diff options
| author | David Faust <david.faust@oracle.com> | 2020-08-07 20:36:47 +0200 |
|---|---|---|
| committer | Jose E. Marchesi <jose.marchesi@oracle.com> | 2020-08-07 20:36:47 +0200 |
| commit | d844f10ac2735da8e5643236d7007a81098cbc2b (patch) | |
| tree | 540b048e134ea051c03c1876ee87340bb1081e0b /bfd/elf64-bpf.c | |
| parent | fe4c3d430b39d4a8760702c4ecc9e4c1803cb077 (diff) | |
| download | binutils-gdb-d844f10ac2735da8e5643236d7007a81098cbc2b.tar.gz | |
bpf: fix false overflow in eBPF ELF backend linker
When performing DISP{16,32} relocations, the eBPF ELF backend linker
needs to convert the relocation from an address into a signed number
of 64-bit words (minus one) to jump.
Because of this unsigned-to-signed conversion, special care needs to
be taken when dividing to ensure the sign bits remain correct.
Otherwise, a false relocation overflow error can be triggered.
bfd/ChangeLog
2020-08-07 David Faust <david.faust@oracle.com>
* elf64-bpf.c (bpf_elf_relocate_section): Ensure signed division for
DISP16 and DISP32 relocations.
ld/ChangeLog
2020-08-07 David Faust <david.faust@oracle.com>
* testsuite/ld-bpf/call-3.s: New file.
* testsuite/ld-bpf/call-3.d: Likewise.
Diffstat (limited to 'bfd/elf64-bpf.c')
| -rw-r--r-- | bfd/elf64-bpf.c | 9 |
1 files changed, 5 insertions, 4 deletions
diff --git a/bfd/elf64-bpf.c b/bfd/elf64-bpf.c index c6a726d9324..d5a160f8f14 100644 --- a/bfd/elf64-bpf.c +++ b/bfd/elf64-bpf.c @@ -442,10 +442,11 @@ bpf_elf_relocate_section (bfd *output_bfd ATTRIBUTE_UNUSED, case R_BPF_INSN_DISP32: { /* Make the relocation PC-relative, and change its unit to - 64-bit words. */ - relocation -= sec_addr (input_section) + rel->r_offset; - /* Make it 64-bit words. */ - relocation = relocation / 8; + 64-bit words. Note we need *signed* arithmetic + here. */ + relocation = ((bfd_signed_vma) relocation + - (sec_addr (input_section) + rel->r_offset)); + relocation = (bfd_signed_vma) relocation / 8; /* Get the addend from the instruction and apply it. */ addend = bfd_get (howto->bitsize, input_bfd, |