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Message-Id: <20170306174909.12395-1-naveen.n.rao@linux.vnet.ibm.com>
Date: Mon, 6 Mar 2017 23:19:09 +0530
From: "Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>
To: Masami Hiramatsu <mhiramat@...nel.org>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>,
Steven Rostedt <rostedt@...dmis.org>,
Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
linuxppc-dev@...ts.ozlabs.org,
Ananth N Mavinakayanahalli <ananth@...ux.vnet.ibm.com>,
Michael Ellerman <mpe@...erman.id.au>
Subject: Re: [PATCH v4 2/3] perf: kretprobes: offset from reloc_sym if kernel supports it
Masami,
Your patch works, thanks! However, I felt we could refactor and reuse
some of the code across kprobes.c for this purpose. Can you please see
if the below patch is fine?
Thanks,
Naveen
--
trace/kprobes: fix check for kretprobe offset within function entry
perf specifies an offset from _text and since this offset is fed
directly into the arch-specific helper, kprobes tracer rejects
installation of kretprobes through perf. Fix this by looking up the
actual offset from a function for the specified sym+offset.
Refactor and reuse existing routines to limit code duplication -- we
repurpose kprobe_addr() for determining final kprobe address and we
split out the function entry offset determination into a separate
generic helper.
Before patch:
naveen@...ntu:~/linux/tools/perf$ sudo ./perf probe -v do_open%return
probe-definition(0): do_open%return
symbol:do_open file:(null) line:0 offset:0 return:1 lazy:(null)
0 arguments
Looking at the vmlinux_path (8 entries long)
Using /boot/vmlinux for symbols
Open Debuginfo file: /boot/vmlinux
Try to find probe point from debuginfo.
Matched function: do_open [2d0c7ff]
Probe point found: do_open+0
Matched function: do_open [35d76dc]
found inline addr: 0xc0000000004ba9c4
Failed to find "do_open%return",
because do_open is an inlined function and has no return point.
An error occurred in debuginfo analysis (-22).
Trying to use symbols.
Opening /sys/kernel/debug/tracing//README write=0
Opening /sys/kernel/debug/tracing//kprobe_events write=1
Writing event: r:probe/do_open _text+4469776
Failed to write event: Invalid argument
Error: Failed to add events. Reason: Invalid argument (Code: -22)
naveen@...ntu:~/linux/tools/perf$ dmesg | tail
<snip>
[ 33.568656] Given offset is not valid for return probe.
After patch:
naveen@...ntu:~/linux/tools/perf$ sudo ./perf probe -v do_open%return
probe-definition(0): do_open%return
symbol:do_open file:(null) line:0 offset:0 return:1 lazy:(null)
0 arguments
Looking at the vmlinux_path (8 entries long)
Using /boot/vmlinux for symbols
Open Debuginfo file: /boot/vmlinux
Try to find probe point from debuginfo.
Matched function: do_open [2d0c7d6]
Probe point found: do_open+0
Matched function: do_open [35d76b3]
found inline addr: 0xc0000000004ba9e4
Failed to find "do_open%return",
because do_open is an inlined function and has no return point.
An error occurred in debuginfo analysis (-22).
Trying to use symbols.
Opening /sys/kernel/debug/tracing//README write=0
Opening /sys/kernel/debug/tracing//kprobe_events write=1
Writing event: r:probe/do_open _text+4469808
Writing event: r:probe/do_open_1 _text+4956344
Added new events:
probe:do_open (on do_open%return)
probe:do_open_1 (on do_open%return)
You can now use it in all perf tools, such as:
perf record -e probe:do_open_1 -aR sleep 1
naveen@...ntu:~/linux/tools/perf$ sudo cat /sys/kernel/debug/kprobes/list
c000000000041370 k kretprobe_trampoline+0x0 [OPTIMIZED]
c0000000004ba0b8 r do_open+0x8 [DISABLED]
c000000000443430 r do_open+0x0 [DISABLED]
Signed-off-by: Naveen N. Rao <naveen.n.rao@...ux.vnet.ibm.com>
---
include/linux/kprobes.h | 1 +
kernel/kprobes.c | 40 ++++++++++++++++++++++++++--------------
kernel/trace/trace_kprobe.c | 2 +-
3 files changed, 28 insertions(+), 15 deletions(-)
diff --git a/include/linux/kprobes.h b/include/linux/kprobes.h
index 862f87adcbb4..6888c9f29cb6 100644
--- a/include/linux/kprobes.h
+++ b/include/linux/kprobes.h
@@ -267,6 +267,7 @@ extern void show_registers(struct pt_regs *regs);
extern void kprobes_inc_nmissed_count(struct kprobe *p);
extern bool arch_within_kprobe_blacklist(unsigned long addr);
extern bool arch_function_offset_within_entry(unsigned long offset);
+extern bool function_offset_within_entry(kprobe_opcode_t *addr, const char *sym, unsigned long offset);
extern bool within_kprobe_blacklist(unsigned long addr);
diff --git a/kernel/kprobes.c b/kernel/kprobes.c
index 524766563896..49f870ea4070 100644
--- a/kernel/kprobes.c
+++ b/kernel/kprobes.c
@@ -1391,21 +1391,19 @@ bool within_kprobe_blacklist(unsigned long addr)
* This returns encoded errors if it fails to look up symbol or invalid
* combination of parameters.
*/
-static kprobe_opcode_t *kprobe_addr(struct kprobe *p)
+static kprobe_opcode_t *_kprobe_addr(kprobe_opcode_t *addr,
+ const char *symbol_name, unsigned int offset)
{
- kprobe_opcode_t *addr = p->addr;
-
- if ((p->symbol_name && p->addr) ||
- (!p->symbol_name && !p->addr))
+ if ((symbol_name && addr) || (!symbol_name && !addr))
goto invalid;
- if (p->symbol_name) {
- kprobe_lookup_name(p->symbol_name, addr);
+ if (symbol_name) {
+ kprobe_lookup_name(symbol_name, addr);
if (!addr)
return ERR_PTR(-ENOENT);
}
- addr = (kprobe_opcode_t *)(((char *)addr) + p->offset);
+ addr = (kprobe_opcode_t *)(((char *)addr) + offset);
if (addr)
return addr;
@@ -1413,6 +1411,11 @@ static kprobe_opcode_t *kprobe_addr(struct kprobe *p)
return ERR_PTR(-EINVAL);
}
+static kprobe_opcode_t *kprobe_addr(struct kprobe *p)
+{
+ return _kprobe_addr(p->addr, p->symbol_name, p->offset);
+}
+
/* Check passed kprobe is valid and return kprobe in kprobe_table. */
static struct kprobe *__get_valid_kprobe(struct kprobe *p)
{
@@ -1874,19 +1877,28 @@ bool __weak arch_function_offset_within_entry(unsigned long offset)
return !offset;
}
+bool function_offset_within_entry(kprobe_opcode_t *addr, const char *sym, unsigned long offset)
+{
+ kprobe_opcode_t *kp_addr = _kprobe_addr(addr, sym, offset);
+
+ if (IS_ERR(kp_addr))
+ return false;
+
+ if (!kallsyms_lookup_size_offset((unsigned long)kp_addr, NULL, &offset) ||
+ !arch_function_offset_within_entry(offset))
+ return false;
+
+ return true;
+}
+
int register_kretprobe(struct kretprobe *rp)
{
int ret = 0;
struct kretprobe_instance *inst;
int i;
void *addr;
- unsigned long offset;
-
- addr = kprobe_addr(&rp->kp);
- if (!kallsyms_lookup_size_offset((unsigned long)addr, NULL, &offset))
- return -EINVAL;
- if (!arch_function_offset_within_entry(offset))
+ if (!function_offset_within_entry(rp->kp.addr, rp->kp.symbol_name, rp->kp.offset))
return -EINVAL;
if (kretprobe_blacklist_size) {
diff --git a/kernel/trace/trace_kprobe.c b/kernel/trace/trace_kprobe.c
index c60f9dc4610e..828ef31a1c27 100644
--- a/kernel/trace/trace_kprobe.c
+++ b/kernel/trace/trace_kprobe.c
@@ -695,7 +695,7 @@ static int create_trace_kprobe(int argc, char **argv)
return ret;
}
if (offset && is_return &&
- !arch_function_offset_within_entry(offset)) {
+ !function_offset_within_entry(NULL, symbol, offset)) {
pr_info("Given offset is not valid for return probe.\n");
return -EINVAL;
}
--
2.11.1
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