Commit cc456c4e authored by Konrad Rzeszutek Wilk's avatar Konrad Rzeszutek Wilk Committed by H. Peter Anvin
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x86, gdt, hibernate: Store/load GDT for hibernate path.

The git commite7a5cd06

("x86-64, gdt: Store/load GDT for ACPI S3 or hibernate/resume path
is not needed.") assumes that for the hibernate path the booting
kernel and the resuming kernel MUST be the same. That is certainly
the case for a 32-bit kernel (see check_image_kernel and

However for 64-bit kernels it is OK to have a different kernel
version (and size of the image) of the booting and resuming kernels.
Hence the above mentioned git commit introduces an regression.

This patch fixes it by introducing a 'struct desc_ptr gdt_desc'
back in the 'struct saved_context'. However instead of having in the
'save_processor_state' and 'restore_processor_state' the
store/load_gdt calls, we are only saving the GDT in the

For the restore path the lgdt operation is done in
hibernate_asm_[32|64].S in the 'restore_registers' path.

The apt reader of this description will recognize that only 64-bit
kernels need this treatment, not 32-bit. This patch adds the logic
in the 32-bit path to be more similar to 64-bit so that in the future
the unification process can take advantage of this.

[ hpa: this also reverts an inadvertent on-disk format change ]
Suggested-by: default avatar"H. Peter Anvin" <>
Acked-by: default avatar"Rafael J. Wysocki" <>
Signed-off-by: default avatarKonrad Rzeszutek Wilk <>

Signed-off-by: default avatarH. Peter Anvin <>
parent 5a148af6
......@@ -15,6 +15,7 @@ struct saved_context {
unsigned long cr0, cr2, cr3, cr4;
u64 misc_enable;
bool misc_enable_saved;
struct desc_ptr gdt_desc;
struct desc_ptr idt;
u16 ldt;
u16 tss;
......@@ -25,6 +25,8 @@ struct saved_context {
u64 misc_enable;
bool misc_enable_saved;
unsigned long efer;
u16 gdt_pad; /* Unused */
struct desc_ptr gdt_desc;
u16 idt_pad;
u16 idt_limit;
unsigned long idt_base;
......@@ -60,6 +60,9 @@ void foo(void)
OFFSET(IA32_RT_SIGFRAME_sigcontext, rt_sigframe, uc.uc_mcontext);
OFFSET(saved_context_gdt_desc, saved_context, gdt_desc);
/* Offset from the sysenter stack to tss.sp0 */
DEFINE(TSS_sysenter_sp0, offsetof(struct tss_struct, x86_tss.sp0) -
sizeof(struct tss_struct));
......@@ -73,6 +73,7 @@ int main(void)
#undef ENTRY
......@@ -25,16 +25,12 @@
#include <asm/cpu.h>
#ifdef CONFIG_X86_32
static struct saved_context saved_context;
unsigned long saved_context_ebx;
unsigned long saved_context_esp, saved_context_ebp;
unsigned long saved_context_esi, saved_context_edi;
unsigned long saved_context_eflags;
/* CONFIG_X86_64 */
struct saved_context saved_context;
struct saved_context saved_context;
* __save_processor_state - save CPU registers before creating a
......@@ -67,6 +63,15 @@ static void __save_processor_state(struct saved_context *ctxt)
/* CONFIG_X86_64 */
store_idt((struct desc_ptr *)&ctxt->idt_limit);
* We save it here, but restore it only in the hibernate case.
* For ACPI S3 resume, this is loaded via 'early_gdt_desc' in 64-bit
* mode in "secondary_startup_64". In 32-bit mode it is done via
* 'pmode_gdt' in wakeup_start.
ctxt->gdt_desc.size = GDT_SIZE - 1;
ctxt->gdt_desc.address = (unsigned long)get_cpu_gdt_table(smp_processor_id());
/* XMM0..XMM15 should be handled by kernel_fpu_begin(). */
......@@ -75,6 +75,10 @@ done:
pushl saved_context_eflags
/* Saved in save_processor_state. */
movl $saved_context, %eax
lgdt saved_context_gdt_desc(%eax)
xorl %eax, %eax
......@@ -139,6 +139,9 @@ ENTRY(restore_registers)
pushq pt_regs_flags(%rax)
/* Saved in save_processor_state. */
lgdt saved_context_gdt_desc(%rax)
xorq %rax, %rax
/* tell the hibernation core that we've just restored the memory */
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