linux-kernel - [PATCH 5.8 056/118] perf test: Fix the "signal" test inline assembly

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Message-Id: <20200921162038.947881580@linuxfoundation.org>
Date:   Mon, 21 Sep 2020 18:27:48 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Jiri Olsa <jolsa@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Michael Petlan <mpetlan@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Wang Nan <wangnan0@...wei.com>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.8 056/118] perf test: Fix the "signal" test inline assembly

From: Jiri Olsa <jolsa@...nel.org>

[ Upstream commit 8a39e8c4d9baf65d88f66d49ac684df381e30055 ]

When compiling with DEBUG=1 on Fedora 32 I'm getting crash for 'perf
test signal':

  Program received signal SIGSEGV, Segmentation fault.
  0x0000000000c68548 in __test_function ()
  (gdb) bt
  #0  0x0000000000c68548 in __test_function ()
  #1  0x00000000004d62e9 in test_function () at tests/bp_signal.c:61
  #2  0x00000000004d689a in test__bp_signal (test=0xa8e280 <generic_ ...
  #3  0x00000000004b7d49 in run_test (test=0xa8e280 <generic_tests+1 ...
  #4  0x00000000004b7e7f in test_and_print (t=0xa8e280 <generic_test ...
  #5  0x00000000004b8927 in __cmd_test (argc=1, argv=0x7fffffffdce0, ...
  ...

It's caused by the symbol __test_function being in the ".bss" section:

  $ readelf -a ./perf | less
    [Nr] Name              Type             Address           Offset
         Size              EntSize          Flags  Link  Info  Align
    ...
    [28] .bss              NOBITS           0000000000c356a0  008346a0
         00000000000511f8  0000000000000000  WA       0     0     32

  $ nm perf | grep __test_function
  0000000000c68548 B __test_function

I guess most of the time we're just lucky the inline asm ended up in the
".text" section, so making it specific explicit with push and pop
section clauses.

  $ readelf -a ./perf | less
    [Nr] Name              Type             Address           Offset
         Size              EntSize          Flags  Link  Info  Align
    ...
    [13] .text             PROGBITS         0000000000431240  00031240
         0000000000306faa  0000000000000000  AX       0     0     16

  $ nm perf | grep __test_function
  00000000004d62c8 T __test_function

Committer testing:

  $ readelf -wi ~/bin/perf | grep producer -m1
    <c>   DW_AT_producer    : (indirect string, offset: 0x254a): GNU C99 10.2.1 20200723 (Red Hat 10.2.1-1) -mtune=generic -march=x86-64 -ggdb3 -std=gnu99 -fno-omit-frame-pointer -funwind-tables -fstack-protector-all
                                                                                                                                         ^^^^^
                                                                                                                                         ^^^^^
                                                                                                                                         ^^^^^
  $

Before:

  $ perf test signal
  20: Breakpoint overflow signal handler                    : FAILED!
  $

After:

  $ perf test signal
  20: Breakpoint overflow signal handler                    : Ok
  $

Fixes: 8fd34e1cce18 ("perf test: Improve bp_signal")
Signed-off-by: Jiri Olsa <jolsa@...nel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@...hat.com>
Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: Michael Petlan <mpetlan@...hat.com>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Wang Nan <wangnan0@...wei.com>
Link: http://lore.kernel.org/lkml/20200911130005.1842138-1-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 tools/perf/tests/bp_signal.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/tools/perf/tests/bp_signal.c b/tools/perf/tests/bp_signal.c
index da8ec1e8e0648..cc9fbcedb3646 100644
--- a/tools/perf/tests/bp_signal.c
+++ b/tools/perf/tests/bp_signal.c
@@ -45,10 +45,13 @@ volatile long the_var;
 #if defined (__x86_64__)
 extern void __test_function(volatile long *ptr);
 asm (
+	".pushsection .text;"
 	".globl __test_function\n"
+	".type __test_function, @function;"
 	"__test_function:\n"
 	"incq (%rdi)\n"
-	"ret\n");
+	"ret\n"
+	".popsection\n");
 #else
 static void __test_function(volatile long *ptr)
 {
-- 
2.25.1