diff options
| -rw-r--r-- | arch/x86/include/asm/ptrace.h | 13 | ||||
| -rw-r--r-- | arch/x86/include/uapi/asm/ptrace-abi.h | 15 | ||||
| -rw-r--r-- | arch/x86/include/uapi/asm/ptrace.h | 13 | ||||
| -rw-r--r-- | arch/x86/kernel/entry_64.S | 18 |
4 files changed, 43 insertions, 16 deletions
diff --git a/arch/x86/include/asm/ptrace.h b/arch/x86/include/asm/ptrace.h index 86fc2bb82287..4077d963a1a0 100644 --- a/arch/x86/include/asm/ptrace.h +++ b/arch/x86/include/asm/ptrace.h @@ -31,13 +31,17 @@ struct pt_regs { #else /* __i386__ */ struct pt_regs { +/* + * C ABI says these regs are callee-preserved. They aren't saved on kernel entry + * unless syscall needs a complete, fully filled "struct pt_regs". + */ unsigned long r15; unsigned long r14; unsigned long r13; unsigned long r12; unsigned long bp; unsigned long bx; -/* arguments: non interrupts/non tracing syscalls only save up to here*/ +/* These regs are callee-clobbered. Always saved on kernel entry. */ unsigned long r11; unsigned long r10; unsigned long r9; @@ -47,9 +51,12 @@ struct pt_regs { unsigned long dx; unsigned long si; unsigned long di; +/* + * On syscall entry, this is syscall#. On CPU exception, this is error code. + * On hw interrupt, it's IRQ number: + */ unsigned long orig_ax; -/* end of arguments */ -/* cpu exception frame or undefined */ +/* Return frame for iretq */ unsigned long ip; unsigned long cs; unsigned long flags; diff --git a/arch/x86/include/uapi/asm/ptrace-abi.h b/arch/x86/include/uapi/asm/ptrace-abi.h index ad115bf779f3..580aee3072e0 100644 --- a/arch/x86/include/uapi/asm/ptrace-abi.h +++ b/arch/x86/include/uapi/asm/ptrace-abi.h @@ -25,13 +25,17 @@ #else /* __i386__ */ #if defined(__ASSEMBLY__) || defined(__FRAME_OFFSETS) +/* + * C ABI says these regs are callee-preserved. They aren't saved on kernel entry + * unless syscall needs a complete, fully filled "struct pt_regs". + */ #define R15 0 #define R14 8 #define R13 16 #define R12 24 #define RBP 32 #define RBX 40 -/* arguments: interrupts/non tracing syscalls only save up to here*/ +/* These regs are callee-clobbered. Always saved on kernel entry. */ #define R11 48 #define R10 56 #define R9 64 @@ -41,9 +45,12 @@ #define RDX 96 #define RSI 104 #define RDI 112 -#define ORIG_RAX 120 /* = ERROR */ -/* end of arguments */ -/* cpu exception frame or undefined in case of fast syscall. */ +/* + * On syscall entry, this is syscall#. On CPU exception, this is error code. + * On hw interrupt, it's IRQ number: + */ +#define ORIG_RAX 120 +/* Return frame for iretq */ #define RIP 128 #define CS 136 #define EFLAGS 144 diff --git a/arch/x86/include/uapi/asm/ptrace.h b/arch/x86/include/uapi/asm/ptrace.h index ac4b9aa4d999..bc16115af39b 100644 --- a/arch/x86/include/uapi/asm/ptrace.h +++ b/arch/x86/include/uapi/asm/ptrace.h @@ -41,13 +41,17 @@ struct pt_regs { #ifndef __KERNEL__ struct pt_regs { +/* + * C ABI says these regs are callee-preserved. They aren't saved on kernel entry + * unless syscall needs a complete, fully filled "struct pt_regs". + */ unsigned long r15; unsigned long r14; unsigned long r13; unsigned long r12; unsigned long rbp; unsigned long rbx; -/* arguments: non interrupts/non tracing syscalls only save up to here*/ +/* These regs are callee-clobbered. Always saved on kernel entry. */ unsigned long r11; unsigned long r10; unsigned long r9; @@ -57,9 +61,12 @@ struct pt_regs { unsigned long rdx; unsigned long rsi; unsigned long rdi; +/* + * On syscall entry, this is syscall#. On CPU exception, this is error code. + * On hw interrupt, it's IRQ number: + */ unsigned long orig_rax; -/* end of arguments */ -/* cpu exception frame or undefined */ +/* Return frame for iretq */ unsigned long rip; unsigned long cs; unsigned long eflags; diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S index e8372e08f8c2..695f4d434a84 100644 --- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -14,9 +14,6 @@ * NOTE: This code handles signal-recognition, which happens every time * after an interrupt and after each system call. * - * Normal syscalls and interrupts don't save a full stack frame, this is - * only done for syscall tracing, signals or fork/exec et.al. - * * A note on terminology: * - top of stack: Architecture defined interrupt frame from SS to RIP * at the top of the kernel process stack. @@ -151,7 +148,7 @@ ENDPROC(native_usergs_sysret64) .endm /* - * initial frame state for interrupts (and exceptions without error code) + * empty frame */ .macro EMPTY_FRAME start=1 offset=0 .if \start @@ -379,7 +376,7 @@ tracesys_phase2: call syscall_trace_enter_phase2 /* - * Reload arg registers from stack in case ptrace changed them. + * Reload registers from stack in case ptrace changed them. * We don't reload %rax because syscall_trace_entry_phase2() returned * the value it wants us to use in the table lookup. */ @@ -629,6 +626,13 @@ END(interrupt) /* 0(%rsp): ~(interrupt number) */ .macro interrupt func cld + /* + * Since nothing in interrupt handling code touches r12...r15 members + * of "struct pt_regs", and since interrupts can nest, we can save + * four stack slots and simultaneously provide + * an unwind-friendly stack layout by saving "truncated" pt_regs + * exactly up to rbp slot, without these members. + */ ALLOC_PT_GPREGS_ON_STACK -RBP SAVE_C_REGS -RBP /* this goes to 0(%rsp) for unwinder, not for saving the value: */ @@ -641,6 +645,7 @@ END(interrupt) SWAPGS 1: /* + * Save previous stack pointer, optionally switch to interrupt stack. * irq_count is used to check if a CPU is already on an interrupt stack * or not. While this is essentially redundant with preempt_count it is * a little cheaper to use a separate counter in the PDA (short of @@ -681,6 +686,7 @@ ret_from_intr: /* Restore saved previous stack */ popq %rsi CFI_DEF_CFA rsi,SS+8-RBP /* reg/off reset after def_cfa_expr */ + /* return code expects complete pt_regs - adjust rsp accordingly: */ leaq ARGOFFSET-RBP(%rsi), %rsp CFI_DEF_CFA_REGISTER rsp CFI_ADJUST_CFA_OFFSET RBP-ARGOFFSET @@ -692,7 +698,7 @@ exit_intr: /* Interrupt came from user space */ /* - * Has a correct top of stack, but a partial stack frame + * Has a correct top of stack. * %rcx: thread info. Interrupts off. */ retint_with_reschedule: |