Re: [PATCH v16 18/18] arm64: vdso: Expose sigreturn address on vdso to the kernel

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

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

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.


Thomas