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x86/asm/entry/64: Use common code for rt_sigreturn() epilogue 

Similarly to stub_execve, we can reuse the epilogue in
stub_rt_sigreturn() and stub_x32_rt_sigreturn().

Add a comment explaining why we can't eliminage SAVE_EXTRA_REGS
here.

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
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: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Drewry <wad@chromium.org>
Link: http://lkml.kernel.org/r/1428439424-7258-1-git-send-email-dvlasenk@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Denys Vlasenko 2015-04-07 22:43:37 +02:00 committed by Ingo Molnar
parent 8b3607b5b8
commit 31f0119b81
1 changed files with 16 additions and 10 deletions
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26
arch/x86/kernel/entry_64.S
View File

@ -527,12 +527,21 @@ END(stub_execveat)
*/
ENTRY(stub_rt_sigreturn)
CFI_STARTPROC
addq $8, %rsp
DEFAULT_FRAME 0
SAVE_EXTRA_REGS
DEFAULT_FRAME 0, 8
/*
* SAVE_EXTRA_REGS result is not normally needed:
* sigreturn overwrites all pt_regs->GPREGS.
* But sigreturn can fail (!), and there is no easy way to detect that.
* To make sure RESTORE_EXTRA_REGS doesn't restore garbage on error,
* we SAVE_EXTRA_REGS here.
*/
SAVE_EXTRA_REGS 8
call sys_rt_sigreturn
movq %rax,RAX(%rsp) # fixme, this could be done at the higher layer
return_from_stub:
addq $8, %rsp
CFI_ADJUST_CFA_OFFSET -8
RESTORE_EXTRA_REGS
movq %rax,RAX(%rsp)
jmp int_ret_from_sys_call
CFI_ENDPROC
END(stub_rt_sigreturn)
@ -540,13 +549,10 @@ END(stub_rt_sigreturn)
#ifdef CONFIG_X86_X32_ABI
ENTRY(stub_x32_rt_sigreturn)
CFI_STARTPROC
addq $8, %rsp
DEFAULT_FRAME 0
SAVE_EXTRA_REGS
DEFAULT_FRAME 0, 8
SAVE_EXTRA_REGS 8
call sys32_x32_rt_sigreturn
movq %rax,RAX(%rsp) # fixme, this could be done at the higher layer
RESTORE_EXTRA_REGS
jmp int_ret_from_sys_call
jmp return_from_stub
CFI_ENDPROC
END(stub_x32_rt_sigreturn)