2024-03-04 08:34:43

by Xin Li (Intel)

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

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 <[email protected]>
Closes: https://lore.kernel.org/oe-lkp/[email protected]
Signed-off-by: Xin Li (Intel) <[email protected]>
---

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

2024-03-06 18:38:26

by Xin Li (Intel)

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

On 3/4/2024 12:33 AM, Xin Li (Intel) wrote:
> 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 <[email protected]>
> Closes: https://lore.kernel.org/oe-lkp/[email protected]
> Signed-off-by: Xin Li (Intel) <[email protected]>
> ---

Should this fix, if it looks good, be included for the coming merge
window?

Thanks!
Xin

>
> 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

2024-03-06 20:40:40

by H. Peter Anvin

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

On March 6, 2024 10:28:25 AM PST, Xin Li <[email protected]> wrote:
>On 3/4/2024 12:33 AM, Xin Li (Intel) wrote:
>> 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 <[email protected]>
>> Closes: https://lore.kernel.org/oe-lkp/[email protected]
>> Signed-off-by: Xin Li (Intel) <[email protected]>
>> ---
>
>Should this fix, if it looks good, be included for the coming merge
>window?
>
>Thanks!
> Xin
>
>>
>> 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
>

Absolutely.

2024-03-07 11:05:13

by tip-bot2 for Jacob Pan

Subject: [tip: x86/fred] x86/fred: Fix init_task thread stack pointer initialization

The following commit has been merged into the x86/fred branch of tip:

Commit-ID: c416b5bac6ad6ffe21e36225553b82ff2ec1558c
Gitweb: https://git.kernel.org/tip/c416b5bac6ad6ffe21e36225553b82ff2ec1558c
Author: Xin Li (Intel) <[email protected]>
AuthorDate: Mon, 04 Mar 2024 00:33:33 -08:00
Committer: Thomas Gleixner <[email protected]>
CommitterDate: Thu, 07 Mar 2024 11:55:36 +01:00

x86/fred: Fix init_task thread stack pointer initialization

As TOP_OF_KERNEL_STACK_PADDING was defined as 0 on x86_64, it went
unnoticed that the initialization of the .sp field in INIT_THREAD and some
calculations in the low level startup code do not take the padding into
account.

FRED enabled kernels require a 16 byte padding, which means that the init
task initialization and the low level startup code use the wrong stack
offset.

Subtract TOP_OF_KERNEL_STACK_PADDING in all affected places to adjust for
this.

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 <[email protected]>
Signed-off-by: Xin Li (Intel) <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Closes: https://lore.kernel.org/oe-lkp/[email protected]
Link: https://lore.kernel.org/r/[email protected]
---
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 26620d7..17fe819 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 d4918d0..c38e435 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 a0ea285..04101b9 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.
*