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authorMasahiro Yamada <masahiroy@kernel.org>2023-06-01 15:10:00 +0300
committerMasahiro Yamada <masahiroy@kernel.org>2023-06-03 19:37:41 +0300
commit3310bae805250aec227eb056e8e61a246678f28a (patch)
tree2c215ea037e2e40865bd4169eb1b185dc4234b8f /scripts/mod/modpost.c
parentcd1824fb7a377882497e8b87a6f3a9ec19be3623 (diff)
downloadlinux-3310bae805250aec227eb056e8e61a246678f28a.tar.xz
modpost: fix section_mismatch message for R_ARM_THM_{CALL,JUMP24,JUMP19}
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 <masahiroy@kernel.org>
Diffstat (limited to 'scripts/mod/modpost.c')
-rw-r--r--scripts/mod/modpost.c53
1 files changed, 47 insertions, 6 deletions
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;