Commit e9660391 authored Feb 20, 2020 by Peter Zijlstra Committed by Thomas Gleixner Jun 11, 2020

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

parent 24ae0c91

arch/x86/kernel/traps.c

+6 −1

Original line number	Diff line number	Diff line
		@@ -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, 58);
		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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