From 2cb7878a3a4341d1faa208de962d66f0817d3e7a Mon Sep 17 00:00:00 2001 From: Rusty Russell Date: Wed, 3 Jun 2009 14:52:24 +0930 Subject: [PATCH] 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: Rusty Russell Acked-by: Tejun Heo Signed-off-by: Linus Torvalds --- arch/x86/lguest/Makefile | 1 + arch/x86/lguest/boot.c | 17 +++++++++++++---- 2 files changed, 14 insertions(+), 4 deletions(-) diff --git a/arch/x86/lguest/Makefile b/arch/x86/lguest/Makefile index 27f0c9e..94e0e54 100644 --- a/arch/x86/lguest/Makefile +++ b/arch/x86/lguest/Makefile @@ -1 +1,2 @@ obj-y := i386_head.o boot.o +CFLAGS_boot.o := $(call cc-option, -fno-stack-protector) diff --git a/arch/x86/lguest/boot.c b/arch/x86/lguest/boot.c index ca7ec44..33a93b4 100644 --- a/arch/x86/lguest/boot.c +++ b/arch/x86/lguest/boot.c @@ -67,6 +67,7 @@ #include #include #include +#include #include /* 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 */ -- 1.8.2.3