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fix SPARC v8/v9 detection code. 

this code uses a trick where the encoding on both v8 and v9 are
the same, and are not illegal instructions, but that the v9 one
has a detectable difference than v8.

the idea is that we perform a "subcc" (set condition codes) which
sets "%ccr" on v9, which is an unimplemented "%asr2" on v8, then
we read %ccr (v9) or %asr2 (v8), which will always be 0x99 on v9,
and .. is non-trapping but impleentation defined on v8.

for many implementations this returns the value of the %y reg.

as nothing actually sets %y in this path, it remains the value it
was most recently set to by something (anything), and if it just
happens to be 0x99 then the v9 paths will be taken on v8.

fix this by clearing the %y register before the potential read.

fixes PR port-sparc/57594.  tested on ss20 and in qemu.  this
version of the patch has been submitted upstream.

XXX: pullup-10, pullup-9, pullup-8.
This commit is contained in:
mrg 2023-09-02 20:07:32 +00:00
parent 6042d5e3e5
commit e8bf6de2c7
1 changed files with 13 additions and 6 deletions
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19
crypto/external/bsd/openssl/dist/crypto/sparccpuid.S vendored
View File

@ -47,10 +47,14 @@ OPENSSL_wipe_cpu:
subcc %g0,1,%o0
! Following is V9 "rd %ccr,%o0" instruction. However! V8
! specification says that it ("rd %asr2,%o0" in V8 terms) does
! not cause illegal_instruction trap. It therefore can be used
! to determine if the CPU the code is executing on is V8- or
! V9-compliant, as V9 returns a distinct value of 0x99,
! "negative" and "borrow" bits set in both %icc and %xcc.
! not cause illegal_instruction trap, however it may read from
! the %y register. It therefore can be used to determine if the
! CPU the code is executing on is V8- or V9-compliant, as V9
! returns a distinct value of 0x99, "negative" and "borrow"
! bits set in both %icc and %xcc. The %y register needs to be
! set away from 0x99 to avoid false-positives matches.
!
wr 0, %y
.word 0x91408000 !rd %ccr,%o0
cmp %o0,0x99
bne .v8
@ -178,6 +182,7 @@ walk_reg_wins:
OPENSSL_atomic_add:
#ifndef ABI64
subcc %g0,1,%o2
wr 0, %y
.word 0x95408000 !rd %ccr,%o2, see comment above
cmp %o2,0x99
be .v9
@ -226,7 +231,8 @@ OPENSSL_atomic_add:
.align 32
_sparcv9_rdtick:
subcc %g0,1,%o0
.word 0x91408000 !rd %ccr,%o0
wr 0, %y
.word 0x91408000 !rd %ccr,%o0, see comment above
cmp %o0,0x99
bne .notick
xor %o0,%o0,%o0
@ -388,7 +394,8 @@ OPENSSL_cleanse:
#ifndef ABI64
subcc %g0,1,%g1
! see above for explanation
.word 0x83408000 !rd %ccr,%g1
wr 0, %y
.word 0x83408000 !rd %ccr,%g1, see comment above
cmp %g1,0x99
bne .v8lot
nop