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authorSuresh Siddha <suresh.b.siddha@intel.com>2012-07-24 16:05:29 -0700
committerH. Peter Anvin <hpa@linux.intel.com>2012-09-18 15:51:48 -0700
commit72a671ced66db6d1c2bfff1c930a101ac8d08204 (patch)
treefb3f58fa735d2d3cffc636e3e0f8114a04b04623 /arch/x86/include/asm/xsave.h
parent0ca5bd0d886578ad0afeceaa83458c0f35cb3c6b (diff)
x86, fpu: Unify signal handling code paths for x86 and x86_64 kernels
Currently for x86 and x86_32 binaries, fpstate in the user sigframe is copied to/from the fpstate in the task struct. And in the case of signal delivery for x86_64 binaries, if the fpstate is live in the CPU registers, then the live state is copied directly to the user sigframe. Otherwise fpstate in the task struct is copied to the user sigframe. During restore, fpstate in the user sigframe is restored directly to the live CPU registers. Historically, different code paths led to different bugs. For example, x86_64 code path was not preemption safe till recently. Also there is lot of code duplication for support of new features like xsave etc. Unify signal handling code paths for x86 and x86_64 kernels. New strategy is as follows: Signal delivery: Both for 32/64-bit frames, align the core math frame area to 64bytes as needed by xsave (this where the main fpu/extended state gets copied to and excludes the legacy compatibility fsave header for the 32-bit [f]xsave frames). If the state is live, copy the register state directly to the user frame. If not live, copy the state in the thread struct to the user frame. And for 32-bit [f]xsave frames, construct the fsave header separately before the actual [f]xsave area. Signal return: As the 32-bit frames with [f]xstate has an additional 'fsave' header, copy everything back from the user sigframe to the fpstate in the task structure and reconstruct the fxstate from the 'fsave' header (Also user passed pointers may not be correctly aligned for any attempt to directly restore any partial state). At the next fpstate usage, everything will be restored to the live CPU registers. For all the 64-bit frames and the 32-bit fsave frame, restore the state from the user sigframe directly to the live CPU registers. 64-bit signals always restored the math frame directly, so we can expect the math frame pointer to be correctly aligned. For 32-bit fsave frames, there are no alignment requirements, so we can restore the state directly. "lat_sig catch" microbenchmark numbers (for x86, x86_64, x86_32 binaries) are with in the noise range with this change. Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com> Link: http://lkml.kernel.org/r/1343171129-2747-4-git-send-email-suresh.b.siddha@intel.com [ Merged in compilation fix ] Link: http://lkml.kernel.org/r/1344544736.8326.17.camel@sbsiddha-desk.sc.intel.com Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Diffstat (limited to 'arch/x86/include/asm/xsave.h')
-rw-r--r--arch/x86/include/asm/xsave.h6
1 files changed, 1 insertions, 5 deletions
diff --git a/arch/x86/include/asm/xsave.h b/arch/x86/include/asm/xsave.h
index aaac810e8613..c1d989a15193 100644
--- a/arch/x86/include/asm/xsave.h
+++ b/arch/x86/include/asm/xsave.h
@@ -38,9 +38,6 @@ extern u64 xstate_fx_sw_bytes[USER_XSTATE_FX_SW_WORDS];
extern void xsave_init(void);
extern void update_regset_xstate_info(unsigned int size, u64 xstate_mask);
extern int init_fpu(struct task_struct *child);
-extern int check_for_xstate(struct i387_fxsave_struct __user *buf,
- void __user *fpstate,
- struct _fpx_sw_bytes *sw);
static inline int fpu_xrstor_checking(struct xsave_struct *fx)
{
@@ -68,8 +65,7 @@ static inline int xsave_user(struct xsave_struct __user *buf)
* Clear the xsave header first, so that reserved fields are
* initialized to zero.
*/
- err = __clear_user(&buf->xsave_hdr,
- sizeof(struct xsave_hdr_struct));
+ err = __clear_user(&buf->xsave_hdr, sizeof(buf->xsave_hdr));
if (unlikely(err))
return -EFAULT;