| Message ID | 20231005220324.3635499-1-irogers@google.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | BPF |
| Headers | show |
| Series | [v5,1/2] bpftool: Align output skeleton ELF code | expand |
On Thu, Oct 5, 2023 at 3:03 PM Ian Rogers <irogers@google.com> 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, 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 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\ Seems like you based this on top of bpf tree, can you please rebase onto bpf-next, it has a small change here and I can't apply it cleanly anymore. Other than that it looks good. Thanks! > \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$d; \n\ > - return (const void *)\"\\ \n\ > - " > - , file_sz, obj_name); > + static const char data[] __attribute__((__aligned__(8))) = \"\\\n\ > + ", > + obj_name > + ); > > /* embed contents of BPF object file */ > print_hex(obj_data, file_sz); > @@ -1231,6 +1231,9 @@ static int do_skeleton(int argc, char **argv) > codegen("\ > \n\ > \"; \n\ > + \n\ > + *sz = sizeof(data) - 1; \n\ > + return (const void *)data; \n\ > } \n\ > \n\ > #ifdef __cplusplus \n\ > -- > 2.42.0.609.gbb76f46606-goog >
On Fri, Oct 6, 2023 at 1:20 PM Andrii Nakryiko <andrii.nakryiko@gmail.com> wrote: > > On Thu, Oct 5, 2023 at 3:03 PM Ian Rogers <irogers@google.com> wrote: > > > > libbpf accesses the ELF data requiring at least 8 byte alignment, > > however, the data is generated into a C string that doesn't guarantee > > alignment. Fix this by assigning to an aligned char array. Use sizeof > > on the array, less one for the \0 terminator, rather than generating a > > constant. > > > > Fixes: a6cc6b34b93e ("bpftool: Provide a helper method for accessing skeleton's embedded ELF data") > > Signed-off-by: Ian Rogers <irogers@google.com> > > Acked-by: Quentin Monnet <quentin@isovalent.com> > > Reviewed-by: Alan Maguire <alan.maguire@oracle.com> > > --- > > tools/bpf/bpftool/gen.c | 15 +++++++++------ > > 1 file changed, 9 insertions(+), 6 deletions(-) > > > > diff --git a/tools/bpf/bpftool/gen.c b/tools/bpf/bpftool/gen.c > > index 2883660d6b67..b8ebcee9bc56 100644 > > --- a/tools/bpf/bpftool/gen.c > > +++ b/tools/bpf/bpftool/gen.c > > @@ -1209,7 +1209,7 @@ static int do_skeleton(int argc, char **argv) > > codegen("\ > > \n\ > > \n\ > > - s->data = (void *)%2$s__elf_bytes(&s->data_sz); \n\ > > + s->data = (void *)%1$s__elf_bytes(&s->data_sz); \n\ > > Seems like you based this on top of bpf tree, can you please rebase > onto bpf-next, it has a small change here and I can't apply it cleanly > anymore. Other than that it looks good. Thanks! Sure thing, sorry for so many V-s, we'll get there in the end. Thanks, Ian > > \n\ > > obj->skeleton = s; \n\ > > return 0; \n\ > > @@ -1218,12 +1218,12 @@ static int do_skeleton(int argc, char **argv) > > return err; \n\ > > } \n\ > > \n\ > > - static inline const void *%2$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 > >
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\
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(-)