1 /* SPDX-License-Identifier: GPL-2.0 */ 2 #ifndef _ASM_X86_IRQ_STACK_H 3 #define _ASM_X86_IRQ_STACK_H 4 5 #include <linux/ptrace.h> 6 7 #include <asm/processor.h> 8 9 #ifdef CONFIG_X86_64 10 11 /* 12 * Macro to inline switching to an interrupt stack and invoking function 13 * calls from there. The following rules apply: 14 * 15 * - Ordering: 16 * 17 * 1. Write the stack pointer into the top most place of the irq 18 * stack. This ensures that the various unwinders can link back to the 19 * original stack. 20 * 21 * 2. Switch the stack pointer to the top of the irq stack. 22 * 23 * 3. Invoke whatever needs to be done (@asm_call argument) 24 * 25 * 4. Pop the original stack pointer from the top of the irq stack 26 * which brings it back to the original stack where it left off. 27 * 28 * - Function invocation: 29 * 30 * To allow flexible usage of the macro, the actual function code including 31 * the store of the arguments in the call ABI registers is handed in via 32 * the @asm_call argument. 33 * 34 * - Local variables: 35 * 36 * @tos: 37 * The @tos variable holds a pointer to the top of the irq stack and 38 * _must_ be allocated in a non-callee saved register as this is a 39 * restriction coming from objtool. 40 * 41 * Note, that (tos) is both in input and output constraints to ensure 42 * that the compiler does not assume that R11 is left untouched in 43 * case this macro is used in some place where the per cpu interrupt 44 * stack pointer is used again afterwards 45 * 46 * - Function arguments: 47 * The function argument(s), if any, have to be defined in register 48 * variables at the place where this is invoked. Storing the 49 * argument(s) in the proper register(s) is part of the @asm_call 50 * 51 * - Constraints: 52 * 53 * The constraints have to be done very carefully because the compiler 54 * does not know about the assembly call. 55 * 56 * output: 57 * As documented already above the @tos variable is required to be in 58 * the output constraints to make the compiler aware that R11 cannot be 59 * reused after the asm() statement. 60 * 61 * For builds with CONFIG_UNWIND_FRAME_POINTER ASM_CALL_CONSTRAINT is 62 * required as well as this prevents certain creative GCC variants from 63 * misplacing the ASM code. 64 * 65 * input: 66 * - func: 67 * Immediate, which tells the compiler that the function is referenced. 68 * 69 * - tos: 70 * Register. The actual register is defined by the variable declaration. 71 * 72 * - function arguments: 73 * The constraints are handed in via the 'argconstr' argument list. They 74 * describe the register arguments which are used in @asm_call. 75 * 76 * clobbers: 77 * Function calls can clobber anything except the callee-saved 78 * registers. Tell the compiler. 79 */ 80 #define call_on_irqstack(func, asm_call, argconstr...) \ 81 { \ 82 register void *tos asm("r11"); \ 83 \ 84 tos = ((void *)__this_cpu_read(hardirq_stack_ptr)); \ 85 \ 86 asm_inline volatile( \ 87 "movq %%rsp, (%[tos]) \n" \ 88 "movq %[tos], %%rsp \n" \ 89 \ 90 asm_call \ 91 \ 92 "popq %%rsp \n" \ 93 \ 94 : "+r" (tos), ASM_CALL_CONSTRAINT \ 95 : [__func] "i" (func), [tos] "r" (tos) argconstr \ 96 : "cc", "rax", "rcx", "rdx", "rsi", "rdi", "r8", "r9", "r10", \ 97 "memory" \ 98 ); \ 99 } 100 101 /* Macros to assert type correctness for run_*_on_irqstack macros */ 102 #define assert_function_type(func, proto) \ 103 static_assert(__builtin_types_compatible_p(typeof(&func), proto)) 104 105 #define assert_arg_type(arg, proto) \ 106 static_assert(__builtin_types_compatible_p(typeof(arg), proto)) 107 108 /* 109 * Macro to invoke system vector and device interrupt C handlers. 110 */ 111 #define call_on_irqstack_cond(func, regs, asm_call, constr, c_args...) \ 112 { \ 113 /* \ 114 * User mode entry and interrupt on the irq stack do not \ 115 * switch stacks. If from user mode the task stack is empty. \ 116 */ \ 117 if (user_mode(regs) || __this_cpu_read(hardirq_stack_inuse)) { \ 118 irq_enter_rcu(); \ 119 func(c_args); \ 120 irq_exit_rcu(); \ 121 } else { \ 122 /* \ 123 * Mark the irq stack inuse _before_ and unmark _after_ \ 124 * switching stacks. Interrupts are disabled in both \ 125 * places. Invoke the stack switch macro with the call \ 126 * sequence which matches the above direct invocation. \ 127 */ \ 128 __this_cpu_write(hardirq_stack_inuse, true); \ 129 call_on_irqstack(func, asm_call, constr); \ 130 __this_cpu_write(hardirq_stack_inuse, false); \ 131 } \ 132 } 133 134 /* 135 * Function call sequence for __call_on_irqstack() for system vectors. 136 * 137 * Note that irq_enter_rcu() and irq_exit_rcu() do not use the input 138 * mechanism because these functions are global and cannot be optimized out 139 * when compiling a particular source file which uses one of these macros. 140 * 141 * The argument (regs) does not need to be pushed or stashed in a callee 142 * saved register to be safe vs. the irq_enter_rcu() call because the 143 * clobbers already prevent the compiler from storing it in a callee 144 * clobbered register. As the compiler has to preserve @regs for the final 145 * call to idtentry_exit() anyway, it's likely that it does not cause extra 146 * effort for this asm magic. 147 */ 148 #define ASM_CALL_SYSVEC \ 149 "call irq_enter_rcu \n" \ 150 "movq %[arg1], %%rdi \n" \ 151 "call %P[__func] \n" \ 152 "call irq_exit_rcu \n" 153 154 #define SYSVEC_CONSTRAINTS , [arg1] "r" (regs) 155 156 #define run_sysvec_on_irqstack_cond(func, regs) \ 157 { \ 158 assert_function_type(func, void (*)(struct pt_regs *)); \ 159 assert_arg_type(regs, struct pt_regs *); \ 160 \ 161 call_on_irqstack_cond(func, regs, ASM_CALL_SYSVEC, \ 162 SYSVEC_CONSTRAINTS, regs); \ 163 } 164 165 /* 166 * As in ASM_CALL_SYSVEC above the clobbers force the compiler to store 167 * @regs and @vector in callee saved registers. 168 */ 169 #define ASM_CALL_IRQ \ 170 "call irq_enter_rcu \n" \ 171 "movq %[arg1], %%rdi \n" \ 172 "movl %[arg2], %%esi \n" \ 173 "call %P[__func] \n" \ 174 "call irq_exit_rcu \n" 175 176 #define IRQ_CONSTRAINTS , [arg1] "r" (regs), [arg2] "r" (vector) 177 178 #define run_irq_on_irqstack_cond(func, regs, vector) \ 179 { \ 180 assert_function_type(func, void (*)(struct pt_regs *, u32)); \ 181 assert_arg_type(regs, struct pt_regs *); \ 182 assert_arg_type(vector, u32); \ 183 \ 184 call_on_irqstack_cond(func, regs, ASM_CALL_IRQ, \ 185 IRQ_CONSTRAINTS, regs, vector); \ 186 } 187 188 #define ASM_CALL_SOFTIRQ \ 189 "call %P[__func] \n" 190 191 /* 192 * Macro to invoke __do_softirq on the irq stack. This is only called from 193 * task context when bottom halves are about to be reenabled and soft 194 * interrupts are pending to be processed. The interrupt stack cannot be in 195 * use here. 196 */ 197 #define do_softirq_own_stack() \ 198 { \ 199 __this_cpu_write(hardirq_stack_inuse, true); \ 200 call_on_irqstack(__do_softirq, ASM_CALL_SOFTIRQ); \ 201 __this_cpu_write(hardirq_stack_inuse, false); \ 202 } 203 204 #else /* CONFIG_X86_64 */ 205 /* System vector handlers always run on the stack they interrupted. */ 206 #define run_sysvec_on_irqstack_cond(func, regs) \ 207 { \ 208 irq_enter_rcu(); \ 209 func(regs); \ 210 irq_exit_rcu(); \ 211 } 212 213 /* Switches to the irq stack within func() */ 214 #define run_irq_on_irqstack_cond(func, regs, vector) \ 215 { \ 216 irq_enter_rcu(); \ 217 func(regs, vector); \ 218 irq_exit_rcu(); \ 219 } 220 221 #endif /* !CONFIG_X86_64 */ 222 223 #endif 224