[tip: x86/boot] x86/boot: Simplify boot stack setup
From: tip-bot2 for Brian Gerst
Date: Thu Mar 21 2024 - 15:29:01 EST
The following commit has been merged into the x86/boot branch of tip:
Commit-ID: 2cb16181a1d1f93a88f2b4640e7638fc0549da93
Gitweb: https://git.kernel.org/tip/2cb16181a1d1f93a88f2b4640e7638fc0549da93
Author: Brian Gerst <brgerst@xxxxxxxxx>
AuthorDate: Thu, 21 Mar 2024 14:05:06 -04:00
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitterDate: Thu, 21 Mar 2024 20:17:54 +01:00
x86/boot: Simplify boot stack setup
Define the symbol __top_init_kernel_stack instead of duplicating
the offset from __end_init_task in multiple places.
Signed-off-by: Brian Gerst <brgerst@xxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Uros Bizjak <ubizjak@xxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20240321180506.89030-1-brgerst@xxxxxxxxx
---
arch/x86/include/asm/processor.h | 6 ++----
arch/x86/kernel/head_32.S | 11 +----------
arch/x86/kernel/head_64.S | 2 +-
arch/x86/kernel/vmlinux.lds.S | 3 +++
arch/x86/xen/xen-head.S | 2 +-
5 files changed, 8 insertions(+), 16 deletions(-)
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 811548f..7fa01d9 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -636,12 +636,10 @@ static __always_inline void prefetchw(const void *x)
#define KSTK_ESP(task) (task_pt_regs(task)->sp)
#else
-extern unsigned long __end_init_task[];
+extern unsigned long __top_init_kernel_stack[];
#define INIT_THREAD { \
- .sp = (unsigned long)&__end_init_task - \
- TOP_OF_KERNEL_STACK_PADDING - \
- sizeof(struct pt_regs), \
+ .sp = (unsigned long)&__top_init_kernel_stack, \
}
extern unsigned long KSTK_ESP(struct task_struct *task);
diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S
index b50f364..a9de527 100644
--- a/arch/x86/kernel/head_32.S
+++ b/arch/x86/kernel/head_32.S
@@ -44,9 +44,6 @@
#define X86_CAPABILITY new_cpu_data+CPUINFO_x86_capability
#define X86_VENDOR_ID new_cpu_data+CPUINFO_x86_vendor_id
-
-#define SIZEOF_PTREGS 17*4
-
/*
* Worst-case size of the kernel mapping we need to make:
* a relocatable kernel can live anywhere in lowmem, so we need to be able
@@ -488,13 +485,7 @@ SYM_DATA_END(initial_page_table)
.data
.balign 4
-/*
- * The SIZEOF_PTREGS gap is a convention which helps the in-kernel unwinder
- * reliably detect the end of the stack.
- */
-SYM_DATA(initial_stack,
- .long init_thread_union + THREAD_SIZE -
- SIZEOF_PTREGS - TOP_OF_KERNEL_STACK_PADDING)
+SYM_DATA(initial_stack, .long __top_init_kernel_stack)
__INITRODATA
int_msg:
diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index d8198fb..b115268 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -66,7 +66,7 @@ SYM_CODE_START_NOALIGN(startup_64)
mov %rsi, %r15
/* Set up the stack for verify_cpu() */
- leaq (__end_init_task - TOP_OF_KERNEL_STACK_PADDING - PTREGS_SIZE)(%rip), %rsp
+ leaq __top_init_kernel_stack(%rip), %rsp
/* Setup GSBASE to allow stack canary access for C code */
movl $MSR_GS_BASE, %ecx
diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S
index 56451fd..91085c3 100644
--- a/arch/x86/kernel/vmlinux.lds.S
+++ b/arch/x86/kernel/vmlinux.lds.S
@@ -172,6 +172,9 @@ SECTIONS
/* init_task */
INIT_TASK_DATA(THREAD_SIZE)
+ /* equivalent to task_pt_regs(&init_task) */
+ __top_init_kernel_stack = __end_init_task - TOP_OF_KERNEL_STACK_PADDING - PTREGS_SIZE;
+
#ifdef CONFIG_X86_32
/* 32 bit has nosave before _edata */
NOSAVE_DATA
diff --git a/arch/x86/xen/xen-head.S b/arch/x86/xen/xen-head.S
index 04101b9..758bcd4 100644
--- a/arch/x86/xen/xen-head.S
+++ b/arch/x86/xen/xen-head.S
@@ -49,7 +49,7 @@ SYM_CODE_START(startup_xen)
ANNOTATE_NOENDBR
cld
- leaq (__end_init_task - TOP_OF_KERNEL_STACK_PADDING - PTREGS_SIZE)(%rip), %rsp
+ leaq __top_init_kernel_stack(%rip), %rsp
/* Set up %gs.
*