path: root/arch/x86/kernel/asm-offsets_32.c
diff options
authorDenys Vlasenko <dvlasenk@redhat.com>2015-03-09 15:52:18 +0100
committerIngo Molnar <mingo@kernel.org>2015-03-17 09:25:29 +0100
commitd828c71fba8922b116b4ec56c3e5bca8c822d5ae (patch)
treee9f6034ed503fcf0f0a8c90ecfe986d5764fb8fa /arch/x86/kernel/asm-offsets_32.c
parent3876488444e71238e287459c39d7692b6f718c3e (diff)
x86/asm/entry/32: Document the 32-bit SYSENTER "emergency stack" better
Before the patch, the 'tss_struct::stack' field was not referenced anywhere. It was used only to set SYSENTER's stack to point after the last byte of tss_struct, thus the trailing field, stack[64], was used. But grep would not know it. You can comment it out, compile, and kernel will even run until an unlucky NMI corrupts io_bitmap[] (which is also not easily detectable). This patch changes code so that the purpose and usage of this field is not mysterious anymore, and can be easily grepped for. This does change generated code, for a subtle reason: since tss_struct is ____cacheline_aligned, there happens to be 5 longs of padding at the end. Old code was using the padding too; new code will strictly use it only for SYSENTER_stack[]. 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: 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: Will Drewry <wad@chromium.org> Link: http://lkml.kernel.org/r/1425912738-559-2-git-send-email-dvlasenk@redhat.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'arch/x86/kernel/asm-offsets_32.c')
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/x86/kernel/asm-offsets_32.c b/arch/x86/kernel/asm-offsets_32.c
index 3b3b9d33ac1d..47703aed74cf 100644
--- a/arch/x86/kernel/asm-offsets_32.c
+++ b/arch/x86/kernel/asm-offsets_32.c
@@ -68,7 +68,7 @@ void foo(void)
/* Offset from the sysenter stack to tss.sp0 */
DEFINE(TSS_sysenter_sp0, offsetof(struct tss_struct, x86_tss.sp0) -
- sizeof(struct tss_struct));
+ offsetofend(struct tss_struct, SYSENTER_stack));