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pahole: fix kernel BTF generation when OBJCOPY carries options

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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 <ricardo.salveti@oss.qualcomm.com>
Signed-off-by: Khem Raj <khem.raj@oss.qualcomm.com>
This commit is contained in:
Ricardo Salveti authored and Khem Raj committed 2026-10-23 08:54:00 -07:00
1 parent cafddff7a7
commit da61e01434
2 files changed
+182
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meta-oe/recipes-devtools/pahole/files/0001-dutil-Split-the-objcopy-command-into-words-in-exec_o.patch
+181
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@@ -0,0 +1,181 @@
From 726ca024c9bfdeee542361ceb2e611e884955050 Mon Sep 17 00:00:00 2001
From: Ricardo Salveti <ricardo.salveti@oss.qualcomm.com>
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 <ricardo.salveti@oss.qualcomm.com>
---
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
meta-oe/recipes-devtools/pahole/pahole_1.32.bb
+1
View File
@@ -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 \
"