- /* Clear %fs and %gs. */
- asm volatile ("movl %0, %%fs; movl %0, %%gs" : : "r" (0));
+ /* Clear %fs. */
+ asm volatile ("mov %0, %%fs" : : "r" (0));
+
+ /* Set %gs for this CPU's PDA */
+ asm volatile ("mov %0, %%gs" : : "r" (__KERNEL_PDA));
I would add memory clobbers here to make sure the dependency on read/write pda
is right.
+1: movw GS(%esp), %gs
movl is recommended in 32bit mode
--- a/arch/i386/kernel/signal.c
+++ b/arch/i386/kernel/signal.c
@@ -128,7 +128,7 @@ restore_sigcontext(struct pt_regs *regs,
X86_EFLAGS_TF | X86_EFLAGS_SF | X86_EFLAGS_ZF | \
X86_EFLAGS_AF | X86_EFLAGS_PF | X86_EFLAGS_CF)
- GET_SEG(gs);
+ COPY_SEG(gs);
GET_SEG(fs);
COPY_SEG(es);
COPY_SEG(ds);
@@ -244,9 +244,7 @@ setup_sigcontext(struct sigcontext __use
{
int tmp, err = 0;
- tmp = 0;
- savesegment(gs, tmp);
- err |= __put_user(tmp, (unsigned int __user *)&sc->gs);
+ err |= __put_user(regs->xgs, (unsigned int __user *)&sc->gs);
savesegment(fs, tmp);
err |= __put_user(tmp, (unsigned int __user *)&sc->fs);
Hmm, changing it for the sc looks a bit bogus. If everything is right nothing should change for user space, but this changes something.
@@ -306,7 +306,7 @@ static void do_sys_vm86(struct kernel_vm
tsk->thread.screen_bitmap = info->screen_bitmap;
if (info->flags & VM86_SCREEN_BITMAP)
mark_screen_rdonly(tsk->mm);
- __asm__ __volatile__("xorl %eax,%eax; movl %eax,%fs; movl %eax,%gs\n\t");
+ __asm__ __volatile__("movl %0,%%fs\n\t" : : "r" (0));
This is actually a useful bug fix on its own.