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Diffstat (limited to 'arch/x86/include/asm/irq_stack.h')
| -rw-r--r-- | arch/x86/include/asm/irq_stack.h | 241 |
1 files changed, 241 insertions, 0 deletions
diff --git a/arch/x86/include/asm/irq_stack.h b/arch/x86/include/asm/irq_stack.h new file mode 100644 index 000000000..147cb8fdd --- /dev/null +++ b/arch/x86/include/asm/irq_stack.h @@ -0,0 +1,241 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _ASM_X86_IRQ_STACK_H +#define _ASM_X86_IRQ_STACK_H + +#include <linux/ptrace.h> +#include <linux/objtool.h> + +#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_UNWINDER_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_stack(stack, func, asm_call, argconstr...) \ +{ \ + register void *tos asm("r11"); \ + \ + tos = ((void *)(stack)); \ + \ + 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" \ + ); \ +} + +#define ASM_CALL_ARG0 \ + "call %P[__func] \n" \ + ASM_REACHABLE + +#define ASM_CALL_ARG1 \ + "movq %[arg1], %%rdi \n" \ + ASM_CALL_ARG0 + +#define ASM_CALL_ARG2 \ + "movq %[arg2], %%rsi \n" \ + ASM_CALL_ARG1 + +#define ASM_CALL_ARG3 \ + "movq %[arg3], %%rdx \n" \ + ASM_CALL_ARG2 + +#define call_on_irqstack(func, asm_call, argconstr...) \ + call_on_stack(__this_cpu_read(hardirq_stack_ptr), \ + func, asm_call, argconstr) + +/* 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)) + +/* + * Macro to invoke system vector and device interrupt C handlers. + */ +#define call_on_irqstack_cond(func, regs, asm_call, constr, c_args...) \ +{ \ + /* \ + * User mode entry and interrupt on the irq stack do not \ + * switch stacks. If from user mode the task stack is empty. \ + */ \ + if (user_mode(regs) || __this_cpu_read(hardirq_stack_inuse)) { \ + irq_enter_rcu(); \ + func(c_args); \ + irq_exit_rcu(); \ + } else { \ + /* \ + * Mark the irq stack inuse _before_ and unmark _after_ \ + * switching stacks. Interrupts are disabled in both \ + * places. Invoke the stack switch macro with the call \ + * sequence which matches the above direct invocation. \ + */ \ + __this_cpu_write(hardirq_stack_inuse, true); \ + call_on_irqstack(func, asm_call, constr); \ + __this_cpu_write(hardirq_stack_inuse, false); \ + } \ +} + +/* + * Function call sequence for __call_on_irqstack() for system vectors. + * + * Note that irq_enter_rcu() and irq_exit_rcu() do not use the input + * mechanism because these functions are global and cannot be optimized out + * when compiling a particular source file which uses one of these macros. + * + * The argument (regs) does not need to be pushed or stashed in a callee + * saved register to be safe vs. the irq_enter_rcu() call because the + * clobbers already prevent the compiler from storing it in a callee + * clobbered register. As the compiler has to preserve @regs for the final + * call to idtentry_exit() anyway, it's likely that it does not cause extra + * effort for this asm magic. + */ +#define ASM_CALL_SYSVEC \ + "call irq_enter_rcu \n" \ + ASM_CALL_ARG1 \ + "call irq_exit_rcu \n" + +#define SYSVEC_CONSTRAINTS , [arg1] "r" (regs) + +#define run_sysvec_on_irqstack_cond(func, regs) \ +{ \ + assert_function_type(func, void (*)(struct pt_regs *)); \ + assert_arg_type(regs, struct pt_regs *); \ + \ + call_on_irqstack_cond(func, regs, ASM_CALL_SYSVEC, \ + SYSVEC_CONSTRAINTS, regs); \ +} + +/* + * As in ASM_CALL_SYSVEC above the clobbers force the compiler to store + * @regs and @vector in callee saved registers. + */ +#define ASM_CALL_IRQ \ + "call irq_enter_rcu \n" \ + ASM_CALL_ARG2 \ + "call irq_exit_rcu \n" + +#define IRQ_CONSTRAINTS , [arg1] "r" (regs), [arg2] "r" ((unsigned long)vector) + +#define run_irq_on_irqstack_cond(func, regs, vector) \ +{ \ + assert_function_type(func, void (*)(struct pt_regs *, u32)); \ + assert_arg_type(regs, struct pt_regs *); \ + assert_arg_type(vector, u32); \ + \ + call_on_irqstack_cond(func, regs, ASM_CALL_IRQ, \ + IRQ_CONSTRAINTS, regs, vector); \ +} + +#ifdef CONFIG_SOFTIRQ_ON_OWN_STACK +/* + * Macro to invoke __do_softirq on the irq stack. This is only called from + * task context when bottom halves are about to be reenabled and soft + * interrupts are pending to be processed. The interrupt stack cannot be in + * use here. + */ +#define do_softirq_own_stack() \ +{ \ + __this_cpu_write(hardirq_stack_inuse, true); \ + call_on_irqstack(__do_softirq, ASM_CALL_ARG0); \ + __this_cpu_write(hardirq_stack_inuse, false); \ +} + +#endif + +#else /* CONFIG_X86_64 */ +/* System vector handlers always run on the stack they interrupted. */ +#define run_sysvec_on_irqstack_cond(func, regs) \ +{ \ + irq_enter_rcu(); \ + func(regs); \ + irq_exit_rcu(); \ +} + +/* Switches to the irq stack within func() */ +#define run_irq_on_irqstack_cond(func, regs, vector) \ +{ \ + irq_enter_rcu(); \ + func(regs, vector); \ + irq_exit_rcu(); \ +} + +#endif /* !CONFIG_X86_64 */ + +#endif |