Patch "modpost: fix section mismatch message for R_ARM_{PC24,CALL,JUMP24}" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    modpost: fix section mismatch message for R_ARM_{PC24,CALL,JUMP24}

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     modpost-fix-section-mismatch-message-for-r_arm_-pc24.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 4e46ee87aee6f5e11fd3189188c6ef9b63cd319f
Author: Masahiro Yamada <masahiroy@xxxxxxxxxx>
Date:   Thu Jun 1 21:09:56 2023 +0900

    modpost: fix section mismatch message for R_ARM_{PC24,CALL,JUMP24}
    
    [ 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@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index 789e0ddb41ae4..78859ef4e03ad 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -1735,12 +1735,20 @@ 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:
@@ -1750,6 +1758,10 @@ 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: