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ARM: 9198/1: spectre-bhb: simplify BPIALL vector macro 

The BPIALL mitigation for Spectre-BHB adds a single instruction to the
handler sequence that doesn't clobber any registers. Given that these
sequences are 10 instructions long, they don't fit neatly into a
cacheline anyway, so we can simply move that single instruction to the
start of the unmitigated one, and rearrange the symbol names accordingly.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
This commit is contained in:
Ard Biesheuvel 2022-04-20 09:55:35 +01:00 committed by Russell King (Oracle)
parent 508074607c
commit c4f486f1e7
1 changed files with 6 additions and 15 deletions
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21
arch/arm/kernel/entry-armv.S
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@ -1078,6 +1078,12 @@ __kuser_helper_end:
*/
.macro vector_stub, name, mode, correction=0
.align 5
#ifdef CONFIG_HARDEN_BRANCH_HISTORY
vector_bhb_bpiall_\name:
mcr p15, 0, r0, c7, c5, 6 @ BPIALL
@ isb not needed due to "movs pc, lr" in the vector stub
@ which gives a "context synchronisation".
#endif
vector_\name:
.if \correction
@ -1129,21 +1135,6 @@ vector_bhb_loop8_\name:
isb
b 2b
ENDPROC(vector_bhb_loop8_\name)
vector_bhb_bpiall_\name:
.if \correction
sub lr, lr, #\correction
.endif
@ Save r0, lr_<exception> (parent PC)
stmia sp, {r0, lr}
@ bhb workaround
mcr p15, 0, r0, c7, c5, 6 @ BPIALL
@ isb not needed due to "movs pc, lr" in the vector stub
@ which gives a "context synchronisation".
b 2b
ENDPROC(vector_bhb_bpiall_\name)
.previous
#endif