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arm64: tags: Preserve tags for addresses translated via TTBR1

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Sign-extending TTBR1 addresses when converting to an untagged address
breaks the documented POSIX semantics for mlock() in some obscure error
cases where we end up returning -EINVAL instead of -ENOMEM as a direct
result of rewriting the upper address bits.

Rework the untagged_addr() macro to preserve the upper address bits for
TTBR1 addresses and only clear the tag bits for user addresses. This
matches the behaviour of the 'clear_address_tag' assembly macro, so
rename that and align the implementations at the same time so that they
use the same instruction sequences for the tag manipulation.

Link: https://lore.kernel.org/stable/20191014162651.GF19200@arrakis.emea.arm.com/
Reported-by: Jan Stancek <jstancek@redhat.com>
Tested-by: Jan Stancek <jstancek@redhat.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Tested-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Tested-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Reviewed-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Will Deacon <will@kernel.org>
This commit is contained in:
Will Deacon
2019-10-15 21:04:18 -07:00
parent 3813733595
commit 597399d0cb
3 changed files with 13 additions and 8 deletions
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7
arch/arm64/include/asm/asm-uaccess.h
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@@ -78,10 +78,9 @@ alternative_else_nop_endif
/*
* Remove the address tag from a virtual address, if present.
*/
.macro clear_address_tag, dst, addr
tst \addr, #(1 << 55)
bic \dst, \addr, #(0xff << 56)
csel \dst, \dst, \addr, eq
.macro untagged_addr, dst, addr
sbfx \dst, \addr, #0, #56
and \dst, \dst, \addr
.endm
#endif