[binutils-gdb] x86: correct overflow checking for 16-bit PC-relative relocs
Jan Beulich
jbeulich@sourceware.org
Mon Apr 26 08:41:53 GMT 2021
https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=a7664973b24a242cd9ea17deb5eaf503065fc0bd
commit a7664973b24a242cd9ea17deb5eaf503065fc0bd
Author: Jan Beulich <jbeulich@suse.com>
Date: Mon Apr 26 10:41:35 2021 +0200
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).
Diff:
---
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(-)
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 <jbeulich@suse.com>
+
+ * 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 <ebotcazou@adacore.com>
* 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 <jbeulich@suse.com>
+
+ * 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 <hongjiu.lu@intel.com>
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"
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