[PATCH v2] ARM: stacktrace: Add USER_STACKTRACE support
From: Jinjie Ruan
Date: Mon Jul 29 2024 - 22:10:05 EST
Currently, userstacktrace is unsupported for ARM. So use the
perf_callchain_user() code as blueprint to implement the
arch_stack_walk_user() which add userstacktrace support on ARM.
Meanwhile, we can use arch_stack_walk_user() to simplify the implementation
of perf_callchain_user().
A ftrace test case is shown as below:
# cd /sys/kernel/debug/tracing
# echo 1 > options/userstacktrace
# echo 1 > options/sym-userobj
# echo 1 > events/sched/sched_process_fork/enable
# cat trace
......
sh-100 [000] ..... 51.779261: sched_process_fork: comm=sh pid=100 child_comm=sh child_pid=108
sh-100 [000] ..... 51.779285: <user stack trace>
=> /lib/libc.so.6[+0xb3c8c]
=> /bin/busybox[+0xffb901f1]
Also a simple perf test is ok as below:
# perf record -e cpu-clock --call-graph fp top
# perf report --call-graph
.....
[[31m 65.00%[[m 0.00% top [kernel.kallsyms] [k] __ret_fast_syscall
|
---__ret_fast_syscall
|
|--[[31m30.00%[[m--__se_sys_getdents64
| iterate_dir
| |
| |--[[31m25.00%[[m--proc_pid_readdir
Signed-off-by: Jinjie Ruan <ruanjinjie@xxxxxxxxxx>
---
v2:
- Update the wrong patch title.
- Take off the merged bugfix patch.
- Remove the Tested-by.
---
arch/arm/Kconfig | 1 +
arch/arm/kernel/perf_callchain.c | 70 +++-----------------------------
arch/arm/kernel/stacktrace.c | 65 +++++++++++++++++++++++++++++
3 files changed, 72 insertions(+), 64 deletions(-)
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 54b2bb817a7f..eb9a587935ef 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -152,6 +152,7 @@ config ARM
select HAVE_ARCH_VMAP_STACK if MMU && ARM_HAS_GROUP_RELOCS
select TRACE_IRQFLAGS_SUPPORT if !CPU_V7M
select USE_OF if !(ARCH_FOOTBRIDGE || ARCH_RPC || ARCH_SA1100)
+ select USER_STACKTRACE_SUPPORT
# Above selects are sorted alphabetically; please add new ones
# according to that. Thanks.
help
diff --git a/arch/arm/kernel/perf_callchain.c b/arch/arm/kernel/perf_callchain.c
index 1d230ac9d0eb..cdb7aa31c6ec 100644
--- a/arch/arm/kernel/perf_callchain.c
+++ b/arch/arm/kernel/perf_callchain.c
@@ -12,70 +12,6 @@
#include <asm/stacktrace.h>
-/*
- * The registers we're interested in are at the end of the variable
- * length saved register structure. The fp points at the end of this
- * structure so the address of this struct is:
- * (struct frame_tail *)(xxx->fp)-1
- *
- * This code has been adapted from the ARM OProfile support.
- */
-struct frame_tail {
- struct frame_tail __user *fp;
- unsigned long sp;
- unsigned long lr;
-} __attribute__((packed));
-
-/*
- * Get the return address for a single stackframe and return a pointer to the
- * next frame tail.
- */
-static struct frame_tail __user *
-user_backtrace(struct frame_tail __user *tail,
- struct perf_callchain_entry_ctx *entry)
-{
- struct frame_tail buftail;
- unsigned long err;
-
- if (!access_ok(tail, sizeof(buftail)))
- return NULL;
-
- pagefault_disable();
- err = __copy_from_user_inatomic(&buftail, tail, sizeof(buftail));
- pagefault_enable();
-
- if (err)
- return NULL;
-
- perf_callchain_store(entry, buftail.lr);
-
- /*
- * Frame pointers should strictly progress back up the stack
- * (towards higher addresses).
- */
- if (tail + 1 >= buftail.fp)
- return NULL;
-
- return buftail.fp - 1;
-}
-
-void
-perf_callchain_user(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs)
-{
- struct frame_tail __user *tail;
-
- perf_callchain_store(entry, regs->ARM_pc);
-
- if (!current->mm)
- return;
-
- tail = (struct frame_tail __user *)regs->ARM_fp - 1;
-
- while ((entry->nr < entry->max_stack) &&
- tail && !((unsigned long)tail & 0x3))
- tail = user_backtrace(tail, entry);
-}
-
/*
* Gets called by walk_stackframe() for every stackframe. This will be called
* whist unwinding the stackframe and is like a subroutine return so we use
@@ -88,6 +24,12 @@ callchain_trace(void *data, unsigned long pc)
return perf_callchain_store(entry, pc) == 0;
}
+void
+perf_callchain_user(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs)
+{
+ arch_stack_walk_user(callchain_trace, entry, regs);
+}
+
void
perf_callchain_kernel(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs)
{
diff --git a/arch/arm/kernel/stacktrace.c b/arch/arm/kernel/stacktrace.c
index 620aa82e3bdd..b744792755b5 100644
--- a/arch/arm/kernel/stacktrace.c
+++ b/arch/arm/kernel/stacktrace.c
@@ -194,4 +194,69 @@ void arch_stack_walk(stack_trace_consume_fn consume_entry, void *cookie,
walk_stackframe(&frame, consume_entry, cookie);
}
+
+/*
+ * The registers we're interested in are at the end of the variable
+ * length saved register structure. The fp points at the end of this
+ * structure so the address of this struct is:
+ * (struct frame_tail *)(xxx->fp)-1
+ *
+ * This code has been adapted from the ARM OProfile support.
+ */
+struct frame_tail {
+ struct frame_tail __user *fp;
+ unsigned long sp;
+ unsigned long lr;
+} __packed;
+
+/*
+ * Get the return address for a single stackframe and return a pointer to the
+ * next frame tail.
+ */
+static struct frame_tail __user *
+unwind_user_frame(struct frame_tail __user *tail, void *cookie,
+ stack_trace_consume_fn consume_entry)
+{
+ struct frame_tail buftail;
+ unsigned long err;
+
+ if (!access_ok(tail, sizeof(buftail)))
+ return NULL;
+
+ pagefault_disable();
+ err = __copy_from_user_inatomic(&buftail, tail, sizeof(buftail));
+ pagefault_enable();
+
+ if (err)
+ return NULL;
+
+ if (!consume_entry(cookie, buftail.lr))
+ return NULL;
+
+ /*
+ * Frame pointers should strictly progress back up the stack
+ * (towards higher addresses).
+ */
+ if (tail + 1 >= buftail.fp)
+ return NULL;
+
+ return buftail.fp - 1;
+}
+
+void arch_stack_walk_user(stack_trace_consume_fn consume_entry, void *cookie,
+ const struct pt_regs *regs)
+{
+ struct frame_tail __user *tail;
+
+ if (!consume_entry(cookie, regs->ARM_pc))
+ return;
+
+ if (!current->mm)
+ return;
+
+ tail = (struct frame_tail __user *)regs->ARM_fp - 1;
+
+ while (tail && !((unsigned long)tail & 0x3))
+ tail = unwind_user_frame(tail, cookie, consume_entry);
+}
#endif
--
2.34.1