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x86/asm/entry/64: Fix comments 

- Misleading and slightly incorrect comments in "struct pt_regs" are
   fixed (four instances).

 - Fix incorrect comment atop EMPTY_FRAME macro.

 - Explain in more detail what we do with stack layout during hw interrupt.

 - Correct comments about "partial stack frame" which are no longer
   true.

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Will Drewry <wad@chromium.org>
Link: http://lkml.kernel.org/r/1423778052-21038-3-git-send-email-dvlasenk@redhat.com
Link: http://lkml.kernel.org/r/e1f4429c491fe6ceeddb879dea2786e0f8920f9c.1424989793.git.luto@amacapital.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Denys Vlasenko 2015-02-26 14:40:28 -08:00 committed by Ingo Molnar
parent 76f5df43ca
commit e90e147cbc
4 changed files with 43 additions and 16 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
arch/x86/include/asm/ptrace.h
View File

@ -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;

15
arch/x86/include/uapi/asm/ptrace-abi.h
View File

@ -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

13
arch/x86/include/uapi/asm/ptrace.h
View File

@ -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;

18
arch/x86/kernel/entry_64.S
View File

@ -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: