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arm64: entry: Make the trampoline cleanup optional

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Subsequent patches will add additional sets of vectors that use
the same tricks as the kpti vectors to reach the full-fat vectors.
The full-fat vectors contain some cleanup for kpti that is patched
in by alternatives when kpti is in use. Once there are additional
vectors, the cleanup will be needed in more cases.

But on big/little systems, the cleanup would be harmful if no
trampoline vector were in use. Instead of forcing CPUs that don't
need a trampoline vector to use one, make the trampoline cleanup
optional.

Entry at the top of the vectors will skip the cleanup. The trampoline
vectors can then skip the first instruction, triggering the cleanup
to run.

Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: James Morse <james.morse@arm.com>
This commit is contained in:
James Morse 2021-11-24 15:36:12 +00:00
parent 5bdf343760
commit d739da1694
1 changed files with 7 additions and 3 deletions
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10
arch/arm64/kernel/entry.S
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@ -40,14 +40,18 @@
.Lventry_start\@:
#ifdef CONFIG_UNMAP_KERNEL_AT_EL0
.if \el == 0
alternative_if ARM64_UNMAP_KERNEL_AT_EL0
/*
* This must be the first instruction of the EL0 vector entries. It is
* skipped by the trampoline vectors, to trigger the cleanup.
*/
b .Lskip_tramp_vectors_cleanup\@
.if \regsize == 64
mrs x30, tpidrro_el0
msr tpidrro_el0, xzr
.else
mov x30, xzr
.endif
alternative_else_nop_endif
.Lskip_tramp_vectors_cleanup\@:
.endif
#endif
@ -661,7 +665,7 @@ alternative_if_not ARM64_WORKAROUND_CAVIUM_TX2_219_PRFM
prfm plil1strm, [x30, #(1b - tramp_vectors)]
alternative_else_nop_endif
msr vbar_el1, x30
add x30, x30, #(1b - tramp_vectors)
add x30, x30, #(1b - tramp_vectors + 4)
isb
ret
.org 1b + 128 // Did we overflow the ventry slot?