Re: [PATCH] x86: General protection fault after STR (32 bit systems only)

Ingo Molnar
2015-06-12T08:36:35Z

* H. Peter Anvin <hpa@zytor.com> wrote:

> %es is used implicitly by string instructions.

Ok, so we are probably better off reloading ES as well early, right
when we return from the firmware, just in case something does
a copy before we hit the ES restore in restore_processor_state(),
which is a generic C function?

Something like the patch below?

I also added FS/GS/SS reloading to make it complete. If this (or a variant
thereof, it's still totally untested) works then we can remove the segment
save/restore layer in __save/restore_processor_state().

Thanks,

Ingo

===========>
arch/x86/kernel/acpi/wakeup_32.S | 13 +++++++++++++
1 file changed, 13 insertions(+)

diff --git a/arch/x86/kernel/acpi/wakeup_32.S b/arch/x86/kernel/acpi/wakeup_32.S
index 665c6b7d2ea9..1376a7fc21b7 100644
--- a/arch/x86/kernel/acpi/wakeup_32.S
+++ b/arch/x86/kernel/acpi/wakeup_32.S
@@ -61,6 +61,19 @@ ENTRY(wakeup_pmode_return)

restore_registers:
+ /*
+ * In case the BIOS corrupted our segment descriptors,
+ * reload them to clear out any shadow descriptor
+ * state:
+ */
+ movl $__USER_DS, %eax
+ movl %eax, %ds
+ movl %eax, %es
+ movl %eax, %fs
+ movl %eax, %gs
+ movl $__KERNEL_DS, %eax
+ movl %eax, %ss
+
movl saved_context_ebp, %ebp
movl saved_context_ebx, %ebx
movl saved_context_esi, %esi