[PATCH v2 48/55] linux-user: Add code for PR_GET/SET_UNALIGN

[Richard Henderson <richard.henderson@linaro.org>]

This requires extra work for each target, but adds the
common syscall code, and the necessary flag in CPUState.

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 include/hw/core/cpu.h |  3 +++
 linux-user/syscall.c  | 21 +++++++++++++++++++--
 2 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/include/hw/core/cpu.h b/include/hw/core/cpu.h
index b7d5bc1200..088b2d1adf 100644
--- a/include/hw/core/cpu.h
+++ b/include/hw/core/cpu.h
@@ -412,6 +412,9 @@ struct CPUState {
 
     bool ignore_memory_transaction_failures;
 
+    /* Used for user-only emulation of prctl(PR_SET_UNALIGN). */
+    bool prctl_unalign_sigbus;
+
     struct hax_vcpu_state *hax_vcpu;
 
     struct hvf_vcpu_state *hvf;
diff --git a/linux-user/syscall.c b/linux-user/syscall.c
index e303a9da7f..b2e3c28b41 100644
--- a/linux-user/syscall.c
+++ b/linux-user/syscall.c
@@ -6640,6 +6640,25 @@ static abi_long do_prctl(CPUArchState *env, abi_long option, abi_long arg2,
         }
         return do_prctl_get_tagged_addr_ctrl(env);
 
+    /*
+     * We only implement PR_UNALIGN_SIGBUS, and only for those targets
+     * who have had their translator updated to insert MO_ALIGN.
+     */
+#if 0
+    case PR_GET_UNALIGN:
+        {
+            CPUState *cs = env_cpu(env);
+            uint32_t res = PR_UNALIGN_NOPRINT;
+            if (cs->prctl_unalign_sigbus) {
+                res |= PR_UNALIGN_SIGBUS;
+            }
+            return put_user_u32(res, arg2);
+        }
+    case PR_SET_UNALIGN:
+        env_cpu(env)->prctl_unalign_sigbus = arg2 & PR_UNALIGN_SIGBUS;
+        return 0;
+#endif
+
     case PR_GET_DUMPABLE:
     case PR_SET_DUMPABLE:
     case PR_GET_KEEPCAPS:
@@ -6682,8 +6701,6 @@ static abi_long do_prctl(CPUArchState *env, abi_long option, abi_long arg2,
     case PR_SET_THP_DISABLE:
     case PR_GET_TSC:
     case PR_SET_TSC:
-    case PR_GET_UNALIGN:
-    case PR_SET_UNALIGN:
     default:
         /* Disable to prevent the target disabling stuff we need. */
         return -TARGET_EINVAL;
-- 
2.25.1