riscv: add tracepoints for page fault

Commit Message

Zhu Hengbo July 15, 2024, 10:13 a.m. UTC

Introduce page_fault_user and page_fault_kernel for riscv page fault.
Help to get more detail information when page fault happen.

---
Simple test go below:

root@riscv-ubuntu2204 ~ # bin/perf list | grep exceptions
  exceptions:page_fault_kernel                       [Tracepoint event]
  exceptions:page_fault_user                         [Tracepoint event]

root@riscv-ubuntu2204 ~ # bin/perf record -e exceptions:page_fault_kernel -e exceptions:page_fault_user
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.091 MB perf.data (19 samples) ]

perf report tracepoint:

perf     826 [007]   894.795520:   exceptions:page_fault_user: user page fault, address=0x7fff95af4400 cause=0xd
perf     826 [007]   894.795970:   exceptions:page_fault_user: user page fault, address=0x7fff95a73400 cause=0xd
perf     826 [007]   894.796738:   exceptions:page_fault_user: user page fault, address=0x7fff959f2400 cause=0xd
perf     826 [007]   894.797088:   exceptions:page_fault_user: user page fault, address=0x7fff95971400 cause=0xd
perf     826 [007]   894.797273:   exceptions:page_fault_user: user page fault, address=0x7fff958f0400 cause=0xd
perf     826 [007]   894.797445:   exceptions:page_fault_user: user page fault, address=0x7fff9586f400 cause=0xd
perf     826 [007]   894.797998: exceptions:page_fault_kernel: kernel page fault, address=0x7fff95870000 cause=0xd

Signed-off-by: Zhu Hengbo <[e-mail]>
---
 arch/riscv/include/asm/trace/exceptions.h | 60 +++++++++++++++++++++++
 arch/riscv/mm/fault.c                     | 15 ++++++
 2 files changed, 75 insertions(+)
 create mode 100644 arch/riscv/include/asm/trace/exceptions.h

Comments

Matthew Wilcox July 15, 2024, 1:36 p.m. UTC | #1

On Mon, Jul 15, 2024 at 10:13:55AM +0000, Zhu Hengbo wrote:
> Introduce page_fault_user and page_fault_kernel for riscv page fault.
> Help to get more detail information when page fault happen.

Why be different from x86?

        TP_printk("address=%ps ip=%ps error_code=0x%lx",
                  (void *)__entry->address, (void *)__entry->ip,
                  __entry->error_code) );

adding the instruction pointer (ip) seems like it would be useful.

> +	TP_printk("user page fault, address=%ps cause=0x%lx",
> +		  (void *)__entry->address, __entry->cause)

Zhu Hengbo July 17, 2024, 7:57 a.m. UTC | #2

On 2024/7/15 21:36, Matthew Wilcox wrote:
> On Mon, Jul 15, 2024 at 10:13:55AM +0000, Zhu Hengbo wrote:
>> Introduce page_fault_user and page_fault_kernel for riscv page fault.
>> Help to get more detail information when page fault happen.
> Why be different from x86?
>
>         TP_printk("address=%ps ip=%ps error_code=0x%lx",
>                   (void *)__entry->address, (void *)__entry->ip,
>                   __entry->error_code) );
>
> adding the instruction pointer (ip) seems like it would be useful.
>
Yes, adding the ip information will indeed be helpful. I will update this patch.

Thanks for the suggestion.

>> +	TP_printk("user page fault, address=%ps cause=0x%lx",
>> +		  (void *)__entry->address, __entry->cause)
> _______________________________________________
> linux-riscv mailing list
> [e-mail]
> http://lists.infradead.org/mailman/listinfo/linux-riscv

Patch

diff --git a/arch/riscv/include/asm/trace/exceptions.h b/arch/riscv/include/asm/trace/exceptions.h
new file mode 100644
index 000000000000..a9a68d471703
--- /dev/null
+++ b/arch/riscv/include/asm/trace/exceptions.h
@@ -0,0 +1,60 @@ 
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Tracepoints for RISC-V exceptions
+ *
+ * Copyright (C) 2024 ISCAS. All rights reserved
+ *
+ */
+
+#if !defined(_TRACE_PAGE_FAULT_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_PAGE_FAULT_H
+
+#include <linux/tracepoint.h>
+
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM exceptions
+
+TRACE_EVENT(page_fault_user,
+	TP_PROTO(struct pt_regs *regs),
+	TP_ARGS(regs),
+
+	TP_STRUCT__entry(
+		__field(unsigned long, address)
+		__field(unsigned long, cause)
+	),
+
+	TP_fast_assign(
+		__entry->address	= regs->badaddr;
+		__entry->cause		= regs->cause;
+	),
+
+	TP_printk("user page fault, address=%ps cause=0x%lx",
+		  (void *)__entry->address, __entry->cause)
+);
+
+TRACE_EVENT(page_fault_kernel,
+	TP_PROTO(struct pt_regs *regs),
+	TP_ARGS(regs),
+
+	TP_STRUCT__entry(
+		__field(unsigned long, address)
+		__field(unsigned long, cause)
+	),
+
+	TP_fast_assign(
+		__entry->address	= regs->badaddr;
+		__entry->cause		= regs->cause;
+	),
+
+	TP_printk("kernel page fault, address=%ps cause=0x%lx",
+		  (void *)__entry->address, __entry->cause)
+);
+
+#undef TRACE_INCLUDE_PATH
+#undef TRACE_INCLUDE_FILE
+#define TRACE_INCLUDE_PATH asm/trace/
+#define TRACE_INCLUDE_FILE exceptions
+#endif /*  _TRACE_PAGE_FAULT_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>
diff --git a/arch/riscv/mm/fault.c b/arch/riscv/mm/fault.c
index 5224f3733802..22874074c5bc 100644
--- a/arch/riscv/mm/fault.c
+++ b/arch/riscv/mm/fault.c
@@ -22,6 +22,10 @@ 
 
 #include "../kernel/head.h"
 
+
+#define CREATE_TRACE_POINTS
+#include <asm/trace/exceptions.h>
+
 static void die_kernel_fault(const char *msg, unsigned long addr,
 		struct pt_regs *regs)
 {
@@ -215,6 +219,15 @@  static inline bool access_error(unsigned long cause, struct vm_area_struct *vma)
 	return false;
 }
 
+
+static inline void trace_page_fault(struct pt_regs *regs)
+{
+	if (user_mode(regs))
+		trace_page_fault_user(regs);
+	else
+		trace_page_fault_kernel(regs);
+}
+
 /*
  * This routine handles page faults.  It determines the address and the
  * problem, and then passes it off to one of the appropriate routines.
@@ -235,6 +248,8 @@  void handle_page_fault(struct pt_regs *regs)
 	tsk = current;
 	mm = tsk->mm;
 
+	trace_page_fault(regs);
+
 	if (kprobe_page_fault(regs, cause))
 		return;