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x86: remove retpoline code

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This code:

1) Doesn't work
2) Hasn't ever been enabled by default
3) We mitigate Spectre V2 via Extended IBRS anyway

Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>
This commit is contained in:
Andrew Boie 2019-12-18 15:11:59 -08:00 • committed by Anas Nashif
commit 07c278382a
6 changed files with 4 additions and 61 deletions
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47
include/arch/x86/ia32/asm.h
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@ -14,53 +14,6 @@
#if defined(_ASMLANGUAGE)
#if defined(CONFIG_X86_RETPOLINE)
/*
* For a description of how retpolines are constructed for both indirect
* jumps and indirect calls, please refer to this documentation:
* https://support.google.com/faqs/answer/7625886
*
* Since these macros are used in a few places in arch/x86/core assembly
* routines, with different reg parameters, it's not possible to use
* the "out of line" construction technique to share a trampoline.
*/
#define INDIRECT_JMP_IMPL(reg, id) \
call .set_up_target ## id; \
.speculative_trap ## id: \
pause; \
jmp .speculative_trap ## id; \
.set_up_target ## id: \
mov reg, (%esp); \
ret
#define INDIRECT_CALL_IMPL(reg, id) \
call .set_up_return ## id; \
.inner_indirect_branch ## id: \
call .set_up_target ## id; \
.speculative_trap ## id: \
pause; \
jmp .speculative_trap ## id; \
.set_up_target ## id: \
mov reg, (%esp); \
ret; \
.set_up_return ## id: \
call .inner_indirect_branch ## id
#define INDIRECT_CALL_IMPL1(reg, id) INDIRECT_CALL_IMPL(reg, id)
#define INDIRECT_JMP_IMPL1(reg, id) INDIRECT_JMP_IMPL(reg, id)
#define INDIRECT_CALL(reg) INDIRECT_CALL_IMPL1(reg, __COUNTER__)
#define INDIRECT_JMP(reg) INDIRECT_JMP_IMPL1(reg, __COUNTER__)
#else
#define INDIRECT_CALL(reg) call *reg
#define INDIRECT_JMP(reg) jmp *reg
#endif /* CONFIG_X86_RETPOLINE */
#ifdef CONFIG_X86_KPTI
GTEXT(z_x86_trampoline_to_user)
GTEXT(z_x86_trampoline_to_kernel)