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authorLinus Torvalds <torvalds@g5.osdl.org>2006-09-18 16:20:40 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2006-09-18 16:20:40 -0700
commit47a5c6fa0e204a2b63309c648bb2fde36836c826 (patch)
tree688b6c12c72fed720dc4a047f310cd292e88a6f1 /include
parent1d19f176a2884d31c4fe2c7018349ff884a819b1 (diff)
x86: save/restore eflags in context switch
(And reset it on new thread creation) It turns out that eflags is important to save and restore not just because of iopl, but due to the magic bits like the NT bit, which we don't want leaking between different threads. Tested-by: Mike Galbraith <efault@gmx.de> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'include')
-rw-r--r--include/asm-i386/system.h8
1 files changed, 7 insertions, 1 deletions
diff --git a/include/asm-i386/system.h b/include/asm-i386/system.h
index 49928eb33f8..098bcee94e3 100644
--- a/include/asm-i386/system.h
+++ b/include/asm-i386/system.h
@@ -11,9 +11,14 @@
struct task_struct; /* one of the stranger aspects of C forward declarations.. */
extern struct task_struct * FASTCALL(__switch_to(struct task_struct *prev, struct task_struct *next));
+/*
+ * Saving eflags is important. It switches not only IOPL between tasks,
+ * it also protects other tasks from NT leaking through sysenter etc.
+ */
#define switch_to(prev,next,last) do { \
unsigned long esi,edi; \
- asm volatile("pushl %%ebp\n\t" \
+ asm volatile("pushfl\n\t" /* Save flags */ \
+ "pushl %%ebp\n\t" \
"movl %%esp,%0\n\t" /* save ESP */ \
"movl %5,%%esp\n\t" /* restore ESP */ \
"movl $1f,%1\n\t" /* save EIP */ \
@@ -21,6 +26,7 @@ extern struct task_struct * FASTCALL(__switch_to(struct task_struct *prev, struc
"jmp __switch_to\n" \
"1:\t" \
"popl %%ebp\n\t" \
+ "popfl" \
:"=m" (prev->thread.esp),"=m" (prev->thread.eip), \
"=a" (last),"=S" (esi),"=D" (edi) \
:"m" (next->thread.esp),"m" (next->thread.eip), \