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| author | Jens Remus <jremus@linux.ibm.com> | 2024-07-12 16:53:47 +0200 |
|---|---|---|
| committer | Jens Remus <jremus@linux.ibm.com> | 2024-07-12 16:53:47 +0200 |
| commit | 6f8b365b653dc9a7370b3bb906a945b5bf5f867c (patch) | |
| tree | b4b64b1751dbe4e3b61ed9d9fc1197821f8b799e /bfd | |
| parent | 83511d2679bbcc4b8d6ac42fb71cfbc35e77107e (diff) | |
| download | gdb-6f8b365b653dc9a7370b3bb906a945b5bf5f867c.zip gdb-6f8b365b653dc9a7370b3bb906a945b5bf5f867c.tar.gz gdb-6f8b365b653dc9a7370b3bb906a945b5bf5f867c.tar.bz2 | |
s390: Avoid reloc overflows on undefined weak symbols (cont)
This complements and reuses logic from Andreas Krebbel's commit
896a639babe2 ("s390: Avoid reloc overflows on undefined weak symbols").
Replace relative long addressing instructions of weak symbols, which
will definitely resolve to zero, with either a load address of 0 or a
a trapping insn.
This prevents the PLT32DBL relocation from overflowing in case the
binary will be loaded at 4GB or more.
bfd/
* elf64-s390.c (elf_s390_relocate_section): Replace
instructions using undefined weak symbols with relative
addressing to avoid relocation overflows.
ld/
* testsuite/ld-s390/s390.exp: Add new test.
* testsuite/ld-s390/weakundef-2.s: New test.
* testsuite/ld-s390/weakundef-2.dd: Likewise.
Reported-by: Alexander Gordeev <agordeev@linux.ibm.com>
Suggested-by: Ilya Leoshkevich <iii@linux.ibm.com>
Suggested-by: Andreas Krebbel <krebbel@linux.ibm.com>
Signed-off-by: Jens Remus <jremus@linux.ibm.com>
Diffstat (limited to 'bfd')
| -rw-r--r-- | bfd/elf64-s390.c | 37 |
1 files changed, 37 insertions, 0 deletions
diff --git a/bfd/elf64-s390.c b/bfd/elf64-s390.c index 2f35da4..f9d9902 100644 --- a/bfd/elf64-s390.c +++ b/bfd/elf64-s390.c @@ -2399,6 +2399,43 @@ elf_s390_relocate_section (bfd *output_bfd, /* We didn't make a PLT entry for this symbol. This happens when statically linking PIC code, or when using -Bsymbolic. */ + + /* Replace relative long addressing instructions of weak + symbols, which will definitely resolve to zero, with + either a load address of 0 or a trapping insn. + This prevents the PLT32DBL relocation from overflowing in + case the binary will be loaded at 4GB or more. */ + if (h->root.type == bfd_link_hash_undefweak + && !h->root.linker_def + && (bfd_link_executable (info) + || ELF_ST_VISIBILITY (h->other) != STV_DEFAULT) + && r_type == R_390_PLT32DBL + && rel->r_offset >= 2) + { + void *insn_start = contents + rel->r_offset - 2; + uint16_t op = bfd_get_16 (input_bfd, insn_start) & 0xff0f; + uint8_t reg = bfd_get_8 (input_bfd, insn_start + 1) & 0xf0; + + /* NOTE: The order of the if's is important! */ + /* Replace load address relative long (larl) with load + address (lay) */ + if (op == 0xc000) + { + /* larl rX,<weak sym> -> lay rX,0(0) */ + bfd_put_16 (output_bfd, 0xe300 | reg, insn_start); + bfd_put_32 (output_bfd, 0x71, insn_start + 2); + continue; + } + /* Replace branch relative and save long (brasl) with a trap. */ + else if (op == 0xc005) + { + /* brasl rX,<weak sym> -> jg .+2 (6-byte trap) */ + bfd_put_16 (output_bfd, 0xc0f4, insn_start); + bfd_put_32 (output_bfd, 0x1, insn_start + 2); + continue; + } + } + break; } if (s390_is_ifunc_symbol_p (h)) |