From 04066fe973c628476fbe9eb65bf62a67334987f7 Mon Sep 17 00:00:00 2001 From: cinap_lenrek Date: Thu, 7 May 2020 23:27:27 +0200 Subject: bcm64: fix kernels cmpswap() function spectacular bug. cmpswap() had a sign extension bug using sign extending MOV to load the old compare value and LDXRW using zero extension while the CMP instruction compared 64 bit registers. this caused cmpswap with negative old value always to fail. interestingly, libc's version of this function was fine. --- sys/src/9/bcm64/l.s | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/sys/src/9/bcm64/l.s b/sys/src/9/bcm64/l.s index 2e7e9ebc1..d6ad02184 100644 --- a/sys/src/9/bcm64/l.s +++ b/sys/src/9/bcm64/l.s @@ -229,8 +229,8 @@ TEXT touser(SB), 1, $-4 TEXT cas(SB), 1, $-4 TEXT cmpswap(SB), 1, $-4 - MOVW ov+8(FP), R1 - MOVW nv+16(FP), R2 + MOVWU ov+8(FP), R1 + MOVWU nv+16(FP), R2 _cas1: LDXRW (R0), R3 CMP R3, R1 -- cgit v1.2.3