[PATCH v2 1/1] x86/fred: Fix init_task thread stack pointer initialization

From: Xin Li (Intel)
Date: Mon Mar 04 2024 - 03:34:42 EST


As TOP_OF_KERNEL_STACK_PADDING is defined as 0 on x86_64, no one noticed
it's missing in the calculation of the .sp field in INIT_THREAD until it
is defined to 16 with CONFIG_X86_FRED=y.

Subtract TOP_OF_KERNEL_STACK_PADDING from the .sp field of INIT_THREAD.

Fixes: 65c9cc9e2c14 ("x86/fred: Reserve space for the FRED stack frame")
Fixes: 3adee777ad0d ("x86/smpboot: Remove initial_stack on 64-bit")
Reported-by: kernel test robot <oliver.sang@xxxxxxxxx>
Closes: https://lore.kernel.org/oe-lkp/202402262159.183c2a37-lkp@xxxxxxxxx
Signed-off-by: Xin Li (Intel) <xin@xxxxxxxxx>
---

Change Since v1:
* Apply offset TOP_OF_KERNEL_STACK_PADDING to all uses of __end_init_task
(Brian Gerst).
---
arch/x86/include/asm/processor.h | 6 ++++--
arch/x86/kernel/head_64.S | 3 ++-
arch/x86/xen/xen-head.S | 2 +-
3 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 26620d7642a9..17fe81998ce4 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -664,8 +664,10 @@ static __always_inline void prefetchw(const void *x)
#else
extern unsigned long __end_init_task[];

-#define INIT_THREAD { \
- .sp = (unsigned long)&__end_init_task - sizeof(struct pt_regs), \
+#define INIT_THREAD { \
+ .sp = (unsigned long)&__end_init_task - \
+ TOP_OF_KERNEL_STACK_PADDING - \
+ sizeof(struct pt_regs), \
}

extern unsigned long KSTK_ESP(struct task_struct *task);
diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index d4918d03efb4..c38e43589046 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -26,6 +26,7 @@
#include <asm/apicdef.h>
#include <asm/fixmap.h>
#include <asm/smp.h>
+#include <asm/thread_info.h>

/*
* We are not able to switch in one step to the final KERNEL ADDRESS SPACE
@@ -66,7 +67,7 @@ SYM_CODE_START_NOALIGN(startup_64)
mov %rsi, %r15

/* Set up the stack for verify_cpu() */
- leaq (__end_init_task - PTREGS_SIZE)(%rip), %rsp
+ leaq (__end_init_task - TOP_OF_KERNEL_STACK_PADDING - PTREGS_SIZE)(%rip), %rsp

leaq _text(%rip), %rdi

diff --git a/arch/x86/xen/xen-head.S b/arch/x86/xen/xen-head.S
index a0ea285878db..04101b984f24 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 - PTREGS_SIZE)(%rip), %rsp
+ leaq (__end_init_task - TOP_OF_KERNEL_STACK_PADDING - PTREGS_SIZE)(%rip), %rsp

/* Set up %gs.
*

base-commit: e13841907b8fda0ae0ce1ec03684665f578416a8
--
2.44.0