[PATCH 1/6] arm64: compat: Use vDSO sigreturn trampolines if available

From: Mark Salyzyn
Date: Wed Nov 15 2017 - 17:06:50 EST


From: Kevin Brodsky <kevin.brodsky@xxxxxxx>

If the compat vDSO is enabled, it replaces the sigreturn page.
Therefore, we use the sigreturn trampolines the vDSO provides instead.

Signed-off-by: Kevin Brodsky <kevin.brodsky@xxxxxxx>
Signed-off-by: Mark Salyzyn <salyzyn@xxxxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Will Deacon <will.deacon@xxxxxxx>
Cc: Dave Martin <Dave.Martin@xxxxxxx>
Cc: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
---
arch/arm64/include/asm/vdso.h | 3 +++
arch/arm64/kernel/signal32.c | 15 +++++++++++++++
2 files changed, 18 insertions(+)

diff --git a/arch/arm64/include/asm/vdso.h b/arch/arm64/include/asm/vdso.h
index 839ce0031bd5..f2a952338f1e 100644
--- a/arch/arm64/include/asm/vdso.h
+++ b/arch/arm64/include/asm/vdso.h
@@ -28,6 +28,9 @@
#ifndef __ASSEMBLY__

#include <generated/vdso-offsets.h>
+#ifdef CONFIG_VDSO32
+#include <generated/vdso32-offsets.h>
+#endif

#define VDSO_SYMBOL(base, name) \
({ \
diff --git a/arch/arm64/kernel/signal32.c b/arch/arm64/kernel/signal32.c
index 4f0c0aa14cba..37095782622d 100644
--- a/arch/arm64/kernel/signal32.c
+++ b/arch/arm64/kernel/signal32.c
@@ -28,6 +28,7 @@
#include <asm/signal32.h>
#include <linux/uaccess.h>
#include <asm/unistd.h>
+#include <asm/vdso.h>

struct compat_vfp_sigframe {
compat_ulong_t magic;
@@ -433,6 +434,19 @@ static void compat_setup_return(struct pt_regs *regs, struct k_sigaction *ka,
retcode = ptr_to_compat(ka->sa.sa_restorer);
} else {
/* Set up sigreturn pointer */
+#ifdef CONFIG_VDSO32
+ void *vdso_base = current->mm->context.vdso;
+ void *trampoline =
+ (ka->sa.sa_flags & SA_SIGINFO
+ ? (thumb
+ ? VDSO_SYMBOL(vdso_base, compat_rt_sigreturn_thumb)
+ : VDSO_SYMBOL(vdso_base, compat_rt_sigreturn_arm))
+ : (thumb
+ ? VDSO_SYMBOL(vdso_base, compat_sigreturn_thumb)
+ : VDSO_SYMBOL(vdso_base, compat_sigreturn_arm)));
+
+ retcode = ptr_to_compat(trampoline) + thumb;
+#else
void *sigreturn_base = current->mm->context.vdso;
unsigned int idx = thumb << 1;

@@ -440,6 +454,7 @@ static void compat_setup_return(struct pt_regs *regs, struct k_sigaction *ka,
idx += 3;

retcode = ptr_to_compat(sigreturn_base) + (idx << 2) + thumb;
+#endif
}

regs->regs[0] = usig;
--
2.15.0.448.gf294e3d99a-goog