linux-user/ppc: Fix msr updates for signal handling

In save_user_regs, there are two bugs where we OR in a bit number
instead of the bit, clobbering the low bits of MSR.  However:

The MSR_VR and MSR_SPE bits control the availability of the insns.
If the bits were not already set in MSR, then any attempt to access
those registers would result in SIGILL.

For linux-user, we always initialize MSR to the capabilities
of the cpu.  We *could* add checks vs MSR where we currently
check insn_flags and insn_flags2, but we know they match.

Also, there's a stray cut-and-paste comment in restore.

Then, do not force little-endian binaries into big-endian mode.

Finally, use ppc_store_msr for the update to affect hflags.
Which is the reason none of these bugs were previously noticed.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-Id: <20210323184340.619757-10-richard.henderson@linaro.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

2 files changed, 14 insertions, 14 deletions

diff --git a/linux-user/ppc/cpu_loop.c b/linux-user/ppc/cpu_loop.c
index df71e15..4a0f6c8 100644
--- a/linux-user/ppc/cpu_loop.c
+++ b/linux-user/ppc/cpu_loop.c
@@ -492,11 +492,12 @@ void target_cpu_copy_regs(CPUArchState *env, struct target_pt_regs *regs)
 #if defined(TARGET_PPC64)
     int flag = (env->insns_flags2 & PPC2_BOOKE206) ? MSR_CM : MSR_SF;
 #if defined(TARGET_ABI32)
-    env->msr &= ~((target_ulong)1 << flag);
+    ppc_store_msr(env, env->msr & ~((target_ulong)1 << flag));
 #else
-    env->msr |= (target_ulong)1 << flag;
+    ppc_store_msr(env, env->msr | (target_ulong)1 << flag);
 #endif
 #endif
+
     env->nip = regs->nip;
     for(i = 0; i < 32; i++) {
         env->gpr[i] = regs->gpr[i];
diff --git a/linux-user/ppc/signal.c b/linux-user/ppc/signal.c
index b78613f..bad38f8 100644
--- a/linux-user/ppc/signal.c
+++ b/linux-user/ppc/signal.c
@@ -261,9 +261,6 @@ static void save_user_regs(CPUPPCState *env, struct target_mcontext *frame)
             __put_user(avr->u64[PPC_VEC_HI], &vreg->u64[0]);
             __put_user(avr->u64[PPC_VEC_LO], &vreg->u64[1]);
         }
-        /* Set MSR_VR in the saved MSR value to indicate that
-           frame->mc_vregs contains valid data.  */
-        msr |= MSR_VR;
 #if defined(TARGET_PPC64)
         vrsave = (uint32_t *)&frame->mc_vregs.altivec[33];
         /* 64-bit needs to put a pointer to the vectors in the frame */
@@ -300,9 +297,6 @@ static void save_user_regs(CPUPPCState *env, struct target_mcontext *frame)
         for (i = 0; i < ARRAY_SIZE(env->gprh); i++) {
             __put_user(env->gprh[i], &frame->mc_vregs.spe[i]);
         }
-        /* Set MSR_SPE in the saved MSR value to indicate that
-           frame->mc_vregs contains valid data.  */
-        msr |= MSR_SPE;
         __put_user(env->spe_fscr, &frame->mc_vregs.spe[32]);
     }
 #endif
@@ -354,8 +348,10 @@ static void restore_user_regs(CPUPPCState *env,
     __get_user(msr, &frame->mc_gregs[TARGET_PT_MSR]);
 
     /* If doing signal return, restore the previous little-endian mode.  */
-    if (sig)
-        env->msr = (env->msr & ~(1ull << MSR_LE)) | (msr & (1ull << MSR_LE));
+    if (sig) {
+        ppc_store_msr(env, ((env->msr & ~(1ull << MSR_LE)) |
+                            (msr & (1ull << MSR_LE))));
+    }
 
     /* Restore Altivec registers if necessary.  */
     if (env->insns_flags & PPC_ALTIVEC) {
@@ -376,8 +372,6 @@ static void restore_user_regs(CPUPPCState *env,
             __get_user(avr->u64[PPC_VEC_HI], &vreg->u64[0]);
             __get_user(avr->u64[PPC_VEC_LO], &vreg->u64[1]);
         }
-        /* Set MSR_VEC in the saved MSR value to indicate that
-           frame->mc_vregs contains valid data.  */
 #if defined(TARGET_PPC64)
         vrsave = (uint32_t *)&v_regs[33];
 #else
@@ -468,7 +462,7 @@ void setup_frame(int sig, struct target_sigaction *ka,
     env->nip = (target_ulong) ka->_sa_handler;
 
     /* Signal handlers are entered in big-endian mode.  */
-    env->msr &= ~(1ull << MSR_LE);
+    ppc_store_msr(env, env->msr & ~(1ull << MSR_LE));
 
     unlock_user_struct(frame, frame_addr, 1);
     return;
@@ -563,8 +557,13 @@ void setup_rt_frame(int sig, struct target_sigaction *ka,
     env->nip = (target_ulong) ka->_sa_handler;
 #endif
 
+#ifdef TARGET_WORDS_BIGENDIAN
     /* Signal handlers are entered in big-endian mode.  */
-    env->msr &= ~(1ull << MSR_LE);
+    ppc_store_msr(env, env->msr & ~(1ull << MSR_LE));
+#else
+    /* Signal handlers are entered in little-endian mode.  */
+    ppc_store_msr(env, env->msr | (1ull << MSR_LE));
+#endif
 
     unlock_user_struct(rt_sf, rt_sf_addr, 1);
     return;