Syscall User Dispatch (SUD) requires the signal trampoline code to not be
intercepted. This is necessary to support returning with a locked selector
while avoiding infinite recursion back into the signal handler.
Implement arch_syscall_is_vdso_sigreturn() for arm64 to support this
exclusion mechanism. For native 64-bit tasks, it checks whether the current
PC matches the 'svc #0' instruction inside the vDSO sigreturn trampoline.
SYM_CODE_START(__kernel_rt_sigreturn)
mov x8, #__NR_rt_sigreturn
svc #0
SYM_CODE_END(__kernel_rt_sigreturn)
For COMPAT tasks, it verifies if the instruction falls within
the architecture's 'sigpage' range, allowing the kernel to safely bypass
dispatching syscalls originating from these areas back to userspace.
Suggested-by: Kevin Brodsky <[email protected]>
Suggested-by: kemal <[email protected]>
Signed-off-by: Jinjie Ruan <[email protected]>
---
arch/arm64/include/asm/elf.h | 1 +
arch/arm64/kernel/vdso.c | 16 ++++++++++++++++
2 files changed, 17 insertions(+)
diff --git a/arch/arm64/include/asm/elf.h b/arch/arm64/include/asm/elf.h
index d2779d604c7b..f43d4dea916a 100644
--- a/arch/arm64/include/asm/elf.h
+++ b/arch/arm64/include/asm/elf.h
@@ -185,6 +185,7 @@ do {
\
struct linux_binprm;
extern int arch_setup_additional_pages(struct linux_binprm *bprm,
int uses_interp);
+extern bool arch_syscall_is_vdso_sigreturn(struct pt_regs *regs);
/* 1GB of VA */
#ifdef CONFIG_COMPAT
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);
+}
--
2.34.1
