| Message ID | 0511638ed6191f4434be23ed7fb56001ccb5b687.1724313164.git.tony.ambardar@gmail.com |
|---|---|
| State | New |
| Headers | show |
| Series | libbpf, selftests/bpf: Support cross-endian usage | expand |
On Thu, Aug 22, 2024 at 2:25 AM Tony Ambardar <tony.ambardar@gmail.com> wrote: > > From: Tony Ambardar <tony.ambardar@gmail.com> > > Allow static linking object files of either endianness, checking that input > files have consistent byte-order, and setting output endianness from input. > > Linking requires in-memory processing of programs, relocations, sections, > etc. in native endianness, and output conversion to target byte-order. This > is enabled by built-in ELF translation and recent BTF/BTF.ext endianness > functions. Further add local functions for swapping byte-order of sections > containing BPF insns. > > Signed-off-by: Tony Ambardar <tony.ambardar@gmail.com> > --- > tools/lib/bpf/linker.c | 106 ++++++++++++++++++++++++++++++++++------- > 1 file changed, 90 insertions(+), 16 deletions(-) > Mostly just stylistic and code organization nits, the change overall looks good. > diff --git a/tools/lib/bpf/linker.c b/tools/lib/bpf/linker.c > index 7489306cd6f7..9bf218db443e 100644 > --- a/tools/lib/bpf/linker.c > +++ b/tools/lib/bpf/linker.c > @@ -135,6 +135,7 @@ struct bpf_linker { > int fd; > Elf *elf; > Elf64_Ehdr *elf_hdr; > + bool swapped_endian; > > /* Output sections metadata */ > struct dst_sec *secs; > @@ -324,13 +325,8 @@ static int init_output_elf(struct bpf_linker *linker, const char *file) > > linker->elf_hdr->e_machine = EM_BPF; > linker->elf_hdr->e_type = ET_REL; > -#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__ > - linker->elf_hdr->e_ident[EI_DATA] = ELFDATA2LSB; > -#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__ > - linker->elf_hdr->e_ident[EI_DATA] = ELFDATA2MSB; > -#else > -#error "Unknown __BYTE_ORDER__" > -#endif > + /* Set unknown ELF endianness, assign later from input files */ > + linker->elf_hdr->e_ident[EI_DATA] = ELFDATANONE; > > /* STRTAB */ > /* initialize strset with an empty string to conform to ELF */ > @@ -541,19 +537,21 @@ static int linker_load_obj_file(struct bpf_linker *linker, const char *filename, > const struct bpf_linker_file_opts *opts, > struct src_obj *obj) > { > -#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__ > - const int host_endianness = ELFDATA2LSB; > -#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__ > - const int host_endianness = ELFDATA2MSB; > -#else > -#error "Unknown __BYTE_ORDER__" > -#endif > int err = 0; > Elf_Scn *scn; > Elf_Data *data; > Elf64_Ehdr *ehdr; > Elf64_Shdr *shdr; > struct src_sec *sec; > + unsigned char obj_byteorder; > + unsigned char *link_byteorder = &linker->elf_hdr->e_ident[EI_DATA]; nit: not a fan of pointer into e_ident, just read local value of byte order, and then assign it directly below (it's only in one of the branches, no duplication, really) > +#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__ > + const unsigned char host_byteorder = ELFDATA2LSB; > +#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__ > + const unsigned char host_byteorder = ELFDATA2MSB; > +#else > +#error "Unknown __BYTE_ORDER__" > +#endif > > pr_debug("linker: adding object file '%s'...\n", filename); > > @@ -579,11 +577,25 @@ static int linker_load_obj_file(struct bpf_linker *linker, const char *filename, > pr_warn_elf("failed to get ELF header for %s", filename); > return err; > } > - if (ehdr->e_ident[EI_DATA] != host_endianness) { > + > + /* Linker output endianness set by first input object */ > + obj_byteorder = ehdr->e_ident[EI_DATA]; > + if (obj_byteorder != ELFDATA2LSB && obj_byteorder != ELFDATA2MSB) { > err = -EOPNOTSUPP; > - pr_warn_elf("unsupported byte order of ELF file %s", filename); > + pr_warn("linker: unknown byte order of ELF file %s\n", filename); > return err; > } > + if (*link_byteorder == ELFDATANONE) { > + *link_byteorder = obj_byteorder; see above, I'd prefer: linker->elf_hdr->e_ident[EI_DATA] = obj_byteorder; > + linker->swapped_endian = obj_byteorder != host_byteorder; > + pr_debug("linker: set %s-endian output byte order\n", > + obj_byteorder == ELFDATA2MSB ? "big" : "little"); > + } else if (*link_byteorder != obj_byteorder) { > + err = -EOPNOTSUPP; > + pr_warn("linker: byte order mismatch with ELF file %s\n", filename); > + return err; > + } > + > if (ehdr->e_type != ET_REL > || ehdr->e_machine != EM_BPF > || ehdr->e_ident[EI_CLASS] != ELFCLASS64) { > @@ -1111,6 +1123,27 @@ static bool sec_content_is_same(struct dst_sec *dst_sec, struct src_sec *src_sec > return true; > } > > +static bool is_exec_sec(struct dst_sec *sec) > +{ > + if (!sec || sec->ephemeral) > + return false; > + return (sec->shdr->sh_type == SHT_PROGBITS) && > + (sec->shdr->sh_flags & SHF_EXECINSTR); > +} > + > +static int exec_sec_bswap(void *raw_data, int size) > +{ > + const int insn_cnt = size / sizeof(struct bpf_insn); > + struct bpf_insn *insn = raw_data; > + int i; > + > + if (size % sizeof(struct bpf_insn)) > + return -EINVAL; > + for (i = 0; i < insn_cnt; i++, insn++) > + bpf_insn_bswap(insn); > + return 0; > +} > + > static int extend_sec(struct bpf_linker *linker, struct dst_sec *dst, struct src_sec *src) > { > void *tmp; > @@ -1170,6 +1203,16 @@ static int extend_sec(struct bpf_linker *linker, struct dst_sec *dst, struct src > memset(dst->raw_data + dst->sec_sz, 0, dst_align_sz - dst->sec_sz); > /* now copy src data at a properly aligned offset */ > memcpy(dst->raw_data + dst_align_sz, src->data->d_buf, src->shdr->sh_size); > + > + /* convert added bpf insns to native byte-order */ > + if (linker->swapped_endian && is_exec_sec(dst)) { > + err = exec_sec_bswap(dst->raw_data + dst_align_sz, > + src->shdr->sh_size); nit: I think exec_sec_bswap() shouldn't ever fail, so given we have is_exec_sec() now, let's do the size alignment check early on (and regardless of swapped_endian), and then just proceed with byte swap that can't fail > + if (err) { > + pr_warn("%s: error changing insns endianness\n", __func__); > + return err; > + } > + } > } > > dst->sec_sz = dst_final_sz; > @@ -2630,6 +2673,14 @@ int bpf_linker__finalize(struct bpf_linker *linker) > if (!sec->scn) > continue; > > + /* restore sections with bpf insns to target byte-order */ > + if (linker->swapped_endian && is_exec_sec(sec)) { > + err = exec_sec_bswap(sec->raw_data, sec->sec_sz); and here we'll know that size is validly aligned anyways, so no checks required > + if (err) { > + pr_warn("error finalizing insns endianness\n"); > + return libbpf_err(err); > + } > + } > sec->data->d_buf = sec->raw_data; > } > > @@ -2696,6 +2747,13 @@ static int emit_elf_data_sec(struct bpf_linker *linker, const char *sec_name, > return 0; > } > > +static enum btf_endianness > +linker_btf_endianness(const struct bpf_linker *linker) > +{ > + unsigned char byteorder = linker->elf_hdr->e_ident[EI_DATA]; empty line between variable declaration and the rest of the code > + return byteorder == ELFDATA2MSB ? BTF_BIG_ENDIAN : BTF_LITTLE_ENDIAN; > +} > + but actually, this whole helper function seems unnecessary, just do everything inside finalize_btf, it's a pretty trivial piece of logic > static int finalize_btf(struct bpf_linker *linker) > { > LIBBPF_OPTS(btf_dedup_opts, opts); > @@ -2742,6 +2800,22 @@ static int finalize_btf(struct bpf_linker *linker) > return err; > } > > + /* Set .BTF and .BTF.ext output byte order */ > + err = btf__set_endianness(linker->btf, > + linker_btf_endianness(linker)); > + if (err) { > + pr_warn("failed to set .BTF output endianness: %d\n", err); nit: you used "linker: " prefix for messages like this, stay consistent? > + return err; > + } > + if (linker->btf_ext) { > + err = btf_ext__set_endianness(linker->btf_ext, > + linker_btf_endianness(linker)); > + if (err) { > + pr_warn("failed to set .BTF.ext output endianness: %d\n", err); > + return err; > + } > + } > + > /* Emit .BTF section */ > raw_data = btf__raw_data(linker->btf, &raw_sz); > if (!raw_data) > -- > 2.34.1 >
On Fri, Aug 23, 2024 at 12:47:52PM -0700, Andrii Nakryiko wrote: > On Thu, Aug 22, 2024 at 2:25 AM Tony Ambardar <tony.ambardar@gmail.com> wrote: > > > > From: Tony Ambardar <tony.ambardar@gmail.com> > > > > Allow static linking object files of either endianness, checking that input > > files have consistent byte-order, and setting output endianness from input. > > > > Linking requires in-memory processing of programs, relocations, sections, > > etc. in native endianness, and output conversion to target byte-order. This > > is enabled by built-in ELF translation and recent BTF/BTF.ext endianness > > functions. Further add local functions for swapping byte-order of sections > > containing BPF insns. > > > > Signed-off-by: Tony Ambardar <tony.ambardar@gmail.com> > > --- > > tools/lib/bpf/linker.c | 106 ++++++++++++++++++++++++++++++++++------- > > 1 file changed, 90 insertions(+), 16 deletions(-) > > > > Mostly just stylistic and code organization nits, the change overall looks good. > > > diff --git a/tools/lib/bpf/linker.c b/tools/lib/bpf/linker.c > > index 7489306cd6f7..9bf218db443e 100644 > > --- a/tools/lib/bpf/linker.c > > +++ b/tools/lib/bpf/linker.c > > @@ -135,6 +135,7 @@ struct bpf_linker { > > int fd; > > Elf *elf; > > Elf64_Ehdr *elf_hdr; > > + bool swapped_endian; > > > > /* Output sections metadata */ > > struct dst_sec *secs; > > @@ -324,13 +325,8 @@ static int init_output_elf(struct bpf_linker *linker, const char *file) > > > > linker->elf_hdr->e_machine = EM_BPF; > > linker->elf_hdr->e_type = ET_REL; > > -#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__ > > - linker->elf_hdr->e_ident[EI_DATA] = ELFDATA2LSB; > > -#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__ > > - linker->elf_hdr->e_ident[EI_DATA] = ELFDATA2MSB; > > -#else > > -#error "Unknown __BYTE_ORDER__" > > -#endif > > + /* Set unknown ELF endianness, assign later from input files */ > > + linker->elf_hdr->e_ident[EI_DATA] = ELFDATANONE; > > > > /* STRTAB */ > > /* initialize strset with an empty string to conform to ELF */ > > @@ -541,19 +537,21 @@ static int linker_load_obj_file(struct bpf_linker *linker, const char *filename, > > const struct bpf_linker_file_opts *opts, > > struct src_obj *obj) > > { > > -#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__ > > - const int host_endianness = ELFDATA2LSB; > > -#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__ > > - const int host_endianness = ELFDATA2MSB; > > -#else > > -#error "Unknown __BYTE_ORDER__" > > -#endif > > int err = 0; > > Elf_Scn *scn; > > Elf_Data *data; > > Elf64_Ehdr *ehdr; > > Elf64_Shdr *shdr; > > struct src_sec *sec; > > + unsigned char obj_byteorder; > > + unsigned char *link_byteorder = &linker->elf_hdr->e_ident[EI_DATA]; > > nit: not a fan of pointer into e_ident, just read local value of byte > order, and then assign it directly below (it's only in one of the > branches, no duplication, really) Yes, it's awkward. Fixed. > > > +#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__ > > + const unsigned char host_byteorder = ELFDATA2LSB; > > +#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__ > > + const unsigned char host_byteorder = ELFDATA2MSB; > > +#else > > +#error "Unknown __BYTE_ORDER__" > > +#endif > > > > pr_debug("linker: adding object file '%s'...\n", filename); > > > > @@ -579,11 +577,25 @@ static int linker_load_obj_file(struct bpf_linker *linker, const char *filename, > > pr_warn_elf("failed to get ELF header for %s", filename); > > return err; > > } > > - if (ehdr->e_ident[EI_DATA] != host_endianness) { > > + > > + /* Linker output endianness set by first input object */ > > + obj_byteorder = ehdr->e_ident[EI_DATA]; > > + if (obj_byteorder != ELFDATA2LSB && obj_byteorder != ELFDATA2MSB) { > > err = -EOPNOTSUPP; > > - pr_warn_elf("unsupported byte order of ELF file %s", filename); > > + pr_warn("linker: unknown byte order of ELF file %s\n", filename); > > return err; > > } > > + if (*link_byteorder == ELFDATANONE) { > > + *link_byteorder = obj_byteorder; > > see above, I'd prefer: > > linker->elf_hdr->e_ident[EI_DATA] = obj_byteorder; > Done. > > + linker->swapped_endian = obj_byteorder != host_byteorder; > > + pr_debug("linker: set %s-endian output byte order\n", > > + obj_byteorder == ELFDATA2MSB ? "big" : "little"); > > + } else if (*link_byteorder != obj_byteorder) { > > + err = -EOPNOTSUPP; > > + pr_warn("linker: byte order mismatch with ELF file %s\n", filename); > > + return err; > > + } > > + > > if (ehdr->e_type != ET_REL > > || ehdr->e_machine != EM_BPF > > || ehdr->e_ident[EI_CLASS] != ELFCLASS64) { > > @@ -1111,6 +1123,27 @@ static bool sec_content_is_same(struct dst_sec *dst_sec, struct src_sec *src_sec > > return true; > > } > > > > +static bool is_exec_sec(struct dst_sec *sec) > > +{ > > + if (!sec || sec->ephemeral) > > + return false; > > + return (sec->shdr->sh_type == SHT_PROGBITS) && > > + (sec->shdr->sh_flags & SHF_EXECINSTR); > > +} > > + > > +static int exec_sec_bswap(void *raw_data, int size) > > +{ > > + const int insn_cnt = size / sizeof(struct bpf_insn); > > + struct bpf_insn *insn = raw_data; > > + int i; > > + > > + if (size % sizeof(struct bpf_insn)) > > + return -EINVAL; > > + for (i = 0; i < insn_cnt; i++, insn++) > > + bpf_insn_bswap(insn); > > + return 0; > > +} > > + > > static int extend_sec(struct bpf_linker *linker, struct dst_sec *dst, struct src_sec *src) > > { > > void *tmp; > > @@ -1170,6 +1203,16 @@ static int extend_sec(struct bpf_linker *linker, struct dst_sec *dst, struct src > > memset(dst->raw_data + dst->sec_sz, 0, dst_align_sz - dst->sec_sz); > > /* now copy src data at a properly aligned offset */ > > memcpy(dst->raw_data + dst_align_sz, src->data->d_buf, src->shdr->sh_size); > > + > > + /* convert added bpf insns to native byte-order */ > > + if (linker->swapped_endian && is_exec_sec(dst)) { > > + err = exec_sec_bswap(dst->raw_data + dst_align_sz, > > + src->shdr->sh_size); > > nit: I think exec_sec_bswap() shouldn't ever fail, so given we have > is_exec_sec() now, let's do the size alignment check early on (and > regardless of swapped_endian), and then just proceed with byte swap > that can't fail Looking more closely, I see we already have this size check from: 32fa058398 ("libbpf: Add pr_warn() for EINVAL cases in linker_sanity_check_elf") So can just drop the error-handling. > > > + if (err) { > > + pr_warn("%s: error changing insns endianness\n", __func__); > > + return err; > > + } > > + } > > } > > > > dst->sec_sz = dst_final_sz; > > @@ -2630,6 +2673,14 @@ int bpf_linker__finalize(struct bpf_linker *linker) > > if (!sec->scn) > > continue; > > > > + /* restore sections with bpf insns to target byte-order */ > > + if (linker->swapped_endian && is_exec_sec(sec)) { > > + err = exec_sec_bswap(sec->raw_data, sec->sec_sz); > > and here we'll know that size is validly aligned anyways, so no checks required > > > + if (err) { > > + pr_warn("error finalizing insns endianness\n"); > > + return libbpf_err(err); > > + } > > + } > > sec->data->d_buf = sec->raw_data; > > } > > > > @@ -2696,6 +2747,13 @@ static int emit_elf_data_sec(struct bpf_linker *linker, const char *sec_name, > > return 0; > > } > > > > +static enum btf_endianness > > +linker_btf_endianness(const struct bpf_linker *linker) > > +{ > > + unsigned char byteorder = linker->elf_hdr->e_ident[EI_DATA]; > > empty line between variable declaration and the rest of the code > > > + return byteorder == ELFDATA2MSB ? BTF_BIG_ENDIAN : BTF_LITTLE_ENDIAN; > > +} > > + > > but actually, this whole helper function seems unnecessary, just do > everything inside finalize_btf, it's a pretty trivial piece of logic OK, merged as it's not complicated. > > > static int finalize_btf(struct bpf_linker *linker) > > { > > LIBBPF_OPTS(btf_dedup_opts, opts); > > @@ -2742,6 +2800,22 @@ static int finalize_btf(struct bpf_linker *linker) > > return err; > > } > > > > + /* Set .BTF and .BTF.ext output byte order */ > > + err = btf__set_endianness(linker->btf, > > + linker_btf_endianness(linker)); > > + if (err) { > > + pr_warn("failed to set .BTF output endianness: %d\n", err); > > nit: you used "linker: " prefix for messages like this, stay consistent? Right, original code used extra "linker:" detail only for "debug" messages and not "warn" level. Changed to do the same. Thanks! > > > > + return err; > > + } > > + if (linker->btf_ext) { > > + err = btf_ext__set_endianness(linker->btf_ext, > > + linker_btf_endianness(linker)); > > + if (err) { > > + pr_warn("failed to set .BTF.ext output endianness: %d\n", err); > > + return err; > > + } > > + } > > + > > /* Emit .BTF section */ > > raw_data = btf__raw_data(linker->btf, &raw_sz); > > if (!raw_data) > > -- > > 2.34.1 > >
diff --git a/tools/lib/bpf/linker.c b/tools/lib/bpf/linker.c index 7489306cd6f7..9bf218db443e 100644 --- a/tools/lib/bpf/linker.c +++ b/tools/lib/bpf/linker.c @@ -135,6 +135,7 @@ struct bpf_linker { int fd; Elf *elf; Elf64_Ehdr *elf_hdr; + bool swapped_endian; /* Output sections metadata */ struct dst_sec *secs; @@ -324,13 +325,8 @@ static int init_output_elf(struct bpf_linker *linker, const char *file) linker->elf_hdr->e_machine = EM_BPF; linker->elf_hdr->e_type = ET_REL; -#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__ - linker->elf_hdr->e_ident[EI_DATA] = ELFDATA2LSB; -#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__ - linker->elf_hdr->e_ident[EI_DATA] = ELFDATA2MSB; -#else -#error "Unknown __BYTE_ORDER__" -#endif + /* Set unknown ELF endianness, assign later from input files */ + linker->elf_hdr->e_ident[EI_DATA] = ELFDATANONE; /* STRTAB */ /* initialize strset with an empty string to conform to ELF */ @@ -541,19 +537,21 @@ static int linker_load_obj_file(struct bpf_linker *linker, const char *filename, const struct bpf_linker_file_opts *opts, struct src_obj *obj) { -#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__ - const int host_endianness = ELFDATA2LSB; -#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__ - const int host_endianness = ELFDATA2MSB; -#else -#error "Unknown __BYTE_ORDER__" -#endif int err = 0; Elf_Scn *scn; Elf_Data *data; Elf64_Ehdr *ehdr; Elf64_Shdr *shdr; struct src_sec *sec; + unsigned char obj_byteorder; + unsigned char *link_byteorder = &linker->elf_hdr->e_ident[EI_DATA]; +#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__ + const unsigned char host_byteorder = ELFDATA2LSB; +#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__ + const unsigned char host_byteorder = ELFDATA2MSB; +#else +#error "Unknown __BYTE_ORDER__" +#endif pr_debug("linker: adding object file '%s'...\n", filename); @@ -579,11 +577,25 @@ static int linker_load_obj_file(struct bpf_linker *linker, const char *filename, pr_warn_elf("failed to get ELF header for %s", filename); return err; } - if (ehdr->e_ident[EI_DATA] != host_endianness) { + + /* Linker output endianness set by first input object */ + obj_byteorder = ehdr->e_ident[EI_DATA]; + if (obj_byteorder != ELFDATA2LSB && obj_byteorder != ELFDATA2MSB) { err = -EOPNOTSUPP; - pr_warn_elf("unsupported byte order of ELF file %s", filename); + pr_warn("linker: unknown byte order of ELF file %s\n", filename); return err; } + if (*link_byteorder == ELFDATANONE) { + *link_byteorder = obj_byteorder; + linker->swapped_endian = obj_byteorder != host_byteorder; + pr_debug("linker: set %s-endian output byte order\n", + obj_byteorder == ELFDATA2MSB ? "big" : "little"); + } else if (*link_byteorder != obj_byteorder) { + err = -EOPNOTSUPP; + pr_warn("linker: byte order mismatch with ELF file %s\n", filename); + return err; + } + if (ehdr->e_type != ET_REL || ehdr->e_machine != EM_BPF || ehdr->e_ident[EI_CLASS] != ELFCLASS64) { @@ -1111,6 +1123,27 @@ static bool sec_content_is_same(struct dst_sec *dst_sec, struct src_sec *src_sec return true; } +static bool is_exec_sec(struct dst_sec *sec) +{ + if (!sec || sec->ephemeral) + return false; + return (sec->shdr->sh_type == SHT_PROGBITS) && + (sec->shdr->sh_flags & SHF_EXECINSTR); +} + +static int exec_sec_bswap(void *raw_data, int size) +{ + const int insn_cnt = size / sizeof(struct bpf_insn); + struct bpf_insn *insn = raw_data; + int i; + + if (size % sizeof(struct bpf_insn)) + return -EINVAL; + for (i = 0; i < insn_cnt; i++, insn++) + bpf_insn_bswap(insn); + return 0; +} + static int extend_sec(struct bpf_linker *linker, struct dst_sec *dst, struct src_sec *src) { void *tmp; @@ -1170,6 +1203,16 @@ static int extend_sec(struct bpf_linker *linker, struct dst_sec *dst, struct src memset(dst->raw_data + dst->sec_sz, 0, dst_align_sz - dst->sec_sz); /* now copy src data at a properly aligned offset */ memcpy(dst->raw_data + dst_align_sz, src->data->d_buf, src->shdr->sh_size); + + /* convert added bpf insns to native byte-order */ + if (linker->swapped_endian && is_exec_sec(dst)) { + err = exec_sec_bswap(dst->raw_data + dst_align_sz, + src->shdr->sh_size); + if (err) { + pr_warn("%s: error changing insns endianness\n", __func__); + return err; + } + } } dst->sec_sz = dst_final_sz; @@ -2630,6 +2673,14 @@ int bpf_linker__finalize(struct bpf_linker *linker) if (!sec->scn) continue; + /* restore sections with bpf insns to target byte-order */ + if (linker->swapped_endian && is_exec_sec(sec)) { + err = exec_sec_bswap(sec->raw_data, sec->sec_sz); + if (err) { + pr_warn("error finalizing insns endianness\n"); + return libbpf_err(err); + } + } sec->data->d_buf = sec->raw_data; } @@ -2696,6 +2747,13 @@ static int emit_elf_data_sec(struct bpf_linker *linker, const char *sec_name, return 0; } +static enum btf_endianness +linker_btf_endianness(const struct bpf_linker *linker) +{ + unsigned char byteorder = linker->elf_hdr->e_ident[EI_DATA]; + return byteorder == ELFDATA2MSB ? BTF_BIG_ENDIAN : BTF_LITTLE_ENDIAN; +} + static int finalize_btf(struct bpf_linker *linker) { LIBBPF_OPTS(btf_dedup_opts, opts); @@ -2742,6 +2800,22 @@ static int finalize_btf(struct bpf_linker *linker) return err; } + /* Set .BTF and .BTF.ext output byte order */ + err = btf__set_endianness(linker->btf, + linker_btf_endianness(linker)); + if (err) { + pr_warn("failed to set .BTF output endianness: %d\n", err); + return err; + } + if (linker->btf_ext) { + err = btf_ext__set_endianness(linker->btf_ext, + linker_btf_endianness(linker)); + if (err) { + pr_warn("failed to set .BTF.ext output endianness: %d\n", err); + return err; + } + } + /* Emit .BTF section */ raw_data = btf__raw_data(linker->btf, &raw_sz); if (!raw_data)