Add rethook arm implementation. Most of the code has been copied from
kretprobes on arm.
Since the arm's ftrace implementation is a bit special, this needs a
special care using from fprobe.
Signed-off-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
---
Changes in v10:
- Fix for the mcount entry.
Changes in v5:
- Fix build error when !CONFIG_KRETPROBES
---
arch/arm/Kconfig | 1
arch/arm/include/asm/stacktrace.h | 4 +
arch/arm/kernel/stacktrace.c | 6 ++
arch/arm/probes/Makefile | 1
arch/arm/probes/rethook.c | 101 +++++++++++++++++++++++++++++++++++++
5 files changed, 111 insertions(+), 2 deletions(-)
create mode 100644 arch/arm/probes/rethook.c
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 4c97cb40eebb..440f69ee8af5 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -107,6 +107,7 @@ config ARM
select HAVE_MOD_ARCH_SPECIFIC
select HAVE_NMI
select HAVE_OPTPROBES if !THUMB2_KERNEL
+ select HAVE_RETHOOK
select HAVE_PERF_EVENTS
select HAVE_PERF_REGS
select HAVE_PERF_USER_STACK_DUMP
diff --git a/arch/arm/include/asm/stacktrace.h b/arch/arm/include/asm/stacktrace.h
index 8f54f9ad8a9b..babed1707ca8 100644
--- a/arch/arm/include/asm/stacktrace.h
+++ b/arch/arm/include/asm/stacktrace.h
@@ -14,7 +14,7 @@ struct stackframe {
unsigned long sp;
unsigned long lr;
unsigned long pc;
-#ifdef CONFIG_KRETPROBES
+#if defined(CONFIG_KRETPROBES) || defined(CONFIG_RETHOOK)
struct llist_node *kr_cur;
struct task_struct *tsk;
#endif
@@ -27,7 +27,7 @@ void arm_get_current_stackframe(struct pt_regs *regs, struct stackframe *frame)
frame->sp = regs->ARM_sp;
frame->lr = regs->ARM_lr;
frame->pc = regs->ARM_pc;
-#ifdef CONFIG_KRETPROBES
+#if defined(CONFIG_KRETPROBES) || defined(CONFIG_RETHOOK)
frame->kr_cur = NULL;
frame->tsk = current;
#endif
diff --git a/arch/arm/kernel/stacktrace.c b/arch/arm/kernel/stacktrace.c
index 75e905508f27..f509c6be4f57 100644
--- a/arch/arm/kernel/stacktrace.c
+++ b/arch/arm/kernel/stacktrace.c
@@ -1,6 +1,7 @@
// SPDX-License-Identifier: GPL-2.0-only
#include <linux/export.h>
#include <linux/kprobes.h>
+#include <linux/rethook.h>
#include <linux/sched.h>
#include <linux/sched/debug.h>
#include <linux/stacktrace.h>
@@ -66,6 +67,11 @@ int notrace unwind_frame(struct stackframe *frame)
frame->sp = *(unsigned long *)(fp - 8);
frame->pc = *(unsigned long *)(fp - 4);
#endif
+#ifdef CONFIG_RETHOOK
+ if (is_rethook_trampoline(frame->pc))
+ frame->pc = rethook_find_ret_addr(frame->tsk, frame->fp,
+ &frame->kr_cur);
+#endif
#ifdef CONFIG_KRETPROBES
if (is_kretprobe_trampoline(frame->pc))
frame->pc = kretprobe_find_ret_addr(frame->tsk,
diff --git a/arch/arm/probes/Makefile b/arch/arm/probes/Makefile
index 8b0ea5ace100..10c083a22223 100644
--- a/arch/arm/probes/Makefile
+++ b/arch/arm/probes/Makefile
@@ -6,3 +6,4 @@ obj-$(CONFIG_KPROBES) += decode-thumb.o
else
obj-$(CONFIG_KPROBES) += decode-arm.o
endif
+obj-$(CONFIG_RETHOOK) += rethook.o
diff --git a/arch/arm/probes/rethook.c b/arch/arm/probes/rethook.c
new file mode 100644
index 000000000000..338ebe964eb1
--- /dev/null
+++ b/arch/arm/probes/rethook.c
@@ -0,0 +1,101 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * arm implementation of rethook. Mostly copied from arch/arm/probes/kprobes/core.c
+ */
+
+#include <linux/kprobes.h>
+#include <linux/rethook.h>
+
+/* Called from arch_rethook_trampoline */
+static __used unsigned long arch_rethook_trampoline_callback(struct pt_regs *regs)
+{
+ return rethook_trampoline_handler(regs, regs->ARM_fp);
+}
+NOKPROBE_SYMBOL(arch_rethook_trampoline_callback);
+
+/*
+ * When a rethook'ed function returns, it returns to arch_rethook_trampoline
+ * which calls rethook callback. We construct a struct pt_regs to
+ * give a view of registers r0-r11, sp, lr, and pc to the user
+ * return-handler. This is not a complete pt_regs structure, but that
+ * should be enough for stacktrace from the return handler with or
+ * without pt_regs.
+ */
+void __naked arch_rethook_trampoline(void)
+{
+ __asm__ __volatile__ (
+#ifdef CONFIG_FRAME_POINTER
+ "ldr lr, =arch_rethook_trampoline \n\t"
+ /* this makes a framepointer on pt_regs. */
+#ifdef CONFIG_CC_IS_CLANG
+ "stmdb sp, {sp, lr, pc} \n\t"
+ "sub sp, sp, #12 \n\t"
+ /* In clang case, pt_regs->ip = lr. */
+ "stmdb sp!, {r0 - r11, lr} \n\t"
+ /* fp points regs->r11 (fp) */
+ "add fp, sp, #44 \n\t"
+#else /* !CONFIG_CC_IS_CLANG */
+ /* In gcc case, pt_regs->ip = fp. */
+ "stmdb sp, {fp, sp, lr, pc} \n\t"
+ "sub sp, sp, #16 \n\t"
+ "stmdb sp!, {r0 - r11} \n\t"
+ /* fp points regs->r15 (pc) */
+ "add fp, sp, #60 \n\t"
+#endif /* CONFIG_CC_IS_CLANG */
+#else /* !CONFIG_FRAME_POINTER */
+ "sub sp, sp, #16 \n\t"
+ "stmdb sp!, {r0 - r11} \n\t"
+#endif /* CONFIG_FRAME_POINTER */
+ "mov r0, sp \n\t"
+ "bl arch_rethook_trampoline_callback \n\t"
+ "mov lr, r0 \n\t"
+ "ldmia sp!, {r0 - r11} \n\t"
+ "add sp, sp, #16 \n\t"
+#ifdef CONFIG_THUMB2_KERNEL
+ "bx lr \n\t"
+#else
+ "mov pc, lr \n\t"
+#endif
+ : : : "memory");
+}
+NOKPROBE_SYMBOL(arch_rethook_trampoline);
+
+/*
+ * At the entry of function with mcount. The stack and registers are prepared
+ * for the mcount function as below.
+ *
+ * mov ip, sp
+ * push {fp, ip, lr, pc}
+ * sub fp, ip, #4 ; FP[0] = PC, FP[-4] = LR, and FP[-12] = call-site FP.
+ * push {lr}
+ * bl <__gnu_mcount_nc> ; call ftrace
+ *
+ * And when returning from the function, call-site FP, SP and PC are restored
+ * from stack as below;
+ *
+ * ldm sp, {fp, sp, pc}
+ *
+ * Thus, if the arch_rethook_prepare() is called from real function entry,
+ * it must change the LR and save FP in pt_regs. But if it is called via
+ * mcount context (ftrace), it must change the LR on stack, which is next
+ * to the PC (= FP[-4]), and save the FP value at FP[-12].
+ */
+void arch_rethook_prepare(struct rethook_node *rh, struct pt_regs *regs, bool mcount)
+{
+ unsigned long *ret_addr, *frame;
+
+ if (mcount) {
+ ret_addr = (unsigned long *)(regs->ARM_fp - 4);
+ frame = (unsigned long *)(regs->ARM_fp - 12);
+ } else {
+ ret_addr = ®s->ARM_lr;
+ frame = ®s->ARM_fp;
+ }
+
+ rh->ret_addr = *ret_addr;
+ rh->frame = *frame;
+
+ /* Replace the return addr with trampoline addr. */
+ *ret_addr = (unsigned long)arch_rethook_trampoline;
+}
+NOKPROBE_SYMBOL(arch_rethook_prepare);
