powerpc: Emulate non privileged DSCR read and write
commit 73d2fb758e678c93bc76d40876c2359f0729b0ef upstream.
POWER8 allows read and write of the DSCR in userspace. We added
kernel emulation so applications could always use the instructions
regardless of the CPU type.
Unfortunately there are two SPRs for the DSCR and we only added
emulation for the privileged one. Add code to match the non
privileged one.
A simple test was created to verify the fix:
http://ozlabs.org/~anton/junkcode/user_dscr_test.c
Without the patch we get a SIGILL and it passes with the patch.
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index ae0843f..3bb7197 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -960,7 +960,10 @@
#ifdef CONFIG_PPC64
/* Emulate the mfspr rD, DSCR. */
- if (((instword & PPC_INST_MFSPR_DSCR_MASK) == PPC_INST_MFSPR_DSCR) &&
+ if ((((instword & PPC_INST_MFSPR_DSCR_USER_MASK) ==
+ PPC_INST_MFSPR_DSCR_USER) ||
+ ((instword & PPC_INST_MFSPR_DSCR_MASK) ==
+ PPC_INST_MFSPR_DSCR)) &&
cpu_has_feature(CPU_FTR_DSCR)) {
PPC_WARN_EMULATED(mfdscr, regs);
rd = (instword >> 21) & 0x1f;
@@ -968,7 +971,10 @@
return 0;
}
/* Emulate the mtspr DSCR, rD. */
- if (((instword & PPC_INST_MTSPR_DSCR_MASK) == PPC_INST_MTSPR_DSCR) &&
+ if ((((instword & PPC_INST_MTSPR_DSCR_USER_MASK) ==
+ PPC_INST_MTSPR_DSCR_USER) ||
+ ((instword & PPC_INST_MTSPR_DSCR_MASK) ==
+ PPC_INST_MTSPR_DSCR)) &&
cpu_has_feature(CPU_FTR_DSCR)) {
PPC_WARN_EMULATED(mtdscr, regs);
rd = (instword >> 21) & 0x1f;