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
Ingo Molnar
Родитель
76f5df43ca
Коммит
e90e147cbc
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@ -31,13 +31,17 @@ struct pt_regs {
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#else /* __i386__ */
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struct pt_regs {
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/*
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* C ABI says these regs are callee-preserved. They aren't saved on kernel entry
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* unless syscall needs a complete, fully filled "struct pt_regs".
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*/
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unsigned long r15;
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unsigned long r14;
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unsigned long r13;
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unsigned long r12;
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unsigned long bp;
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unsigned long bx;
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/* arguments: non interrupts/non tracing syscalls only save up to here*/
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/* These regs are callee-clobbered. Always saved on kernel entry. */
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unsigned long r11;
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unsigned long r10;
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unsigned long r9;
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@ -47,9 +51,12 @@ struct pt_regs {
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unsigned long dx;
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unsigned long si;
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unsigned long di;
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/*
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* On syscall entry, this is syscall#. On CPU exception, this is error code.
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* On hw interrupt, it's IRQ number:
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*/
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unsigned long orig_ax;
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/* end of arguments */
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/* cpu exception frame or undefined */
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/* Return frame for iretq */
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unsigned long ip;
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unsigned long cs;
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unsigned long flags;
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@ -25,13 +25,17 @@
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#else /* __i386__ */
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#if defined(__ASSEMBLY__) || defined(__FRAME_OFFSETS)
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/*
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* C ABI says these regs are callee-preserved. They aren't saved on kernel entry
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* unless syscall needs a complete, fully filled "struct pt_regs".
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*/
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#define R15 0
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#define R14 8
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#define R13 16
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#define R12 24
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#define RBP 32
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#define RBX 40
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/* arguments: interrupts/non tracing syscalls only save up to here*/
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/* These regs are callee-clobbered. Always saved on kernel entry. */
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#define R11 48
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#define R10 56
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#define R9 64
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@ -41,9 +45,12 @@
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#define RDX 96
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#define RSI 104
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#define RDI 112
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#define ORIG_RAX 120 /* = ERROR */
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/* end of arguments */
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/* cpu exception frame or undefined in case of fast syscall. */
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/*
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* On syscall entry, this is syscall#. On CPU exception, this is error code.
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* On hw interrupt, it's IRQ number:
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*/
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#define ORIG_RAX 120
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/* Return frame for iretq */
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#define RIP 128
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#define CS 136
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#define EFLAGS 144
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@ -41,13 +41,17 @@ struct pt_regs {
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#ifndef __KERNEL__
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struct pt_regs {
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/*
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* C ABI says these regs are callee-preserved. They aren't saved on kernel entry
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* unless syscall needs a complete, fully filled "struct pt_regs".
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*/
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unsigned long r15;
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unsigned long r14;
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unsigned long r13;
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unsigned long r12;
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unsigned long rbp;
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unsigned long rbx;
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/* arguments: non interrupts/non tracing syscalls only save up to here*/
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/* These regs are callee-clobbered. Always saved on kernel entry. */
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unsigned long r11;
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unsigned long r10;
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unsigned long r9;
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@ -57,9 +61,12 @@ struct pt_regs {
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unsigned long rdx;
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unsigned long rsi;
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unsigned long rdi;
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/*
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* On syscall entry, this is syscall#. On CPU exception, this is error code.
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* On hw interrupt, it's IRQ number:
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*/
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unsigned long orig_rax;
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/* end of arguments */
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/* cpu exception frame or undefined */
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/* Return frame for iretq */
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unsigned long rip;
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unsigned long cs;
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unsigned long eflags;
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@ -14,9 +14,6 @@
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* NOTE: This code handles signal-recognition, which happens every time
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* after an interrupt and after each system call.
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*
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* Normal syscalls and interrupts don't save a full stack frame, this is
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* only done for syscall tracing, signals or fork/exec et.al.
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*
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* A note on terminology:
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* - top of stack: Architecture defined interrupt frame from SS to RIP
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* at the top of the kernel process stack.
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@ -151,7 +148,7 @@ ENDPROC(native_usergs_sysret64)
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.endm
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/*
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* initial frame state for interrupts (and exceptions without error code)
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* empty frame
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*/
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.macro EMPTY_FRAME start=1 offset=0
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.if \start
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@ -379,7 +376,7 @@ tracesys_phase2:
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call syscall_trace_enter_phase2
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/*
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* Reload arg registers from stack in case ptrace changed them.
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* Reload registers from stack in case ptrace changed them.
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* We don't reload %rax because syscall_trace_entry_phase2() returned
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* the value it wants us to use in the table lookup.
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*/
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@ -629,6 +626,13 @@ END(interrupt)
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/* 0(%rsp): ~(interrupt number) */
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.macro interrupt func
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cld
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/*
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* Since nothing in interrupt handling code touches r12...r15 members
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* of "struct pt_regs", and since interrupts can nest, we can save
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* four stack slots and simultaneously provide
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* an unwind-friendly stack layout by saving "truncated" pt_regs
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* exactly up to rbp slot, without these members.
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*/
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ALLOC_PT_GPREGS_ON_STACK -RBP
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SAVE_C_REGS -RBP
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/* this goes to 0(%rsp) for unwinder, not for saving the value: */
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@ -641,6 +645,7 @@ END(interrupt)
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SWAPGS
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1:
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/*
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* Save previous stack pointer, optionally switch to interrupt stack.
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* irq_count is used to check if a CPU is already on an interrupt stack
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* or not. While this is essentially redundant with preempt_count it is
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* a little cheaper to use a separate counter in the PDA (short of
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@ -681,6 +686,7 @@ ret_from_intr:
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/* Restore saved previous stack */
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popq %rsi
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CFI_DEF_CFA rsi,SS+8-RBP /* reg/off reset after def_cfa_expr */
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/* return code expects complete pt_regs - adjust rsp accordingly: */
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leaq ARGOFFSET-RBP(%rsi), %rsp
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CFI_DEF_CFA_REGISTER rsp
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CFI_ADJUST_CFA_OFFSET RBP-ARGOFFSET
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@ -692,7 +698,7 @@ exit_intr:
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/* Interrupt came from user space */
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/*
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* Has a correct top of stack, but a partial stack frame
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* Has a correct top of stack.
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* %rcx: thread info. Interrupts off.
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*/
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retint_with_reschedule:
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