Messages in this thread | | | From | Andi Kleen <> | Subject | Re: [PATCH RFC 3/6] Use %gs as the PDA base-segment in the kernel. | Date | Sun, 27 Aug 2006 17:57:18 +0200 |
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> > - /* 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.
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