[src-draft/trunk]: src/sys/arch/x86 Use static constant rather than stack mem...

[Taylor R Campbell <riastradh%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src-all/rev/be4174d6c523
branches:  trunk
changeset: 934576:be4174d6c523
user:      Taylor R Campbell <riastradh%NetBSD.org@localhost>
date:      Sun Jun 14 05:15:54 2020 +0000

description:
Use static constant rather than stack memset buffer for zero fpregs.

diffstat:

 sys/arch/x86/include/cpufunc.h |  6 +++---
 sys/arch/x86/include/fpu.h     |  2 +-
 sys/arch/x86/x86/fpu.c         |  5 ++---
 3 files changed, 6 insertions(+), 7 deletions(-)

diffs (71 lines):

diff -r 75dbad3a3753 -r be4174d6c523 sys/arch/x86/include/cpufunc.h
--- a/sys/arch/x86/include/cpufunc.h    Sun Jun 14 00:57:26 2020 +0000
+++ b/sys/arch/x86/include/cpufunc.h    Sun Jun 14 05:15:54 2020 +0000
@@ -381,7 +381,7 @@
 }
 
 static inline void
-frstor(void *addr)
+frstor(const void *addr)
 {
        const uint8_t *area = addr;
 
@@ -407,7 +407,7 @@
 }
 
 static inline void
-fxrstor(void *addr)
+fxrstor(const void *addr)
 {
        const uint8_t *area = addr;
 
@@ -452,7 +452,7 @@
 }
 
 static inline void
-xrstor(void *addr, uint64_t mask)
+xrstor(const void *addr, uint64_t mask)
 {
        const uint8_t *area = addr;
        uint32_t low, high;
diff -r 75dbad3a3753 -r be4174d6c523 sys/arch/x86/include/fpu.h
--- a/sys/arch/x86/include/fpu.h        Sun Jun 14 00:57:26 2020 +0000
+++ b/sys/arch/x86/include/fpu.h        Sun Jun 14 05:15:54 2020 +0000
@@ -15,7 +15,7 @@
 void fpuinit_mxcsr_mask(void);
 
 void fpu_area_save(void *, uint64_t);
-void fpu_area_restore(void *, uint64_t);
+void fpu_area_restore(const void *, uint64_t);
 
 void fpu_save(void);
 
diff -r 75dbad3a3753 -r be4174d6c523 sys/arch/x86/x86/fpu.c
--- a/sys/arch/x86/x86/fpu.c    Sun Jun 14 00:57:26 2020 +0000
+++ b/sys/arch/x86/x86/fpu.c    Sun Jun 14 05:15:54 2020 +0000
@@ -269,7 +269,7 @@
 }
 
 void
-fpu_area_restore(void *area, uint64_t xsave_features)
+fpu_area_restore(const void *area, uint64_t xsave_features)
 {
        clts();
 
@@ -435,7 +435,7 @@
 void
 fpu_kern_leave(void)
 {
-       union savefpu zero_fpu __aligned(64);
+       static const union savefpu zero_fpu __aligned(64);
        struct cpu_info *ci = curcpu();
        int s;
 
@@ -447,7 +447,6 @@
         * through Spectre-class attacks to userland, even if there are
         * no bugs in fpu state management.
         */
-       memset(&zero_fpu, 0, sizeof(zero_fpu));
        fpu_area_restore(&zero_fpu, x86_xsave_features);
 
        /*