/* 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 \ "1: call %c[__func] \n" \ ANNOTATE_REACHABLE(1b) " \n" #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
