Re: [PATCH] dutil: Split the objcopy command into words in exec_objcopy()

[Alan Maguire <almagui@kernel.org>]

> From: Ricardo Salveti <ricardo.salveti@oss.qualcomm.com>
> To: dwarves@vger.kernel.org
> Cc: acme@kernel.org, alan.maguire@oracle.com, bpf@vger.kernel.org
> Subject: [PATCH] dutil: Split the objcopy command into words in exec_objcopy()
> Date: Thu, 22 Oct 2026 03:56:04 +0000	[thread overview]
> Message-ID: <20261022035604.3183589-1-ricardo.salveti@oss.qualcomm.com> (raw)
> 
> 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
> Signed-off-by: Ricardo Salveti <ricardo.salveti@oss.qualcomm.com>

Applied, thank you!