linux-user/ppc: Fix XER access in save/restore_user_regs

We should use cpu_read_xer/cpu_write_xer to save/restore the complete
register since some of its bits are in other fields of CPUPPCState. A
test is added to prevent future regressions.

Fixes: da91a00f191f ("target-ppc: Split out SO, OV, CA fields from XER")
Signed-off-by: Matheus Ferst <matheus.ferst@eldorado.org.br>
Message-Id: <20211014223234.127012-2-matheus.ferst@eldorado.org.br>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

4 files changed, 52 insertions, 3 deletions

diff --git a/linux-user/ppc/signal.c b/linux-user/ppc/signal.c
index c37744c..90a0369 100644
--- a/linux-user/ppc/signal.c
+++ b/linux-user/ppc/signal.c
@@ -242,7 +242,7 @@ static void save_user_regs(CPUPPCState *env, struct target_mcontext *frame)
     __put_user(env->nip, &frame->mc_gregs[TARGET_PT_NIP]);
     __put_user(env->ctr, &frame->mc_gregs[TARGET_PT_CTR]);
     __put_user(env->lr, &frame->mc_gregs[TARGET_PT_LNK]);
-    __put_user(env->xer, &frame->mc_gregs[TARGET_PT_XER]);
+    __put_user(cpu_read_xer(env), &frame->mc_gregs[TARGET_PT_XER]);
 
     for (i = 0; i < ARRAY_SIZE(env->crf); i++) {
         ccr |= env->crf[i] << (32 - ((i + 1) * 4));
@@ -315,6 +315,7 @@ static void restore_user_regs(CPUPPCState *env,
 {
     target_ulong save_r2 = 0;
     target_ulong msr;
+    target_ulong xer;
     target_ulong ccr;
 
     int i;
@@ -330,9 +331,11 @@ static void restore_user_regs(CPUPPCState *env,
     __get_user(env->nip, &frame->mc_gregs[TARGET_PT_NIP]);
     __get_user(env->ctr, &frame->mc_gregs[TARGET_PT_CTR]);
     __get_user(env->lr, &frame->mc_gregs[TARGET_PT_LNK]);
-    __get_user(env->xer, &frame->mc_gregs[TARGET_PT_XER]);
-    __get_user(ccr, &frame->mc_gregs[TARGET_PT_CCR]);
 
+    __get_user(xer, &frame->mc_gregs[TARGET_PT_XER]);
+    cpu_write_xer(env, xer);
+
+    __get_user(ccr, &frame->mc_gregs[TARGET_PT_CCR]);
     for (i = 0; i < ARRAY_SIZE(env->crf); i++) {
         env->crf[i] = (ccr >> (32 - ((i + 1) * 4))) & 0xf;
     }
diff --git a/tests/tcg/ppc64/Makefile.target b/tests/tcg/ppc64/Makefile.target
index a6a4dda..6ab7934 100644
--- a/tests/tcg/ppc64/Makefile.target
+++ b/tests/tcg/ppc64/Makefile.target
@@ -23,4 +23,6 @@ run-plugin-byte_reverse-with-%:
 	$(call skip-test, "RUN of byte_reverse ($*)", "not built")
 endif
 
+PPC64_TESTS += signal_save_restore_xer
+
 TESTS += $(PPC64_TESTS)
diff --git a/tests/tcg/ppc64le/Makefile.target b/tests/tcg/ppc64le/Makefile.target
index c0c14ff..5e65b15 100644
--- a/tests/tcg/ppc64le/Makefile.target
+++ b/tests/tcg/ppc64le/Makefile.target
@@ -22,4 +22,6 @@ run-plugin-byte_reverse-with-%:
 	$(call skip-test, "RUN of byte_reverse ($*)", "not built")
 endif
 
+PPC64LE_TESTS += signal_save_restore_xer
+
 TESTS += $(PPC64LE_TESTS)
diff --git a/tests/tcg/ppc64le/signal_save_restore_xer.c b/tests/tcg/ppc64le/signal_save_restore_xer.c
new file mode 100644
index 0000000..e4f8a07
--- /dev/null
+++ b/tests/tcg/ppc64le/signal_save_restore_xer.c
@@ -0,0 +1,42 @@
+#include <assert.h>
+#include <stdint.h>
+#include <signal.h>
+#include <sys/user.h>
+
+#define XER_SO   (1 << 31)
+#define XER_OV   (1 << 30)
+#define XER_CA   (1 << 29)
+#define XER_OV32 (1 << 19)
+#define XER_CA32 (1 << 18)
+
+uint64_t saved;
+
+void sigill_handler(int sig, siginfo_t *si, void *ucontext)
+{
+    ucontext_t *uc = ucontext;
+    uc->uc_mcontext.regs->nip += 4;
+    saved = uc->uc_mcontext.regs->xer;
+    uc->uc_mcontext.regs->xer |= XER_OV | XER_OV32;
+}
+
+int main(void)
+{
+    uint64_t initial = XER_CA | XER_CA32, restored;
+    struct sigaction sa = {
+        .sa_sigaction = sigill_handler,
+        .sa_flags = SA_SIGINFO
+    };
+
+    sigaction(SIGILL, &sa, NULL);
+
+    asm("mtspr 1, %1\n\t"
+        ".long 0x0\n\t"
+        "mfspr %0, 1\n\t"
+        : "=r" (restored)
+        : "r" (initial));
+
+    assert(saved == initial);
+    assert(restored == (XER_OV | XER_OV32 | XER_CA | XER_CA32));
+
+    return 0;
+}