diff options
| -rw-r--r-- | arch/x86/include/asm/irq_stack.h | 98 |
1 files changed, 98 insertions, 0 deletions
diff --git a/arch/x86/include/asm/irq_stack.h b/arch/x86/include/asm/irq_stack.h index 554f84bca1c3..d5b7bc6b7a58 100644 --- a/arch/x86/include/asm/irq_stack.h +++ b/arch/x86/include/asm/irq_stack.h @@ -7,6 +7,104 @@ #include <asm/processor.h> #ifdef CONFIG_X86_64 + +/* + * Macro to inline switching to an interrupt stack and invoking function + * calls from there. The following rules apply: + * + * - Ordering: + * + * 1. Write the stack pointer into the top most place of the irq + * stack. This ensures that the various unwinders can link back to the + * original stack. + * + * 2. Switch the stack pointer to the top of the irq stack. + * + * 3. Invoke whatever needs to be done (@asm_call argument) + * + * 4. Pop the original stack pointer from the top of the irq stack + * which brings it back to the original stack where it left off. + * + * - Function invocation: + * + * To allow flexible usage of the macro, the actual function code including + * the store of the arguments in the call ABI registers is handed in via + * the @asm_call argument. + * + * - Local variables: + * + * @tos: + * The @tos variable holds a pointer to the top of the irq stack and + * _must_ be allocated in a non-callee saved register as this is a + * restriction coming from objtool. + * + * Note, that (tos) is both in input and output constraints to ensure + * that the compiler does not assume that R11 is left untouched in + * case this macro is used in some place where the per cpu interrupt + * stack pointer is used again afterwards + * + * - Function arguments: + * The function argument(s), if any, have to be defined in register + * variables at the place where this is invoked. Storing the + * argument(s) in the proper register(s) is part of the @asm_call + * + * - Constraints: + * + * The constraints have to be done very carefully because the compiler + * does not know about the assembly call. + * + * output: + * As documented already above the @tos variable is required to be in + * the output constraints to make the compiler aware that R11 cannot be + * reused after the asm() statement. + * + * For builds with CONFIG_UNWIND_FRAME_POINTER ASM_CALL_CONSTRAINT is + * required as well as this prevents certain creative GCC variants from + * misplacing the ASM code. + * + * input: + * - func: + * Immediate, which tells the compiler that the function is referenced. + * + * - tos: + * Register. The actual register is defined by the variable declaration. + * + * - function arguments: + * The constraints are handed in via the 'argconstr' argument list. They + * describe the register arguments which are used in @asm_call. + * + * clobbers: + * Function calls can clobber anything except the callee-saved + * registers. Tell the compiler. + */ +#define call_on_irqstack(func, asm_call, argconstr...) \ +{ \ + register void *tos asm("r11"); \ + \ + tos = ((void *)__this_cpu_read(hardirq_stack_ptr)); \ + \ + asm_inline volatile( \ + "movq %%rsp, (%[tos]) \n" \ + "movq %[tos], %%rsp \n" \ + \ + asm_call \ + \ + "popq %%rsp \n" \ + \ + : "+r" (tos), ASM_CALL_CONSTRAINT \ + : [__func] "i" (func), [tos] "r" (tos) argconstr \ + : "cc", "rax", "rcx", "rdx", "rsi", "rdi", "r8", "r9", "r10", \ + "memory" \ + ); \ +} + +/* Macros to assert type correctness for run_*_on_irqstack macros */ +#define assert_function_type(func, proto) \ + static_assert(__builtin_types_compatible_p(typeof(&func), proto)) + +#define assert_arg_type(arg, proto) \ + static_assert(__builtin_types_compatible_p(typeof(arg), proto)) + static __always_inline bool irqstack_active(void) { return __this_cpu_read(hardirq_stack_inuse); |