Re: [PATCH 2/3] perf-probe: Check address correctness by map instead of _etext

Em Thu, Apr 23, 2020 at 08:01:13PM +0900, Masami Hiramatsu escreveu:

Since commit 03db8b583d1c ("perf tools: Fix maps__find_symbol_by_name()") introduced map address range check in maps__find_symbol_by_name(), we can not get "_etext" from kernel map because _etext is placed on the edge of the kernel .text section (= kernel map in perf.)

To fix this issue, this checks the address correctness by map address range information (map->start and map->end) instead of using _etext address.

This can cause an error if the target inlined function is embedded in both __init function and normal function.

For exaample, request_resource() is a normal function but also embedded in __init reserve_setup(). In this case, the probe point in reserve_setup() must be skipped. However, without this fix, it failes to setup all probe points. ================ # ./perf probe -v request_resource probe-definition(0): request_resource symbol:request_resource file:(null) line:0 offset:0 return:0 lazy:(null) 0 arguments Looking at the vmlinux_path (8 entries long) Using /usr/lib/debug/lib/modules/5.5.17-200.fc31.x86_64/vmlinux for symbols Open Debuginfo file: /usr/lib/debug/lib/modules/5.5.17-200.fc31.x86_64/vmlinux Try to find probe point from debuginfo. Matched function: request_resource [15e29ad] found inline addr: 0xffffffff82fbf892 Probe point found: reserve_setup+204 found inline addr: 0xffffffff810e9790 Probe point found: request_resource+0 Found 2 probe_trace_events. Opening /sys/kernel/debug/tracing//kprobe_events write=1 Opening /sys/kernel/debug/tracing//README write=0 Writing event: p:probe/request_resource _text+33290386 Failed to write event: Invalid argument Error: Failed to add events. Reason: Invalid argument (Code: -22) ================

With this fix,

================ # ./perf probe request_resource reserve_setup is out of .text, skip it. Added new events: (null):(null) (on request_resource)

But what is this (null):(null) probe? Confusing :-)

Thanks for working on this!

- Arnaldo

probe:request_resource (on request_resource)

You can now use it in all perf tools, such as:

perf record -e probe:request_resource -aR sleep 1

================

Fixes: 03db8b583d1c ("perf tools: Fix maps__find_symbol_by_name()") Reported-by: Arnaldo Carvalho de Melo acme@kernel.org Signed-off-by: Masami Hiramatsu mhiramat@kernel.org Cc: stable@vger.kernel.org

---

tools/perf/util/probe-event.c | 25 +++++++++++++------------ 1 file changed, 13 insertions(+), 12 deletions(-)

diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c index f75df63309be..a5387e03e365 100644 --- a/tools/perf/util/probe-event.c +++ b/tools/perf/util/probe-event.c @@ -236,21 +236,22 @@ static void clear_probe_trace_events(struct probe_trace_event *tevs, int ntevs) static bool kprobe_blacklist__listed(unsigned long address); static bool kprobe_warn_out_range(const char *symbol, unsigned long address) {

• u64 etext_addr = 0;
• int ret;
• /* Get the address of _etext for checking non-probable text symbol */
• ret = kernel_get_symbol_address_by_name("_etext", &etext_addr,

• 				false, false);
  

• struct map *map;
• bool ret = false;

• if (ret == 0 && etext_addr < address)

• pr_warning("%s is out of .text, skip it.\n", symbol);
  

• else if (kprobe_blacklist__listed(address))

• map = kernel_get_module_map(NULL);
• if (map) {

• ret = address <= map->start || map->end < address;
  

• if (ret)
  

• 	pr_warning("%s is out of .text, skip it.\n", symbol);
  

• map__put(map);
  

• }
• if (!ret && kprobe_blacklist__listed(address)) { pr_warning("%s is blacklisted function, skip it.\n", symbol);

• else

• return false;
  

• ret = true;
  

• }

• return true;

• return ret;

} /*