Commit e3a9e681 authored by Peter Zijlstra's avatar Peter Zijlstra
Browse files

x86/entry: Fixup bad_iret vs noinstr 



vmlinux.o: warning: objtool: fixup_bad_iret()+0x8e: call to memcpy() leaves .noinstr.text section

Worse, when KASAN there is no telling what memcpy() actually is. Force
the use of __memcpy() which is our assmebly implementation.

Reported-by: default avatarMarco Elver <elver@google.com>
Suggested-by: default avatarMarco Elver <elver@google.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: default avatarMarco Elver <elver@google.com>
Link: https://lkml.kernel.org/r/20200618144801.760070502@infradead.org
parent 734d099b

arch/x86/kernel/traps.c

+3 −3
Original line number Diff line number Diff line
@@ -690,13 +690,13 @@ struct bad_iret_stack *fixup_bad_iret(struct bad_iret_stack *s) 
		(struct bad_iret_stack *)__this_cpu_read(cpu_tss_rw.x86_tss.sp0) - 1;



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

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

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



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

	memcpy(&tmp, 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));

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



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

	return new_stack;

arch/x86/lib/memcpy_64.S

+4 −0
Original line number Diff line number Diff line
@@ -8,6 +8,8 @@ 
#include <asm/alternative-asm.h>

#include <asm/export.h>



.pushsection .noinstr.text, "ax"



/*

 * We build a jump to memcpy_orig by default which gets NOPped out on

 * the majority of x86 CPUs which set REP_GOOD. In addition, CPUs which
@@ -184,6 +186,8 @@ SYM_FUNC_START_LOCAL(memcpy_orig) 
	retq

SYM_FUNC_END(memcpy_orig)



.popsection



#ifndef CONFIG_UML



MCSAFE_TEST_CTL

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