ARM: rethook: Add rethook arm implementation

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@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Tested-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/164735289643.1084943.15184590256680485720.stgit@devnote2

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 4c97cb4..440f69e 100644 (file)
--- 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 8f54f9a..babed17 100644 (file)
--- 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 75e9055..f509c6b 100644 (file)
--- 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 8b0ea5a..10c083a 100644 (file)
--- 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 (file)
index 0000000..1c1357a
--- /dev/null
+++ b/arch/arm/probes/rethook.c
@@ -0,0 +1,103 @@
+// 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.
+ */
+asm(
+       ".text\n"
+       ".global arch_rethook_trampoline\n"
+       ".type arch_rethook_trampoline, %function\n"
+       "arch_rethook_trampoline:\n"
+#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
+       ".size arch_rethook_trampoline, .-arch_rethook_trampoline\n"
+);
+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 = &regs->ARM_lr;
+               frame = &regs->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);