| Message ID | 20230620120521.688124-1-masahiroy@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [1/3] modpost: factor out inst location calculation to section_rel() | expand |
On Tue, Jun 20, 2023 at 5:05 AM Masahiro Yamada <masahiroy@kernel.org> wrote: > > All the addend_*_rel() functions calculate the instruction location in > the same way. > > Factor out the similar code to the caller. Squash reloc_location() too. > > Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> > --- > > scripts/mod/modpost.c | 28 ++++++++++++---------------- > 1 file changed, 12 insertions(+), 16 deletions(-) > > diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c > index 6e0b8be32648..2551ac9d5bd3 100644 > --- a/scripts/mod/modpost.c > +++ b/scripts/mod/modpost.c > @@ -1256,16 +1256,9 @@ static void check_section_mismatch(struct module *mod, struct elf_info *elf, > tosec, taddr); > } > > -static unsigned int *reloc_location(struct elf_info *elf, > - Elf_Shdr *sechdr, Elf_Rela *r) > -{ > - return sym_get_data_by_offset(elf, sechdr->sh_info, r->r_offset); > -} > - > -static int addend_386_rel(struct elf_info *elf, Elf_Shdr *sechdr, Elf_Rela *r) > +static int addend_386_rel(uint32_t *location, Elf_Rela *r) > { > unsigned int r_typ = ELF_R_TYPE(r->r_info); > - unsigned int *location = reloc_location(elf, sechdr, r); > > switch (r_typ) { > case R_386_32: > @@ -1302,11 +1295,10 @@ static int32_t sign_extend32(int32_t value, int index) > return (int32_t)(value << shift) >> shift; > } > > -static int addend_arm_rel(struct elf_info *elf, Elf_Shdr *sechdr, Elf_Rela *r) > +static int addend_arm_rel(void *loc, struct elf_info *elf, Elf_Rela *r) > { > unsigned int r_typ = ELF_R_TYPE(r->r_info); > Elf_Sym *sym = elf->symtab_start + ELF_R_SYM(r->r_info); > - void *loc = reloc_location(elf, sechdr, r); > uint32_t inst, upper, lower, sign, j1, j2; > int32_t offset; > > @@ -1396,11 +1388,10 @@ static int addend_arm_rel(struct elf_info *elf, Elf_Shdr *sechdr, Elf_Rela *r) > return 0; > } > > -static int addend_mips_rel(struct elf_info *elf, Elf_Shdr *sechdr, Elf_Rela *r) > +static int addend_mips_rel(uint32_t *location, Elf_Rela *r) > { > unsigned int r_typ = ELF_R_TYPE(r->r_info); > - unsigned int *location = reloc_location(elf, sechdr, r); > - unsigned int inst; > + uint32_t inst; > > if (r_typ == R_MIPS_HI16) > return 1; /* skip this */ > @@ -1502,6 +1493,8 @@ static void section_rel(struct module *mod, struct elf_info *elf, > return; > > for (rel = start; rel < stop; rel++) { > + void *loc; > + > r.r_offset = TO_NATIVE(rel->r_offset); > #if KERNEL_ELFCLASS == ELFCLASS64 > if (elf->hdr->e_machine == EM_MIPS) { > @@ -1519,17 +1512,20 @@ static void section_rel(struct module *mod, struct elf_info *elf, > r_sym = ELF_R_SYM(r.r_info); > #endif > r.r_addend = 0; > + > + loc = sym_get_data_by_offset(elf, fsecndx, r.r_offset); Can we compute `loc` only for the three machine types? > + > switch (elf->hdr->e_machine) { > case EM_386: > - if (addend_386_rel(elf, sechdr, &r)) > + if (addend_386_rel(loc, &r)) > continue; > break; > case EM_ARM: > - if (addend_arm_rel(elf, sechdr, &r)) > + if (addend_arm_rel(loc, elf, &r)) > continue; > break; > case EM_MIPS: > - if (addend_mips_rel(elf, sechdr, &r)) > + if (addend_mips_rel(loc, &r)) > continue; > break; > default: > -- > 2.39.2 >
On Fri, Jun 23, 2023 at 3:25 AM Nick Desaulniers <ndesaulniers@google.com> wrote: > > On Tue, Jun 20, 2023 at 5:05 AM Masahiro Yamada <masahiroy@kernel.org> wrote: > > > > All the addend_*_rel() functions calculate the instruction location in > > the same way. > > > > Factor out the similar code to the caller. Squash reloc_location() too. > > > > Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> > > --- > > > > scripts/mod/modpost.c | 28 ++++++++++++---------------- > > 1 file changed, 12 insertions(+), 16 deletions(-) > > > > diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c > > index 6e0b8be32648..2551ac9d5bd3 100644 > > --- a/scripts/mod/modpost.c > > +++ b/scripts/mod/modpost.c > > @@ -1256,16 +1256,9 @@ static void check_section_mismatch(struct module *mod, struct elf_info *elf, > > tosec, taddr); > > } > > > > -static unsigned int *reloc_location(struct elf_info *elf, > > - Elf_Shdr *sechdr, Elf_Rela *r) > > -{ > > - return sym_get_data_by_offset(elf, sechdr->sh_info, r->r_offset); > > -} > > - > > -static int addend_386_rel(struct elf_info *elf, Elf_Shdr *sechdr, Elf_Rela *r) > > +static int addend_386_rel(uint32_t *location, Elf_Rela *r) > > { > > unsigned int r_typ = ELF_R_TYPE(r->r_info); > > - unsigned int *location = reloc_location(elf, sechdr, r); > > > > switch (r_typ) { > > case R_386_32: > > @@ -1302,11 +1295,10 @@ static int32_t sign_extend32(int32_t value, int index) > > return (int32_t)(value << shift) >> shift; > > } > > > > -static int addend_arm_rel(struct elf_info *elf, Elf_Shdr *sechdr, Elf_Rela *r) > > +static int addend_arm_rel(void *loc, struct elf_info *elf, Elf_Rela *r) > > { > > unsigned int r_typ = ELF_R_TYPE(r->r_info); > > Elf_Sym *sym = elf->symtab_start + ELF_R_SYM(r->r_info); > > - void *loc = reloc_location(elf, sechdr, r); > > uint32_t inst, upper, lower, sign, j1, j2; > > int32_t offset; > > > > @@ -1396,11 +1388,10 @@ static int addend_arm_rel(struct elf_info *elf, Elf_Shdr *sechdr, Elf_Rela *r) > > return 0; > > } > > > > -static int addend_mips_rel(struct elf_info *elf, Elf_Shdr *sechdr, Elf_Rela *r) > > +static int addend_mips_rel(uint32_t *location, Elf_Rela *r) > > { > > unsigned int r_typ = ELF_R_TYPE(r->r_info); > > - unsigned int *location = reloc_location(elf, sechdr, r); > > - unsigned int inst; > > + uint32_t inst; > > > > if (r_typ == R_MIPS_HI16) > > return 1; /* skip this */ > > @@ -1502,6 +1493,8 @@ static void section_rel(struct module *mod, struct elf_info *elf, > > return; > > > > for (rel = start; rel < stop; rel++) { > > + void *loc; > > + > > r.r_offset = TO_NATIVE(rel->r_offset); > > #if KERNEL_ELFCLASS == ELFCLASS64 > > if (elf->hdr->e_machine == EM_MIPS) { > > @@ -1519,17 +1512,20 @@ static void section_rel(struct module *mod, struct elf_info *elf, > > r_sym = ELF_R_SYM(r.r_info); > > #endif > > r.r_addend = 0; > > + > > + loc = sym_get_data_by_offset(elf, fsecndx, r.r_offset); > > Can we compute `loc` only for the three machine types? I believe you can compute the location in the same way for any architecture because it is mentioned in ELF spec. https://refspecs.linuxfoundation.org/elf/elf.pdf Page 36. r_offset This member gives the location at which to apply the relocation action. For a relocatable file, the value is the byte offset from the beginning of the section to the storage unit affected by the relocation.
On Thu, Jun 22, 2023 at 10:38 PM Masahiro Yamada <masahiroy@kernel.org> wrote: > > On Fri, Jun 23, 2023 at 3:25 AM Nick Desaulniers > <ndesaulniers@google.com> wrote: > > > > On Tue, Jun 20, 2023 at 5:05 AM Masahiro Yamada <masahiroy@kernel.org> wrote: > > > > > > diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c > > > index 6e0b8be32648..2551ac9d5bd3 100644 > > > --- a/scripts/mod/modpost.c > > > +++ b/scripts/mod/modpost.c > > > @@ -1519,17 +1512,20 @@ static void section_rel(struct module *mod, struct elf_info *elf, > > > r_sym = ELF_R_SYM(r.r_info); > > > #endif > > > r.r_addend = 0; > > > + > > > + loc = sym_get_data_by_offset(elf, fsecndx, r.r_offset); > > > > Can we compute `loc` only for the three machine types? > > > > I believe you can compute the location in the same way for any architecture > because it is mentioned in ELF spec. Sure, but perhaps it's wasted work for other machine types?
On Sat, Jun 24, 2023 at 2:01 AM Nick Desaulniers <ndesaulniers@google.com> wrote: > > On Thu, Jun 22, 2023 at 10:38 PM Masahiro Yamada <masahiroy@kernel.org> wrote: > > > > On Fri, Jun 23, 2023 at 3:25 AM Nick Desaulniers > > <ndesaulniers@google.com> wrote: > > > > > > On Tue, Jun 20, 2023 at 5:05 AM Masahiro Yamada <masahiroy@kernel.org> wrote: > > > > > > > > diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c > > > > index 6e0b8be32648..2551ac9d5bd3 100644 > > > > --- a/scripts/mod/modpost.c > > > > +++ b/scripts/mod/modpost.c > > > > @@ -1519,17 +1512,20 @@ static void section_rel(struct module *mod, struct elf_info *elf, > > > > r_sym = ELF_R_SYM(r.r_info); > > > > #endif > > > > r.r_addend = 0; > > > > + > > > > + loc = sym_get_data_by_offset(elf, fsecndx, r.r_offset); > > > > > > Can we compute `loc` only for the three machine types? > > > > > > > > I believe you can compute the location in the same way for any architecture > > because it is mentioned in ELF spec. > > Sure, but perhaps it's wasted work for other machine types? I guess you missed the following code: switch (elf->hdr->e_machine) { case EM_386: ... break; case EM_ARM: ... break; case EM_MIPS: ... break; default: fatal("Please add code to calculate addend for this architecture\n"); } I believe other machines never call this function. If it occurred, fatal() would immediately errors out, but I have not heard such a breakage for far. I believe only i386, mips and arm use REL. The other architectures are RELA.
diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c index 6e0b8be32648..2551ac9d5bd3 100644 --- a/scripts/mod/modpost.c +++ b/scripts/mod/modpost.c @@ -1256,16 +1256,9 @@ static void check_section_mismatch(struct module *mod, struct elf_info *elf, tosec, taddr); } -static unsigned int *reloc_location(struct elf_info *elf, - Elf_Shdr *sechdr, Elf_Rela *r) -{ - return sym_get_data_by_offset(elf, sechdr->sh_info, r->r_offset); -} - -static int addend_386_rel(struct elf_info *elf, Elf_Shdr *sechdr, Elf_Rela *r) +static int addend_386_rel(uint32_t *location, Elf_Rela *r) { unsigned int r_typ = ELF_R_TYPE(r->r_info); - unsigned int *location = reloc_location(elf, sechdr, r); switch (r_typ) { case R_386_32: @@ -1302,11 +1295,10 @@ static int32_t sign_extend32(int32_t value, int index) return (int32_t)(value << shift) >> shift; } -static int addend_arm_rel(struct elf_info *elf, Elf_Shdr *sechdr, Elf_Rela *r) +static int addend_arm_rel(void *loc, struct elf_info *elf, Elf_Rela *r) { unsigned int r_typ = ELF_R_TYPE(r->r_info); Elf_Sym *sym = elf->symtab_start + ELF_R_SYM(r->r_info); - void *loc = reloc_location(elf, sechdr, r); uint32_t inst, upper, lower, sign, j1, j2; int32_t offset; @@ -1396,11 +1388,10 @@ static int addend_arm_rel(struct elf_info *elf, Elf_Shdr *sechdr, Elf_Rela *r) return 0; } -static int addend_mips_rel(struct elf_info *elf, Elf_Shdr *sechdr, Elf_Rela *r) +static int addend_mips_rel(uint32_t *location, Elf_Rela *r) { unsigned int r_typ = ELF_R_TYPE(r->r_info); - unsigned int *location = reloc_location(elf, sechdr, r); - unsigned int inst; + uint32_t inst; if (r_typ == R_MIPS_HI16) return 1; /* skip this */ @@ -1502,6 +1493,8 @@ static void section_rel(struct module *mod, struct elf_info *elf, return; for (rel = start; rel < stop; rel++) { + void *loc; + r.r_offset = TO_NATIVE(rel->r_offset); #if KERNEL_ELFCLASS == ELFCLASS64 if (elf->hdr->e_machine == EM_MIPS) { @@ -1519,17 +1512,20 @@ static void section_rel(struct module *mod, struct elf_info *elf, r_sym = ELF_R_SYM(r.r_info); #endif r.r_addend = 0; + + loc = sym_get_data_by_offset(elf, fsecndx, r.r_offset); + switch (elf->hdr->e_machine) { case EM_386: - if (addend_386_rel(elf, sechdr, &r)) + if (addend_386_rel(loc, &r)) continue; break; case EM_ARM: - if (addend_arm_rel(elf, sechdr, &r)) + if (addend_arm_rel(loc, elf, &r)) continue; break; case EM_MIPS: - if (addend_mips_rel(elf, sechdr, &r)) + if (addend_mips_rel(loc, &r)) continue; break; default:
All the addend_*_rel() functions calculate the instruction location in the same way. Factor out the similar code to the caller. Squash reloc_location() too. Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> --- scripts/mod/modpost.c | 28 ++++++++++++---------------- 1 file changed, 12 insertions(+), 16 deletions(-)