Commit d73a3329 authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

x86/traps: Mark fixup_bad_iret() noinstr 



This is called from deep entry ASM in a situation where instrumentation
will cause more harm than providing useful information.

Switch from memmove() to memcpy() because memmove() can't be called
from noinstr code. 

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Reviewed-by: default avatarAlexandre Chartre <alexandre.chartre@oracle.com>
Reviewed-by: default avatarMasami Hiramatsu <mhiramat@kernel.org>
Acked-by: default avatarPeter Zijlstra <peterz@infradead.org>
Acked-by: default avatarAndy Lutomirski <luto@kernel.org>
Link: https://lkml.kernel.org/r/20200505134903.346741553@linutronix.de
parent 1c3e5d3f

arch/x86/kernel/traps.c

+9 −7
Original line number Diff line number Diff line
@@ -578,7 +578,7 @@ struct bad_iret_stack { 
	struct pt_regs regs;

};



asmlinkage __visible notrace

asmlinkage __visible noinstr

struct bad_iret_stack *fixup_bad_iret(struct bad_iret_stack *s)

{

	/*
@@ -589,19 +589,21 @@ struct bad_iret_stack *fixup_bad_iret(struct bad_iret_stack *s) 
	 * just below the IRET frame) and we want to pretend that the

	 * exception came from the IRET target.

	 */

	struct bad_iret_stack *new_stack =

		(struct bad_iret_stack *)this_cpu_read(cpu_tss_rw.x86_tss.sp0) - 1;

	struct bad_iret_stack tmp, *new_stack =

		(struct bad_iret_stack *)__this_cpu_read(cpu_tss_rw.x86_tss.sp0) - 1;



	/* Copy the IRET target to the new stack. */

	memmove(&new_stack->regs.ip, (void *)s->regs.sp, 5*8);

	/* Copy the IRET target to the temporary storage. */

	memcpy(&tmp.regs.ip, (void *)s->regs.sp, 5*8);



	/* Copy the remainder of the stack from the current stack. */

	memmove(new_stack, s, offsetof(struct bad_iret_stack, regs.ip));

	memcpy(&tmp, s, offsetof(struct bad_iret_stack, regs.ip));



	/* Update the entry stack */

	memcpy(new_stack, &tmp, sizeof(tmp));



	BUG_ON(!user_mode(&new_stack->regs));

	return new_stack;

}

NOKPROBE_SYMBOL(fixup_bad_iret);

#endif



static bool is_sysenter_singlestep(struct pt_regs *regs)

CRA Git | Maintained and supported by SUSTech CRA and CCSE