From: Masahiro Yamada masahiroy@kernel.org
[ Upstream commit 56a24b8ce6a7f9c4a21b2276a8644f6f3d8fc14d ]
addend_arm_rel() processes R_ARM_PC24, R_ARM_CALL, R_ARM_JUMP24 in a wrong way.
Here, test code.
[test code for R_ARM_JUMP24]
.section .init.text,"ax" bar: bx lr
.section .text,"ax" .globl foo foo: b bar
[test code for R_ARM_CALL]
.section .init.text,"ax" bar: bx lr
.section .text,"ax" .globl foo foo: push {lr} bl bar pop {pc}
If you compile it with ARM multi_v7_defconfig, modpost will show the symbol name, (unknown).
WARNING: modpost: vmlinux.o: section mismatch in reference: foo (section: .text) -> (unknown) (section: .init.text)
(You need to use GNU linker instead of LLD to reproduce it.)
Fix the code to make modpost show the correct symbol name.
I imported (with adjustment) sign_extend32() from include/linux/bitops.h.
The '+8' is the compensation for pc-relative instruction. It is documented in "ELF for the Arm Architecture" [1].
"If the relocation is pc-relative then compensation for the PC bias (the PC value is 8 bytes ahead of the executing instruction in Arm state and 4 bytes in Thumb state) must be encoded in the relocation by the object producer."
[1]: https://github.com/ARM-software/abi-aa/blob/main/aaelf32/aaelf32.rst
Fixes: 56a974fa2d59 ("kbuild: make better section mismatch reports on arm") Fixes: 6e2e340b59d2 ("ARM: 7324/1: modpost: Fix section warnings for ARM for many compilers") Signed-off-by: Masahiro Yamada masahiroy@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- scripts/mod/modpost.c | 12 ++++++++++++ 1 file changed, 12 insertions(+)
diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c index f7a67f111d846..9e370e77f52d1 100644 --- a/scripts/mod/modpost.c +++ b/scripts/mod/modpost.c @@ -1419,12 +1419,20 @@ static int addend_386_rel(struct elf_info *elf, Elf_Shdr *sechdr, Elf_Rela *r) #define R_ARM_THM_JUMP19 51 #endif
+static int32_t sign_extend32(int32_t value, int index) +{ + uint8_t shift = 31 - index; + + return (int32_t)(value << shift) >> shift; +} + 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); Elf_Sym *sym = elf->symtab_start + ELF_R_SYM(r->r_info); void *loc = reloc_location(elf, sechdr, r); uint32_t inst; + int32_t offset;
switch (r_typ) { case R_ARM_ABS32: @@ -1434,6 +1442,10 @@ static int addend_arm_rel(struct elf_info *elf, Elf_Shdr *sechdr, Elf_Rela *r) case R_ARM_PC24: case R_ARM_CALL: case R_ARM_JUMP24: + inst = TO_NATIVE(*(uint32_t *)loc); + offset = sign_extend32((inst & 0x00ffffff) << 2, 25); + r->r_addend = offset + sym->st_value + 8; + break; case R_ARM_THM_CALL: case R_ARM_THM_JUMP24: case R_ARM_THM_JUMP19: