Messages in this thread Patch in this message | | | From | Denys Vlasenko <> | Subject | [PATCH 3/4] x86: open-code register save/restore in trace_hardirqs thunks | Date | Sat, 10 Jan 2015 23:00:09 +0100 |
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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 pt_regs handling code, namely 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 insns.
Take a page from thunk_32.S and use push/pop insns instead of movq, they are far shorter: 1 or 2 bytes versus 5, and no need for insns 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
Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com> CC: Linus Torvalds <torvalds@linux-foundation.org> CC: Oleg Nesterov <oleg@redhat.com> CC: "H. Peter Anvin" <hpa@zytor.com> CC: Borislav Petkov <bp@alien8.de> CC: Andy Lutomirski <luto@amacapital.net> CC: Frederic Weisbecker <fweisbec@gmail.com> CC: X86 ML <x86@kernel.org> CC: Alexei Starovoitov <ast@plumgrid.com> CC: Will Drewry <wad@chromium.org> CC: Kees Cook <keescook@chromium.org> CC: linux-kernel@vger.kernel.org --- arch/x86/lib/thunk_64.S | 46 ++++++++++++++++++++++++++++++++++++++++++---- 1 file changed, 42 insertions(+), 4 deletions(-)
diff --git a/arch/x86/lib/thunk_64.S b/arch/x86/lib/thunk_64.S index b30b5eb..8ec443a 100644 --- a/arch/x86/lib/thunk_64.S +++ b/arch/x86/lib/thunk_64.S @@ -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 -- 1.8.1.4
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