[PATCH v3] target/ppc: check tb_env != 0 before printing TBU/TBL/DECR

[Matheus Ferst]

When using "-machine none", env->tb_env is not allocated, causing the
segmentation fault reported in issue #85 (launchpad bug #811683). To
avoid this problem, check if the pointer != NULL before calling the
methods to print TBU/TBL/DECR.

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/85
Signed-off-by: Matheus Ferst <matheus.ferst@eldorado.org.br>
---
v3:
  - Only check env->tb_env in softmmu, linux-user get timebase from
    elsewhere. Also, try to make the qemu_fprintf call more readable.
  - Link to v2: 
https://lists.gnu.org/archive/html/qemu-ppc/2022-07/msg00193.html
---
 target/ppc/cpu_init.c | 18 ++++++++----------
 target/ppc/monitor.c  |  9 +++++++++
 2 files changed, 17 insertions(+), 10 deletions(-)

diff --git a/target/ppc/cpu_init.c b/target/ppc/cpu_init.c
index 86ad28466a..313c8bb300 100644
--- a/target/ppc/cpu_init.c
+++ b/target/ppc/cpu_init.c
@@ -7476,17 +7476,15 @@ void ppc_cpu_dump_state(CPUState *cs, FILE *f, int 
flags)
                  "%08x iidx %d didx %d\n",
                  env->msr, env->spr[SPR_HID0], env->hflags,
                  cpu_mmu_index(env, true), cpu_mmu_index(env, false));
-#if !defined(NO_TIMER_DUMP)
-    qemu_fprintf(f, "TB %08" PRIu32 " %08" PRIu64
 #if !defined(CONFIG_USER_ONLY)
-                 " DECR " TARGET_FMT_lu
-#endif
-                 "\n",
-                 cpu_ppc_load_tbu(env), cpu_ppc_load_tbl(env)
-#if !defined(CONFIG_USER_ONLY)
-                 , cpu_ppc_load_decr(env)
-#endif
-        );
+    if (env->tb_env) {
+        qemu_fprintf(f, "TB %08" PRIu32 " %08" PRIu64
+                     " DECR " TARGET_FMT_lu "\n", cpu_ppc_load_tbu(env),
+                     cpu_ppc_load_tbl(env), cpu_ppc_load_decr(env));
+    }
+#else
+    qemu_fprintf(f, "TB %08" PRIu32 " %08" PRIu64 "\n", cpu_ppc_load_tbu(env),
+                 cpu_ppc_load_tbl(env));
 #endif
     for (i = 0; i < 32; i++) {
         if ((i & (RGPL - 1)) == 0) {
diff --git a/target/ppc/monitor.c b/target/ppc/monitor.c
index 0b805ef6e9..8250b1304e 100644
--- a/target/ppc/monitor.c
+++ b/target/ppc/monitor.c
@@ -55,6 +55,9 @@ static target_long monitor_get_decr(Monitor *mon, const 
struct MonitorDef *md,
                                     int val)
 {
     CPUArchState *env = mon_get_cpu_env(mon);
+    if (!env->tb_env) {
+        return 0;
+    }
     return cpu_ppc_load_decr(env);
 }
 
@@ -62,6 +65,9 @@ static target_long monitor_get_tbu(Monitor *mon, const struct 
MonitorDef *md,
                                    int val)
 {
     CPUArchState *env = mon_get_cpu_env(mon);
+    if (!env->tb_env) {
+        return 0;
+    }
     return cpu_ppc_load_tbu(env);
 }
 
@@ -69,6 +75,9 @@ static target_long monitor_get_tbl(Monitor *mon, const struct 
MonitorDef *md,
                                    int val)
 {
     CPUArchState *env = mon_get_cpu_env(mon);
+    if (!env->tb_env) {
+        return 0;
+    }
     return cpu_ppc_load_tbl(env);
 }
 
-- 
2.25.1