mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
synced 2025-01-16 18:08:20 +00:00
5a6ea7022f
Commit [0] breaks samples/bpf build:
$ make M=samples/bpf
...
make -C /path/to/kernel/samples/bpf/../../tools/lib/bpf \
...
EXTRA_CFLAGS=" \
...
-fsanitize=bounds \
-I/path/to/kernel/usr/include \
...
/path/to/kernel/samples/bpf/libbpf/libbpf.a install_headers
CC /path/to/kernel/samples/bpf/libbpf/staticobjs/libbpf.o
In file included from libbpf.c:29:
/path/to/kernel/tools/include/linux/err.h:35:8: error: 'inline' can only appear on functions
35 | static inline void * __must_check ERR_PTR(long error_)
| ^
The error is caused by `objtree` variable changing definition from `.`
(dot) to an absolute path:
- The variable TPROGS_CFLAGS is constructed as follows:
...
TPROGS_CFLAGS += -I$(objtree)/usr/include
- It is passed as EXTRA_CFLAGS for libbpf compilation:
$(LIBBPF): ...
...
$(MAKE) -C $(LIBBPF_SRC) RM='rm -rf' EXTRA_CFLAGS="$(TPROGS_CFLAGS)"
- Before commit [0], the line passed to libbpf makefile was
'-I./usr/include', where '.' referred to LIBBPF_SRC due to -C flag.
The directory $(LIBBPF_SRC)/usr/include does not exist and thus
was never resolved by C compiler.
- After commit [0], the line passed to libbpf makefile became:
'<output-dir>/usr/include', this directory exists and is resolved by
C compiler.
- Both 'tools/include' and 'usr/include' define files err.h and types.h.
- libbpf expects headers like 'linux/err.h' and 'linux/types.h'
defined in 'tools/include', not 'usr/include', hence the compilation
error.
This commit removes unnecessary -I flags from libbpf compilation.
(libbpf sets up the necessary includes at lib/bpf/Makefile:63).
Changes v1 [1] -> v2:
- dropped unnecessary replacement of KBUILD_OUTPUT with $(objtree)
(Andrii)
Changes v2 [2] -> v3:
- make sure --sysroot option is set for libbpf's EXTRA_CFLAGS,
if $(SYSROOT) is set (Stanislav)
[0] commit 13b25489b6f8 ("kbuild: change working directory to external module directory with M=")
[1] https://lore.kernel.org/bpf/20241202212154.3174402-1-eddyz87@gmail.com/
[2] https://lore.kernel.org/bpf/20241202234741.3492084-1-eddyz87@gmail.com/
Fixes: 13b25489b6f8 ("kbuild: change working directory to external module directory with M=")
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Link: https://lore.kernel.org/bpf/20241203182222.3915763-1-eddyz87@gmail.com
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.