powerpc: Ignore reserved field in DCSR and PVR reads and writes

IBM bit 31 (for the rest of us - bit 0) is a reserved field in the
instruction definition of mtspr and mfspr. Hardware is encouraged to
(and does) ignore it.

As a result, if userspace executes an mtspr DSCR with the reserved bit
set, we get a DSCR facility unavailable exception. The kernel fails to
match against the expected value/mask, and we silently return to
userspace to try and re-execute the same mtspr DSCR instruction. We
loop forever until the process is killed.

We should do something here, and it seems mirroring what hardware does
is the better option vs killing the process. While here, relax the
matching of mfspr PVR too.

Cc: stable@vger.kernel.org
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

diff --git a/arch/powerpc/include/asm/ppc-opcode.h b/arch/powerpc/include/asm/ppc-opcode.h
index c56ea8c84abb1771ff65f66ba91ffff02bff5fae..c4ced1d01d579fe0b7aeb13a71b21eb2ffb7072c 100644 (file)
--- a/arch/powerpc/include/asm/ppc-opcode.h
+++ b/arch/powerpc/include/asm/ppc-opcode.h
@@ -157,7 +157,7 @@
 #define PPC_INST_MCRXR                 0x7c000400
 #define PPC_INST_MCRXR_MASK            0xfc0007fe
 #define PPC_INST_MFSPR_PVR             0x7c1f42a6
-#define PPC_INST_MFSPR_PVR_MASK                0xfc1fffff
+#define PPC_INST_MFSPR_PVR_MASK                0xfc1ffffe
 #define PPC_INST_MFTMR                 0x7c0002dc
 #define PPC_INST_MSGSND                        0x7c00019c
 #define PPC_INST_MSGCLR                        0x7c0001dc
@@ -174,13 +174,13 @@
 #define PPC_INST_RFDI                  0x4c00004e
 #define PPC_INST_RFMCI                 0x4c00004c
 #define PPC_INST_MFSPR_DSCR            0x7c1102a6
-#define PPC_INST_MFSPR_DSCR_MASK       0xfc1fffff
+#define PPC_INST_MFSPR_DSCR_MASK       0xfc1ffffe
 #define PPC_INST_MTSPR_DSCR            0x7c1103a6
-#define PPC_INST_MTSPR_DSCR_MASK       0xfc1fffff
+#define PPC_INST_MTSPR_DSCR_MASK       0xfc1ffffe
 #define PPC_INST_MFSPR_DSCR_USER       0x7c0302a6
-#define PPC_INST_MFSPR_DSCR_USER_MASK  0xfc1fffff
+#define PPC_INST_MFSPR_DSCR_USER_MASK  0xfc1ffffe
 #define PPC_INST_MTSPR_DSCR_USER       0x7c0303a6
-#define PPC_INST_MTSPR_DSCR_USER_MASK  0xfc1fffff
+#define PPC_INST_MTSPR_DSCR_USER_MASK  0xfc1ffffe
 #define PPC_INST_MFVSRD                        0x7c000066
 #define PPC_INST_MTVSRD                        0x7c000166
 #define PPC_INST_SLBFEE                        0x7c0007a7