From da61e01434e60500ef87bd49c6e8945e2d4161f6 Mon Sep 17 00:00:00 2001 From: Ricardo Salveti Date: Fri, 23 Oct 2026 02:31:56 +0000 Subject: [PATCH] pahole: fix kernel BTF generation when OBJCOPY carries options pahole 1.32 takes the whole value of LLVM_OBJCOPY as the objcopy program name. Kernels up to v6.19, such as the 6.18 LTS, set it from $(OBJCOPY), which ends with a blank in OE builds, so the kernel link fails when generating BTF: btf_encoder__write_elf: failed to add .BTF section to '.tmp_vmlinux1' Bring the fix submitted upstream, which splits the command into words. Signed-off-by: Ricardo Salveti Signed-off-by: Khem Raj --- ...objcopy-command-into-words-in-exec_o.patch | 181 ++++++++++++++++++ .../recipes-devtools/pahole/pahole_1.32.bb | 1 + 2 files changed, 182 insertions(+) create mode 100644 meta-oe/recipes-devtools/pahole/files/0001-dutil-Split-the-objcopy-command-into-words-in-exec_o.patch diff --git a/meta-oe/recipes-devtools/pahole/files/0001-dutil-Split-the-objcopy-command-into-words-in-exec_o.patch b/meta-oe/recipes-devtools/pahole/files/0001-dutil-Split-the-objcopy-command-into-words-in-exec_o.patch new file mode 100644 index 0000000000..70ca794834 --- /dev/null +++ b/meta-oe/recipes-devtools/pahole/files/0001-dutil-Split-the-objcopy-command-into-words-in-exec_o.patch @@ -0,0 +1,181 @@ +From 726ca024c9bfdeee542361ceb2e611e884955050 Mon Sep 17 00:00:00 2001 +From: Ricardo Salveti +Date: Wed, 21 Oct 2026 20:05:39 +0000 +Subject: [PATCH] dutil: Split the objcopy command into words in exec_objcopy() + +pahole 1.31 ran objcopy through system(), so LLVM_OBJCOPY was a command +line that could carry options, like the $(OBJCOPY) make variable the +kernel build sets it from. Since the switch to exec_objcopy() the whole +value of LLVM_OBJCOPY or OBJCOPY is passed to posix_spawnp() as the +program name, so a value such as "objcopy --some-option", or one with a +trailing blank, fails with ENOENT. + +Kernel builds up to v6.19, including the LTS branches, run +LLVM_OBJCOPY="${OBJCOPY}" pahole -J from link-vmlinux.sh and use +${OBJCOPY} unquoted for their own objcopy calls in the same script, so +an OBJCOPY that works for the rest of the build now stops the link with: + + btf_encoder__write_elf: failed to add .BTF section to '.tmp_vmlinux1' + +This breaks OpenEmbedded kernel builds, where OBJCOPY carries the +machine's objcopy options and ends with a blank when there are none. + +Split the command on blanks, like the shell's word splitting did with +system(), for OBJCOPY as well. Quotes are not interpreted, so a path +containing blanks can no longer be used, either quoted as with system() +or as is as with v1.32. Name the file as both input and output, so that +a stray word in the command makes objcopy fail instead of being taken +as its input file and replacing the target. + +Extend btf_write_elf.sh to check that options in LLVM_OBJCOPY reach +objcopy. + +Fixes: 6789ef8a16d5 ("btf_encoder: Fall back to objcopy when llvm-objcopy is not available") +Assisted-by: Claude Code:claude-opus-5-5 +Upstream-Status: Submitted [https://lore.kernel.org/dwarves/20261022035604.3183589-1-ricardo.salveti@oss.qualcomm.com/] +Signed-off-by: Ricardo Salveti +--- + dutil.c | 55 +++++++++++++++++++++++++++++++++--------- + tests/btf_write_elf.sh | 34 ++++++++++++++++++++++++++ + 2 files changed, 78 insertions(+), 11 deletions(-) + +diff --git a/dutil.c b/dutil.c +index 38101f1..d333d41 100644 +--- a/dutil.c ++++ b/dutil.c +@@ -248,15 +248,43 @@ int exec_objcopy(const char *objcopy, const char *add_section, + struct sigaction ign, old_int, old_quit; + posix_spawnattr_t attr; + sigset_t child_default; ++ char *cmd, *word, *saveptr, **argv; ++ int argc = 0; + pid_t pid; + int rc; + +- char *argv[] = { +- (char *)objcopy, +- "--add-section", (char *)add_section, +- "--", (char *)filename, +- NULL +- }; ++ /* ++ * objcopy may come from $LLVM_OBJCOPY or $OBJCOPY, which the kernel ++ * build sets from its $(OBJCOPY) make variable, a command line that ++ * can carry options, so split it into words on blanks, as the shell ++ * did with system(), but without interpreting quotes or escapes. ++ * A string of n characters has at most (n + 1) / 2 words. ++ */ ++ cmd = strdup(objcopy); ++ argv = calloc((strlen(objcopy) + 1) / 2 + 6, sizeof(*argv)); ++ if (cmd == NULL || argv == NULL) { ++ rc = -1; ++ goto out_free; ++ } ++ ++ for (word = strtok_r(cmd, " \t\n", &saveptr); word != NULL; ++ word = strtok_r(NULL, " \t\n", &saveptr)) ++ argv[argc++] = word; ++ ++ if (argc == 0) { ++ rc = -ENOENT; ++ goto out_free; ++ } ++ ++ argv[argc++] = "--add-section"; ++ argv[argc++] = (char *)add_section; ++ /* ++ * Name the output file too, so that a stray word in the command ++ * makes objcopy fail instead of becoming its input file. ++ */ ++ argv[argc++] = "--"; ++ argv[argc++] = (char *)filename; ++ argv[argc++] = (char *)filename; + + /* Ignore SIGINT/SIGQUIT in parent while waiting, per POSIX system() */ + ign.sa_handler = SIG_IGN; +@@ -278,14 +306,15 @@ int exec_objcopy(const char *objcopy, const char *add_section, + posix_spawnattr_setflags(&attr, + POSIX_SPAWN_SETSIGDEF | POSIX_SPAWN_SETSIGMASK); + +- rc = posix_spawnp(&pid, objcopy, NULL, &attr, argv, environ); ++ rc = posix_spawnp(&pid, argv[0], NULL, &attr, argv, environ); + posix_spawnattr_destroy(&attr); + + if (rc != 0) { + sigaction(SIGINT, &old_int, NULL); + sigaction(SIGQUIT, &old_quit, NULL); + pthread_sigmask(SIG_SETMASK, &orig, NULL); +- return rc == ENOENT ? -ENOENT : -1; ++ rc = rc == ENOENT ? -ENOENT : -1; ++ goto out_free; + } + + int status; +@@ -302,7 +331,11 @@ int exec_objcopy(const char *objcopy, const char *add_section, + pthread_sigmask(SIG_SETMASK, &orig, NULL); + + if (status == -1 || !WIFEXITED(status)) +- return -1; +- +- return WEXITSTATUS(status) == 0 ? 0 : -1; ++ rc = -1; ++ else ++ rc = WEXITSTATUS(status) == 0 ? 0 : -1; ++out_free: ++ free(argv); ++ free(cmd); ++ return rc; + } +diff --git a/tests/btf_write_elf.sh b/tests/btf_write_elf.sh +index 64ce128..dc512e0 100755 +--- a/tests/btf_write_elf.sh ++++ b/tests/btf_write_elf.sh +@@ -14,6 +14,9 @@ + # exists from the first encode. pahole opens the ELF with ELF_C_RDWR, + # overwrites the Elf_Data buffer in place, and calls elf_update() -- + # no objcopy needed. This is the "Existing .BTF section found" path. ++# ++# Path 1 is run again with options in LLVM_OBJCOPY, as kernel builds up to ++# v6.19 pass their $(OBJCOPY) command line there. + + . "$(dirname "$0")/test_lib.sh" + outdir=$(make_tmpdir) +@@ -115,4 +118,35 @@ if [ "$has_bpftool" -eq 1 ]; then + info_log "BTF content valid after overwrite (elf_test found): ok" + fi + ++# --- Path 1 with options in LLVM_OBJCOPY --- ++# Kernel builds up to v6.19 run LLVM_OBJCOPY="${OBJCOPY}" pahole -J, and ++# $(OBJCOPY) is a command line that may carry options or trailing whitespace. ++# --preserve-dates keeps the old timestamp only if the option reaches objcopy. ++ ++objcopy=${LLVM_OBJCOPY:-$OBJCOPY} ++if [ -z "$objcopy" ]; then ++ objcopy=objcopy ++ command -v llvm-objcopy > /dev/null 2>&1 && objcopy=llvm-objcopy ++fi ++args_obj="$outdir/write_elf_args_test.o" ++args_ref="$outdir/write_elf_args_test.ref" ++cp "$obj" "$args_obj" ++touch -t 200001010000 "$args_obj" "$args_ref" ++ ++if ! LLVM_OBJCOPY="$objcopy --preserve-dates " pahole -J "$args_obj" 2>/dev/null; then ++ error_log "FAIL: pahole -J with options in LLVM_OBJCOPY failed (exit code != 0)" ++ test_fail ++fi ++ ++if ! readelf -S "$args_obj" 2>/dev/null | grep -q '\.BTF[[:space:]]'; then ++ error_log "FAIL: .BTF section not found with options in LLVM_OBJCOPY" ++ test_fail ++fi ++ ++if [ -n "$(find "$args_obj" -newer "$args_ref")" ]; then ++ error_log "FAIL: options in LLVM_OBJCOPY did not reach objcopy" ++ test_fail ++fi ++info_log "pahole -J with options in LLVM_OBJCOPY: ok" ++ + test_pass +-- +2.43.0 + diff --git a/meta-oe/recipes-devtools/pahole/pahole_1.32.bb b/meta-oe/recipes-devtools/pahole/pahole_1.32.bb index 331b93abf6..68797fc7ec 100644 --- a/meta-oe/recipes-devtools/pahole/pahole_1.32.bb +++ b/meta-oe/recipes-devtools/pahole/pahole_1.32.bb @@ -12,6 +12,7 @@ COMPATIBLE_HOST = "(x86_64|i.86|arm|aarch64|riscv64|powerpc|powerpc64|mips64).*- SRCREV = "fa725d687ce3a712ef296b46bc63ea57ef466014" SRC_URI = "git://git.kernel.org/pub/scm/devel/pahole/pahole.git;branch=master;tag=v${PV} \ file://0001-Use-usr-bin-env-python3-instead-of-just-usr-bin-pyth.patch \ + file://0001-dutil-Split-the-objcopy-command-into-words-in-exec_o.patch \ "