diff options
author | Tejun Heo <tj@kernel.org> | 2009-02-09 08:17:40 -0500 |
---|---|---|
committer | Ingo Molnar <mingo@elte.hu> | 2009-02-09 18:42:00 -0500 |
commit | ccbeed3a05908d201b47b6c3dd1a373138bba566 (patch) | |
tree | e834d548c70426aa3885dd2169be1a79be4a617b /arch/x86/lguest/boot.c | |
parent | d9a89a26e02ef9ed03f74a755a8b4d8f3a066622 (diff) |
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/lguest/boot.c')
-rw-r--r-- | arch/x86/lguest/boot.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/x86/lguest/boot.c b/arch/x86/lguest/boot.c index 19e33b6cd593..da2e314f61b5 100644 --- a/arch/x86/lguest/boot.c +++ b/arch/x86/lguest/boot.c | |||
@@ -283,7 +283,7 @@ static void lguest_load_tls(struct thread_struct *t, unsigned int cpu) | |||
283 | /* There's one problem which normal hardware doesn't have: the Host | 283 | /* There's one problem which normal hardware doesn't have: the Host |
284 | * can't handle us removing entries we're currently using. So we clear | 284 | * can't handle us removing entries we're currently using. So we clear |
285 | * the GS register here: if it's needed it'll be reloaded anyway. */ | 285 | * the GS register here: if it's needed it'll be reloaded anyway. */ |
286 | loadsegment(gs, 0); | 286 | lazy_load_gs(0); |
287 | lazy_hcall(LHCALL_LOAD_TLS, __pa(&t->tls_array), cpu, 0); | 287 | lazy_hcall(LHCALL_LOAD_TLS, __pa(&t->tls_array), cpu, 0); |
288 | } | 288 | } |
289 | 289 | ||