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e805606193
The RTM vzeroupper mitigation has no way of replacing inline
vzeroupper not before a return.
This can be useful when hoisting a vzeroupper to save code size
for example:
```
L(foo):
cmpl %eax, %edx
jz L(bar)
tzcntl %eax, %eax
addq %rdi, %rax
VZEROUPPER_RETURN
L(bar):
xorl %eax, %eax
VZEROUPPER_RETURN
```
Can become:
```
L(foo):
COND_VZEROUPPER
cmpl %eax, %edx
jz L(bar)
tzcntl %eax, %eax
addq %rdi, %rax
ret
L(bar):
xorl %eax, %eax
ret
```
This code does not change any existing functionality.
There is no difference in the objdump of libc.so before and after this
patch.
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
(cherry picked from commit dd5c483b25)
170 lines
4.8 KiB
C
170 lines
4.8 KiB
C
/* Assembler macros for x86-64.
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Copyright (C) 2001-2021 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#ifndef _X86_64_SYSDEP_H
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#define _X86_64_SYSDEP_H 1
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#include <sysdeps/x86/sysdep.h>
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#ifdef __ASSEMBLER__
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/* Syntactic details of assembler. */
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/* This macro is for setting proper CFI with DW_CFA_expression describing
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the register as saved relative to %rsp instead of relative to the CFA.
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Expression is DW_OP_drop, DW_OP_breg7 (%rsp is register 7), sleb128 offset
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from %rsp. */
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#define cfi_offset_rel_rsp(regn, off) .cfi_escape 0x10, regn, 0x4, 0x13, \
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0x77, off & 0x7F | 0x80, off >> 7
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/* If compiled for profiling, call `mcount' at the start of each function. */
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#ifdef PROF
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/* The mcount code relies on a normal frame pointer being on the stack
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to locate our caller, so push one just for its benefit. */
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#define CALL_MCOUNT \
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pushq %rbp; \
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cfi_adjust_cfa_offset(8); \
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movq %rsp, %rbp; \
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cfi_def_cfa_register(%rbp); \
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call JUMPTARGET(mcount); \
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popq %rbp; \
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cfi_def_cfa(rsp,8);
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#else
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#define CALL_MCOUNT /* Do nothing. */
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#endif
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#define PSEUDO(name, syscall_name, args) \
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lose: \
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jmp JUMPTARGET(syscall_error) \
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.globl syscall_error; \
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ENTRY (name) \
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DO_CALL (syscall_name, args); \
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jb lose
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#undef JUMPTARGET
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#ifdef SHARED
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# ifdef BIND_NOW
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# define JUMPTARGET(name) *name##@GOTPCREL(%rip)
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# else
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# define JUMPTARGET(name) name##@PLT
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# endif
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#else
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/* For static archives, branch to target directly. */
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# define JUMPTARGET(name) name
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#endif
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/* Long and pointer size in bytes. */
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#define LP_SIZE 8
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/* Instruction to operate on long and pointer. */
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#define LP_OP(insn) insn##q
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/* Assembler address directive. */
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#define ASM_ADDR .quad
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/* Registers to hold long and pointer. */
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#define RAX_LP rax
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#define RBP_LP rbp
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#define RBX_LP rbx
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#define RCX_LP rcx
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#define RDI_LP rdi
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#define RDX_LP rdx
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#define RSI_LP rsi
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#define RSP_LP rsp
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#define R8_LP r8
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#define R9_LP r9
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#define R10_LP r10
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#define R11_LP r11
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#define R12_LP r12
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#define R13_LP r13
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#define R14_LP r14
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#define R15_LP r15
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/* Zero upper vector registers and return with xtest. NB: Use VZEROALL
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to avoid RTM abort triggered by VZEROUPPER inside transactionally. */
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#define ZERO_UPPER_VEC_REGISTERS_RETURN_XTEST \
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xtest; \
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jz 1f; \
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vzeroall; \
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ret; \
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1: \
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vzeroupper; \
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ret
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/* Can be used to replace vzeroupper that is not directly before a
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return. This is useful when hoisting a vzeroupper from multiple
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return paths to decrease the total number of vzerouppers and code
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size. */
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#define COND_VZEROUPPER_XTEST \
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xtest; \
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jz 1f; \
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vzeroall; \
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jmp 2f; \
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1: \
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vzeroupper; \
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2:
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/* In RTM define this as COND_VZEROUPPER_XTEST. */
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#ifndef COND_VZEROUPPER
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# define COND_VZEROUPPER vzeroupper
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#endif
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/* Zero upper vector registers and return. */
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#ifndef ZERO_UPPER_VEC_REGISTERS_RETURN
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# define ZERO_UPPER_VEC_REGISTERS_RETURN \
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VZEROUPPER; \
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ret
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#endif
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#ifndef VZEROUPPER_RETURN
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# define VZEROUPPER_RETURN VZEROUPPER; ret
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#endif
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#else /* __ASSEMBLER__ */
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/* Long and pointer size in bytes. */
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#define LP_SIZE "8"
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/* Instruction to operate on long and pointer. */
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#define LP_OP(insn) #insn "q"
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/* Assembler address directive. */
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#define ASM_ADDR ".quad"
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/* Registers to hold long and pointer. */
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#define RAX_LP "rax"
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#define RBP_LP "rbp"
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#define RBX_LP "rbx"
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#define RCX_LP "rcx"
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#define RDI_LP "rdi"
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#define RDX_LP "rdx"
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#define RSI_LP "rsi"
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#define RSP_LP "rsp"
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#define R8_LP "r8"
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#define R9_LP "r9"
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#define R10_LP "r10"
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#define R11_LP "r11"
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#define R12_LP "r12"
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#define R13_LP "r13"
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#define R14_LP "r14"
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#define R15_LP "r15"
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#endif /* __ASSEMBLER__ */
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#endif /* _X86_64_SYSDEP_H */
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