[PATCH v3 2/2] arm64: Implement HAVE_LIVEPATCH

Song Liu
2025-03-20T17:16:23Z

This is largely based on [1] by Suraj Jitindar Singh.

Test coverage:

- Passed manual tests with samples/livepatch.
- Passed all but test-kprobe.sh in selftests/livepatch.
test-kprobe.sh is expected to fail, because arm64 doesn't have
KPROBES_ON_FTRACE.
- Passed tests with kpatch-build [2]. (This version includes commits that
are not merged to upstream kpatch yet).

[1] https://lore.kernel.org/all/20210604235930.603-1-surajjs@amazon.com/
[2] https://github.com/liu-song-6/kpatch/tree/fb-6.13
Cc: Suraj Jitindar Singh <surajjs@amazon.com>
Cc: Torsten Duwe <duwe@suse.de>
Signed-off-by: Song Liu <song@kernel.org>
Acked-by: Miroslav Benes <mbenes@suse.cz>
Tested-by: Breno Leitao <leitao@debian.org>
---
arch/arm64/Kconfig | 3 +++
arch/arm64/include/asm/thread_info.h | 4 +++-
arch/arm64/kernel/entry-common.c | 4 ++++
3 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 31d5e1ee6089..dbd237b13b21 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -277,6 +277,7 @@ config ARM64
select USER_STACKTRACE_SUPPORT
select VDSO_GETRANDOM
select HAVE_RELIABLE_STACKTRACE
+ select HAVE_LIVEPATCH
help
ARM 64-bit (AArch64) Linux support.

@@ -2501,3 +2502,5 @@ endmenu # "CPU Power Management"
source "drivers/acpi/Kconfig"

source "arch/arm64/kvm/Kconfig"
+
+source "kernel/livepatch/Kconfig"
diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h
index 1114c1c3300a..4ac42e13032b 100644
--- a/arch/arm64/include/asm/thread_info.h
+++ b/arch/arm64/include/asm/thread_info.h
@@ -64,6 +64,7 @@ void arch_setup_new_exec(void);
#define TIF_UPROBE 4 /* uprobe breakpoint or singlestep */
#define TIF_MTE_ASYNC_FAULT 5 /* MTE Asynchronous Tag Check Fault */
#define TIF_NOTIFY_SIGNAL 6 /* signal notifications exist */
+#define TIF_PATCH_PENDING 7 /* pending live patching update */
#define TIF_SYSCALL_TRACE 8 /* syscall trace active */
#define TIF_SYSCALL_AUDIT 9 /* syscall auditing */
#define TIF_SYSCALL_TRACEPOINT 10 /* syscall tracepoint for ftrace */
@@ -92,6 +93,7 @@ void arch_setup_new_exec(void);
#define _TIF_SYSCALL_TRACEPOINT (1 << TIF_SYSCALL_TRACEPOINT)
#define _TIF_SECCOMP (1 << TIF_SECCOMP)
#define _TIF_SYSCALL_EMU (1 << TIF_SYSCALL_EMU)
+#define _TIF_PATCH_PENDING (1 << TIF_PATCH_PENDING)
#define _TIF_UPROBE (1 << TIF_UPROBE)
#define _TIF_SINGLESTEP (1 << TIF_SINGLESTEP)
#define _TIF_32BIT (1 << TIF_32BIT)
@@ -103,7 +105,7 @@ void arch_setup_new_exec(void);
#define _TIF_WORK_MASK (_TIF_NEED_RESCHED | _TIF_SIGPENDING | \
_TIF_NOTIFY_RESUME | _TIF_FOREIGN_FPSTATE | \
_TIF_UPROBE | _TIF_MTE_ASYNC_FAULT | \
- _TIF_NOTIFY_SIGNAL)
+ _TIF_NOTIFY_SIGNAL | _TIF_PATCH_PENDING)

#define _TIF_SYSCALL_WORK (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | \
_TIF_SYSCALL_TRACEPOINT | _TIF_SECCOMP | \
diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c
index b260ddc4d3e9..b537af333b42 100644
--- a/arch/arm64/kernel/entry-common.c
+++ b/arch/arm64/kernel/entry-common.c
@@ -8,6 +8,7 @@
#include <linux/context_tracking.h>
#include <linux/kasan.h>
#include <linux/linkage.h>
+#include <linux/livepatch.h>
#include <linux/lockdep.h>
#include <linux/ptrace.h>
#include <linux/resume_user_mode.h>
@@ -144,6 +145,9 @@ static void do_notify_resume(struct pt_regs *regs, unsigned long thread_flags)
(void __user *)NULL, current);
}

+ if (thread_flags & _TIF_PATCH_PENDING)
+ klp_update_patch_state(current);
+
if (thread_flags & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL))
do_signal(regs);

--
2.47.1