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x86/asm/64: Open-code register save/restore in trace_hardirqs*() thunks

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This is a preparatory patch for change in "struct pt_regs"
handling in entry_64.S.

trace_hardirqs*() thunks were (ab)using a part of the
'pt_regs' handling code, namely the SAVE_ARGS/RESTORE_ARGS
macros, to save/restore registers across C function calls.

Since SAVE_ARGS is going to be changed, open-code
register saving/restoring here.

Incidentally, this removes a bit of dead code:
one SAVE_ARGS was used just to emit a CFI annotation,
but it also generated unreachable assembly instructions.

Take a page from thunk_32.S and use push/pop instructions
instead of movq, they are far shorter:
1 or 2 bytes versus 5, and no need for instructions to adjust %rsp:

   text	   data	    bss	    dec	    hex	filename
    333	     40	      0	    373	    175	thunk_64_movq.o
    104	     40	      0	    144	     90	thunk_64_push_pop.o

[ This is ugly as sin, but we'll fix up the ugliness in the next
  patch. I see no point in reordering patches just to avoid an
  ugly intermediate state.  --Andy ]

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/1420927210-19738-4-git-send-email-dvlasenk@redhat.com
Link: http://lkml.kernel.org/r/4c979ad604f0f02c5ade3b3da308b53eabd5e198.1424989793.git.luto@amacapital.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Denys Vlasenko
2015-02-26 14:40:24 -08:00
committed by Ingo Molnar
parent f8e92fb4b0
commit 69e8544cd0
1 changed files with 42 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files

46
arch/x86/lib/thunk_64.S
View File

@@ -17,9 +17,27 @@
CFI_STARTPROC
/* this one pushes 9 elems, the next one would be %rIP */
SAVE_ARGS
pushq_cfi %rdi
CFI_REL_OFFSET rdi, 0
pushq_cfi %rsi
CFI_REL_OFFSET rsi, 0
pushq_cfi %rdx
CFI_REL_OFFSET rdx, 0
pushq_cfi %rcx
CFI_REL_OFFSET rcx, 0
pushq_cfi %rax
CFI_REL_OFFSET rax, 0
pushq_cfi %r8
CFI_REL_OFFSET r8, 0
pushq_cfi %r9
CFI_REL_OFFSET r9, 0
pushq_cfi %r10
CFI_REL_OFFSET r10, 0
pushq_cfi %r11
CFI_REL_OFFSET r11, 0
.if \put_ret_addr_in_rdi
/* 9*8(%rsp) is return addr on stack */
movq_cfi_restore 9*8, rdi
.endif
@@ -45,11 +63,31 @@
#endif
#endif
/* SAVE_ARGS below is used only for the .cfi directives it contains. */
#if defined(CONFIG_TRACE_IRQFLAGS) \
|| defined(CONFIG_DEBUG_LOCK_ALLOC) \
|| defined(CONFIG_PREEMPT)
CFI_STARTPROC
SAVE_ARGS
CFI_ADJUST_CFA_OFFSET 9*8
restore:
RESTORE_ARGS
popq_cfi %r11
CFI_RESTORE r11
popq_cfi %r10
CFI_RESTORE r10
popq_cfi %r9
CFI_RESTORE r9
popq_cfi %r8
CFI_RESTORE r8
popq_cfi %rax
CFI_RESTORE rax
popq_cfi %rcx
CFI_RESTORE rcx
popq_cfi %rdx
CFI_RESTORE rdx
popq_cfi %rsi
CFI_RESTORE rsi
popq_cfi %rdi
CFI_RESTORE rdi
ret
CFI_ENDPROC
_ASM_NOKPROBE(restore)
#endif