aboutsummaryrefslogtreecommitdiff
path: root/arch/x86/kernel/cpu/common.c
diff options
context:
space:
mode:
authorTejun Heo <tj@kernel.org>2009-02-09 22:17:40 +0900
committerIngo Molnar <mingo@elte.hu>2009-02-10 00:42:01 +0100
commit60a5317ff0f42dd313094b88f809f63041568b08 (patch)
tree307dfd9715fbc9ff83c3c3ae3b0e8f03888083f2 /arch/x86/kernel/cpu/common.c
parentccbeed3a05908d201b47b6c3dd1a373138bba566 (diff)
x86: implement x86_32 stack protector
Impact: stack protector for x86_32 Implement stack protector for x86_32. GDT entry 28 is used for it. It's set to point to stack_canary-20 and have the length of 24 bytes. CONFIG_CC_STACKPROTECTOR turns off CONFIG_X86_32_LAZY_GS and sets %gs to the stack canary segment on entry. As %gs is otherwise unused by the kernel, the canary can be anywhere. It's defined as a percpu variable. x86_32 exception handlers take register frame on stack directly as struct pt_regs. With -fstack-protector turned on, gcc copies the whole structure after the stack canary and (of course) doesn't copy back on return thus losing all changed. For now, -fno-stack-protector is added to all files which contain those functions. We definitely need something better. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'arch/x86/kernel/cpu/common.c')
-rw-r--r--arch/x86/kernel/cpu/common.c17
1 files changed, 11 insertions, 6 deletions
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 41b0de6df87..260fe4cb2c8 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -39,6 +39,7 @@
#include <asm/sections.h>
#include <asm/setup.h>
#include <asm/hypervisor.h>
+#include <asm/stackprotector.h>
#include "cpu.h"
@@ -122,6 +123,7 @@ DEFINE_PER_CPU_PAGE_ALIGNED(struct gdt_page, gdt_page) = { .gdt = {
[GDT_ENTRY_ESPFIX_SS] = { { { 0x00000000, 0x00c09200 } } },
[GDT_ENTRY_PERCPU] = { { { 0x0000ffff, 0x00cf9200 } } },
+ GDT_STACK_CANARY_INIT
#endif
} };
EXPORT_PER_CPU_SYMBOL_GPL(gdt_page);
@@ -261,6 +263,7 @@ void load_percpu_segment(int cpu)
loadsegment(gs, 0);
wrmsrl(MSR_GS_BASE, (unsigned long)per_cpu(irq_stack_union.gs_base, cpu));
#endif
+ load_stack_canary_segment();
}
/* Current gdt points %fs at the "master" per-cpu area: after this,
@@ -946,16 +949,21 @@ unsigned long kernel_eflags;
*/
DEFINE_PER_CPU(struct orig_ist, orig_ist);
-#else
+#else /* x86_64 */
+
+#ifdef CONFIG_CC_STACKPROTECTOR
+DEFINE_PER_CPU(unsigned long, stack_canary);
+#endif
-/* Make sure %fs is initialized properly in idle threads */
+/* Make sure %fs and %gs are initialized properly in idle threads */
struct pt_regs * __cpuinit idle_regs(struct pt_regs *regs)
{
memset(regs, 0, sizeof(struct pt_regs));
regs->fs = __KERNEL_PERCPU;
+ regs->gs = __KERNEL_STACK_CANARY;
return regs;
}
-#endif
+#endif /* x86_64 */
/*
* cpu_init() initializes state that is per-CPU. Some data is already
@@ -1120,9 +1128,6 @@ void __cpuinit cpu_init(void)
__set_tss_desc(cpu, GDT_ENTRY_DOUBLEFAULT_TSS, &doublefault_tss);
#endif
- /* Clear %gs. */
- asm volatile ("mov %0, %%gs" : : "r" (0));
-
/* Clear all 6 debug registers: */
set_debugreg(0, 0);
set_debugreg(0, 1);