From a7664973b24a242cd9ea17deb5eaf503065fc0bd Mon Sep 17 00:00:00 2001 From: Jan Beulich Date: Mon, 26 Apr 2021 10:41:35 +0200 Subject: [PATCH] x86: correct overflow checking for 16-bit PC-relative relocs The only insn requiring a truly 16-bit PC-relative relocation outside of 16-bit mode is XBEGIN (with an operand size override). For it, the relocation generated should behave similar to 8- and (for 64-bit) 32-bit PC-relatives ones, i.e. be checked for a signed value to fit the field. This same mode is also correct for 16-bit code. Outside of 16-bit code, branches with operand size overrides act in a truly PC-relative way only when living in the low 32k of address space, as they truncate rIP to 16 bits. This can't be expressed by a PC-relative relocation. Putting in place a new testcase, I'd like to note that the two existing ones (pcrel16 and pcrel16abs) appear to be pretty pointless: They don't expect any error despite supposedly checking for overflow, and in fact there can't possibly be any error for the - former since gas doesn't emit any relocation in the first place there, - latter because the way the relocation gets expressed by gas doesn't allow the linker to notice the overflow; it should be detected by gas if at all, but see above (an error would be reported here for x86-64 afaict, but this test doesn't get re-used there). --- bfd/ChangeLog | 7 +++++++ bfd/elf32-i386.c | 2 +- bfd/elf64-x86-64.c | 2 +- ld/ChangeLog | 7 +++++++ ld/testsuite/ld-i386/i386.exp | 1 + ld/testsuite/ld-i386/pcrel16-2.d | 5 +++++ ld/testsuite/ld-i386/pcrel16-2.s | 12 ++++++++++++ ld/testsuite/ld-x86-64/pcrel16-2.d | 5 +++++ ld/testsuite/ld-x86-64/x86-64.exp | 1 + 9 files changed, 40 insertions(+), 2 deletions(-) create mode 100644 ld/testsuite/ld-i386/pcrel16-2.d create mode 100644 ld/testsuite/ld-i386/pcrel16-2.s create mode 100644 ld/testsuite/ld-x86-64/pcrel16-2.d diff --git a/bfd/ChangeLog b/bfd/ChangeLog index 701357c3ad7..45397ef04b9 100644 --- a/bfd/ChangeLog +++ b/bfd/ChangeLog @@ -1,3 +1,10 @@ +2021-04-26 Jan Beulich + + * elf32-i386.c (elf_howto_table): Switch R_386_PC16 to + complain_overflow_signed. + * elf64-x86-64.c (x86_64_elf_howto_table): Switch R_X86_64_PC16 + to complain_overflow_signed. + 2021-04-23 Eric Botcazou * elf.c (special_sections_p): Add .persistent.bss. diff --git a/bfd/elf32-i386.c b/bfd/elf32-i386.c index dee5352a0b6..ffe764422ff 100644 --- a/bfd/elf32-i386.c +++ b/bfd/elf32-i386.c @@ -93,7 +93,7 @@ static reloc_howto_type elf_howto_table[]= HOWTO(R_386_16, 0, 1, 16, false, 0, complain_overflow_bitfield, bfd_elf_generic_reloc, "R_386_16", true, 0xffff, 0xffff, false), - HOWTO(R_386_PC16, 0, 1, 16, true, 0, complain_overflow_bitfield, + HOWTO(R_386_PC16, 0, 1, 16, true, 0, complain_overflow_signed, bfd_elf_generic_reloc, "R_386_PC16", true, 0xffff, 0xffff, true), HOWTO(R_386_8, 0, 0, 8, false, 0, complain_overflow_bitfield, diff --git a/bfd/elf64-x86-64.c b/bfd/elf64-x86-64.c index 1204b29e396..840555c2000 100644 --- a/bfd/elf64-x86-64.c +++ b/bfd/elf64-x86-64.c @@ -82,7 +82,7 @@ static reloc_howto_type x86_64_elf_howto_table[] = false), HOWTO(R_X86_64_16, 0, 1, 16, false, 0, complain_overflow_bitfield, bfd_elf_generic_reloc, "R_X86_64_16", false, 0xffff, 0xffff, false), - HOWTO(R_X86_64_PC16,0, 1, 16, true, 0, complain_overflow_bitfield, + HOWTO(R_X86_64_PC16, 0, 1, 16, true, 0, complain_overflow_signed, bfd_elf_generic_reloc, "R_X86_64_PC16", false, 0xffff, 0xffff, true), HOWTO(R_X86_64_8, 0, 0, 8, false, 0, complain_overflow_bitfield, bfd_elf_generic_reloc, "R_X86_64_8", false, 0xff, 0xff, false), diff --git a/ld/ChangeLog b/ld/ChangeLog index b736aa805de..9bb178e4248 100644 --- a/ld/ChangeLog +++ b/ld/ChangeLog @@ -1,3 +1,10 @@ +2021-04-26 Jan Beulich + + * testsuite/ld-i386/pcrel16-2.s, testsuite/ld-i386/pcrel16-2.d, + testsuite/ld-x86-64/pcrel16-2.d: New. + * testsuite/ld-i386/i386.exp: Run new test. + * testsuite/ld-x86-64/x86-64.exp: Likewise. + 2021-04-23 H.J. Lu PR ld/27771 diff --git a/ld/testsuite/ld-i386/i386.exp b/ld/testsuite/ld-i386/i386.exp index 6ad69a818f5..d0b3f69fb8d 100644 --- a/ld/testsuite/ld-i386/i386.exp +++ b/ld/testsuite/ld-i386/i386.exp @@ -297,6 +297,7 @@ run_dump_test "abs" run_dump_test "pcrel8" run_dump_test "pcrel16" run_dump_test "pcrel16abs" +run_dump_test "pcrel16-2" run_dump_test "alloc" run_dump_test "warn1" run_dump_test "tlsgd2" diff --git a/ld/testsuite/ld-i386/pcrel16-2.d b/ld/testsuite/ld-i386/pcrel16-2.d new file mode 100644 index 00000000000..c1c340fc75c --- /dev/null +++ b/ld/testsuite/ld-i386/pcrel16-2.d @@ -0,0 +1,5 @@ +#name: PCREL16 overflow (2) +#as: --32 +#ld: -melf_i386 +#error: .*relocation truncated to fit: R_386_PC16 .*t16.* +#error: .*relocation truncated to fit: R_386_PC16 .*_start.* diff --git a/ld/testsuite/ld-i386/pcrel16-2.s b/ld/testsuite/ld-i386/pcrel16-2.s new file mode 100644 index 00000000000..2e974175ae8 --- /dev/null +++ b/ld/testsuite/ld-i386/pcrel16-2.s @@ -0,0 +1,12 @@ + .text + .global _start +_start: + data16 xbegin t16 + ret + + .fill 0x8000,1,0xcc + + .global t16 +t16: + data16 xbegin _start + ret diff --git a/ld/testsuite/ld-x86-64/pcrel16-2.d b/ld/testsuite/ld-x86-64/pcrel16-2.d new file mode 100644 index 00000000000..5346a5b619d --- /dev/null +++ b/ld/testsuite/ld-x86-64/pcrel16-2.d @@ -0,0 +1,5 @@ +#name: PCREL16 overflow (2) +#source: ../ld-i386/pcrel16-2.s +#ld: +#error: .*relocation truncated to fit: R_X86_64_PC16 .*t16.* +#error: .*relocation truncated to fit: R_X86_64_PC16 .*_start.* diff --git a/ld/testsuite/ld-x86-64/x86-64.exp b/ld/testsuite/ld-x86-64/x86-64.exp index 877d6ba5fa4..269f70d05b2 100644 --- a/ld/testsuite/ld-x86-64/x86-64.exp +++ b/ld/testsuite/ld-x86-64/x86-64.exp @@ -261,6 +261,7 @@ run_dump_test "abs-l1om" run_dump_test "apic" run_dump_test "pcrel8" run_dump_test "pcrel16" +run_dump_test "pcrel16-2" run_dump_test "tlsgd2" run_dump_test "tlsgd3" run_dump_test "tlsgd12" -- 2.39.5