, we have to get the base of bounds directory and save it -into struct mm_struct to be used in future during PR_MPX_ENABLE_MANAGEMENT -command execution. - - -Special rules -============= - -1) If userspace is requesting help from the kernel to do the management -of bounds tables, it may not create or modify entries in the bounds directory. - -Certainly users can allocate bounds tables and forcibly point the bounds -directory at them through XSAVE instruction, and then set valid bit -of bounds entry to have this entry valid. But, the kernel will decline -to assist in managing these tables. - -2) Userspace may not take multiple bounds directory entries and point -them at the same bounds table. - -This is allowed architecturally. See more information "Intel(R) Architecture -Instruction Set Extensions Programming Reference" (9.3.4). - -However, if users did this, the kernel might be fooled in to unmapping an -in-use bounds table since it does not recognize sharing. diff --git a/arch/x86/include/asm/bugs.h b/arch/x86/include/asm/bugs.h index 794eb21..92ae283 100644 --- a/arch/x86/include/asm/bugs.h +++ b/arch/x86/include/asm/bugs.h @@ -6,12 +6,6 @@ extern void check_bugs(void); -#if defined(CONFIG_CPU_SUP_INTEL) -void check_mpx_erratum(struct cpuinfo_x86 *c); -#else -static inline void check_mpx_erratum(struct cpuinfo_x86 *c) {} -#endif - #if defined(CONFIG_CPU_SUP_INTEL) && defined(CONFIG_X86_32) int ppro_with_ram_bug(void); #else diff --git a/arch/x86/include/asm/disabled-features.h b/arch/x86/include/asm/disabled-features.h index a5ea841..41d069f 100644 --- a/arch/x86/include/asm/disabled-features.h +++ b/arch/x86/include/asm/disabled-features.h @@ -10,12 +10,6 @@ * cpu_feature_enabled(). */ -#ifdef CONFIG_X86_INTEL_MPX -# define DISABLE_MPX 0 -#else -# define DISABLE_MPX (1<<(X86_FEATURE_MPX & 31)) -#endif - #ifdef CONFIG_X86_SMAP # define DISABLE_SMAP 0 #else @@ -74,7 +68,7 @@ #define DISABLED_MASK6 0 #define DISABLED_MASK7 (DISABLE_PTI) #define DISABLED_MASK8 0 -#define DISABLED_MASK9 (DISABLE_MPX|DISABLE_SMAP) +#define DISABLED_MASK9 (DISABLE_SMAP) #define DISABLED_MASK10 0 #define DISABLED_MASK11 0 #define DISABLED_MASK12 0 diff --git a/arch/x86/include/asm/mmu.h b/arch/x86/include/asm/mmu.h index e78c7db..bdeae92 100644 --- a/arch/x86/include/asm/mmu.h +++ b/arch/x86/include/asm/mmu.h @@ -50,10 +50,6 @@ typedef struct { u16 pkey_allocation_map; s16 execute_only_pkey; #endif -#ifdef CONFIG_X86_INTEL_MPX - /* address of the bounds directory */ - void __user *bd_addr; -#endif } mm_context_t; #define INIT_MM_CONTEXT(mm) \ diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mmu_context.h index b7135e9..a3e1c72 100644 --- a/arch/x86/include/asm/mmu_context.h +++ b/arch/x86/include/asm/mmu_context.h @@ -12,7 +12,6 @@ #include #include #include -#include #include extern atomic64_t last_mm_ctx_id; @@ -275,25 +274,6 @@ static inline bool is_64bit_mm(struct mm_struct *mm) static inline void arch_unmap(struct mm_struct *mm, unsigned long start, unsigned long end) { - /* - * mpx_notify_unmap() goes and reads a rarely-hot - * cacheline in the mm_struct. That can be expensive - * enough to be seen in profiles. - * - * The mpx_notify_unmap() call and its contents have been - * observed to affect munmap() performance on hardware - * where MPX is not present. - * - * The unlikely() optimizes for the fast case: no MPX - * in the CPU, or no MPX use in the process. Even if - * we get this wrong (in the unlikely event that MPX - * is widely enabled on some system) the overhead of - * MPX itself (reading bounds tables) is expected to - * overwhelm the overhead of getting this unlikely() - * consistently wrong. - */ - if (unlikely(cpu_feature_enabled(X86_FEATURE_MPX))) - mpx_notify_unmap(mm, start, end); } /* diff --git a/arch/x86/include/asm/mpx.h b/arch/x86/include/asm/mpx.h deleted file mode 100644 index 143a5c1..0000000 --- a/arch/x86/include/asm/mpx.h +++ /dev/null @@ -1,116 +0,0 @@ -/* SPDX-License-Identifier: GPL-2.0 */ -#ifndef _ASM_X86_MPX_H -#define _ASM_X86_MPX_H - -#include -#include - -#include -#include - -/* - * NULL is theoretically a valid place to put the bounds - * directory, so point this at an invalid address. - */ -#define MPX_INVALID_BOUNDS_DIR ((void __user *)-1) -#define MPX_BNDCFG_ENABLE_FLAG 0x1 -#define MPX_BD_ENTRY_VALID_FLAG 0x1 - -/* - * The upper 28 bits [47:20] of the virtual address in 64-bit - * are used to index into bounds directory (BD). - * - * The directory is 2G (2^31) in size, and with 8-byte entries - * it has 2^28 entries. - */ -#define MPX_BD_SIZE_BYTES_64 (1UL<<31) -#define MPX_BD_ENTRY_BYTES_64 8 -#define MPX_BD_NR_ENTRIES_64 (MPX_BD_SIZE_BYTES_64/MPX_BD_ENTRY_BYTES_64) - -/* - * The 32-bit directory is 4MB (2^22) in size, and with 4-byte - * entries it has 2^20 entries. - */ -#define MPX_BD_SIZE_BYTES_32 (1UL<<22) -#define MPX_BD_ENTRY_BYTES_32 4 -#define MPX_BD_NR_ENTRIES_32 (MPX_BD_SIZE_BYTES_32/MPX_BD_ENTRY_BYTES_32) - -/* - * A 64-bit table is 4MB total in size, and an entry is - * 4 64-bit pointers in size. - */ -#define MPX_BT_SIZE_BYTES_64 (1UL<<22) -#define MPX_BT_ENTRY_BYTES_64 32 -#define MPX_BT_NR_ENTRIES_64 (MPX_BT_SIZE_BYTES_64/MPX_BT_ENTRY_BYTES_64) - -/* - * A 32-bit table is 16kB total in size, and an entry is - * 4 32-bit pointers in size. - */ -#define MPX_BT_SIZE_BYTES_32 (1UL<<14) -#define MPX_BT_ENTRY_BYTES_32 16 -#define MPX_BT_NR_ENTRIES_32 (MPX_BT_SIZE_BYTES_32/MPX_BT_ENTRY_BYTES_32) - -#define MPX_BNDSTA_TAIL 2 -#define MPX_BNDCFG_TAIL 12 -#define MPX_BNDSTA_ADDR_MASK (~((1UL<context.bd_addr != MPX_INVALID_BOUNDS_DIR); -} - -static inline void mpx_mm_init(struct mm_struct *mm) -{ - /* - * NULL is theoretically a valid place to put the bounds - * directory, so point this at an invalid address. - */ - mm->context.bd_addr = MPX_INVALID_BOUNDS_DIR; -} - -extern void mpx_notify_unmap(struct mm_struct *mm, unsigned long start, unsigned long end); -extern unsigned long mpx_unmapped_area_check(unsigned long addr, unsigned long len, unsigned long flags); - -#else -static inline int mpx_fault_info(struct mpx_fault_info *info, struct pt_regs *regs) -{ - return -EINVAL; -} -static inline int mpx_handle_bd_fault(void) -{ - return -EINVAL; -} -static inline int kernel_managing_mpx_tables(struct mm_struct *mm) -{ - return 0; -} -static inline void mpx_mm_init(struct mm_struct *mm) -{ -} -static inline void mpx_notify_unmap(struct mm_struct *mm, - unsigned long start, unsigned long end) -{ -} - -static inline unsigned long mpx_unmapped_area_check(unsigned long addr, - unsigned long len, unsigned long flags) -{ - return addr; -} -#endif /* CONFIG_X86_INTEL_MPX */ - -#endif /* _ASM_X86_MPX_H */ diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index 54f5d54..4482f14 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -915,24 +915,6 @@ extern int set_tsc_mode(unsigned int val); DECLARE_PER_CPU(u64, msr_misc_features_shadow); -/* Register/unregister a process' MPX related resource */ -#define MPX_ENABLE_MANAGEMENT() mpx_enable_management() -#define MPX_DISABLE_MANAGEMENT() mpx_disable_management() - -#ifdef CONFIG_X86_INTEL_MPX -extern int mpx_enable_management(void); -extern int mpx_disable_management(void); -#else -static inline int mpx_enable_management(void) -{ - return -EINVAL; -} -static inline int mpx_disable_management(void) -{ - return -EINVAL; -} -#endif /* CONFIG_X86_INTEL_MPX */ - #ifdef CONFIG_CPU_SUP_AMD extern u16 amd_get_nb_id(int cpu); extern u32 amd_get_nodes_per_socket(void); diff --git a/arch/x86/include/asm/trace/mpx.h b/arch/x86/include/asm/trace/mpx.h deleted file mode 100644 index 5413301..0000000 --- a/arch/x86/include/asm/trace/mpx.h +++ /dev/null @@ -1,134 +0,0 @@ -/* SPDX-License-Identifier: GPL-2.0 */ -#undef TRACE_SYSTEM -#define TRACE_SYSTEM mpx - -#if !defined(_TRACE_MPX_H) || defined(TRACE_HEADER_MULTI_READ) -#define _TRACE_MPX_H - -#include - -#ifdef CONFIG_X86_INTEL_MPX - -TRACE_EVENT(mpx_bounds_register_exception, - - TP_PROTO(void __user *addr_referenced, - const struct mpx_bndreg *bndreg), - TP_ARGS(addr_referenced, bndreg), - - TP_STRUCT__entry( - __field(void __user *, addr_referenced) - __field(u64, lower_bound) - __field(u64, upper_bound) - ), - - TP_fast_assign( - __entry->addr_referenced = addr_referenced; - __entry->lower_bound = bndreg->lower_bound; - __entry->upper_bound = bndreg->upper_bound; - ), - /* - * Note that we are printing out the '~' of the upper - * bounds register here. It is actually stored in its - * one's complement form so that its 'init' state - * corresponds to all 0's. But, that looks like - * gibberish when printed out, so print out the 1's - * complement instead of the actual value here. Note - * though that you still need to specify filters for the - * actual value, not the displayed one. - */ - TP_printk("address referenced: 0x%p bounds: lower: 0x%llx ~upper: 0x%llx", - __entry->addr_referenced, - __entry->lower_bound, - ~__entry->upper_bound - ) -); - -TRACE_EVENT(bounds_exception_mpx, - - TP_PROTO(const struct mpx_bndcsr *bndcsr), - TP_ARGS(bndcsr), - - TP_STRUCT__entry( - __field(u64, bndcfgu) - __field(u64, bndstatus) - ), - - TP_fast_assign( - /* need to get rid of the 'const' on bndcsr */ - __entry->bndcfgu = (u64)bndcsr->bndcfgu; - __entry->bndstatus = (u64)bndcsr->bndstatus; - ), - - TP_printk("bndcfgu:0x%llx bndstatus:0x%llx", - __entry->bndcfgu, - __entry->bndstatus) -); - -DECLARE_EVENT_CLASS(mpx_range_trace, - - TP_PROTO(unsigned long start, - unsigned long end), - TP_ARGS(start, end), - - TP_STRUCT__entry( - __field(unsigned long, start) - __field(unsigned long, end) - ), - - TP_fast_assign( - __entry->start = start; - __entry->end = end; - ), - - TP_printk("[0x%p:0x%p]", - (void *)__entry->start, - (void *)__entry->end - ) -); - -DEFINE_EVENT(mpx_range_trace, mpx_unmap_zap, - TP_PROTO(unsigned long start, unsigned long end), - TP_ARGS(start, end) -); - -DEFINE_EVENT(mpx_range_trace, mpx_unmap_search, - TP_PROTO(unsigned long start, unsigned long end), - TP_ARGS(start, end) -); - -TRACE_EVENT(mpx_new_bounds_table, - - TP_PROTO(unsigned long table_vaddr), - TP_ARGS(table_vaddr), - - TP_STRUCT__entry( - __field(unsigned long, table_vaddr) - ), - - TP_fast_assign( - __entry->table_vaddr = table_vaddr; - ), - - TP_printk("table vaddr:%p", (void *)__entry->table_vaddr) -); - -#else - -/* - * This gets used outside of MPX-specific code, so we need a stub. - */ -static inline -void trace_bounds_exception_mpx(const struct mpx_bndcsr *bndcsr) -{ -} - -#endif /* CONFIG_X86_INTEL_MPX */ - -#undef TRACE_INCLUDE_PATH -#define TRACE_INCLUDE_PATH asm/trace/ -#undef TRACE_INCLUDE_FILE -#define TRACE_INCLUDE_FILE mpx -#endif /* _TRACE_MPX_H */ - -/* This part must be outside protection */ -#include diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index fffe219..be2c85b 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -165,22 +165,6 @@ DEFINE_PER_CPU_PAGE_ALIGNED(struct gdt_page, gdt_page) = { .gdt = { } }; EXPORT_PER_CPU_SYMBOL_GPL(gdt_page); -static int __init x86_mpx_setup(char *s) -{ - /* require an exact match without trailing characters */ - if (strlen(s)) - return 0; - - /* do not emit a message if the feature is not present */ - if (!boot_cpu_has(X86_FEATURE_MPX)) - return 1; - - setup_clear_cpu_cap(X86_FEATURE_MPX); - pr_info("nompx: Intel Memory Protection Extensions (MPX) disabled\n"); - return 1; -} -__setup("nompx", x86_mpx_setup); - #ifdef CONFIG_X86_64 static int __init x86_nopcid_setup(char *s) { @@ -307,8 +291,6 @@ static inline void squash_the_stupid_serial_number(struct cpuinfo_x86 *c) static __init int setup_disable_smep(char *arg) { setup_clear_cpu_cap(X86_FEATURE_SMEP); - /* Check for things that depend on SMEP being enabled: */ - check_mpx_erratum(&boot_cpu_data); return 1; } __setup("nosmep", setup_disable_smep); diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c index 11d5c59..ea5899f 100644 --- a/arch/x86/kernel/cpu/intel.c +++ b/arch/x86/kernel/cpu/intel.c @@ -32,41 +32,6 @@ #endif /* - * Just in case our CPU detection goes bad, or you have a weird system, - * allow a way to override the automatic disabling of MPX. - */ -static int forcempx; - -static int __init forcempx_setup(char *__unused) -{ - forcempx = 1; - - return 1; -} -__setup("intel-skd-046-workaround=disable", forcempx_setup); - -void check_mpx_erratum(struct cpuinfo_x86 *c) -{ - if (forcempx) - return; - /* - * Turn off the MPX feature on CPUs where SMEP is not - * available or disabled. - * - * Works around Intel Erratum SKD046: "Branch Instructions - * May Initialize MPX Bound Registers Incorrectly". - * - * This might falsely disable MPX on systems without - * SMEP, like Atom processors without SMEP. But there - * is no such hardware known at the moment. - */ - if (cpu_has(c, X86_FEATURE_MPX) && !cpu_has(c, X86_FEATURE_SMEP)) { - setup_clear_cpu_cap(X86_FEATURE_MPX); - pr_warn("x86/mpx: Disabling MPX since SMEP not present\n"); - } -} - -/* * Processors which have self-snooping capability can handle conflicting * memory type across CPUs by snooping its own cache. However, there exists * CPU models in which having conflicting memory types still leads to @@ -330,7 +295,6 @@ static void early_init_intel(struct cpuinfo_x86 *c) c->x86_coreid_bits = get_count_order((ebx >> 16) & 0xff); } - check_mpx_erratum(c); check_memory_type_self_snoop_errata(c); /* diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c index 77ea96b..6cf2068 100644 --- a/arch/x86/kernel/setup.c +++ b/arch/x86/kernel/setup.c @@ -947,8 +947,6 @@ void __init setup_arch(char **cmdline_p) init_mm.end_data = (unsigned long) _edata; init_mm.brk = _brk_end; - mpx_mm_init(&init_mm); - code_resource.start = __pa_symbol(_text); code_resource.end = __pa_symbol(_etext)-1; data_resource.start = __pa_symbol(_etext); diff --git a/arch/x86/kernel/sys_x86_64.c b/arch/x86/kernel/sys_x86_64.c index f7476ce..ca3c11a 100644 --- a/arch/x86/kernel/sys_x86_64.c +++ b/arch/x86/kernel/sys_x86_64.c @@ -22,7 +22,6 @@ #include #include #include -#include /* * Align a virtual address to avoid aliasing in the I$ on AMD F15h. @@ -137,10 +136,6 @@ arch_get_unmapped_area(struct file *filp, unsigned long addr, struct vm_unmapped_area_info info; unsigned long begin, end; - addr = mpx_unmapped_area_check(addr, len, flags); - if (IS_ERR_VALUE(addr)) - return addr; - if (flags & MAP_FIXED) return addr; @@ -180,10 +175,6 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0, unsigned long addr = addr0; struct vm_unmapped_area_info info; - addr = mpx_unmapped_area_check(addr, len, flags); - if (IS_ERR_VALUE(addr)) - return addr; - /* requested length too big for entire address space */ if (len > TASK_SIZE) return -ENOMEM; diff --git a/arch/x86/mm/hugetlbpage.c b/arch/x86/mm/hugetlbpage.c index fab0953..5bfd5ae 100644 --- a/arch/x86/mm/hugetlbpage.c +++ b/arch/x86/mm/hugetlbpage.c @@ -19,7 +19,6 @@ #include #include #include -#include #if 0 /* This is just for testing */ struct page * @@ -151,10 +150,6 @@ hugetlb_get_unmapped_area(struct file *file, unsigned long addr, if (len & ~huge_page_mask(h)) return -EINVAL; - addr = mpx_unmapped_area_check(addr, len, flags); - if (IS_ERR_VALUE(addr)) - return addr; - if (len > TASK_SIZE) return -ENOMEM; diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c index aae9a93..cb91ecc 100644 --- a/arch/x86/mm/mmap.c +++ b/arch/x86/mm/mmap.c @@ -163,8 +163,6 @@ unsigned long get_mmap_base(int is_legacy) const char *arch_vma_name(struct vm_area_struct *vma) { - if (vma->vm_flags & VM_MPX) - return "[mpx]"; return NULL; } diff --git a/arch/x86/mm/mpx.c b/arch/x86/mm/mpx.c deleted file mode 100644 index 895fb7a..0000000 --- a/arch/x86/mm/mpx.c +++ /dev/null @@ -1,938 +0,0 @@ -// SPDX-License-Identifier: GPL-2.0 -/* - * mpx.c - Memory Protection eXtensions - * - * Copyright (c) 2014, Intel Corporation. - * Qiaowei Ren - * Dave Hansen - */ -#include -#include -#include -#include -#include -#include - -#include -#include -#include -#include -#include -#include - -#define CREATE_TRACE_POINTS -#include - -static inline unsigned long mpx_bd_size_bytes(struct mm_struct *mm) -{ - if (is_64bit_mm(mm)) - return MPX_BD_SIZE_BYTES_64; - else - return MPX_BD_SIZE_BYTES_32; -} - -static inline unsigned long mpx_bt_size_bytes(struct mm_struct *mm) -{ - if (is_64bit_mm(mm)) - return MPX_BT_SIZE_BYTES_64; - else - return MPX_BT_SIZE_BYTES_32; -} - -/* - * This is really a simplified "vm_mmap". it only handles MPX - * bounds tables (the bounds directory is user-allocated). - */ -static unsigned long mpx_mmap(unsigned long len) -{ - struct mm_struct *mm = current->mm; - unsigned long addr, populate; - - /* Only bounds table can be allocated here */ - if (len != mpx_bt_size_bytes(mm)) - return -EINVAL; - - down_write(&mm->mmap_sem); - addr = do_mmap(NULL, 0, len, PROT_READ | PROT_WRITE, - MAP_ANONYMOUS | MAP_PRIVATE, VM_MPX, 0, &populate, NULL); - up_write(&mm->mmap_sem); - if (populate) - mm_populate(addr, populate); - - return addr; -} - -static int mpx_insn_decode(struct insn *insn, - struct pt_regs *regs) -{ - unsigned char buf[MAX_INSN_SIZE]; - int x86_64 = !test_thread_flag(TIF_IA32); - int not_copied; - int nr_copied; - - not_copied = copy_from_user(buf, (void __user *)regs->ip, sizeof(buf)); - nr_copied = sizeof(buf) - not_copied; - /* - * The decoder _should_ fail nicely if we pass it a short buffer. - * But, let's not depend on that implementation detail. If we - * did not get anything, just error out now. - */ - if (!nr_copied) - return -EFAULT; - insn_init(insn, buf, nr_copied, x86_64); - insn_get_length(insn); - /* - * copy_from_user() tries to get as many bytes as we could see in - * the largest possible instruction. If the instruction we are - * after is shorter than that _and_ we attempt to copy from - * something unreadable, we might get a short read. This is OK - * as long as the read did not stop in the middle of the - * instruction. Check to see if we got a partial instruction. - */ - if (nr_copied < insn->length) - return -EFAULT; - - insn_get_opcode(insn); - /* - * We only _really_ need to decode bndcl/bndcn/bndcu - * Error out on anything else. - */ - if (insn->opcode.bytes[0] != 0x0f) - goto bad_opcode; - if ((insn->opcode.bytes[1] != 0x1a) && - (insn->opcode.bytes[1] != 0x1b)) - goto bad_opcode; - - return 0; -bad_opcode: - return -EINVAL; -} - -/* - * If a bounds overflow occurs then a #BR is generated. This - * function decodes MPX instructions to get violation address - * and set this address into extended struct siginfo. - * - * Note that this is not a super precise way of doing this. - * Userspace could have, by the time we get here, written - * anything it wants in to the instructions. We can not - * trust anything about it. They might not be valid - * instructions or might encode invalid registers, etc... - */ -int mpx_fault_info(struct mpx_fault_info *info, struct pt_regs *regs) -{ - const struct mpx_bndreg_state *bndregs; - const struct mpx_bndreg *bndreg; - struct insn insn; - uint8_t bndregno; - int err; - - err = mpx_insn_decode(&insn, regs); - if (err) - goto err_out; - - /* - * We know at this point that we are only dealing with - * MPX instructions. - */ - insn_get_modrm(&insn); - bndregno = X86_MODRM_REG(insn.modrm.value); - if (bndregno > 3) { - err = -EINVAL; - goto err_out; - } - /* get bndregs field from current task's xsave area */ - bndregs = get_xsave_field_ptr(XFEATURE_BNDREGS); - if (!bndregs) { - err = -EINVAL; - goto err_out; - } - /* now go select the individual register in the set of 4 */ - bndreg = &bndregs->bndreg[bndregno]; - - /* - * The registers are always 64-bit, but the upper 32 - * bits are ignored in 32-bit mode. Also, note that the - * upper bounds are architecturally represented in 1's - * complement form. - * - * The 'unsigned long' cast is because the compiler - * complains when casting from integers to different-size - * pointers. - */ - info->lower = (void __user *)(unsigned long)bndreg->lower_bound; - info->upper = (void __user *)(unsigned long)~bndreg->upper_bound; - info->addr = insn_get_addr_ref(&insn, regs); - - /* - * We were not able to extract an address from the instruction, - * probably because there was something invalid in it. - */ - if (info->addr == (void __user *)-1) { - err = -EINVAL; - goto err_out; - } - trace_mpx_bounds_register_exception(info->addr, bndreg); - return 0; -err_out: - /* info might be NULL, but kfree() handles that */ - return err; -} - -static __user void *mpx_get_bounds_dir(void) -{ - const struct mpx_bndcsr *bndcsr; - - if (!cpu_feature_enabled(X86_FEATURE_MPX)) - return MPX_INVALID_BOUNDS_DIR; - - /* - * The bounds directory pointer is stored in a register - * only accessible if we first do an xsave. - */ - bndcsr = get_xsave_field_ptr(XFEATURE_BNDCSR); - if (!bndcsr) - return MPX_INVALID_BOUNDS_DIR; - - /* - * Make sure the register looks valid by checking the - * enable bit. - */ - if (!(bndcsr->bndcfgu & MPX_BNDCFG_ENABLE_FLAG)) - return MPX_INVALID_BOUNDS_DIR; - - /* - * Lastly, mask off the low bits used for configuration - * flags, and return the address of the bounds table. - */ - return (void __user *)(unsigned long) - (bndcsr->bndcfgu & MPX_BNDCFG_ADDR_MASK); -} - -int mpx_enable_management(void) -{ - void __user *bd_base = MPX_INVALID_BOUNDS_DIR; - struct mm_struct *mm = current->mm; - int ret = 0; - - /* - * runtime in the userspace will be responsible for allocation of - * the bounds directory. Then, it will save the base of the bounds - * directory into XSAVE/XRSTOR Save Area and enable MPX through - * XRSTOR instruction. - * - * The copy_xregs_to_kernel() beneath get_xsave_field_ptr() is - * expected to be relatively expensive. Storing the bounds - * directory here means that we do not have to do xsave in the - * unmap path; we can just use mm->context.bd_addr instead. - */ - bd_base = mpx_get_bounds_dir(); - down_write(&mm->mmap_sem); - - /* MPX doesn't support addresses above 47 bits yet. */ - if (find_vma(mm, DEFAULT_MAP_WINDOW)) { - pr_warn_once("%s (%d): MPX cannot handle addresses " - "above 47-bits. Disabling.", - current->comm, current->pid); - ret = -ENXIO; - goto out; - } - mm->context.bd_addr = bd_base; - if (mm->context.bd_addr == MPX_INVALID_BOUNDS_DIR) - ret = -ENXIO; -out: - up_write(&mm->mmap_sem); - return ret; -} - -int mpx_disable_management(void) -{ - struct mm_struct *mm = current->mm; - - if (!cpu_feature_enabled(X86_FEATURE_MPX)) - return -ENXIO; - - down_write(&mm->mmap_sem); - mm->context.bd_addr = MPX_INVALID_BOUNDS_DIR; - up_write(&mm->mmap_sem); - return 0; -} - -static int mpx_cmpxchg_bd_entry(struct mm_struct *mm, - unsigned long *curval, - unsigned long __user *addr, - unsigned long old_val, unsigned long new_val) -{ - int ret; - /* - * user_atomic_cmpxchg_inatomic() actually uses sizeof() - * the pointer that we pass to it to figure out how much - * data to cmpxchg. We have to be careful here not to - * pass a pointer to a 64-bit data type when we only want - * a 32-bit copy. - */ - if (is_64bit_mm(mm)) { - ret = user_atomic_cmpxchg_inatomic(curval, - addr, old_val, new_val); - } else { - u32 uninitialized_var(curval_32); - u32 old_val_32 = old_val; - u32 new_val_32 = new_val; - u32 __user *addr_32 = (u32 __user *)addr; - - ret = user_atomic_cmpxchg_inatomic(&curval_32, - addr_32, old_val_32, new_val_32); - *curval = curval_32; - } - return ret; -} - -/* - * With 32-bit mode, a bounds directory is 4MB, and the size of each - * bounds table is 16KB. With 64-bit mode, a bounds directory is 2GB, - * and the size of each bounds table is 4MB. - */ -static int allocate_bt(struct mm_struct *mm, long __user *bd_entry) -{ - unsigned long expected_old_val = 0; - unsigned long actual_old_val = 0; - unsigned long bt_addr; - unsigned long bd_new_entry; - int ret = 0; - - /* - * Carve the virtual space out of userspace for the new - * bounds table: - */ - bt_addr = mpx_mmap(mpx_bt_size_bytes(mm)); - if (IS_ERR((void *)bt_addr)) - return PTR_ERR((void *)bt_addr); - /* - * Set the valid flag (kinda like _PAGE_PRESENT in a pte) - */ - bd_new_entry = bt_addr | MPX_BD_ENTRY_VALID_FLAG; - - /* - * Go poke the address of the new bounds table in to the - * bounds directory entry out in userspace memory. Note: - * we may race with another CPU instantiating the same table. - * In that case the cmpxchg will see an unexpected - * 'actual_old_val'. - * - * This can fault, but that's OK because we do not hold - * mmap_sem at this point, unlike some of the other part - * of the MPX code that have to pagefault_disable(). - */ - ret = mpx_cmpxchg_bd_entry(mm, &actual_old_val, bd_entry, - expected_old_val, bd_new_entry); - if (ret) - goto out_unmap; - - /* - * The user_atomic_cmpxchg_inatomic() will only return nonzero - * for faults, *not* if the cmpxchg itself fails. Now we must - * verify that the cmpxchg itself completed successfully. - */ - /* - * We expected an empty 'expected_old_val', but instead found - * an apparently valid entry. Assume we raced with another - * thread to instantiate this table and desclare succecss. - */ - if (actual_old_val & MPX_BD_ENTRY_VALID_FLAG) { - ret = 0; - goto out_unmap; - } - /* - * We found a non-empty bd_entry but it did not have the - * VALID_FLAG set. Return an error which will result in - * a SEGV since this probably means that somebody scribbled - * some invalid data in to a bounds table. - */ - if (expected_old_val != actual_old_val) { - ret = -EINVAL; - goto out_unmap; - } - trace_mpx_new_bounds_table(bt_addr); - return 0; -out_unmap: - vm_munmap(bt_addr, mpx_bt_size_bytes(mm)); - return ret; -} - -/* - * When a BNDSTX instruction attempts to save bounds to a bounds - * table, it will first attempt to look up the table in the - * first-level bounds directory. If it does not find a table in - * the directory, a #BR is generated and we get here in order to - * allocate a new table. - * - * With 32-bit mode, the size of BD is 4MB, and the size of each - * bound table is 16KB. With 64-bit mode, the size of BD is 2GB, - * and the size of each bound table is 4MB. - */ -static int do_mpx_bt_fault(void) -{ - unsigned long bd_entry, bd_base; - const struct mpx_bndcsr *bndcsr; - struct mm_struct *mm = current->mm; - - bndcsr = get_xsave_field_ptr(XFEATURE_BNDCSR); - if (!bndcsr) - return -EINVAL; - /* - * Mask off the preserve and enable bits - */ - bd_base = bndcsr->bndcfgu & MPX_BNDCFG_ADDR_MASK; - /* - * The hardware provides the address of the missing or invalid - * entry via BNDSTATUS, so we don't have to go look it up. - */ - bd_entry = bndcsr->bndstatus & MPX_BNDSTA_ADDR_MASK; - /* - * Make sure the directory entry is within where we think - * the directory is. - */ - if ((bd_entry < bd_base) || - (bd_entry >= bd_base + mpx_bd_size_bytes(mm))) - return -EINVAL; - - return allocate_bt(mm, (long __user *)bd_entry); -} - -int mpx_handle_bd_fault(void) -{ - /* - * Userspace never asked us to manage the bounds tables, - * so refuse to help. - */ - if (!kernel_managing_mpx_tables(current->mm)) - return -EINVAL; - - return do_mpx_bt_fault(); -} - -/* - * A thin wrapper around get_user_pages(). Returns 0 if the - * fault was resolved or -errno if not. - */ -static int mpx_resolve_fault(long __user *addr, int write) -{ - long gup_ret; - int nr_pages = 1; - - gup_ret = get_user_pages((unsigned long)addr, nr_pages, - write ? FOLL_WRITE : 0, NULL, NULL); - /* - * get_user_pages() returns number of pages gotten. - * 0 means we failed to fault in and get anything, - * probably because 'addr' is bad. - */ - if (!gup_ret) - return -EFAULT; - /* Other error, return it */ - if (gup_ret < 0) - return gup_ret; - /* must have gup'd a page and gup_ret>0, success */ - return 0; -} - -static unsigned long mpx_bd_entry_to_bt_addr(struct mm_struct *mm, - unsigned long bd_entry) -{ - unsigned long bt_addr = bd_entry; - int align_to_bytes; - /* - * Bit 0 in a bt_entry is always the valid bit. - */ - bt_addr &= ~MPX_BD_ENTRY_VALID_FLAG; - /* - * Tables are naturally aligned at 8-byte boundaries - * on 64-bit and 4-byte boundaries on 32-bit. The - * documentation makes it appear that the low bits - * are ignored by the hardware, so we do the same. - */ - if (is_64bit_mm(mm)) - align_to_bytes = 8; - else - align_to_bytes = 4; - bt_addr &= ~(align_to_bytes-1); - return bt_addr; -} - -/* - * We only want to do a 4-byte get_user() on 32-bit. Otherwise, - * we might run off the end of the bounds table if we are on - * a 64-bit kernel and try to get 8 bytes. - */ -static int get_user_bd_entry(struct mm_struct *mm, unsigned long *bd_entry_ret, - long __user *bd_entry_ptr) -{ - u32 bd_entry_32; - int ret; - - if (is_64bit_mm(mm)) - return get_user(*bd_entry_ret, bd_entry_ptr); - - /* - * Note that get_user() uses the type of the *pointer* to - * establish the size of the get, not the destination. - */ - ret = get_user(bd_entry_32, (u32 __user *)bd_entry_ptr); - *bd_entry_ret = bd_entry_32; - return ret; -} - -/* - * Get the base of bounds tables pointed by specific bounds - * directory entry. - */ -static int get_bt_addr(struct mm_struct *mm, - long __user *bd_entry_ptr, - unsigned long *bt_addr_result) -{ - int ret; - int valid_bit; - unsigned long bd_entry; - unsigned long bt_addr; - - if (!access_ok((bd_entry_ptr), sizeof(*bd_entry_ptr))) - return -EFAULT; - - while (1) { - int need_write = 0; - - pagefault_disable(); - ret = get_user_bd_entry(mm, &bd_entry, bd_entry_ptr); - pagefault_enable(); - if (!ret) - break; - if (ret == -EFAULT) - ret = mpx_resolve_fault(bd_entry_ptr, need_write); - /* - * If we could not resolve the fault, consider it - * userspace's fault and error out. - */ - if (ret) - return ret; - } - - valid_bit = bd_entry & MPX_BD_ENTRY_VALID_FLAG; - bt_addr = mpx_bd_entry_to_bt_addr(mm, bd_entry); - - /* - * When the kernel is managing bounds tables, a bounds directory - * entry will either have a valid address (plus the valid bit) - * *OR* be completely empty. If we see a !valid entry *and* some - * data in the address field, we know something is wrong. This - * -EINVAL return will cause a SIGSEGV. - */ - if (!valid_bit && bt_addr) - return -EINVAL; - /* - * Do we have an completely zeroed bt entry? That is OK. It - * just means there was no bounds table for this memory. Make - * sure to distinguish this from -EINVAL, which will cause - * a SEGV. - */ - if (!valid_bit) - return -ENOENT; - - *bt_addr_result = bt_addr; - return 0; -} - -static inline int bt_entry_size_bytes(struct mm_struct *mm) -{ - if (is_64bit_mm(mm)) - return MPX_BT_ENTRY_BYTES_64; - else - return MPX_BT_ENTRY_BYTES_32; -} - -/* - * Take a virtual address and turns it in to the offset in bytes - * inside of the bounds table where the bounds table entry - * controlling 'addr' can be found. - */ -static unsigned long mpx_get_bt_entry_offset_bytes(struct mm_struct *mm, - unsigned long addr) -{ - unsigned long bt_table_nr_entries; - unsigned long offset = addr; - - if (is_64bit_mm(mm)) { - /* Bottom 3 bits are ignored on 64-bit */ - offset >>= 3; - bt_table_nr_entries = MPX_BT_NR_ENTRIES_64; - } else { - /* Bottom 2 bits are ignored on 32-bit */ - offset >>= 2; - bt_table_nr_entries = MPX_BT_NR_ENTRIES_32; - } - /* - * We know the size of the table in to which we are - * indexing, and we have eliminated all the low bits - * which are ignored for indexing. - * - * Mask out all the high bits which we do not need - * to index in to the table. Note that the tables - * are always powers of two so this gives us a proper - * mask. - */ - offset &= (bt_table_nr_entries-1); - /* - * We now have an entry offset in terms of *entries* in - * the table. We need to scale it back up to bytes. - */ - offset *= bt_entry_size_bytes(mm); - return offset; -} - -/* - * How much virtual address space does a single bounds - * directory entry cover? - * - * Note, we need a long long because 4GB doesn't fit in - * to a long on 32-bit. - */ -static inline unsigned long bd_entry_virt_space(struct mm_struct *mm) -{ - unsigned long long virt_space; - unsigned long long GB = (1ULL << 30); - - /* - * This covers 32-bit emulation as well as 32-bit kernels - * running on 64-bit hardware. - */ - if (!is_64bit_mm(mm)) - return (4ULL * GB) / MPX_BD_NR_ENTRIES_32; - - /* - * 'x86_virt_bits' returns what the hardware is capable - * of, and returns the full >32-bit address space when - * running 32-bit kernels on 64-bit hardware. - */ - virt_space = (1ULL << boot_cpu_data.x86_virt_bits); - return virt_space / MPX_BD_NR_ENTRIES_64; -} - -/* - * Free the backing physical pages of bounds table 'bt_addr'. - * Assume start...end is within that bounds table. - */ -static noinline int zap_bt_entries_mapping(struct mm_struct *mm, - unsigned long bt_addr, - unsigned long start_mapping, unsigned long end_mapping) -{ - struct vm_area_struct *vma; - unsigned long addr, len; - unsigned long start; - unsigned long end; - - /* - * if we 'end' on a boundary, the offset will be 0 which - * is not what we want. Back it up a byte to get the - * last bt entry. Then once we have the entry itself, - * move 'end' back up by the table entry size. - */ - start = bt_addr + mpx_get_bt_entry_offset_bytes(mm, start_mapping); - end = bt_addr + mpx_get_bt_entry_offset_bytes(mm, end_mapping - 1); - /* - * Move end back up by one entry. Among other things - * this ensures that it remains page-aligned and does - * not screw up zap_page_range() - */ - end += bt_entry_size_bytes(mm); - - /* - * Find the first overlapping vma. If vma->vm_start > start, there - * will be a hole in the bounds table. This -EINVAL return will - * cause a SIGSEGV. - */ - vma = find_vma(mm, start); - if (!vma || vma->vm_start > start) - return -EINVAL; - - /* - * A NUMA policy on a VM_MPX VMA could cause this bounds table to - * be split. So we need to look across the entire 'start -> end' - * range of this bounds table, find all of the VM_MPX VMAs, and - * zap only those. - */ - addr = start; - while (vma && vma->vm_start < end) { - /* - * We followed a bounds directory entry down - * here. If we find a non-MPX VMA, that's bad, - * so stop immediately and return an error. This - * probably results in a SIGSEGV. - */ - if (!(vma->vm_flags & VM_MPX)) - return -EINVAL; - - len = min(vma->vm_end, end) - addr; - zap_page_range(vma, addr, len); - trace_mpx_unmap_zap(addr, addr+len); - - vma = vma->vm_next; - addr = vma->vm_start; - } - return 0; -} - -static unsigned long mpx_get_bd_entry_offset(struct mm_struct *mm, - unsigned long addr) -{ - /* - * There are several ways to derive the bd offsets. We - * use the following approach here: - * 1. We know the size of the virtual address space - * 2. We know the number of entries in a bounds table - * 3. We know that each entry covers a fixed amount of - * virtual address space. - * So, we can just divide the virtual address by the - * virtual space used by one entry to determine which - * entry "controls" the given virtual address. - */ - if (is_64bit_mm(mm)) { - int bd_entry_size = 8; /* 64-bit pointer */ - /* - * Take the 64-bit addressing hole in to account. - */ - addr &= ((1UL << boot_cpu_data.x86_virt_bits) - 1); - return (addr / bd_entry_virt_space(mm)) * bd_entry_size; - } else { - int bd_entry_size = 4; /* 32-bit pointer */ - /* - * 32-bit has no hole so this case needs no mask - */ - return (addr / bd_entry_virt_space(mm)) * bd_entry_size; - } - /* - * The two return calls above are exact copies. If we - * pull out a single copy and put it in here, gcc won't - * realize that we're doing a power-of-2 divide and use - * shifts. It uses a real divide. If we put them up - * there, it manages to figure it out (gcc 4.8.3). - */ -} - -static int unmap_entire_bt(struct mm_struct *mm, - long __user *bd_entry, unsigned long bt_addr) -{ - unsigned long expected_old_val = bt_addr | MPX_BD_ENTRY_VALID_FLAG; - unsigned long uninitialized_var(actual_old_val); - int ret; - - while (1) { - int need_write = 1; - unsigned long cleared_bd_entry = 0; - - pagefault_disable(); - ret = mpx_cmpxchg_bd_entry(mm, &actual_old_val, - bd_entry, expected_old_val, cleared_bd_entry); - pagefault_enable(); - if (!ret) - break; - if (ret == -EFAULT) - ret = mpx_resolve_fault(bd_entry, need_write); - /* - * If we could not resolve the fault, consider it - * userspace's fault and error out. - */ - if (ret) - return ret; - } - /* - * The cmpxchg was performed, check the results. - */ - if (actual_old_val != expected_old_val) { - /* - * Someone else raced with us to unmap the table. - * That is OK, since we were both trying to do - * the same thing. Declare success. - */ - if (!actual_old_val) - return 0; - /* - * Something messed with the bounds directory - * entry. We hold mmap_sem for read or write - * here, so it could not be a _new_ bounds table - * that someone just allocated. Something is - * wrong, so pass up the error and SIGSEGV. - */ - return -EINVAL; - } - /* - * Note, we are likely being called under do_munmap() already. To - * avoid recursion, do_munmap() will check whether it comes - * from one bounds table through VM_MPX flag. - */ - return do_munmap(mm, bt_addr, mpx_bt_size_bytes(mm), NULL); -} - -static int try_unmap_single_bt(struct mm_struct *mm, - unsigned long start, unsigned long end) -{ - struct vm_area_struct *next; - struct vm_area_struct *prev; - /* - * "bta" == Bounds Table Area: the area controlled by the - * bounds table that we are unmapping. - */ - unsigned long bta_start_vaddr = start & ~(bd_entry_virt_space(mm)-1); - unsigned long bta_end_vaddr = bta_start_vaddr + bd_entry_virt_space(mm); - unsigned long uninitialized_var(bt_addr); - void __user *bde_vaddr; - int ret; - /* - * We already unlinked the VMAs from the mm's rbtree so 'start' - * is guaranteed to be in a hole. This gets us the first VMA - * before the hole in to 'prev' and the next VMA after the hole - * in to 'next'. - */ - next = find_vma_prev(mm, start, &prev); - /* - * Do not count other MPX bounds table VMAs as neighbors. - * Although theoretically possible, we do not allow bounds - * tables for bounds tables so our heads do not explode. - * If we count them as neighbors here, we may end up with - * lots of tables even though we have no actual table - * entries in use. - */ - while (next && (next->vm_flags & VM_MPX)) - next = next->vm_next; - while (prev && (prev->vm_flags & VM_MPX)) - prev = prev->vm_prev; - /* - * We know 'start' and 'end' lie within an area controlled - * by a single bounds table. See if there are any other - * VMAs controlled by that bounds table. If there are not - * then we can "expand" the are we are unmapping to possibly - * cover the entire table. - */ - next = find_vma_prev(mm, start, &prev); - if ((!prev || prev->vm_end <= bta_start_vaddr) && - (!next || next->vm_start >= bta_end_vaddr)) { - /* - * No neighbor VMAs controlled by same bounds - * table. Try to unmap the whole thing - */ - start = bta_start_vaddr; - end = bta_end_vaddr; - } - - bde_vaddr = mm->context.bd_addr + mpx_get_bd_entry_offset(mm, start); - ret = get_bt_addr(mm, bde_vaddr, &bt_addr); - /* - * No bounds table there, so nothing to unmap. - */ - if (ret == -ENOENT) { - ret = 0; - return 0; - } - if (ret) - return ret; - /* - * We are unmapping an entire table. Either because the - * unmap that started this whole process was large enough - * to cover an entire table, or that the unmap was small - * but was the area covered by a bounds table. - */ - if ((start == bta_start_vaddr) && - (end == bta_end_vaddr)) - return unmap_entire_bt(mm, bde_vaddr, bt_addr); - return zap_bt_entries_mapping(mm, bt_addr, start, end); -} - -static int mpx_unmap_tables(struct mm_struct *mm, - unsigned long start, unsigned long end) -{ - unsigned long one_unmap_start; - trace_mpx_unmap_search(start, end); - - one_unmap_start = start; - while (one_unmap_start < end) { - int ret; - unsigned long next_unmap_start = ALIGN(one_unmap_start+1, - bd_entry_virt_space(mm)); - unsigned long one_unmap_end = end; - /* - * if the end is beyond the current bounds table, - * move it back so we only deal with a single one - * at a time - */ - if (one_unmap_end > next_unmap_start) - one_unmap_end = next_unmap_start; - ret = try_unmap_single_bt(mm, one_unmap_start, one_unmap_end); - if (ret) - return ret; - - one_unmap_start = next_unmap_start; - } - return 0; -} - -/* - * Free unused bounds tables covered in a virtual address region being - * munmap()ed. Assume end > start. - * - * This function will be called by do_munmap(), and the VMAs covering - * the virtual address region start...end have already been split if - * necessary, and the 'vma' is the first vma in this range (start -> end). - */ -void mpx_notify_unmap(struct mm_struct *mm, unsigned long start, - unsigned long end) -{ - struct vm_area_struct *vma; - int ret; - - /* - * Refuse to do anything unless userspace has asked - * the kernel to help manage the bounds tables, - */ - if (!kernel_managing_mpx_tables(current->mm)) - return; - /* - * This will look across the entire 'start -> end' range, - * and find all of the non-VM_MPX VMAs. - * - * To avoid recursion, if a VM_MPX vma is found in the range - * (start->end), we will not continue follow-up work. This - * recursion represents having bounds tables for bounds tables, - * which should not occur normally. Being strict about it here - * helps ensure that we do not have an exploitable stack overflow. - */ - vma = find_vma(mm, start); - while (vma && vma->vm_start < end) { - if (vma->vm_flags & VM_MPX) - return; - vma = vma->vm_next; - } - - ret = mpx_unmap_tables(mm, start, end); - if (ret) - force_sig(SIGSEGV); -} - -/* MPX cannot handle addresses above 47 bits yet. */ -unsigned long mpx_unmapped_area_check(unsigned long addr, unsigned long len, - unsigned long flags) -{ - if (!kernel_managing_mpx_tables(current->mm)) - return addr; - if (addr + len <= DEFAULT_MAP_WINDOW) - return addr; - if (flags & MAP_FIXED) - return -ENOMEM; - - /* - * Requested len is larger than the whole area we're allowed to map in. - * Resetting hinting address wouldn't do much good -- fail early. - */ - if (len > DEFAULT_MAP_WINDOW) - return -ENOMEM; - - /* Look for unmap area within DEFAULT_MAP_WINDOW */ - return 0; -}