From 3310bae805250aec227eb056e8e61a246678f28a Mon Sep 17 00:00:00 2001 From: Masahiro Yamada Date: Thu, 1 Jun 2023 21:10:00 +0900 Subject: modpost: fix section_mismatch message for R_ARM_THM_{CALL,JUMP24,JUMP19} MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit addend_arm_rel() processes R_ARM_THM_CALL, R_ARM_THM_JUMP24, R_ARM_THM_JUMP19 in a wrong way. Here, test code. [test code for R_ARM_THM_JUMP24]   .section .init.text,"ax"   bar:           bx      lr   .section .text,"ax"   .globl foo   foo:           b       bar [test code for R_ARM_THM_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 CONFIG_THUMB2_KERNEL=y, 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 checked arch/arm/kernel/module.c to learn the encoding of R_ARM_THM_CALL and R_ARM_THM_JUMP24. The module does not support R_ARM_THM_JUMP19, but I checked its encoding in ARM ARM. The '+4' 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: c9698e5cd6ad ("ARM: 7964/1: Detect section mismatches in thumb relocations") Signed-off-by: Masahiro Yamada --- scripts/mod/modpost.c | 53 +++++++++++++++++++++++++++++++++++++++++++++------ 1 file changed, 47 insertions(+), 6 deletions(-) (limited to 'scripts/mod/modpost.c') diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c index ec16f4d7e55a..4e911ab711d4 100644 --- a/scripts/mod/modpost.c +++ b/scripts/mod/modpost.c @@ -1276,7 +1276,7 @@ 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, upper, lower; + uint32_t inst, upper, lower, sign, j1, j2; int32_t offset; switch (r_typ) { @@ -1309,13 +1309,54 @@ static int addend_arm_rel(struct elf_info *elf, Elf_Shdr *sechdr, Elf_Rela *r) 15); r->r_addend = offset + sym->st_value; break; + case R_ARM_THM_JUMP19: + /* + * Encoding T3: + * S = upper[10] + * imm6 = upper[5:0] + * J1 = lower[13] + * J2 = lower[11] + * imm11 = lower[10:0] + * imm32 = SignExtend(S:J2:J1:imm6:imm11:'0') + */ + upper = TO_NATIVE(*(uint16_t *)loc); + lower = TO_NATIVE(*((uint16_t *)loc + 1)); + + sign = (upper >> 10) & 1; + j1 = (lower >> 13) & 1; + j2 = (lower >> 11) & 1; + offset = sign_extend32((sign << 20) | (j2 << 19) | (j1 << 18) | + ((upper & 0x03f) << 12) | + ((lower & 0x07ff) << 1), + 20); + r->r_addend = offset + sym->st_value + 4; + break; case R_ARM_THM_CALL: case R_ARM_THM_JUMP24: - case R_ARM_THM_JUMP19: - /* From ARM ABI: ((S + A) | T) - P */ - r->r_addend = (int)(long)(elf->hdr + - sechdr->sh_offset + - (r->r_offset - sechdr->sh_addr)); + /* + * Encoding T4: + * S = upper[10] + * imm10 = upper[9:0] + * J1 = lower[13] + * J2 = lower[11] + * imm11 = lower[10:0] + * I1 = NOT(J1 XOR S) + * I2 = NOT(J2 XOR S) + * imm32 = SignExtend(S:I1:I2:imm10:imm11:'0') + */ + upper = TO_NATIVE(*(uint16_t *)loc); + lower = TO_NATIVE(*((uint16_t *)loc + 1)); + + sign = (upper >> 10) & 1; + j1 = (lower >> 13) & 1; + j2 = (lower >> 11) & 1; + offset = sign_extend32((sign << 24) | + ((~(j1 ^ sign) & 1) << 23) | + ((~(j2 ^ sign) & 1) << 22) | + ((upper & 0x03ff) << 12) | + ((lower & 0x07ff) << 1), + 24); + r->r_addend = offset + sym->st_value + 4; break; default: return 1; -- cgit