| 1 | |
| 2 |
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| 3 | #include <linux/compiler.h>
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| 4 | #include <linux/context_tracking.h>
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| 5 | #include <linux/errno.h>
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| 6 | #include <linux/nospec.h>
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| 7 | #include <linux/ptrace.h>
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| 8 | #include <linux/randomize_kstack.h>
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| 9 | #include <linux/syscalls.h>
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| 10 |
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| 11 | #include <asm/debug-monitors.h>
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| 12 | #include <asm/exception.h>
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| 13 | #include <asm/fpsimd.h>
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| 14 | #include <asm/syscall.h>
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| 15 | #include <asm/thread_info.h>
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| 16 | #include <asm/unistd.h>
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| 17 | #include <asm/unistd_compat_32.h>
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| 18 |
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| 19 | long compat_arm_syscall(struct pt_regs *regs, int scno);
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| 20 | long sys_ni_syscall(void);
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| 21 |
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| 22 | static long do_ni_syscall(struct pt_regs *regs, int scno)
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| 23 | {
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| 24 | if (is_compat_task()) {
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| 25 | long ret = compat_arm_syscall(regs, scno);
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| 26 | if (ret != -ENOSYS)
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| 27 | return ret;
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| 28 | }
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| 29 |
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| 30 | return sys_ni_syscall();
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| 31 | }
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| 32 |
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| 33 | static long __invoke_syscall(struct pt_regs *regs, syscall_fn_t syscall_fn)
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| 34 | {
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| 35 | return syscall_fn(regs);
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| 36 | }
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| 37 |
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| 38 | static void invoke_syscall(struct pt_regs *regs, unsigned int scno,
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| 39 | unsigned int sc_nr,
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| 40 | const syscall_fn_t syscall_table[])
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| 41 | {
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| 42 | long ret;
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| 43 |
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| 44 | add_random_kstack_offset();
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| 45 |
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| 46 | if (likely(scno < sc_nr)) {
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| 47 | syscall_fn_t syscall_fn;
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| 48 | syscall_fn = syscall_table[array_index_nospec(scno, sc_nr)];
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| 49 | ret = __invoke_syscall(regs, syscall_fn);
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| 50 | } else {
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| 51 | ret = do_ni_syscall(regs, scno);
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| 52 | }
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| 53 |
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| 54 | syscall_set_return_value(current, regs, 0, ret);
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| 55 | }
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| 56 |
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| 57 | static inline bool has_syscall_work(unsigned long flags)
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| 58 | {
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| 59 | return unlikely(flags & _TIF_SYSCALL_WORK);
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| 60 | }
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| 61 |
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| 62 | static void el0_svc_common(struct pt_regs *regs, int scno, int sc_nr,
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| 63 | const syscall_fn_t syscall_table[])
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| 64 | {
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| 65 | unsigned long flags = read_thread_flags();
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| 66 |
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| 67 | regs->orig_x0 = regs->regs[0];
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| 68 | regs->syscallno = scno;
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| 69 |
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| 70 | |
| 71 | * BTI note:
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| 72 | * The architecture does not guarantee that SPSR.BTYPE is zero
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| 73 | * on taking an SVC, so we could return to userspace with a
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| 74 | * non-zero BTYPE after the syscall.
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| 75 | *
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| 76 | * This shouldn't matter except when userspace is explicitly
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| 77 | * doing something stupid, such as setting PROT_BTI on a page
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| 78 | * that lacks conforming BTI/PACIxSP instructions, falling
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| 79 | * through from one executable page to another with differing
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| 80 | * PROT_BTI, or messing with BTYPE via ptrace: in such cases,
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| 81 | * userspace should not be surprised if a SIGILL occurs on
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| 82 | * syscall return.
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| 83 | *
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| 84 | * So, don't touch regs->pstate & PSR_BTYPE_MASK here.
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| 85 | * (Similarly for HVC and SMC elsewhere.)
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| 86 |
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| 87 |
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| 88 | if (unlikely(flags & _TIF_MTE_ASYNC_FAULT)) {
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| 89 | |
| 90 | * Process the asynchronous tag check fault before the actual
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| 91 | * syscall. do_notify_resume() will send a signal to userspace
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| 92 | * before the syscall is restarted.
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| 93 |
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| 94 | syscall_set_return_value(current, regs, -ERESTARTNOINTR, 0);
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| 95 | return;
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| 96 | }
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| 97 |
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| 98 | if (has_syscall_work(flags)) {
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| 99 | |
| 100 | * The de-facto standard way to skip a system call using ptrace
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| 101 | * is to set the system call to -1 (NO_SYSCALL) and set x0 to a
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| 102 | * suitable error code for consumption by userspace. However,
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| 103 | * this cannot be distinguished from a user-issued syscall(-1)
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| 104 | * and so we must set x0 to -ENOSYS here in case the tracer doesn't
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| 105 | * issue the skip and we fall into trace_exit with x0 preserved.
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| 106 | *
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| 107 | * This is slightly odd because it also means that if a tracer
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| 108 | * sets the system call number to -1 but does not initialise x0,
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| 109 | * then x0 will be preserved for all system calls apart from a
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| 110 | * user-issued syscall(-1). However, requesting a skip and not
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| 111 | * setting the return value is unlikely to do anything sensible
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| 112 | * anyway.
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| 113 |
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| 114 | if (scno == NO_SYSCALL)
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| 115 | syscall_set_return_value(current, regs, -ENOSYS, 0);
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| 116 | scno = syscall_trace_enter(regs);
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| 117 | if (scno == NO_SYSCALL)
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| 118 | goto trace_exit;
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| 119 | }
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| 120 |
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| 121 | invoke_syscall(regs, scno, sc_nr, syscall_table);
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| 122 |
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| 123 | |
| 124 | * The tracing status may have changed under our feet, so we have to
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| 125 | * check again. However, if we were tracing entry, then we always trace
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| 126 | * exit regardless, as the old entry assembly did.
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| 127 |
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| 128 | if (!has_syscall_work(flags) && !IS_ENABLED(CONFIG_DEBUG_RSEQ)) {
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| 129 | flags = read_thread_flags();
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| 130 | if (!has_syscall_work(flags) && !(flags & _TIF_SINGLESTEP))
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| 131 | return;
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| 132 | }
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| 133 |
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| 134 | trace_exit:
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| 135 | syscall_trace_exit(regs);
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| 136 | }
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| 137 |
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| 138 | void do_el0_svc(struct pt_regs *regs)
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| 139 | {
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| 140 | el0_svc_common(regs, regs->regs[8], __NR_syscalls, sys_call_table);
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| 141 | }
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| 142 |
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| 143 | #ifdef CONFIG_COMPAT
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| 144 | void do_el0_svc_compat(struct pt_regs *regs)
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| 145 | {
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| 146 | el0_svc_common(regs, regs->regs[7], __NR_compat32_syscalls,
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| 147 | compat_sys_call_table);
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| 148 | }
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| 149 | #endif
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