[PATCH] riscv: stacktrace: Add USER_STACKTRACE support

[PATCH] riscv: stacktrace: Add USER_STACKTRACE support

[Jinjie Ruan]

Currently, userstacktrace is unsupported for riscv. So use the
perf_callchain_user() code as blueprint to implement the
arch_stack_walk_user() which add userstacktrace support on riscv.
Meanwhile, we can use arch_stack_walk_user() to simplify the implementation
of perf_callchain_user().

Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
---
 arch/riscv/Kconfig                 |  1 +
 arch/riscv/kernel/perf_callchain.c | 46 ++----------------------------
 arch/riscv/kernel/stacktrace.c     | 43 ++++++++++++++++++++++++++++
 3 files changed, 47 insertions(+), 43 deletions(-)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index b94176e25be1..4a7ba6a08dee 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -193,6 +193,7 @@ config RISCV
 	select THREAD_INFO_IN_TASK
 	select TRACE_IRQFLAGS_SUPPORT
 	select UACCESS_MEMCPY if !MMU
+	select USER_STACKTRACE_SUPPORT
 	select ZONE_DMA32 if 64BIT
 
 config CLANG_SUPPORTS_DYNAMIC_FTRACE
diff --git a/arch/riscv/kernel/perf_callchain.c b/arch/riscv/kernel/perf_callchain.c
index 3348a61de7d9..c7468af77c66 100644
--- a/arch/riscv/kernel/perf_callchain.c
+++ b/arch/riscv/kernel/perf_callchain.c
@@ -6,37 +6,9 @@
 
 #include <asm/stacktrace.h>
 
-/*
- * Get the return address for a single stackframe and return a pointer to the
- * next frame tail.
- */
-static unsigned long user_backtrace(struct perf_callchain_entry_ctx *entry,
-				    unsigned long fp, unsigned long reg_ra)
+static bool fill_callchain(void *entry, unsigned long pc)
 {
-	struct stackframe buftail;
-	unsigned long ra = 0;
-	unsigned long __user *user_frame_tail =
-		(unsigned long __user *)(fp - sizeof(struct stackframe));
-
-	/* Check accessibility of one struct frame_tail beyond */
-	if (!access_ok(user_frame_tail, sizeof(buftail)))
-		return 0;
-	if (__copy_from_user_inatomic(&buftail, user_frame_tail,
-				      sizeof(buftail)))
-		return 0;
-
-	if (reg_ra != 0)
-		ra = reg_ra;
-	else
-		ra = buftail.ra;
-
-	fp = buftail.fp;
-	if (ra != 0)
-		perf_callchain_store(entry, ra);
-	else
-		return 0;
-
-	return fp;
+	return perf_callchain_store(entry, pc) == 0;
 }
 
 /*
@@ -56,19 +28,7 @@ static unsigned long user_backtrace(struct perf_callchain_entry_ctx *entry,
 void perf_callchain_user(struct perf_callchain_entry_ctx *entry,
 			 struct pt_regs *regs)
 {
-	unsigned long fp = 0;
-
-	fp = regs->s0;
-	perf_callchain_store(entry, regs->epc);
-
-	fp = user_backtrace(entry, fp, regs->ra);
-	while (fp && !(fp & 0x3) && entry->nr < entry->max_stack)
-		fp = user_backtrace(entry, fp, 0);
-}
-
-static bool fill_callchain(void *entry, unsigned long pc)
-{
-	return perf_callchain_store(entry, pc) == 0;
+	arch_stack_walk_user(fill_callchain, entry, regs);
 }
 
 void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry,
diff --git a/arch/riscv/kernel/stacktrace.c b/arch/riscv/kernel/stacktrace.c
index 528ec7cc9a62..e0f556b680d8 100644
--- a/arch/riscv/kernel/stacktrace.c
+++ b/arch/riscv/kernel/stacktrace.c
@@ -161,3 +161,46 @@ noinline void arch_stack_walk(stack_trace_consume_fn consume_entry, void *cookie
 {
 	walk_stackframe(task, regs, consume_entry, cookie);
 }
+
+/*
+ * Get the return address for a single stackframe and return a pointer to the
+ * next frame tail.
+ */
+static unsigned long unwind_user_frame(stack_trace_consume_fn consume_entry,
+				       void *cookie, unsigned long fp,
+				       unsigned long reg_ra)
+{
+	struct stackframe buftail;
+	unsigned long ra = 0;
+	unsigned long __user *user_frame_tail =
+		(unsigned long __user *)(fp - sizeof(struct stackframe));
+
+	/* Check accessibility of one struct frame_tail beyond */
+	if (!access_ok(user_frame_tail, sizeof(buftail)))
+		return 0;
+	if (__copy_from_user_inatomic(&buftail, user_frame_tail,
+				      sizeof(buftail)))
+		return 0;
+
+	ra = reg_ra ? : buftail.ra;
+
+	fp = buftail.fp;
+	if (!ra || (ra && !consume_entry(cookie, ra)))
+		return 0;
+
+	return fp;
+}
+
+void arch_stack_walk_user(stack_trace_consume_fn consume_entry, void *cookie,
+			  const struct pt_regs *regs)
+{
+	unsigned long fp = 0;
+
+	fp = regs->s0;
+	if (!consume_entry(cookie, regs->epc))
+		return;
+
+	fp = unwind_user_frame(consume_entry, cookie, fp, regs->ra);
+	while (fp && !(fp & 0x3))
+		fp = unwind_user_frame(consume_entry, cookie, fp, 0);
+}
-- 
2.34.1

Re: [PATCH] riscv: stacktrace: Add USER_STACKTRACE support

[kernel test robot]

Hi Jinjie,

kernel test robot noticed the following build warnings:

[auto build test WARNING on perf-tools-next/perf-tools-next]
[also build test WARNING on tip/perf/core perf-tools/perf-tools linus/master acme/perf/core v6.10-rc1 next-20240531]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Jinjie-Ruan/riscv-stacktrace-Add-USER_STACKTRACE-support/20240531-163624
base:   https://git.kernel.org/pub/scm/linux/kernel/git/perf/perf-tools-next.git perf-tools-next
patch link:    https://lore.kernel.org/r/20240531083258.386709-1-ruanjinjie%40huawei.com
patch subject: [PATCH] riscv: stacktrace: Add USER_STACKTRACE support
config: riscv-randconfig-r061-20240601 (https://download.01.org/0day-ci/archive/20240601/202406012109.PDAjXm2i-lkp@intel.com/config)
compiler: riscv64-linux-gcc (GCC) 13.2.0

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202406012109.PDAjXm2i-lkp@intel.com/

cocci warnings: (new ones prefixed by >>)
>> arch/riscv/kernel/stacktrace.c:188:16-18: WARNING !A || A && B is equivalent to !A || B

vim +188 arch/riscv/kernel/stacktrace.c

   164	
   165	/*
   166	 * Get the return address for a single stackframe and return a pointer to the
   167	 * next frame tail.
   168	 */
   169	static unsigned long unwind_user_frame(stack_trace_consume_fn consume_entry,
   170					       void *cookie, unsigned long fp,
   171					       unsigned long reg_ra)
   172	{
   173		struct stackframe buftail;
   174		unsigned long ra = 0;
   175		unsigned long __user *user_frame_tail =
   176			(unsigned long __user *)(fp - sizeof(struct stackframe));
   177	
   178		/* Check accessibility of one struct frame_tail beyond */
   179		if (!access_ok(user_frame_tail, sizeof(buftail)))
   180			return 0;
   181		if (__copy_from_user_inatomic(&buftail, user_frame_tail,
   182					      sizeof(buftail)))
   183			return 0;
   184	
   185		ra = reg_ra ? : buftail.ra;
   186	
   187		fp = buftail.fp;
 > 188		if (!ra || (ra && !consume_entry(cookie, ra)))
   189			return 0;
   190	
   191		return fp;
   192	}
   193	

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki