It's my understanding that the two pieces of work required to enable live patching on arm are in flight upstream; - Reliable stack traces as implemented by Madhavan T. Venkataraman [1] - Objtool as implemented by Julien Thierry [2] This is the remaining part required to enable live patching on arm. Based on work by Torsten Duwe [3] Allocate a task flag used to represent the patch pending state for the task. Also implement generic functions klp_arch_set_pc() & klp_get_ftrace_location(). In klp_arch_set_pc() it is sufficient to set regs->pc as in ftrace_common_return() the return address is loaded from the stack. ldr x9, [sp, #S_PC] <snip> ret x9 In klp_get_ftrace_location() it is necessary to advance the address by AARCH64_INSN_SIZE (4) to point to the BL in the callsite as 2 nops were placed at the start of the function, one to be patched to save the LR and another to be patched to branch to the ftrace call, and klp_get_ftrace_location() is expected to return the address of the BL. It may also be necessary to advance the address by another AARCH64_INSN_SIZE if CONFIG_ARM64_BTI_KERNEL is enabled due to the instruction placed at the branch target to satisfy BTI, Signed-off-by: Suraj Jitindar Singh <surajjs@xxxxxxxxxx> [1] https://lkml.org/lkml/2021/5/26/1212 [2] https://lkml.org/lkml/2021/3/3/1135 [3] https://lkml.org/lkml/2018/10/26/536 --- arch/arm64/Kconfig | 3 ++ arch/arm64/include/asm/livepatch.h | 42 ++++++++++++++++++++++++++++ arch/arm64/include/asm/thread_info.h | 4 ++- arch/arm64/kernel/signal.c | 4 +++ 4 files changed, 52 insertions(+), 1 deletion(-) create mode 100644 arch/arm64/include/asm/livepatch.h diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index b098dabed8c2..c4636990c01d 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -187,6 +187,7 @@ config ARM64 select HAVE_GCC_PLUGINS select HAVE_HW_BREAKPOINT if PERF_EVENTS select HAVE_IRQ_TIME_ACCOUNTING + select HAVE_LIVEPATCH select HAVE_NMI select HAVE_PATA_PLATFORM select HAVE_PERF_EVENTS @@ -1946,3 +1947,5 @@ source "arch/arm64/kvm/Kconfig" if CRYPTO source "arch/arm64/crypto/Kconfig" endif + +source "kernel/livepatch/Kconfig" diff --git a/arch/arm64/include/asm/livepatch.h b/arch/arm64/include/asm/livepatch.h new file mode 100644 index 000000000000..72d7cd86f158 --- /dev/null +++ b/arch/arm64/include/asm/livepatch.h @@ -0,0 +1,42 @@ +/* SPDX-License-Identifier: GPL-2.0 + * + * livepatch.h - arm64-specific Kernel Live Patching Core + */ +#ifndef _ASM_ARM64_LIVEPATCH_H +#define _ASM_ARM64_LIVEPATCH_H + +#include <linux/ftrace.h> + +static inline void klp_arch_set_pc(struct ftrace_regs *fregs, unsigned long ip) +{ + struct pt_regs *regs = ftrace_get_regs(fregs); + + regs->pc = ip; +} + +/* + * klp_get_ftrace_location is expected to return the address of the BL to the + * relevant ftrace handler in the callsite. The location of this can vary based + * on several compilation options. + * CONFIG_DYNAMIC_FTRACE_WITH_REGS + * - Inserts 2 nops on function entry the second of which is the BL + * referenced above. (See ftrace_init_nop() for the callsite sequence) + * (this is required by livepatch and must be selected) + * CONFIG_ARM64_BTI_KERNEL: + * - Inserts a hint #0x22 on function entry if the function is called + * indirectly (to satisfy BTI requirements), which is inserted before + * the two nops from above. + */ +#define klp_get_ftrace_location klp_get_ftrace_location +static inline unsigned long klp_get_ftrace_location(unsigned long faddr) +{ + unsigned long addr = faddr + AARCH64_INSN_SIZE; + +#if IS_ENABLED(CONFIG_ARM64_BTI_KERNEL) + addr = ftrace_location_range(addr, addr + AARCH64_INSN_SIZE); +#endif + + return addr; +} + +#endif /* _ASM_ARM64_LIVEPATCH_H */ diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h index 6623c99f0984..cca936d53a40 100644 --- a/arch/arm64/include/asm/thread_info.h +++ b/arch/arm64/include/asm/thread_info.h @@ -67,6 +67,7 @@ int arch_dup_task_struct(struct task_struct *dst, #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 */ @@ -97,11 +98,12 @@ int arch_dup_task_struct(struct task_struct *dst, #define _TIF_SVE (1 << TIF_SVE) #define _TIF_MTE_ASYNC_FAULT (1 << TIF_MTE_ASYNC_FAULT) #define _TIF_NOTIFY_SIGNAL (1 << TIF_NOTIFY_SIGNAL) +#define _TIF_PATCH_PENDING (1 << TIF_PATCH_PENDING) #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/signal.c b/arch/arm64/kernel/signal.c index 6237486ff6bb..d1eedb0589a7 100644 --- a/arch/arm64/kernel/signal.c +++ b/arch/arm64/kernel/signal.c @@ -18,6 +18,7 @@ #include <linux/sizes.h> #include <linux/string.h> #include <linux/tracehook.h> +#include <linux/livepatch.h> #include <linux/ratelimit.h> #include <linux/syscalls.h> @@ -932,6 +933,9 @@ asmlinkage void do_notify_resume(struct pt_regs *regs, (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); -- 2.17.1
