[PATCH v1.1] x86: Do not dump DS/CS segment overrides for branch hints
Borislav Petkov
bp@alien8.de
Sun Nov 29 14:57:33 GMT 2020
From: Borislav Petkov <bp@suse.de>
The previous change
"x86: Ignore CS/DS/ES/SS segment-override prefixes in 64-bit mode"
to ignore segment override prefixes in 64-bit mode lead to dumping
branch hints as excessive prefixes:
ffffffff8109d5a0 <vmx_get_rflags>:
...
ffffffff8109d601: 3e 77 0a ds ja,pt ffffffff8109d60e <vmx_get_rflags+0x6e>
^^^^^
In this particular case, those prefixes are not excessive but are used
to provide branch hints - taken/not-taken - to the CPU.
Assign active_seg_prefix in that particular case to consume them.
gas/
2002-11-29 Borislav Petkov <bp@suse.de>
* testsuite/gas/i386/branch.d: Add new branch insns test.
* testsuite/gas/i386/branch.s: Likewise.
* testsuite/gas/i386/i386.exp: Insert the new branch test.
* testsuite/gas/i386/x86-64-branch.d: Test for branch hints insns.
* testsuite/gas/i386/x86-64-branch.s: Likewise.
* testsuite/gas/i386/ilp32/x86-64-branch.d: Likewise.
opcodes /
2020-11-28 Borislav Petkov <bp@suse.de>
* i386-dis.c (print_insn): Set active_seg_prefix for branch hint insns
to not dump branch hint prefixes 0x2E and 0x3E as unused prefixes.
---
gas/ChangeLog | 9 +++++++++
gas/testsuite/gas/i386/branch.d | 12 ++++++++++++
gas/testsuite/gas/i386/branch.s | 4 ++++
gas/testsuite/gas/i386/i386.exp | 1 +
gas/testsuite/gas/i386/ilp32/x86-64-branch.d | 2 ++
gas/testsuite/gas/i386/x86-64-branch.d | 2 ++
gas/testsuite/gas/i386/x86-64-branch.s | 4 ++++
opcodes/ChangeLog | 5 +++++
opcodes/i386-dis.c | 13 +++++++++++--
9 files changed, 50 insertions(+), 2 deletions(-)
create mode 100644 gas/testsuite/gas/i386/branch.d
create mode 100644 gas/testsuite/gas/i386/branch.s
diff --git a/gas/ChangeLog b/gas/ChangeLog
index 97754267be9b..8d07dc9bbb9a 100644
--- a/gas/ChangeLog
+++ b/gas/ChangeLog
@@ -1,3 +1,12 @@
+2002-11-29 Borislav Petkov <bp@suse.de>
+
+ * testsuite/gas/i386/branch.d: Add new branch insns test.
+ * testsuite/gas/i386/branch.s: Likewise.
+ * testsuite/gas/i386/i386.exp: Insert the new branch test.
+ * testsuite/gas/i386/x86-64-branch.d: Test for branch hints insns.
+ * testsuite/gas/i386/x86-64-branch.s: Likewise.
+ * testsuite/gas/i386/ilp32/x86-64-branch.d: Likewise.
+
2020-11-27 Jozef Lawrynowicz <jozef.l@mittosystems.com>
* testsuite/gas/elf/elf.exp: Run new tests.
diff --git a/gas/testsuite/gas/i386/branch.d b/gas/testsuite/gas/i386/branch.d
new file mode 100644
index 000000000000..6d25b950830f
--- /dev/null
+++ b/gas/testsuite/gas/i386/branch.d
@@ -0,0 +1,12 @@
+#as: -J
+#objdump: -dw
+#name: i386 branch
+
+.*: +file format .*
+
+Disassembly of section .text:
+
+0+ <.text>:
+[ ]*[a-f0-9]+: 3e 74 03[ ]+je,pt +0x[0-9a-f]+
+[ ]*[a-f0-9]+: 2e 74 00[ ]+je,pn +0x[0-9a-f]+
+#pass
diff --git a/gas/testsuite/gas/i386/branch.s b/gas/testsuite/gas/i386/branch.s
new file mode 100644
index 000000000000..968a1818970f
--- /dev/null
+++ b/gas/testsuite/gas/i386/branch.s
@@ -0,0 +1,4 @@
+.text
+ jz,pt .Llabel
+ jz,pn .Llabel
+.Llabel:
diff --git a/gas/testsuite/gas/i386/i386.exp b/gas/testsuite/gas/i386/i386.exp
index c85ced1c9181..432cf0192d49 100644
--- a/gas/testsuite/gas/i386/i386.exp
+++ b/gas/testsuite/gas/i386/i386.exp
@@ -565,6 +565,7 @@ if [gas_32_check] then {
run_dump_test "lfence-ret-c"
run_dump_test "lfence-ret-d"
run_dump_test "lfence-byte"
+ run_dump_test "branch"
# These tests require support for 8 and 16 bit relocs,
# so we only run them for ELF and COFF targets.
diff --git a/gas/testsuite/gas/i386/ilp32/x86-64-branch.d b/gas/testsuite/gas/i386/ilp32/x86-64-branch.d
index 8be91de922f3..d5f2358546fc 100644
--- a/gas/testsuite/gas/i386/ilp32/x86-64-branch.d
+++ b/gas/testsuite/gas/i386/ilp32/x86-64-branch.d
@@ -25,6 +25,8 @@ Disassembly of section .text:
[ ]*[a-f0-9]+: 66 0f 82 00 00 00 00 data16 jb 0x37 33: R_X86_64_PLT32 foo-0x4
[ ]*[a-f0-9]+: 66 c3 data16 ret *
[ ]*[a-f0-9]+: 66 c2 08 00 data16 ret \$0x8
+[ ]*[a-f0-9]+: 3e 74 03[ ]+je,pt +0x[0-9a-f]+
+[ ]*[a-f0-9]+: 2e 74 00[ ]+je,pn +0x[0-9a-f]+
[ ]*[a-f0-9]+: ff d0 call \*%rax
[ ]*[a-f0-9]+: ff d0 call \*%rax
[ ]*[a-f0-9]+: 66 ff d0 data16 call \*%rax
diff --git a/gas/testsuite/gas/i386/x86-64-branch.d b/gas/testsuite/gas/i386/x86-64-branch.d
index 2618134b4011..b963f9f051e4 100644
--- a/gas/testsuite/gas/i386/x86-64-branch.d
+++ b/gas/testsuite/gas/i386/x86-64-branch.d
@@ -24,6 +24,8 @@ Disassembly of section .text:
[ ]*[a-f0-9]+: 66 0f 82 00 00 00 00 data16 jb (0x37|37 <.text\+0x37>)
[ ]*[a-f0-9]+: 66 c3 data16 ret *
[ ]*[a-f0-9]+: 66 c2 08 00 data16 ret \$0x8
+[ ]*[a-f0-9]+: 3e 74 03[ ]+je,pt +0x[0-9a-f]+
+[ ]*[a-f0-9]+: 2e 74 00[ ]+je,pn +0x[0-9a-f]+
[ ]*[a-f0-9]+: ff d0 call \*%rax
[ ]*[a-f0-9]+: ff d0 call \*%rax
[ ]*[a-f0-9]+: 66 ff d0 data16 call \*%rax
diff --git a/gas/testsuite/gas/i386/x86-64-branch.s b/gas/testsuite/gas/i386/x86-64-branch.s
index eb40dd4d4cd1..496e1bb089fb 100644
--- a/gas/testsuite/gas/i386/x86-64-branch.s
+++ b/gas/testsuite/gas/i386/x86-64-branch.s
@@ -22,6 +22,10 @@
retw
retw $8
+ jz,pt .Llabel
+ jz,pn .Llabel
+.Llabel:
+
.intel_syntax noprefix
call rax
callq rax
diff --git a/opcodes/ChangeLog b/opcodes/ChangeLog
index 1e7e40fd9664..02fd2f5b5837 100644
--- a/opcodes/ChangeLog
+++ b/opcodes/ChangeLog
@@ -1,3 +1,8 @@
+2020-11-28 Borislav Petkov <bp@suse.de>
+
+ * i386-dis.c (print_insn): Set active_seg_prefix for branch hint insns
+ to not dump branch hint prefixes 0x2E and 0x3E as unused prefixes.
+
2020-11-16 Przemyslaw Wirkus <przemyslaw.wirkus@arm.com>
* aarch64-tbl.h (FLAGM): Handle for FLAGM feature.
diff --git a/opcodes/i386-dis.c b/opcodes/i386-dis.c
index 58cf001080bc..189dc0d371a9 100644
--- a/opcodes/i386-dis.c
+++ b/opcodes/i386-dis.c
@@ -10910,10 +10910,19 @@ putop (const char *in_template, int sizeflag)
used_prefixes |= prefixes & (PREFIX_CS | PREFIX_DS);
*obufp++ = ',';
*obufp++ = 'p';
+
+ /* Set active_seg_prefix even if not set in 64-bit mode because
+ * here it is a valid branch hint. */
if (prefixes & PREFIX_DS)
- *obufp++ = 't';
+ {
+ active_seg_prefix = PREFIX_DS;
+ *obufp++ = 't';
+ }
else
- *obufp++ = 'n';
+ {
+ active_seg_prefix = PREFIX_CS;
+ *obufp++ = 'n';
+ }
}
break;
case 'K':
--
2.21.0
More information about the Binutils
mailing list