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Commit 2cb7878a authored by Rusty Russell's avatar Rusty Russell Committed by Linus Torvalds
Browse files

lguest: fix 'unhandled trap 13' with CONFIG_CC_STACKPROTECTOR 



We don't set up the canary; let's disable stack protector on boot.c so
we can get into lguest_init, then set it up.  As a side effect,
switch_to_new_gdt() sets up %fs for us properly too.

Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
Acked-by: default avatarTejun Heo <tj@kernel.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 9fa7eb28

arch/x86/lguest/Makefile

+1 −0
Original line number Diff line number Diff line 
obj-y		:= i386_head.o boot.o

CFLAGS_boot.o	:= $(call cc-option, -fno-stack-protector)

arch/x86/lguest/boot.c

+13 −4
Original line number Diff line number Diff line
@@ -67,6 +67,7 @@ 
#include <asm/mce.h>

#include <asm/io.h>

#include <asm/i387.h>

#include <asm/stackprotector.h>

#include <asm/reboot.h>		/* for struct machine_ops */



/*G:010 Welcome to the Guest!
@@ -1088,13 +1089,21 @@ __init void lguest_init(void) 
	 * lguest_init() where the rest of the fairly chaotic boot setup

	 * occurs. */



	/* The stack protector is a weird thing where gcc places a canary

	 * value on the stack and then checks it on return.  This file is

	 * compiled with -fno-stack-protector it, so we got this far without

	 * problems.  The value of the canary is kept at offset 20 from the

	 * %gs register, so we need to set that up before calling C functions

	 * in other files. */

	setup_stack_canary_segment(0);

	/* We could just call load_stack_canary_segment(), but we might as

	 * call switch_to_new_gdt() which loads the whole table and sets up

	 * the per-cpu segment descriptor register %fs as well. */

	switch_to_new_gdt(0);



	/* As described in head_32.S, we map the first 128M of memory. */

	max_pfn_mapped = (128*1024*1024) >> PAGE_SHIFT;



	/* Load the %fs segment register (the per-cpu segment register) with

	 * the normal data segment to get through booting. */

	asm volatile ("mov %0, %%fs" : : "r" (__KERNEL_DS) : "memory");



	/* The Host<->Guest Switcher lives at the top of our address space, and

	 * the Host told us how big it is when we made LGUEST_INIT hypercall:

	 * it put the answer in lguest_data.reserve_mem  */