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x86/doublefault: Remove memmove() call 

Use of memmove() in #DF is problematic considered tracing and other
instrumentation.

Remove the memmove() call and simply write out what needs doing; this
even clarifies the code, win-win! The code copies from the espfix64
stack to the normal task stack, there is no possible way for that to
overlap.

Survives selftests/x86, specifically sigreturn_64.

Suggested-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Acked-by: Andy Lutomirski <luto@kernel.org>
Link: https://lkml.kernel.org/r/20200505134058.863038566@linutronix.de
This commit is contained in:
Peter Zijlstra 2020-02-20 13:17:27 +01:00 committed by Thomas Gleixner
parent 24ae0c91cb
commit e9660391d0
1 changed files with 6 additions and 1 deletions
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7
arch/x86/kernel/traps.c
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@ -299,6 +299,7 @@ dotraplinkage void do_double_fault(struct pt_regs *regs, long error_code, unsign
regs->ip == (unsigned long)native_irq_return_iret)
{
struct pt_regs *gpregs = (struct pt_regs *)this_cpu_read(cpu_tss_rw.x86_tss.sp0) - 1;
unsigned long *p = (unsigned long *)regs->sp;
/*
* regs->sp points to the failing IRET frame on the
@ -306,7 +307,11 @@ dotraplinkage void do_double_fault(struct pt_regs *regs, long error_code, unsign
* in gpregs->ss through gpregs->ip.
*
*/
memmove(&gpregs->ip, (void *)regs->sp, 5*8);
gpregs->ip = p[0];
gpregs->cs = p[1];
gpregs->flags = p[2];
gpregs->sp = p[3];
gpregs->ss = p[4];
gpregs->orig_ax = 0; /* Missing (lost) #GP error code */
/*