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>

3 files changed, 46 insertions, 0 deletions

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;
+}