[PATCH v2 06/11] x86/percpu/64: Remove fixed_percpu_data

Brian Gerst
2023-10-26T16:01:54Z

Now that the stack protector canary value is a normal percpu variable,
fixed_percpu_data is unused and can be removed.

Signed-off-by: Brian Gerst <brgerst@gmail.com>
---
arch/x86/include/asm/processor.h | 13 +++++--------
arch/x86/kernel/cpu/common.c | 4 ----
arch/x86/kernel/head_64.S | 11 ++++++-----
arch/x86/kernel/vmlinux.lds.S | 6 ------
arch/x86/platform/pvh/head.S | 7 ++++++-
arch/x86/tools/relocs.c | 1 -
arch/x86/xen/xen-head.S | 11 ++++++++---
7 files changed, 25 insertions(+), 28 deletions(-)

diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 2b6531d90273..d5a4044dba8f 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -393,16 +393,13 @@ struct irq_stack {
} __aligned(IRQ_STACK_SIZE);

#ifdef CONFIG_X86_64
-struct fixed_percpu_data {
- char gs_base[40];
-};
-
-DECLARE_PER_CPU_FIRST(struct fixed_percpu_data, fixed_percpu_data) __visible;
-DECLARE_INIT_PER_CPU(fixed_percpu_data);
-
static inline unsigned long cpu_kernelmode_gs_base(int cpu)
{
- return (unsigned long)per_cpu(fixed_percpu_data.gs_base, cpu);
+#ifdef CONFIG_SMP
+ return per_cpu_offset(cpu);
+#else
+ return 0;
+#endif
}

extern asmlinkage void entry_SYSCALL32_ignore(void);
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index fb8f0371ffc3..32ae76cf4508 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -2052,10 +2052,6 @@ EXPORT_PER_CPU_SYMBOL(pcpu_hot);
EXPORT_PER_CPU_SYMBOL(const_pcpu_hot);

#ifdef CONFIG_X86_64
-DEFINE_PER_CPU_FIRST(struct fixed_percpu_data,
- fixed_percpu_data) __aligned(PAGE_SIZE) __visible;
-EXPORT_PER_CPU_SYMBOL_GPL(fixed_percpu_data);
-
static void wrmsrl_cstar(unsigned long val)
{
/*
diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index 0d94d2a091fe..f2453eb38417 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -72,9 +72,14 @@ SYM_CODE_START_NOALIGN(startup_64)

/* Setup GSBASE to allow stack canary access for C code */
movl $MSR_GS_BASE, %ecx
- leaq INIT_PER_CPU_VAR(fixed_percpu_data)(%rip), %rdx
+#ifdef CONFIG_SMP
+ leaq __per_cpu_load(%rip), %rdx
movl %edx, %eax
shrq $32, %rdx
+#else
+ xorl %eax, %eax
+ xorl %edx, %edx
+#endif
wrmsr

call startup_64_setup_env
@@ -345,14 +350,10 @@ SYM_INNER_LABEL(secondary_startup_64_no_verify, SYM_L_GLOBAL)

/* Set up %gs.
*
- * The base of %gs always points to fixed_percpu_data.
* Note that, on SMP, the boot cpu uses init data section until
* the per cpu areas are set up.
*/
movl $MSR_GS_BASE,%ecx
-#ifndef CONFIG_SMP
- leaq INIT_PER_CPU_VAR(fixed_percpu_data)(%rip), %rdx
-#endif
movl %edx, %eax
shrq $32, %rdx
wrmsr
diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index 1239be7cc8d8..e6126cd21615 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -510,14 +510,8 @@ SECTIONS
*/
#define INIT_PER_CPU(x) init_per_cpu__##x = ABSOLUTE(x) + __per_cpu_load
INIT_PER_CPU(gdt_page);
-INIT_PER_CPU(fixed_percpu_data);
INIT_PER_CPU(irq_stack_backing_store);

-#ifdef CONFIG_SMP
-. = ASSERT((fixed_percpu_data == 0),
- "fixed_percpu_data is not at start of per-cpu area");
-#endif
-
#ifdef CONFIG_CPU_UNRET_ENTRY
. = ASSERT((retbleed_return_thunk & 0x3f) == 0, "retbleed_return_thunk not cacheline-aligned");
#endif
diff --git a/arch/x86/platform/pvh/head.S b/arch/x86/platform/pvh/head.S
index be8d973c0528..d215b16bf89f 100644
--- a/arch/x86/platform/pvh/head.S
+++ b/arch/x86/platform/pvh/head.S
@@ -96,9 +96,14 @@ SYM_CODE_START_LOCAL(pvh_start_xen)
1:
/* Set base address in stack canary descriptor. */
mov $MSR_GS_BASE,%ecx
- lea INIT_PER_CPU_VAR(fixed_percpu_data)(%rip), %rdx
+#ifdef CONFIG_SMP
+ lea __per_cpu_load(%rip), %rdx
mov %edx, %eax
shr $32, %rdx
+#else
+ xor %eax, %eax
+ xor %edx, %edx
+#endif
wrmsr

call xen_prepare_pvh
diff --git a/arch/x86/tools/relocs.c b/arch/x86/tools/relocs.c
index d30949e25ebd..3ccd9d4fcf9c 100644
--- a/arch/x86/tools/relocs.c
+++ b/arch/x86/tools/relocs.c
@@ -811,7 +811,6 @@ static void percpu_init(void)
* __per_cpu_load
*
* The "gold" linker incorrectly associates:
- * init_per_cpu__fixed_percpu_data
* init_per_cpu__gdt_page
*/
static int is_percpu_sym(ElfW(Sym) *sym, const char *symname)
diff --git a/arch/x86/xen/xen-head.S b/arch/x86/xen/xen-head.S
index 30f27e757354..9ce0d9d268bb 100644
--- a/arch/x86/xen/xen-head.S
+++ b/arch/x86/xen/xen-head.S
@@ -53,13 +53,18 @@ SYM_CODE_START(startup_xen)

/* Set up %gs.
*
- * The base of %gs always points to fixed_percpu_data.
* Note that, on SMP, the boot cpu uses init data section until
* the per cpu areas are set up.
*/
movl $MSR_GS_BASE,%ecx
- movq $INIT_PER_CPU_VAR(fixed_percpu_data),%rax
- cdq
+#ifdef CONFIG_SMP
+ leaq __per_cpu_load(%rip), %rdx
+ movl %edx, %eax
+ shrq $32, %rdx
+#else
+ xorl %eax, %eax
+ xorl %edx, %edx
+#endif
wrmsr

mov %rsi, %rdi
--
2.41.0