From d92d184fd9a85ab6ecbcf91dc9eadc1cab9c9e81 Mon Sep 17 00:00:00 2001 From: Pavel Shirov Date: Mon, 2 Dec 2024 09:34:12 +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 --- ...6.12-fix-libbpf-Wmaybe-uninitialized.patch | 58 +++++++++++++++++++ 1 file changed, 58 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 00000000000000..1eaa073955c761 --- /dev/null +++ b/target/linux/generic/backport-6.6/192-v6.12-fix-libbpf-Wmaybe-uninitialized.patch @@ -0,0 +1,58 @@ +From: Sam James +Date: Tue, 13 Aug 2024 20:49:06 +0100 +Subject: [PATCH v4] libbpf: workaround -Wmaybe-uninitialized false positive + +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. + +v4: Initialize elf and fd members in elf_open to avoid meddling with +callers. + +Link: https://gcc.gnu.org/PR114952 +Signed-off-by: Sam James +Link: https://lore.kernel.org/bpf/14ec488a1cac02794c2fa2b83ae0cef1bce2cb36.1723578546.git.sam@gentoo.org/ +[nstorm.ahoy166@silomails.com: refreshed patch, formatted message, added link and tested] +Signed-off-by: Pavel Shirov +--- + 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;