[PATCH v12 08/11] x86/smpboot: Remove initial_gs

Usama Arif
2023-02-26T11:08:45Z

From: Brian Gerst <brgerst@gmail.com>

Use the percpu offset directly to set GSBASE.

Signed-off-by: Brian Gerst <brgerst@gmail.com>
Reviewed-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Tested-by: Usama Arif <usama.arif@bytedance.com>
Signed-off-by: Usama Arif <usama.arif@bytedance.com>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
---
arch/x86/include/asm/realmode.h | 1 -
arch/x86/kernel/acpi/sleep.c | 1 -
arch/x86/kernel/head_64.S | 22 ++++++++--------------
arch/x86/kernel/smpboot.c | 2 --
4 files changed, 8 insertions(+), 18 deletions(-)

diff --git a/arch/x86/include/asm/realmode.h b/arch/x86/include/asm/realmode.h
index a336feef0af1..f6a1737c77be 100644
--- a/arch/x86/include/asm/realmode.h
+++ b/arch/x86/include/asm/realmode.h
@@ -59,7 +59,6 @@ extern struct real_mode_header *real_mode_header;
extern unsigned char real_mode_blob_end[];

extern unsigned long initial_code;
-extern unsigned long initial_gs;
extern unsigned long initial_stack;
#ifdef CONFIG_AMD_MEM_ENCRYPT
extern unsigned long initial_vc_handler;
diff --git a/arch/x86/kernel/acpi/sleep.c b/arch/x86/kernel/acpi/sleep.c
index 236f2423454d..9d2d88424c77 100644
--- a/arch/x86/kernel/acpi/sleep.c
+++ b/arch/x86/kernel/acpi/sleep.c
@@ -112,7 +112,6 @@ int x86_acpi_suspend_lowlevel(void)
#else /* CONFIG_64BIT */
#ifdef CONFIG_SMP
current->thread.sp = (unsigned long)temp_stack + sizeof(temp_stack);
- initial_gs = per_cpu_offset(smp_processor_id());
smpboot_control = smp_processor_id();
#endif
initial_code = (unsigned long)wakeup_long64;
diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index 0ccca297e90e..069191e33490 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -66,18 +66,10 @@ SYM_CODE_START_NOALIGN(startup_64)

leaq _text(%rip), %rdi

- /*
- * initial_gs points to initial fixed_percpu_data struct with storage for
- * the stack protector canary. Global pointer fixups are needed at this
- * stage, so apply them as is done in fixup_pointer(), and initialize %gs
- * such that the canary can be accessed at %gs:40 for subsequent C calls.
- */
+ /* Setup GSBASE to allow stack canary access for C code */
movl $MSR_GS_BASE, %ecx
- movq initial_gs(%rip), %rax
- movq $_text, %rdx
- subq %rdx, %rax
- addq %rdi, %rax
- movq %rax, %rdx
+ leaq INIT_PER_CPU_VAR(fixed_percpu_data)(%rip), %rdx
+ movl %edx, %eax
shrq $32, %rdx
wrmsr

@@ -294,8 +286,11 @@ SYM_INNER_LABEL(secondary_startup_64_no_verify, SYM_L_GLOBAL)
* the per cpu areas are set up.
*/
movl $MSR_GS_BASE,%ecx
- movl initial_gs(%rip),%eax
- movl initial_gs+4(%rip),%edx
+#ifndef CONFIG_SMP
+ leaq INIT_PER_CPU_VAR(fixed_percpu_data)(%rip), %rdx
+#endif
+ movl %edx, %eax
+ shrq $32, %rdx
wrmsr

/* Setup and Load IDT */
@@ -437,7 +432,6 @@ SYM_CODE_END(vc_boot_ghcb)
__REFDATA
.balign 8
SYM_DATA(initial_code, .quad x86_64_start_kernel)
-SYM_DATA(initial_gs, .quad INIT_PER_CPU_VAR(fixed_percpu_data))
#ifdef CONFIG_AMD_MEM_ENCRYPT
SYM_DATA(initial_vc_handler, .quad handle_vc_boot_ghcb)
#endif
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index a22460a07cf8..b04520085582 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -1084,8 +1084,6 @@ int common_cpu_up(unsigned int cpu, struct task_struct *idle)
#ifdef CONFIG_X86_32
/* Stack for startup_32 can be just as for start_secondary onwards */
per_cpu(pcpu_hot.top_of_stack, cpu) = task_top_of_stack(idle);
-#else
- initial_gs = per_cpu_offset(cpu);
#endif
return 0;
}
--
2.25.1