The branch main has been updated by pkubaj (ports committer):
URL:
https://cgit.FreeBSD.org/src/commit/?id=76ff03aef7411e601673dfc997bd6d691bd9a14e
commit 76ff03aef7411e601673dfc997bd6d691bd9a14e
Author: Justin Hibbits <chmeeed...@gmail.com>
AuthorDate: 2020-12-08 22:49:25 +0000
Commit: Piotr Kubaj <pku...@freebsd.org>
CommitDate: 2020-12-30 22:45:44 +0000
powerpc: Fix copyin/copyout race condition
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.
---
sys/powerpc/powerpc/support.S | 16 ++++++----------
1 file changed, 6 insertions(+), 10 deletions(-)
diff --git a/sys/powerpc/powerpc/support.S b/sys/powerpc/powerpc/support.S
index 9ff1bcc02437..10d3192972d5 100644
--- a/sys/powerpc/powerpc/support.S
+++ b/sys/powerpc/powerpc/support.S
@@ -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)
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