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bpftool: Align output skeleton ELF code

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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>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Reviewed-by: Alan Maguire <alan.maguire@oracle.com>
Acked-by: Quentin Monnet <quentin@isovalent.com>
Link: https://lore.kernel.org/bpf/20231007044439.25171-1-irogers@google.com
This commit is contained in:
Ian Rogers 2023-10-06 21:44:38 -07:00 committed by Andrii Nakryiko
parent 0d7ae06860
commit 23671f4dfd
1 changed files with 9 additions and 6 deletions
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15
tools/bpf/bpftool/gen.c
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@ -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\