xiaomi-sm8450/android_kernel_xiaomi_sm8450
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

i387: Uninline the generic FP helpers that we expose to kernel modules

Browse Source 
Instead of exporting the very low-level internals of the FPU state
save/restore code (ie things like 'fpu_owner_task'), we should export
the higher-level interfaces.

Inlining these things is pointless anyway: sure, sometimes the end
result is small, but while 'stts()' can result in just three x86
instructions, those are not cheap instructions (writing %cr0 is a
serializing instruction and a very slow one at that).

So the overhead of a function call is not noticeable, and we really
don't want random modules mucking about with our internal state save
logic anyway.

So this unexports 'fpu_owner_task', and instead uninlines and exports
the actual functions that modules can use: fpu_kernel_begin/end() and
unlazy_fpu().

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/alpine.LFD.2.02.1202211339590.5354@i5.linux-foundation.org
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
This commit is contained in:
Linus Torvalds
2012-02-21 10:25:45 -08:00
committed by H. Peter Anvin
parent 27e74da980
commit 8546c00892
3 changed files with 84 additions and 76 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
arch/x86/kernel/cpu/common.c
View File

@@ -1045,7 +1045,6 @@ DEFINE_PER_CPU(char *, irq_stack_ptr) =
DEFINE_PER_CPU(unsigned int, irq_count) = -1;
DEFINE_PER_CPU(struct task_struct *, fpu_owner_task);
EXPORT_PER_CPU_SYMBOL(fpu_owner_task);
/*
* Special IST stacks which the CPU switches to when it calls
@@ -1115,7 +1114,6 @@ void debug_stack_reset(void)
DEFINE_PER_CPU(struct task_struct *, current_task) = &init_task;
EXPORT_PER_CPU_SYMBOL(current_task);
DEFINE_PER_CPU(struct task_struct *, fpu_owner_task);
EXPORT_PER_CPU_SYMBOL(fpu_owner_task);
#ifdef CONFIG_CC_STACKPROTECTOR
DEFINE_PER_CPU_ALIGNED(struct stack_canary, stack_canary);