From 69e8544cd0056e02965ffb5e8414fb7501a2ee2e Mon Sep 17 00:00:00 2001 From: Denys Vlasenko Date: Thu, 26 Feb 2015 14:40:24 -0800 Subject: [PATCH] x86/asm/64: Open-code register save/restore in trace_hardirqs*() thunks 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 Signed-off-by: Andy Lutomirski Cc: Alexei Starovoitov Cc: Borislav Petkov Cc: Frederic Weisbecker Cc: H. Peter Anvin Cc: Kees Cook Cc: Linus Torvalds Cc: Oleg Nesterov Cc: Will Drewry 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 --- 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 b30b5ebd614a..8ec443a0777b 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