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powerpc: Fix copyin/copyout race condition

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It's possible for a context switch, and CPU migration, to occur between
fetching the PCPU context and extracting the pc_curpcb.  This can cause
the fault handler to be installed for the wrong thread, leading to a
panic in copyin()/copyout().  Since curthread is already in %r13, just
use that directly, as GPRs are migrated, so there is no migration race
risk.
This commit is contained in:
Justin Hibbits 2020-12-08 16:49:25 -06:00 committed by Piotr Kubaj
parent 6260bfb087
commit 76ff03aef7
1 changed files with 6 additions and 10 deletions
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16
sys/powerpc/powerpc/support.S
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@ -61,6 +61,7 @@
/* log_2(8 * WORD) */
#define LOOP_LOG 6
#define LOG_WORD 3
#define CURTHREAD %r13
#else
#define LOAD lwz
#define STORE stw
@ -70,6 +71,7 @@
/* log_2(8 * WORD) */
#define LOOP_LOG 5
#define LOG_WORD 2
#define CURTHREAD %r2
#endif
#ifdef AIM
@ -149,32 +151,26 @@
#endif
#define PCPU(reg) mfsprg reg, 0
#define SET_COPYFAULT(raddr, rpcb, len) \
VALIDATE_ADDR_COPY(raddr, len) ;\
PCPU(%r9) ;\
li %r0, COPYFAULT ;\
LOAD rpcb, PC_CURPCB(%r9) ;\
LOAD rpcb, TD_PCB(CURTHREAD) ;\
STORE %r0, PCB_ONFAULT(rpcb) ;\
#define SET_COPYFAULT_TRUNCATE(raddr, rpcb, len)\
VALIDATE_TRUNCATE_ADDR_COPY(raddr, len) ;\
PCPU(%r9) ;\
li %r0, COPYFAULT ;\
LOAD rpcb, PC_CURPCB(%r9) ;\
LOAD rpcb, TD_PCB(CURTHREAD) ;\
STORE %r0, PCB_ONFAULT(rpcb)
#define SET_FUSUFAULT(raddr, rpcb) \
VALIDATE_ADDR_FUSU(raddr) ;\
PCPU(%r9) ;\
li %r0, FUSUFAULT ;\
LOAD rpcb, PC_CURPCB(%r9) ;\
LOAD rpcb, TD_PCB(CURTHREAD) ;\
STORE %r0, PCB_ONFAULT(rpcb)
#define CLEAR_FAULT_NO_CLOBBER(rpcb) \
PCPU(%r9) ;\
LOAD rpcb, PC_CURPCB(%r9) ;\
LOAD rpcb, TD_PCB(CURTHREAD) ;\
li %r0, 0 ;\
STORE %r0, PCB_ONFAULT(rpcb)