From: Ian Rogers <irogers@google.com>
To: Quentin Monnet <quentin@isovalent.com>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
Martin KaFai Lau <martin.lau@linux.dev>,
Song Liu <song@kernel.org>,
Yonghong Song <yonghong.song@linux.dev>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@kernel.org>,
Stanislav Fomichev <sdf@google.com>, Hao Luo <haoluo@google.com>,
Jiri Olsa <jolsa@kernel.org>, Matt Smith <alastorze@fb.com>,
bpf@vger.kernel.org, linux-kernel@vger.kernel.org,
Alan Maguire <alan.maguire@oracle.com>
Cc: Ian Rogers <irogers@google.com>
Subject: [PATCH v6 1/2] bpftool: Align output skeleton ELF code
Date: Fri, 6 Oct 2023 21:44:38 -0700 [thread overview]
Message-ID: <20231007044439.25171-1-irogers@google.com> (raw)
libbpf accesses the ELF data requiring at least 8 byte alignment,
however, the data is generated into a C string that doesn't guarantee
alignment. Fix this by assigning to an aligned char array. Use sizeof
on the array, less one for the \0 terminator, rather than generating a
constant.
Fixes: a6cc6b34b93e ("bpftool: Provide a helper method for accessing skeleton's embedded ELF data")
Signed-off-by: Ian Rogers <irogers@google.com>
Acked-by: Quentin Monnet <quentin@isovalent.com>
Reviewed-by: Alan Maguire <alan.maguire@oracle.com>
---
tools/bpf/bpftool/gen.c | 15 +++++++++------
1 file changed, 9 insertions(+), 6 deletions(-)
diff --git a/tools/bpf/bpftool/gen.c b/tools/bpf/bpftool/gen.c
index 04c47745b3ea..882bf8e6e70e 100644
--- a/tools/bpf/bpftool/gen.c
+++ b/tools/bpf/bpftool/gen.c
@@ -1209,7 +1209,7 @@ static int do_skeleton(int argc, char **argv)
codegen("\
\n\
\n\
- s->data = %2$s__elf_bytes(&s->data_sz); \n\
+ s->data = %1$s__elf_bytes(&s->data_sz); \n\
\n\
obj->skeleton = s; \n\
return 0; \n\
@@ -1218,12 +1218,12 @@ static int do_skeleton(int argc, char **argv)
return err; \n\
} \n\
\n\
- static inline const void *%2$s__elf_bytes(size_t *sz) \n\
+ static inline const void *%1$s__elf_bytes(size_t *sz) \n\
{ \n\
- *sz = %1$d; \n\
- return (const void *)\"\\ \n\
- "
- , file_sz, obj_name);
+ static const char data[] __attribute__((__aligned__(8))) = \"\\\n\
+ ",
+ obj_name
+ );
/* embed contents of BPF object file */
print_hex(obj_data, file_sz);
@@ -1231,6 +1231,9 @@ static int do_skeleton(int argc, char **argv)
codegen("\
\n\
\"; \n\
+ \n\
+ *sz = sizeof(data) - 1; \n\
+ return (const void *)data; \n\
} \n\
\n\
#ifdef __cplusplus \n\
--
2.42.0.609.gbb76f46606-goog
next reply other threads:[~2023-10-07 4:45 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-07 4:44 Ian Rogers [this message]
2023-10-07 4:44 ` [PATCH v6 2/2] bpftool: Align bpf_load_and_run_opts insns and data Ian Rogers
2023-10-09 16:50 ` [PATCH v6 1/2] bpftool: Align output skeleton ELF code patchwork-bot+netdevbpf
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