On Mon, Oct 2, 2023 at 3:32 PM Ian Rogers <irogers@xxxxxxxxxx> wrote: > > 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. > > Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx> > --- Perhaps this could have a fixes tag: Fixes: d510296d331a ("bpftool: Use syscall/loader program in "prog load" and "gen skeleton" command.") The unaligned problem was seen in perf's offcpu code as well as bcc's libbpf_tools. I didn't see problems with map data and opts data, but inspection of the code shows they likely have the same issue. I was testing with -fsanitize=alignment and -fsanitize-undefined-trap-on-error. Thanks, Ian > 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 2883660d6b67..b8ebcee9bc56 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 = (void *)%2$s__elf_bytes(&s->data_sz); \n\ > + s->data = (void *)%1$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\ > -- > 2.42.0.582.g8ccd20d70d-goog >