[hardknott][PATCH 24/28] dwarfsrcfiles: Avoid races over debug-link files

Anuj Mittal
2021-07-16T02:43:07Z

From: Richard Purdie <richard.purdie@linuxfoundation.org>

We use dwarfsrcfiles in package.bbclass to list the source files used by a binary.
This is done before they're stripped and linked to debug symbols in separate files.

It is possible a binary may already have a link to separate debug symbols, e.g.
some of the test binaries in lttng-tools ptest. In those cases, the linked binary
may be changed by package.bbclass code whilst dwarfsrcfiles is reading it. That
would result in a rare SIGBUS race causing the binary to fail.

To avoid this, break the debug file search path so no other binaries are found.

Also fix a segfault if no binary is specified while here.

[YOCTO #14400]

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit efef732859e265533acf16f2f4da3b29d50e0df4)
Signed-off-by: Anuj Mittal <anuj.mittal@intel.com>
---
.../dwarfsrcfiles/files/dwarfsrcfiles.c | 13 ++++++++++---
1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/meta/recipes-devtools/dwarfsrcfiles/files/dwarfsrcfiles.c b/meta/recipes-devtools/dwarfsrcfiles/files/dwarfsrcfiles.c
index af7af524eb..9eb5ca807a 100644
--- a/meta/recipes-devtools/dwarfsrcfiles/files/dwarfsrcfiles.c
+++ b/meta/recipes-devtools/dwarfsrcfiles/files/dwarfsrcfiles.c
@@ -9,6 +9,7 @@

#include <argp.h>
#include <stdio.h>
+#include <stdlib.h>

#include <dwarf.h>
#include <elfutils/libdw.h>
@@ -83,13 +84,15 @@ process_cu (Dwarf_Die *cu_die)
int
main (int argc, char **argv)
{
- char* args[3];
+ char* args[5];
int res = 0;
Dwfl *dwfl;
Dwarf_Addr bias;

- if (argc != 2)
+ if (argc != 2) {
fprintf(stderr, "Usage %s <file>", argv[0]);
+ exit(EXIT_FAILURE);
+ }

// Pretend "dwarfsrcfiles -e <file>" was given, so we can use standard
// dwfl argp parser to open the file for us and get our Dwfl. Useful
@@ -98,8 +101,12 @@ main (int argc, char **argv)
args[0] = argv[0];
args[1] = "-e";
args[2] = argv[1];
+ // We don't want to follow debug linked files due to the way OE processes
+ // files, could race against changes in the linked binary (e.g. objcopy on it)
+ args[3] = "--debuginfo-path";
+ args[4] = "/not/exist";

- argp_parse (dwfl_standard_argp (), 3, args, 0, NULL, &dwfl);
+ argp_parse (dwfl_standard_argp (), 5, args, 0, NULL, &dwfl);

Dwarf_Die *cu = NULL;
while ((cu = dwfl_nextcu (dwfl, cu, &bias)) != NULL)
--
2.31.1