[PATCH RFC 2/8] arm64: stacktrace: Add arch_within_stack_frames

[He Zhe]

This function checks if the given address range crosses frame boundary.
It is based on the existing x86 algorithm, but implemented via stacktrace.
This can be tested by USERCOPY_STACK_FRAME_FROM and
USERCOPY_STACK_FRAME_TO in lkdtm.

Signed-off-by: He Zhe <zhe...@windriver.com>
---
 arch/arm64/Kconfig                   |  1 +
 arch/arm64/include/asm/thread_info.h | 12 +++++
 arch/arm64/kernel/stacktrace.c       | 76 ++++++++++++++++++++++++++--
 3 files changed, 85 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 57c4c995965f..0f52a83d7771 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -165,6 +165,7 @@ config ARM64
        select HAVE_ARCH_TRACEHOOK
        select HAVE_ARCH_TRANSPARENT_HUGEPAGE
        select HAVE_ARCH_VMAP_STACK
+       select HAVE_ARCH_WITHIN_STACK_FRAMES
        select HAVE_ARM_SMCCC
        select HAVE_ASM_MODVERSIONS
        select HAVE_EBPF_JIT
diff --git a/arch/arm64/include/asm/thread_info.h 
b/arch/arm64/include/asm/thread_info.h
index e1317b7c4525..b839ad9f2248 100644
--- a/arch/arm64/include/asm/thread_info.h
+++ b/arch/arm64/include/asm/thread_info.h
@@ -58,6 +58,18 @@ void arch_setup_new_exec(void);
 void arch_release_task_struct(struct task_struct *tsk);
 int arch_dup_task_struct(struct task_struct *dst,
                                struct task_struct *src);
+/*
+ * Walks up the stack frames to make sure that the specified object is
+ * entirely contained by a single stack frame.
+ *
+ * Returns:
+ *     GOOD_FRAME      if within a frame
+ *     BAD_STACK       if placed across a frame boundary (or outside stack)
+ *     NOT_STACK       unable to determine (no frame pointers, etc)
+ */
+int arch_within_stack_frames(const void * const stack,
+               const void * const stackend,
+               const void *obj, unsigned long len);
 
 #endif
 
diff --git a/arch/arm64/kernel/stacktrace.c b/arch/arm64/kernel/stacktrace.c
index e4103e085681..219b90c1de12 100644
--- a/arch/arm64/kernel/stacktrace.c
+++ b/arch/arm64/kernel/stacktrace.c
@@ -145,12 +145,17 @@ NOKPROBE_SYMBOL(unwind_frame);
 
 static void notrace walk_stackframe(struct task_struct *tsk,
                                    struct stackframe *frame,
-                                   bool (*fn)(void *, unsigned long), void 
*data)
+                                   stack_trace_consume_fn fn, void *data)
 {
+       struct frame_info fi;
+
        while (1) {
                int ret;
 
-               if (!fn(data, frame->pc))
+               fi.pc = frame->pc;
+               fi.fp = frame->fp;
+               fi.prev_fp = frame->prev_fp;
+               if (!fn(data, &fi))
                        break;
                ret = unwind_frame(tsk, frame);
                if (ret < 0)
@@ -159,10 +164,10 @@ static void notrace walk_stackframe(struct task_struct 
*tsk,
 }
 NOKPROBE_SYMBOL(walk_stackframe);
 
-static bool dump_backtrace_entry(void *arg, unsigned long where)
+static bool dump_backtrace_entry(void *arg, struct frame_info *fi)
 {
        char *loglvl = arg;
-       printk("%s %pSb\n", loglvl, (void *)where);
+       printk("%s %pSb\n", loglvl, (void *)fi->pc);
        return true;
 }
 
@@ -210,3 +215,66 @@ noinline notrace void 
arch_stack_walk(stack_trace_consume_fn consume_entry,
 
        walk_stackframe(task, &frame, consume_entry, cookie);
 }
+
+struct arch_stack_object {
+       unsigned long start;
+       unsigned long len;
+       int flag;
+};
+
+static bool arch_stack_object_check(void *data, struct frame_info *fi)
+{
+       struct arch_stack_object *obj = (struct arch_stack_object *)data;
+
+       /* Skip the frame of arch_within_stack_frames itself */
+       if (fi->prev_fp == 0)
+               return true;
+
+       /*
+        * low ----------------------------------------------> high
+        * [saved bp][saved ip][args][local vars][saved bp][saved ip]
+        *                     ^----------------^
+        *               allow copies only within here
+        */
+       if (obj->start + obj->len <= fi->fp) {
+               obj->flag = obj->start >=
+                       fi->prev_fp + 2 * sizeof(void *) ?
+                       GOOD_FRAME : BAD_STACK;
+               return false;
+       } else
+               return true;
+}
+
+/*
+ * Walks up the stack frames to make sure that the specified object is
+ * entirely contained by a single stack frame.
+ *
+ * Returns:
+ *     GOOD_FRAME      if within a frame
+ *     BAD_STACK       if placed across a frame boundary (or outside stack)
+ *     NOT_STACK       unable to determine (no frame pointers, etc)
+ */
+int arch_within_stack_frames(const void * const stack,
+               const void * const stackend,
+               const void *obj, unsigned long len)
+{
+#if defined(CONFIG_FRAME_POINTER)
+       struct arch_stack_object object;
+       struct pt_regs regs;
+
+       if (__builtin_frame_address(1) == 0)
+               return NOT_STACK;
+
+       object.start = (unsigned long)obj;
+       object.len = len;
+       object.flag = NOT_STACK;
+
+       regs.regs[29] = (u64)__builtin_frame_address(1);
+
+       arch_stack_walk(arch_stack_object_check, (void *)&object, NULL, &regs);
+
+       return object.flag;
+#else
+       return NOT_STACK;
+#endif
+}
-- 
2.25.1