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 <[email protected]> CC: Linus Torvalds <[email protected]> CC: Steven Rostedt <[email protected]> CC: Ingo Molnar <[email protected]> CC: Borislav Petkov <[email protected]> CC: "H. Peter Anvin" <[email protected]> CC: Andy Lutomirski <[email protected]> CC: Oleg Nesterov <[email protected]> CC: Frederic Weisbecker <[email protected]> CC: Alexei Starovoitov <[email protected]> CC: Will Drewry <[email protected]> CC: Kees Cook <[email protected]> CC: [email protected] CC: [email protected] --- arch/x86/kernel/entry_64.S | 26 ++++++++++++++++---------- 1 file changed, 16 insertions(+), 10 deletions(-) diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S index 15261ba..994f3cb 100644 --- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -450,12 +450,21 @@ 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) @@ -463,13 +472,10 @@ 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) -- 1.8.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
