On 7/9/2026 3:17 PM, Thomas Weißschuh wrote:

On Thu, Jul 09, 2026 at 02:37:05PM +0800, Jinjie Ruan wrote:

quoted

On 6/30/2026 11:32 PM, Thomas Weißschuh wrote:

quoted

On Mon, Jun 29, 2026 at 09:06:16PM +0800, Jinjie Ruan wrote:

(..)

quoted

quoted

quoted

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