| 1 |
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| 2 | #ifndef _ASM_X86_IRQ_STACK_H
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| 3 | #define _ASM_X86_IRQ_STACK_H
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| 4 |
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| 5 | #include <linux/ptrace.h>
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| 6 | #include <linux/objtool.h>
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| 7 |
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| 8 | #include <asm/processor.h>
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| 9 |
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| 10 | #ifdef CONFIG_X86_64
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| 11 |
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| 12 | |
| 13 | * Macro to inline switching to an interrupt stack and invoking function
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| 14 | * calls from there. The following rules apply:
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| 15 | *
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| 16 | * - Ordering:
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| 17 | *
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| 18 | * 1. Write the stack pointer into the top most place of the irq
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| 19 | * stack. This ensures that the various unwinders can link back to the
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| 20 | * original stack.
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| 21 | *
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| 22 | * 2. Switch the stack pointer to the top of the irq stack.
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| 23 | *
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| 24 | * 3. Invoke whatever needs to be done (@asm_call argument)
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| 25 | *
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| 26 | * 4. Pop the original stack pointer from the top of the irq stack
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| 27 | * which brings it back to the original stack where it left off.
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| 28 | *
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| 29 | * - Function invocation:
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| 30 | *
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| 31 | * To allow flexible usage of the macro, the actual function code including
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| 32 | * the store of the arguments in the call ABI registers is handed in via
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| 33 | * the @asm_call argument.
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| 34 | *
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| 35 | * - Local variables:
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| 36 | *
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| 37 | * @tos:
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| 38 | * The @tos variable holds a pointer to the top of the irq stack and
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| 39 | * _must_ be allocated in a non-callee saved register as this is a
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| 40 | * restriction coming from objtool.
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| 41 | *
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| 42 | * Note, that (tos) is both in input and output constraints to ensure
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| 43 | * that the compiler does not assume that R11 is left untouched in
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| 44 | * case this macro is used in some place where the per cpu interrupt
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| 45 | * stack pointer is used again afterwards
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| 46 | *
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| 47 | * - Function arguments:
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| 48 | * The function argument(s), if any, have to be defined in register
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| 49 | * variables at the place where this is invoked. Storing the
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| 50 | * argument(s) in the proper register(s) is part of the @asm_call
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| 51 | *
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| 52 | * - Constraints:
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| 53 | *
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| 54 | * The constraints have to be done very carefully because the compiler
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| 55 | * does not know about the assembly call.
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| 56 | *
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| 57 | * output:
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| 58 | * As documented already above the @tos variable is required to be in
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| 59 | * the output constraints to make the compiler aware that R11 cannot be
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| 60 | * reused after the asm() statement.
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| 61 | *
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| 62 | * For builds with CONFIG_UNWINDER_FRAME_POINTER, ASM_CALL_CONSTRAINT is
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| 63 | * required as well as this prevents certain creative GCC variants from
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| 64 | * misplacing the ASM code.
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| 65 | *
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| 66 | * input:
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| 67 | * - func:
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| 68 | * Immediate, which tells the compiler that the function is referenced.
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| 69 | *
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| 70 | * - tos:
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| 71 | * Register. The actual register is defined by the variable declaration.
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| 72 | *
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| 73 | * - function arguments:
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| 74 | * The constraints are handed in via the 'argconstr' argument list. They
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| 75 | * describe the register arguments which are used in @asm_call.
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| 76 | *
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| 77 | * clobbers:
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| 78 | * Function calls can clobber anything except the callee-saved
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| 79 | * registers. Tell the compiler.
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| 80 |
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| 81 | #define call_on_stack(stack, func, asm_call, argconstr...) \
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| 82 | { \
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| 83 | register void *tos asm("r11"); \
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| 84 | \
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| 85 | tos = ((void *)(stack)); \
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| 86 | \
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| 87 | asm_inline volatile( \
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| 88 | "movq %%rsp, (%[tos]) \n" \
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| 89 | "movq %[tos], %%rsp \n" \
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| 90 | \
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| 91 | asm_call \
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| 92 | \
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| 93 | "popq %%rsp \n" \
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| 94 | \
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| 95 | : "+r" (tos), ASM_CALL_CONSTRAINT \
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| 96 | : [__func] "i" (func), [tos] "r" (tos) argconstr \
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| 97 | : "cc", "rax", "rcx", "rdx", "rsi", "rdi", "r8", "r9", "r10", \
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| 98 | "memory" \
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| 99 | ); \
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| 100 | }
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| 101 |
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| 102 | #define ASM_CALL_ARG0 \
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| 103 | "1: call %c[__func] \n" \
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| 104 | ANNOTATE_REACHABLE(1b) " \n"
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| 105 |
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| 106 | #define ASM_CALL_ARG1 \
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| 107 | "movq %[arg1], %%rdi \n" \
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| 108 | ASM_CALL_ARG0
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| 109 |
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| 110 | #define ASM_CALL_ARG2 \
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| 111 | "movq %[arg2], %%rsi \n" \
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| 112 | ASM_CALL_ARG1
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| 113 |
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| 114 | #define ASM_CALL_ARG3 \
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| 115 | "movq %[arg3], %%rdx \n" \
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| 116 | ASM_CALL_ARG2
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| 117 |
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| 118 | #define call_on_irqstack(func, asm_call, argconstr...) \
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| 119 | call_on_stack(__this_cpu_read(hardirq_stack_ptr), \
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| 120 | func, asm_call, argconstr)
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| 121 |
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| 122 |
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| 123 | #define assert_function_type(func, proto) \
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| 124 | static_assert(__builtin_types_compatible_p(typeof(&func), proto))
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| 125 |
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| 126 | #define assert_arg_type(arg, proto) \
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| 127 | static_assert(__builtin_types_compatible_p(typeof(arg), proto))
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| 128 |
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| 129 | |
| 130 | * Macro to invoke system vector and device interrupt C handlers.
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| 131 |
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| 132 | #define call_on_irqstack_cond(func, regs, asm_call, constr, c_args...) \
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| 133 | { \
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| 134 | |
| 135 | * User mode entry and interrupt on the irq stack do not \
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| 136 | * switch stacks. If from user mode the task stack is empty. \
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| 137 | \
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| 138 | if (user_mode(regs) || __this_cpu_read(hardirq_stack_inuse)) { \
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| 139 | irq_enter_rcu(); \
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| 140 | func(c_args); \
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| 141 | irq_exit_rcu(); \
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| 142 | } else { \
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| 143 | |
| 144 | * Mark the irq stack inuse _before_ and unmark _after_ \
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| 145 | * switching stacks. Interrupts are disabled in both \
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| 146 | * places. Invoke the stack switch macro with the call \
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| 147 | * sequence which matches the above direct invocation. \
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| 148 | \
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| 149 | __this_cpu_write(hardirq_stack_inuse, true); \
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| 150 | call_on_irqstack(func, asm_call, constr); \
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| 151 | __this_cpu_write(hardirq_stack_inuse, false); \
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| 152 | } \
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| 153 | }
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| 154 |
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| 155 | |
| 156 | * Function call sequence for __call_on_irqstack() for system vectors.
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| 157 | *
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| 158 | * Note that irq_enter_rcu() and irq_exit_rcu() do not use the input
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| 159 | * mechanism because these functions are global and cannot be optimized out
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| 160 | * when compiling a particular source file which uses one of these macros.
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| 161 | *
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| 162 | * The argument (regs) does not need to be pushed or stashed in a callee
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| 163 | * saved register to be safe vs. the irq_enter_rcu() call because the
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| 164 | * clobbers already prevent the compiler from storing it in a callee
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| 165 | * clobbered register. As the compiler has to preserve @regs for the final
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| 166 | * call to idtentry_exit() anyway, it's likely that it does not cause extra
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| 167 | * effort for this asm magic.
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| 168 |
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| 169 | #define ASM_CALL_SYSVEC \
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| 170 | "call irq_enter_rcu \n" \
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| 171 | ASM_CALL_ARG1 \
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| 172 | "call irq_exit_rcu \n"
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| 173 |
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| 174 | #define SYSVEC_CONSTRAINTS , [arg1] "r" (regs)
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| 175 |
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| 176 | #define run_sysvec_on_irqstack_cond(func, regs) \
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| 177 | { \
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| 178 | assert_function_type(func, void (*)(struct pt_regs *)); \
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| 179 | assert_arg_type(regs, struct pt_regs *); \
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| 180 | \
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| 181 | call_on_irqstack_cond(func, regs, ASM_CALL_SYSVEC, \
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| 182 | SYSVEC_CONSTRAINTS, regs); \
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| 183 | }
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| 184 |
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| 185 | |
| 186 | * As in ASM_CALL_SYSVEC above the clobbers force the compiler to store
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| 187 | * @regs and @vector in callee saved registers.
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| 188 |
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| 189 | #define ASM_CALL_IRQ \
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| 190 | "call irq_enter_rcu \n" \
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| 191 | ASM_CALL_ARG2 \
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| 192 | "call irq_exit_rcu \n"
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| 193 |
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| 194 | #define IRQ_CONSTRAINTS , [arg1] "r" (regs), [arg2] "r" ((unsigned long)vector)
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| 195 |
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| 196 | #define run_irq_on_irqstack_cond(func, regs, vector) \
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| 197 | { \
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| 198 | assert_function_type(func, void (*)(struct pt_regs *, u32)); \
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| 199 | assert_arg_type(regs, struct pt_regs *); \
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| 200 | assert_arg_type(vector, u32); \
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| 201 | \
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| 202 | call_on_irqstack_cond(func, regs, ASM_CALL_IRQ, \
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| 203 | IRQ_CONSTRAINTS, regs, vector); \
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| 204 | }
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| 205 |
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| 206 | #ifdef CONFIG_SOFTIRQ_ON_OWN_STACK
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| 207 | |
| 208 | * Macro to invoke __do_softirq on the irq stack. This is only called from
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| 209 | * task context when bottom halves are about to be reenabled and soft
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| 210 | * interrupts are pending to be processed. The interrupt stack cannot be in
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| 211 | * use here.
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| 212 |
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| 213 | #define do_softirq_own_stack() \
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| 214 | { \
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| 215 | __this_cpu_write(hardirq_stack_inuse, true); \
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| 216 | call_on_irqstack(__do_softirq, ASM_CALL_ARG0); \
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| 217 | __this_cpu_write(hardirq_stack_inuse, false); \
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| 218 | }
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| 219 |
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| 220 | #endif
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| 221 |
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| 222 | #else
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| 223 |
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| 224 | #define run_sysvec_on_irqstack_cond(func, regs) \
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| 225 | { \
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| 226 | irq_enter_rcu(); \
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| 227 | func(regs); \
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| 228 | irq_exit_rcu(); \
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| 229 | }
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| 230 |
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| 231 |
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| 232 | #define run_irq_on_irqstack_cond(func, regs, vector) \
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| 233 | { \
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| 234 | irq_enter_rcu(); \
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| 235 | func(regs, vector); \
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| 236 | irq_exit_rcu(); \
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| 237 | }
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| 238 |
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| 239 | #endif
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| 240 |
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| 241 | #endif
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