alinux: arm64: add livepatch support

Now we support FTRACE_WITH_REGS with -fpatchable-function-entry, here
enable the livepatch support depend on FTRACE_WITH_REGS.

Use task flag bit 6 to track patch transisiton state for the consistency
model. Add it to the work mask so it gets cleared on all kernel exits to
userland.

Tell livepatch regs->pc + 2*AARCH64_INSN_SIZE is the place to change the
return address.

these codes have a big change against reference link, beacause we use new
gcc featrue.

References:
https://patchwork.kernel.org/patch/10657431/

Based-on-code-from: Torsten Duwe <duwe@suse.de>
Signed-off-by: NZou Cao <zoucao@linux.alibaba.com>
Acked-by: NCaspar Zhang <caspar@linux.alibaba.com>

arch/arm64/Kconfig

@@ -170,6 +170,7 @@ config ARM64
 	select SWIOTLB
 	select SYSCTL_EXCEPTION_TRACE
 	select THREAD_INFO_IN_TASK
+	select HAVE_LIVEPATCH
 	help
 	  ARM 64-bit (AArch64) Linux support.
 
@@ -1359,6 +1360,8 @@ source "drivers/acpi/Kconfig"
 
 source "arch/arm64/kvm/Kconfig"
 
+source "kernel/livepatch/Kconfig"
+
 if CRYPTO
 source "arch/arm64/crypto/Kconfig"
 endif

arch/arm64/include/asm/livepatch.h

+#ifndef _ASM_ARM64_LIVEPATCH_H
+#define _ASM_ARM64_LIVEPATCH_H
+
+#include <linux/module.h>
+#include <linux/ftrace.h>
+
+#ifdef CONFIG_LIVEPATCH
+
+#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
+static inline int klp_check_compiler_support(void)
+{
+	return 0;
+}
+
+static inline void klp_arch_set_pc(struct pt_regs *regs, unsigned long pc)
+{
+	regs->pc = pc + 2*AARCH64_INSN_SIZE;
+}
+
+#define klp_get_ftrace_location klp_get_ftrace_location
+static inline unsigned long klp_get_ftrace_location(unsigned long faddr)
+{
+	return faddr + AARCH64_INSN_SIZE;
+}
+
+#else
+static inline int  klp_check_compiler_support(void)
+{
+	return 1;
+}
+
+static inline void klp_arch_set_pc(struct pt_regs *regs, unsigned long pc)
+{
+}
+
+#define klp_get_ftrace_location klp_get_ftrace_location
+static inline unsigned long klp_get_ftrace_location(unsigned long faddr)
+{
+	return faddr + AARCH64_INSN_SIZE;
+}
+#endif
+
+#else
+#error Live patching support is disabled; check CONFIG_LIVEPATCH
+#endif
+
+#endif /* _ASM_ARM64_LIVEPATCH_H */

arch/arm64/include/asm/thread_info.h

@@ -76,6 +76,7 @@ void arch_release_task_struct(struct task_struct *tsk);
 #define TIF_FOREIGN_FPSTATE	3	/* CPU's FP state is not current's */
 #define TIF_UPROBE		4	/* uprobe breakpoint or singlestep */
 #define TIF_FSCHECK		5	/* Check FS is USER_DS on return */
+#define TIF_PATCH_PENDING	6
 #define TIF_NOHZ		7
 #define TIF_SYSCALL_TRACE	8
 #define TIF_SYSCALL_AUDIT	9
@@ -94,6 +95,7 @@ void arch_release_task_struct(struct task_struct *tsk);
 #define _TIF_NEED_RESCHED	(1 << TIF_NEED_RESCHED)
 #define _TIF_NOTIFY_RESUME	(1 << TIF_NOTIFY_RESUME)
 #define _TIF_FOREIGN_FPSTATE	(1 << TIF_FOREIGN_FPSTATE)
+#define _TIF_PATCH_PENDING	(1 << TIF_PATCH_PENDING)
 #define _TIF_NOHZ		(1 << TIF_NOHZ)
 #define _TIF_SYSCALL_TRACE	(1 << TIF_SYSCALL_TRACE)
 #define _TIF_SYSCALL_AUDIT	(1 << TIF_SYSCALL_AUDIT)
@@ -106,7 +108,9 @@ void arch_release_task_struct(struct task_struct *tsk);
 
 #define _TIF_WORK_MASK		(_TIF_NEED_RESCHED | _TIF_SIGPENDING | \
 				 _TIF_NOTIFY_RESUME | _TIF_FOREIGN_FPSTATE | \
-				 _TIF_UPROBE | _TIF_FSCHECK)
+				 _TIF_UPROBE | _TIF_FSCHECK | \
+				 _TIF_PATCH_PENDING)
+
 
 #define _TIF_SYSCALL_WORK	(_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | \
 				 _TIF_SYSCALL_TRACEPOINT | _TIF_SECCOMP | \

arch/arm64/kernel/signal.c

@@ -29,6 +29,7 @@
 #include <linux/sizes.h>
 #include <linux/string.h>
 #include <linux/tracehook.h>
+#include <linux/livepatch.h>
 #include <linux/ratelimit.h>
 #include <linux/syscalls.h>
 
@@ -937,6 +938,9 @@ asmlinkage void do_notify_resume(struct pt_regs *regs,
 			if (thread_flags & _TIF_UPROBE)
 				uprobe_notify_resume(regs);
 
+			if (thread_flags & _TIF_PATCH_PENDING)
+				klp_update_patch_state(current);
+
 			if (thread_flags & _TIF_SIGPENDING)
 				do_signal(regs);