| Date | Tue, 19 May 2020 19:58:50 -0000 | From | "tip-bot2 for Peter Zijlstra" <> | Subject | [tip: x86/entry] x86/doublefault: Remove memmove() call |
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The following commit has been merged into the x86/entry branch of tip:
Commit-ID: f44e70325748c7998cf089d2ae67b4b5bc8d8ad9 Gitweb: https://git.kernel.org/tip/f44e70325748c7998cf089d2ae67b4b5bc8d8ad9 Author: Peter Zijlstra <peterz@infradead.org> AuthorDate: Thu, 20 Feb 2020 13:17:27 +01:00 Committer: Thomas Gleixner <tglx@linutronix.de> CommitterDate: Fri, 15 May 2020 20:03:04 +02:00
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
--- arch/x86/kernel/traps.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index e85561f..75fa765 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -369,6 +369,7 @@ 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 @@ -376,7 +377,11 @@ 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 */ /*
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