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arm64: entry: Add vectors that have the bhb mitigation sequences

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Some CPUs affected by Spectre-BHB need a sequence of branches, or a
firmware call to be run before any indirect branch. This needs to go
in the vectors. No CPU needs both.

While this can be patched in, it would run on all CPUs as there is a
single set of vectors. If only one part of a big/little combination is
affected, the unaffected CPUs have to run the mitigation too.

Create extra vectors that include the sequence. Subsequent patches will
allow affected CPUs to select this set of vectors. Later patches will
modify the loop count to match what the CPU requires.

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: James Morse <james.morse@arm.com>
This commit is contained in:
James Morse
2021-11-18 13:59:46 +00:00
parent aff65393fa
commit ba2689234b
5 changed files with 123 additions and 9 deletions
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24
arch/arm64/include/asm/assembler.h
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@@ -850,4 +850,28 @@ alternative_endif
#endif /* GNU_PROPERTY_AARCH64_FEATURE_1_DEFAULT */
.macro __mitigate_spectre_bhb_loop tmp
#ifdef CONFIG_MITIGATE_SPECTRE_BRANCH_HISTORY
mov \tmp, #32
.Lspectre_bhb_loop\@:
b . + 4
subs \tmp, \tmp, #1
b.ne .Lspectre_bhb_loop\@
sb
#endif /* CONFIG_MITIGATE_SPECTRE_BRANCH_HISTORY */
.endm
/* Save/restores x0-x3 to the stack */
.macro __mitigate_spectre_bhb_fw
#ifdef CONFIG_MITIGATE_SPECTRE_BRANCH_HISTORY
stp x0, x1, [sp, #-16]!
stp x2, x3, [sp, #-16]!
mov w0, #ARM_SMCCC_ARCH_WORKAROUND_3
alternative_cb smccc_patch_fw_mitigation_conduit
nop // Patched to SMC/HVC #0
alternative_cb_end
ldp x2, x3, [sp], #16
ldp x0, x1, [sp], #16
#endif /* CONFIG_MITIGATE_SPECTRE_BRANCH_HISTORY */
.endm
#endif /* __ASM_ASSEMBLER_H */