cb76371441
The newly added 'llvm.opts' variable allows passing options directly to
llc, like needed to get sane DWARF in BPF ELF debug sections:
With:
[root@seventh perf]# cat ~/.perfconfig
[llvm]
dump-obj = true
clang-opt = -g
[root@seventh perf]#
We get:
[root@seventh perf]# perf trace -e tools/perf/examples/bpf/hello.c cat /etc/passwd > /dev/null
LLVM: dumping tools/perf/examples/bpf/hello.o
0.000 __bpf_stdout__:Hello, world
0.015 __bpf_stdout__:Hello, world
0.187 __bpf_stdout__:Hello, world
[root@seventh perf]# pahole tools/perf/examples/bpf/hello.o
struct clang version 8.0.0 (http://llvm.org/git/clang.git 8587270a739ee30c926a76d5657e65e85b560f6e) (http://llvm.org/git/llvm.git 0566eefef9c3777bd780ec4cbb9efa764633b76c) {
clang version 8.0.0 (http://llvm.org/git/clang.git 8587270a739ee30c926a76d5657e65e85b560f6e) (http://llvm.org/git/llvm.git 0566e.org clang version 8.0.0 (http://llvm.org/git/clang.git 8587270a739ee30c926a76d5657e65e85b560f6e) (http://llvm.org/git/llvm.git 0566eefef9c3777bd780ec4cbb9efa764633b76c); /* 0 4 */
clang version 8.0.0 (http://llvm.org/git/clang.git 8587270a739ee30c926a76d5657e65e85b560f6e) (http://llvm.org/git/llvm.git 0566e.org clang version 8.0.0 (http://llvm.org/git/clang.git 8587270a739ee30c926a76d5657e65e85b560f6e) (http://llvm.org/git/llvm.git 0566eefef9c3777bd780ec4cbb9efa764633b76c); /* 4 4 */
clang version 8.0.0 (http://llvm.org/git/clang.git 8587270a739ee30c926a76d5657e65e85b560f6e) (http://llvm.org/git/llvm.git 0566e.org clang version 8.0.0 (http://llvm.org/git/clang.git 8587270a739ee30c926a76d5657e65e85b560f6e) (http://llvm.org/git/llvm.git 0566eefef9c3777bd780ec4cbb9efa764633b76c); /* 8 4 */
clang version 8.0.0 (http://llvm.org/git/clang.git 8587270a739ee30c926a76d5657e65e85b560f6e) (http://llvm.org/git/llvm.git 0566e.org clang version 8.0.0 (http://llvm.org/git/clang.git 8587270a739ee30c926a76d5657e65e85b560f6e) (http://llvm.org/git/llvm.git 0566eefef9c3777bd780ec4cbb9efa764633b76c); /* 12 4 */
clang version 8.0.0 (http://llvm.org/git/clang.git 8587270a739ee30c926a76d5657e65e85b560f6e) (http://llvm.org/git/llvm.git 0566e.org clang version 8.0.0 (http://llvm.org/git/clang.git 8587270a739ee30c926a76d5657e65e85b560f6e) (http://llvm.org/git/llvm.git 0566eefef9c3777bd780ec4cbb9efa764633b76c); /* 16 4 */
clang version 8.0.0 (http://llvm.org/git/clang.git 8587270a739ee30c926a76d5657e65e85b560f6e) (http://llvm.org/git/llvm.git 0566e.org clang version 8.0.0 (http://llvm.org/git/clang.git 8587270a739ee30c926a76d5657e65e85b560f6e) (http://llvm.org/git/llvm.git 0566eefef9c3777bd780ec4cbb9efa764633b76c); /* 20 4 */
clang version 8.0.0 (http://llvm.org/git/clang.git 8587270a739ee30c926a76d5657e65e85b560f6e) (http://llvm.org/git/llvm.git 0566e.org clang version 8.0.0 (http://llvm.org/git/clang.git 8587270a739ee30c926a76d5657e65e85b560f6e) (http://llvm.org/git/llvm.git 0566eefef9c3777bd780ec4cbb9efa764633b76c); /* 24 4 */
/* size: 28, cachelines: 1, members: 7 */
/* last cacheline: 28 bytes */
};
[root@seventh perf]#
Adding these options to be passed to llvm's llc:
[root@seventh perf]# cat ~/.perfconfig
[llvm]
dump-obj = true
clang-opt = -g
opts = -mattr=dwarfris
[root@seventh perf]#
We get sane output:
[root@seventh perf]# perf trace -e tools/perf/examples/bpf/hello.c cat /etc/passwd > /dev/null
LLVM: dumping tools/perf/examples/bpf/hello.o
0.000 __bpf_stdout__:Hello, world
0.015 __bpf_stdout__:Hello, world
0.185 __bpf_stdout__:Hello, world
[root@seventh perf]# pahole tools/perf/examples/bpf/hello.o
struct bpf_map {
unsigned int type; /* 0 4 */
unsigned int key_size; /* 4 4 */
unsigned int value_size; /* 8 4 */
unsigned int max_entries; /* 12 4 */
unsigned int map_flags; /* 16 4 */
unsigned int inner_map_idx; /* 20 4 */
unsigned int numa_node; /* 24 4 */
/* size: 28, cachelines: 1, members: 7 */
/* last cacheline: 28 bytes */
};
[root@seventh perf]#
Cc: Alexei Starovoitov <ast@fb.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Martin KaFai Lau <kafai@fb.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>,
Cc: Yonghong Song <yhs@fb.com>
Link: https://lkml.kernel.org/n/tip-0lrwmrip4dru1651rm8xa7tq@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.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 Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.
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.