[PATCH 1/2] tools/perf: Fix the file mode with copyfile while adding file to build-id cache

[Athira Rajeev]

The test "build id cache operations" fails on powerpc
As below:

	Adding 5a0fd882b53084224ba47b624c55a469 ./tests/shell/../pe-file.exe: Ok
	build id: 5a0fd882b53084224ba47b624c55a469
	link: /tmp/perf.debug.ZTu/.build-id/5a/0fd882b53084224ba47b624c55a469
	file: /tmp/perf.debug.ZTu/.build-id/5a/../../root/linux/tools/perf/tests/pe-file.exe/5a0fd882b53084224ba47b624c55a469/elf
	failed: file /tmp/perf.debug.ZTu/.build-id/5a/../../root/linux/tools/perf/tests/pe-file.exe/5a0fd882b53084224ba47b624c55a469/elf does not exist
	test child finished with -1
	---- end ----
	build id cache operations: FAILED!

The failing test is when trying to add pe-file.exe to
build id cache.

Perf buildid-cache can be used to add/remove/manage
files from the build-id cache. "-a" option is used to
add a file to the build-id cache.

Simple command to do so for a PE exe file:
 # ls -ltr tests/pe-file.exe
 -rw-r--r--. 1 root root 75595 Jan 10 23:35 tests/pe-file.exe
 The file is in home directory.

 # mkdir  /tmp/perf.debug.TeY1
 # perf --buildid-dir /tmp/perf.debug.TeY1 buildid-cache -v
   -a tests/pe-file.exe

The above will create ".build-id" folder in build id
directory, which is /tmp/perf.debug.TeY1. Also adds file
to this folder under build id. Example:

 # ls -ltr /tmp/perf.debug.TeY1/.build-id/5a/0fd882b53084224ba47b624c55a469/
 total 76
 -rw-r--r--. 1 root root     0 Jan 11 00:38 probes
 -rwxr-xr-x. 1 root root 75595 Jan 11 00:38 elf

We can see in the results that file mode for original
file and file in build id directory is different. ie,
build id file has executable permission whereas original
file doesn’t have.

The code path and function ( build_id_cache__add ) to
add file to cache is in "util/build-id.c". In
build_id_cache__add() function, it first attempts to link
the original file to destination cache folder. If linking
the file fails ( which can happen if the destination and
source is on a different mount points ), it will copy the
file to destination. Here copyfile() routine explicitly uses
mode as "755" and hence file in the destination will have
executable permission.

Code snippet:

 if (link(realname, filename) && errno != EEXIST &&
                               copyfile(name, filename))

Strace logs:

	172285 link("/home/<user_name>/linux/tools/perf/tests/pe-file.exe", "/tmp/perf.debug.TeY1/home/<user_name>/linux/tools/perf/tests/pe-file.exe/5a0fd882b53084224ba47b624c55a469/elf") = -1 EXDEV (Invalid cross-device link)
	172285 newfstatat(AT_FDCWD, "tests/pe-file.exe", {st_mode=S_IFREG|0644, st_size=75595, ...}, 0) = 0
	172285 openat(AT_FDCWD, "/tmp/perf.debug.TeY1/home/<user_name>/linux/tools/perf/tests/pe-file.exe/5a0fd882b53084224ba47b624c55a469/.elf.KbAnsl", O_RDWR|O_CREAT|O_EXCL, 0600) = 3
	172285 fchmod(3, 0755)                  = 0
	172285 openat(AT_FDCWD, "tests/pe-file.exe", O_RDONLY) = 4
	172285 mmap(NULL, 75595, PROT_READ, MAP_PRIVATE, 4, 0) = 0x7fffa5cd0000
	172285 pwrite64(3, "MZ\220\0\3\0\0\0\4\0\0\0\377\377\0\0\270\0\0\0\0\0\0\0@\0\0\0\0\0\0\0"..., 75595, 0) = 75595

Whereas if the link succeeds, it succeeds in the first
attempt itself and the file in the build-id dir will
have same permission as original file.

Example, above uses /tmp. Instead if we use
"--buildid-dir /home/build", linking will work here
since mount points are same. Hence the destination file
will not have executable permission.

Since the testcase "tests/shell/buildid.sh" always looks
for executable file, test fails in powerpc environment
when test is run from /root.

The patch adds a change in build_id_cache__add to use
copyfile_mode which also passes the file’s original mode as
argument. This way the destination file mode also will
be same as original file.

Signed-off-by: Athira Rajeev <atrajeev at linux.vnet.ibm.com>
---
 tools/perf/util/build-id.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/tools/perf/util/build-id.c b/tools/perf/util/build-id.c
index a839b30c981b..ea9c083ab1e3 100644
--- a/tools/perf/util/build-id.c
+++ b/tools/perf/util/build-id.c
@@ -715,9 +715,13 @@ build_id_cache__add(const char *sbuild_id, const char *name, const char *realnam
 		} else if (nsi && nsinfo__need_setns(nsi)) {
 			if (copyfile_ns(name, filename, nsi))
 				goto out_free;
-		} else if (link(realname, filename) && errno != EEXIST &&
-				copyfile(name, filename))
-			goto out_free;
+		} else if (link(realname, filename) && errno != EEXIST) {
+			struct stat f_stat;
+
+			if (!(stat(name, &f_stat) < 0) &&
+					copyfile_mode(name, filename, f_stat.st_mode))
+				goto out_free;
+		}
 	}
 
 	/* Some binaries are stripped, but have .debug files with their symbol
-- 
2.31.1