From 0826b224b5210fc6f0681c9324dca974d507a8f7 Mon Sep 17 00:00:00 2001 From: Pavel Shirov Date: Sat, 7 Dec 2024 15:29:28 +0300 Subject: [PATCH] kernel: packages: fix building package/devel/perf with -O3 Add patch to fix failure to build package/devel/perf when CONFIG_TARGET_OPTIMIZATION has -O3 enabled with this error: ``` In function 'elf_close', inlined from 'elf_close' at elf.c:41:6, inlined from 'elf_find_func_offset_from_file' at elf.c:267:2: elf.c:45:9: error: 'elf_fd.elf' may be used uninitialized [-Werror=maybe-uninitialized] 45 | elf_end(elf_fd->elf); | ^~~~~~~~~~~~~~~~~~~~ elf.c: In function 'elf_find_func_offset_from_file': elf.c:260:23: note: 'elf_fd.elf' was declared here 260 | struct elf_fd elf_fd; | ^~~~~~ In function 'elf_close', inlined from 'elf_close' at elf.c:41:6, inlined from 'elf_find_func_offset_from_file' at elf.c:267:2: elf.c:46:9: error: 'elf_fd.fd' may be used uninitialized [-Werror=maybe-uninitialized] 46 | close(elf_fd->fd); | ^~~~~~~~~~~~~~~~~ elf.c: In function 'elf_find_func_offset_from_file': elf.c:260:23: note: 'elf_fd.fd' was declared here 260 | struct elf_fd elf_fd; | ^~~~~~ ``` Link: https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git/commit/?id=fab45b962749 Signed-off-by: Pavel Shirov Link: https://github.com/openwrt/openwrt/pull/17141 Signed-off-by: Hauke Mehrtens --- ...6.12-fix-libbpf-Wmaybe-uninitialized.patch | 59 +++++++++++++++++++ 1 file changed, 59 insertions(+) create mode 100644 target/linux/generic/backport-6.6/192-v6.12-fix-libbpf-Wmaybe-uninitialized.patch diff --git a/target/linux/generic/backport-6.6/192-v6.12-fix-libbpf-Wmaybe-uninitialized.patch b/target/linux/generic/backport-6.6/192-v6.12-fix-libbpf-Wmaybe-uninitialized.patch new file mode 100644 index 0000000000..638fe4bc4a --- /dev/null +++ b/target/linux/generic/backport-6.6/192-v6.12-fix-libbpf-Wmaybe-uninitialized.patch @@ -0,0 +1,59 @@ +From fab45b962749184e1a1a57c7c583782b78fad539 Mon Sep 17 00:00:00 2001 +From: Sam James +Date: Tue, 13 Aug 2024 20:49:06 +0100 +Subject: [PATCH] libbpf: Workaround -Wmaybe-uninitialized false positive +MIME-Version: 1.0 +Content-Type: text/plain; charset=UTF-8 +Content-Transfer-Encoding: 8bit + +In `elf_close`, we get this with GCC 15 -O3 (at least): +``` +In function ‘elf_close’, + inlined from ‘elf_close’ at elf.c:53:6, + inlined from ‘elf_find_func_offset_from_file’ at elf.c:384:2: +elf.c:57:9: warning: ‘elf_fd.elf’ may be used uninitialized [-Wmaybe-uninitialized] + 57 | elf_end(elf_fd->elf); + | ^~~~~~~~~~~~~~~~~~~~ +elf.c: In function ‘elf_find_func_offset_from_file’: +elf.c:377:23: note: ‘elf_fd.elf’ was declared here + 377 | struct elf_fd elf_fd; + | ^~~~~~ +In function ‘elf_close’, + inlined from ‘elf_close’ at elf.c:53:6, + inlined from ‘elf_find_func_offset_from_file’ at elf.c:384:2: +elf.c:58:9: warning: ‘elf_fd.fd’ may be used uninitialized [-Wmaybe-uninitialized] + 58 | close(elf_fd->fd); + | ^~~~~~~~~~~~~~~~~ +elf.c: In function ‘elf_find_func_offset_from_file’: +elf.c:377:23: note: ‘elf_fd.fd’ was declared here + 377 | struct elf_fd elf_fd; + | ^~~~~~ +``` + +In reality, our use is fine, it's just that GCC doesn't model errno +here (see linked GCC bug). Suppress -Wmaybe-uninitialized accordingly +by initializing elf_fd.fd to -1 and elf_fd.elf to NULL. + +I've done this in two other functions as well given it could easily +occur there too (same access/use pattern). + +Signed-off-by: Sam James +Signed-off-by: Andrii Nakryiko +Link: https://gcc.gnu.org/PR114952 +Link: https://lore.kernel.org/bpf/14ec488a1cac02794c2fa2b83ae0cef1bce2cb36.1723578546.git.sam@gentoo.org +--- + tools/lib/bpf/elf.c | 3 +++ + 1 file changed, 3 insertions(+) + +--- a/tools/lib/bpf/elf.c ++++ b/tools/lib/bpf/elf.c +@@ -16,6 +16,9 @@ int elf_open(const char *binary_path, st + int fd, ret; + Elf *elf; + ++ elf_fd->elf = NULL; ++ elf_fd->fd = -1; ++ + if (elf_version(EV_CURRENT) == EV_NONE) { + pr_warn("elf: failed to init libelf for %s\n", binary_path); + return -LIBBPF_ERRNO__LIBELF; -- 2.30.2