On 7/9/2026 3:17 PM, Thomas Weißschuh wrote:
> On Thu, Jul 09, 2026 at 02:37:05PM +0800, Jinjie Ruan wrote:
>> On 6/30/2026 11:32 PM, Thomas Weißschuh wrote:
>>> On Mon, Jun 29, 2026 at 09:06:16PM +0800, Jinjie Ruan wrote:
> (..)
>
>>>> diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c
>>>> index 592dd8668de4..5a0314a3c26e 100644
>>>> --- a/arch/arm64/kernel/vdso.c
>>>> +++ b/arch/arm64/kernel/vdso.c
>>>> @@ -343,3 +343,19 @@ int arch_setup_additional_pages(struct linux_binprm
>>>> *bprm, int uses_interp)
>>>>
>>>> return ret;
>>>> }
>>>> +
>>>> +bool arch_syscall_is_vdso_sigreturn(struct pt_regs *regs)
>>>> +{
>>>> + unsigned long sigtramp;
>>>> +
>>>> +#ifdef CONFIG_COMPAT
>>>> + if (is_compat_task()) {
>>>> + unsigned long sigpage = (unsigned
>>>> long)current->mm->context.sigpage;
>>>> +
>>>> + return regs->pc >= sigpage && regs->pc < (sigpage + PAGE_SIZE);
>>>> + }
>>>> +#endif
>>>> + sigtramp = (unsigned long)VDSO_SYMBOL(current->mm->context.vdso,
>>>> sigtramp);
>>>> +
>>>> + return regs->pc == (sigtramp + 8);
>>>
>>> Instead of hardcoding 'sigtramp + 8' you could add a new label to the 'svc
>>> #0'
>>> instruction and use that with VDSO_SYMBOL().
>>
>> It seems that the modification of __kernel_rt_sigreturn() is not recommended
>
> For the changes to the object code of the function this is obvious and
> well explained in the comments.
>
> Such a label however would not change the object code of the function.
> In fact it would not change any bit whatsoever in the final vDSO,
> save for a new build ID.
Yes, and using labels is easier to maintain than hardcoding offsets
directly.
Similar to the code below?
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -86,6 +86,7 @@ config ARM64
select ARCH_SUPPORTS_SCHED_SMT
select ARCH_SUPPORTS_SCHED_CLUSTER
select ARCH_SUPPORTS_SCHED_MC
+ select ARCH_SUPPORTS_SYSCALL_USER_DISPATCH
select ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH
select ARCH_WANT_COMPAT_IPC_PARSE_VERSION if COMPAT
select ARCH_WANT_DEFAULT_BPF_JIT
diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h
index d2779d604c7b..a8b232c5c6d9 100644
--- a/arch/arm64/include/asm/elf.h
+++ b/arch/arm64/include/asm/elf.h
@@ -293,6 +293,7 @@ static inline int arch_check_elf(void *ehdr, bool
has_interp,
return 0;
}
+extern bool arch_syscall_is_vdso_sigreturn(struct pt_regs *regs);
#endif /* !__ASSEMBLER__ */
#endif
diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c
index 592dd8668de4..609d7bcd8308 100644
--- a/arch/arm64/kernel/vdso.c
+++ b/arch/arm64/kernel/vdso.c
@@ -343,3 +343,19 @@ int arch_setup_additional_pages(struct linux_binprm
*bprm, int uses_interp)
return ret;
}
+
+bool arch_syscall_is_vdso_sigreturn(struct pt_regs *regs)
+{
+ unsigned long sigtramp;
+
+#ifdef CONFIG_COMPAT
+ if (is_compat_task()) {
+ unsigned long sigpage = (unsigned
long)current->mm->context.sigpage;
+
+ return regs->pc >= sigpage && regs->pc < (sigpage +
PAGE_SIZE);
+ }
+#endif
+ sigtramp = (unsigned long)VDSO_SYMBOL(current->mm->context.vdso,
sigreturn_landing_pad);
+
+ return regs->pc == sigtramp;
+}
diff --git a/arch/arm64/kernel/vdso/sigreturn.S
b/arch/arm64/kernel/vdso/sigreturn.S
index 0e18729abc3b..8d2d413ff45e 100644
--- a/arch/arm64/kernel/vdso/sigreturn.S
+++ b/arch/arm64/kernel/vdso/sigreturn.S
@@ -73,6 +73,7 @@ SYM_CODE_START(__kernel_rt_sigreturn)
mov x8, #__NR_rt_sigreturn
// PLEASE DO NOT MODIFY
svc #0
+ SYM_INNER_LABEL(__sigreturn_landing_pad, SYM_L_GLOBAL)
// PLEASE DO NOT MODIFY
// .cfi_endproc
SYM_CODE_END(__kernel_rt_sigreturn)
diff --git a/arch/arm64/kernel/vdso/vdso.lds.S
b/arch/arm64/kernel/vdso/vdso.lds.S
index 52314be29191..5fee2927e4c5 100644
--- a/arch/arm64/kernel/vdso/vdso.lds.S
+++ b/arch/arm64/kernel/vdso/vdso.lds.S
@@ -104,6 +104,7 @@ VERSION
__kernel_clock_gettime;
__kernel_clock_getres;
__kernel_getrandom;
+ __sigreturn_landing_pad;
local: *;
};
}
@@ -112,3 +113,4 @@ VERSION
* Make the sigreturn code visible to the kernel.
*/
VDSO_sigtramp = __kernel_rt_sigreturn;
+VDSO_sigreturn_landing_pad = __sigreturn_landing_pad;
>
>
> Thomas
>
