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authorTejun Heo <tj@kernel.org>2009-02-09 22:17:40 +0900
committerIngo Molnar <mingo@elte.hu>2009-02-10 00:42:00 +0100
commitccbeed3a05908d201b47b6c3dd1a373138bba566 (patch)
treee834d548c70426aa3885dd2169be1a79be4a617b /arch/x86/kernel/asm-offsets_32.c
parentd9a89a26e02ef9ed03f74a755a8b4d8f3a066622 (diff)
downloadlinux-ccbeed3a05908d201b47b6c3dd1a373138bba566.tar.gz
x86: make lazy %gs optional on x86_32
Impact: pt_regs changed, lazy gs handling made optional, add slight overhead to SAVE_ALL, simplifies error_code path a bit On x86_32, %gs hasn't been used by kernel and handled lazily. pt_regs doesn't have place for it and gs is saved/loaded only when necessary. In preparation for stack protector support, this patch makes lazy %gs handling optional by doing the followings. * Add CONFIG_X86_32_LAZY_GS and place for gs in pt_regs. * Save and restore %gs along with other registers in entry_32.S unless LAZY_GS. Note that this unfortunately adds "pushl $0" on SAVE_ALL even when LAZY_GS. However, it adds no overhead to common exit path and simplifies entry path with error code. * Define different user_gs accessors depending on LAZY_GS and add lazy_save_gs() and lazy_load_gs() which are noop if !LAZY_GS. The lazy_*_gs() ops are used to save, load and clear %gs lazily. * Define ELF_CORE_COPY_KERNEL_REGS() which always read %gs directly. xen and lguest changes need to be verified. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Jeremy Fitzhardinge <jeremy@xensource.com> Cc: Rusty Russell <rusty@rustcorp.com.au> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'arch/x86/kernel/asm-offsets_32.c')
-rw-r--r--arch/x86/kernel/asm-offsets_32.c1
1 files changed, 1 insertions, 0 deletions
diff --git a/arch/x86/kernel/asm-offsets_32.c b/arch/x86/kernel/asm-offsets_32.c
index ee4df08feee6..fbf2f33e3080 100644
--- a/arch/x86/kernel/asm-offsets_32.c
+++ b/arch/x86/kernel/asm-offsets_32.c
@@ -75,6 +75,7 @@ void foo(void)
OFFSET(PT_DS, pt_regs, ds);
OFFSET(PT_ES, pt_regs, es);
OFFSET(PT_FS, pt_regs, fs);
+ OFFSET(PT_GS, pt_regs, gs);
OFFSET(PT_ORIG_EAX, pt_regs, orig_ax);
OFFSET(PT_EIP, pt_regs, ip);
OFFSET(PT_CS, pt_regs, cs);