| Message ID | 20230515005419.1293357-1-masahiroy@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | modpost: fix section mismatch message for R_ARM_ABS32 | expand |
On Sun, May 14, 2023 at 5:54 PM Masahiro Yamada <masahiroy@kernel.org> wrote: > > The section mismatch check does not show proper warning messages for ARM. > > Here, very simple test code. > > #include <linux/init.h> > > static int __initdata foo; > > void set_foo(int x) > { > foo = x; > } > > int get_foo(int x) > { > return foo; > } > > If I compile it for ARM, modpost does not show the symbol name. > > WARNING: modpost: vmlinux.o: section mismatch in reference: set_foo (section: .text) -> (unknown) (section: .init.data) > WARNING: modpost: vmlinux.o: section mismatch in reference: get_foo (section: .text) -> (unknown) (section: .init.data) > > If I compile it for other architectures, modpost shows the correct symbol name. > > WARNING: modpost: vmlinux.o: section mismatch in reference: set_foo (section: .text) -> foo (section: .init.data) > WARNING: modpost: vmlinux.o: section mismatch in reference: get_foo (section: .text) -> foo (section: .init.data) > > For R_ARM_ABS32, addend_arm_rel() sets r->r_addend to a wrong value. > > arch/arm/kernel/module.c handles R_ARM_ABS32 as follows: > > case R_ARM_ABS32: > case R_ARM_TARGET1: > *(u32 *)loc += sym->st_value; > > I just mimicked it in modpost. > > Fixes: 56a974fa2d59 ("kbuild: make better section mismatch reports on arm") > Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> > --- > > scripts/mod/modpost.c | 7 ++++--- > 1 file changed, 4 insertions(+), 3 deletions(-) > > diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c > index d4531d09984d..c93780d93caf 100644 > --- a/scripts/mod/modpost.c > +++ b/scripts/mod/modpost.c > @@ -1460,12 +1460,13 @@ static int addend_386_rel(struct elf_info *elf, Elf_Shdr *sechdr, Elf_Rela *r) > static int addend_arm_rel(struct elf_info *elf, Elf_Shdr *sechdr, Elf_Rela *r) > { > unsigned int r_typ = ELF_R_TYPE(r->r_info); > + unsigned int *location = reloc_location(elf, sechdr, r); If `location` is only used in one case of the switch, consider computing `location` only in that case. > + Elf_Sym *sym; > > switch (r_typ) { > case R_ARM_ABS32: > - /* From ARM ABI: (S + A) | T */ > - r->r_addend = (int)(long) > - (elf->symtab_start + ELF_R_SYM(r->r_info)); > + sym = elf->symtab_start + ELF_R_SYM(r->r_info); > + r->r_addend = TO_NATIVE(*location) + sym->st_value; > break; > case R_ARM_PC24: > case R_ARM_CALL: > -- > 2.39.2 >
On Thu, May 18, 2023 at 6:41 AM Nick Desaulniers <ndesaulniers@google.com> wrote: > > On Sun, May 14, 2023 at 5:54 PM Masahiro Yamada <masahiroy@kernel.org> wrote: > > > > The section mismatch check does not show proper warning messages for ARM. > > > > Here, very simple test code. > > > > #include <linux/init.h> > > > > static int __initdata foo; > > > > void set_foo(int x) > > { > > foo = x; > > } > > > > int get_foo(int x) > > { > > return foo; > > } > > > > If I compile it for ARM, modpost does not show the symbol name. > > > > WARNING: modpost: vmlinux.o: section mismatch in reference: set_foo (section: .text) -> (unknown) (section: .init.data) > > WARNING: modpost: vmlinux.o: section mismatch in reference: get_foo (section: .text) -> (unknown) (section: .init.data) > > > > If I compile it for other architectures, modpost shows the correct symbol name. > > > > WARNING: modpost: vmlinux.o: section mismatch in reference: set_foo (section: .text) -> foo (section: .init.data) > > WARNING: modpost: vmlinux.o: section mismatch in reference: get_foo (section: .text) -> foo (section: .init.data) > > > > For R_ARM_ABS32, addend_arm_rel() sets r->r_addend to a wrong value. > > > > arch/arm/kernel/module.c handles R_ARM_ABS32 as follows: > > > > case R_ARM_ABS32: > > case R_ARM_TARGET1: > > *(u32 *)loc += sym->st_value; > > > > I just mimicked it in modpost. > > > > Fixes: 56a974fa2d59 ("kbuild: make better section mismatch reports on arm") > > Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> > > --- > > > > scripts/mod/modpost.c | 7 ++++--- > > 1 file changed, 4 insertions(+), 3 deletions(-) > > > > diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c > > index d4531d09984d..c93780d93caf 100644 > > --- a/scripts/mod/modpost.c > > +++ b/scripts/mod/modpost.c > > @@ -1460,12 +1460,13 @@ static int addend_386_rel(struct elf_info *elf, Elf_Shdr *sechdr, Elf_Rela *r) > > static int addend_arm_rel(struct elf_info *elf, Elf_Shdr *sechdr, Elf_Rela *r) > > { > > unsigned int r_typ = ELF_R_TYPE(r->r_info); > > + unsigned int *location = reloc_location(elf, sechdr, r); > > If `location` is only used in one case of the switch, consider > computing `location` only in that case. I really suspect the other case labels are also wrong. For example, see R_ARM_PC24 in arch/arm/kernel/module.c The offset is encoded in the instruction. If you can compute the addend without reading the instruction, I do not know how. Anyway, I will fix another breakage. It will need 'location' as well. > > > + Elf_Sym *sym; > > > > switch (r_typ) { > > case R_ARM_ABS32: > > - /* From ARM ABI: (S + A) | T */ > > - r->r_addend = (int)(long) > > - (elf->symtab_start + ELF_R_SYM(r->r_info)); > > + sym = elf->symtab_start + ELF_R_SYM(r->r_info); > > + r->r_addend = TO_NATIVE(*location) + sym->st_value; > > break; > > case R_ARM_PC24: > > case R_ARM_CALL: > > -- > > 2.39.2 > > > > > -- > Thanks, > ~Nick Desaulniers
diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c index d4531d09984d..c93780d93caf 100644 --- a/scripts/mod/modpost.c +++ b/scripts/mod/modpost.c @@ -1460,12 +1460,13 @@ static int addend_386_rel(struct elf_info *elf, Elf_Shdr *sechdr, Elf_Rela *r) static int addend_arm_rel(struct elf_info *elf, Elf_Shdr *sechdr, Elf_Rela *r) { unsigned int r_typ = ELF_R_TYPE(r->r_info); + unsigned int *location = reloc_location(elf, sechdr, r); + Elf_Sym *sym; switch (r_typ) { case R_ARM_ABS32: - /* From ARM ABI: (S + A) | T */ - r->r_addend = (int)(long) - (elf->symtab_start + ELF_R_SYM(r->r_info)); + sym = elf->symtab_start + ELF_R_SYM(r->r_info); + r->r_addend = TO_NATIVE(*location) + sym->st_value; break; case R_ARM_PC24: case R_ARM_CALL:
The section mismatch check does not show proper warning messages for ARM. Here, very simple test code. #include <linux/init.h> static int __initdata foo; void set_foo(int x) { foo = x; } int get_foo(int x) { return foo; } If I compile it for ARM, modpost does not show the symbol name. WARNING: modpost: vmlinux.o: section mismatch in reference: set_foo (section: .text) -> (unknown) (section: .init.data) WARNING: modpost: vmlinux.o: section mismatch in reference: get_foo (section: .text) -> (unknown) (section: .init.data) If I compile it for other architectures, modpost shows the correct symbol name. WARNING: modpost: vmlinux.o: section mismatch in reference: set_foo (section: .text) -> foo (section: .init.data) WARNING: modpost: vmlinux.o: section mismatch in reference: get_foo (section: .text) -> foo (section: .init.data) For R_ARM_ABS32, addend_arm_rel() sets r->r_addend to a wrong value. arch/arm/kernel/module.c handles R_ARM_ABS32 as follows: case R_ARM_ABS32: case R_ARM_TARGET1: *(u32 *)loc += sym->st_value; I just mimicked it in modpost. Fixes: 56a974fa2d59 ("kbuild: make better section mismatch reports on arm") Signed-off-by: Masahiro Yamada <masahiroy@kernel.org> --- scripts/mod/modpost.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)