[Qemu-arm] [PATCH v4 4/5] aarch64-linux-user: Add support for EXTRA signal frame records

[Richard Henderson]

The EXTRA record allows for additional space to be allocated
beyon what is currently reserved.  Add code to emit and read
this record type.

Nothing uses extra space yet.

Signed-off-by: Richard Henderson <address@hidden>
---
 linux-user/signal.c | 74 +++++++++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 63 insertions(+), 11 deletions(-)

diff --git a/linux-user/signal.c b/linux-user/signal.c
index f9eef3d753..c31cf0601d 100644
--- a/linux-user/signal.c
+++ b/linux-user/signal.c
@@ -1443,6 +1443,15 @@ struct target_fpsimd_context {
     uint64_t vregs[32 * 2]; /* really uint128_t vregs[32] */
 };
 
+#define TARGET_EXTRA_MAGIC  0x45585401
+
+struct target_extra_context {
+    struct target_aarch64_ctx head;
+    uint64_t datap; /* 16-byte aligned pointer to extra space cast to __u64 */
+    uint32_t size; /* size in bytes of the extra space */
+    uint32_t reserved[3];
+};
+
 struct target_rt_sigframe {
     struct target_siginfo info;
     struct target_ucontext uc;
@@ -1502,6 +1511,15 @@ static void target_setup_fpsimd_record(struct 
target_fpsimd_context *fpsimd,
     }
 }
 
+static void target_setup_extra_record(struct target_extra_context *extra,
+                                      uint64_t datap, uint32_t extra_size)
+{
+    __put_user(TARGET_EXTRA_MAGIC, &extra->head.magic);
+    __put_user(sizeof(struct target_extra_context), &extra->head.size);
+    __put_user(datap, &extra->datap);
+    __put_user(extra_size, &extra->size);
+}
+
 static void target_setup_end_record(struct target_aarch64_ctx *end)
 {
     __put_user(0, &end->magic);
@@ -1554,48 +1572,74 @@ static void target_restore_fpsimd_record(CPUARMState 
*env,
 static int target_restore_sigframe(CPUARMState *env,
                                    struct target_rt_sigframe *sf)
 {
-    struct target_aarch64_ctx *ctx;
+    struct target_aarch64_ctx *ctx, *extra = NULL;
     struct target_fpsimd_context *fpsimd = NULL;
+    uint64_t extra_datap = 0;
+    bool used_extra = false;
+    bool err = false;
 
     target_restore_general_frame(env, sf);
 
     ctx = (struct target_aarch64_ctx *)sf->uc.tuc_mcontext.__reserved;
     while (ctx) {
-        uint32_t magic, size;
+        uint32_t magic, size, extra_size;
 
         __get_user(magic, &ctx->magic);
         __get_user(size, &ctx->size);
         switch (magic) {
         case 0:
             if (size != 0) {
-                return 1;
+                err = true;
+                goto exit;
+            }
+            if (used_extra) {
+                ctx = NULL;
+            } else {
+                ctx = extra;
+                used_extra = true;
             }
-            ctx = NULL;
             continue;
 
         case TARGET_FPSIMD_MAGIC:
             if (fpsimd || size != sizeof(struct target_fpsimd_context)) {
-                return 1;
+                err = true;
+                goto exit;
             }
             fpsimd = (struct target_fpsimd_context *)ctx;
             break;
 
+        case TARGET_EXTRA_MAGIC:
+            if (extra || size != sizeof(struct target_extra_context)) {
+                err = true;
+                goto exit;
+            }
+            __get_user(extra_datap,
+                       &((struct target_extra_context *)ctx)->datap);
+            __get_user(extra_size,
+                       &((struct target_extra_context *)ctx)->size);
+            extra = lock_user(VERIFY_READ, extra_datap, extra_size, 0);
+            break;
+
         default:
             /* Unknown record -- we certainly didn't generate it.
              * Did we in fact get out of sync?
              */
-            return 1;
+            err = true;
+            goto exit;
         }
         ctx = (void *)ctx + size;
     }
 
     /* Require FPSIMD always.  */
-    if (!fpsimd) {
-        return 1;
+    if (fpsimd) {
+        target_restore_fpsimd_record(env, fpsimd);
+    } else {
+        err = true;
     }
-    target_restore_fpsimd_record(env, fpsimd);
 
-    return 0;
+ exit:
+    unlock_user(extra, extra_datap, 0);
+    return err;
 }
 
 static abi_ulong get_sigframe(struct target_sigaction *ka, CPUARMState *env)
@@ -1621,7 +1665,8 @@ static void target_setup_frame(int usig, struct 
target_sigaction *ka,
                                CPUARMState *env)
 {
     int size = offsetof(struct target_rt_sigframe, uc.tuc_mcontext.__reserved);
-    int fpsimd_ofs, end1_ofs, fr_ofs;
+    int fpsimd_ofs, end1_ofs, fr_ofs, end2_ofs = 0;
+    int extra_ofs = 0, extra_base = 0, extra_size = 0;
     struct target_rt_sigframe *frame;
     struct target_rt_frame_record *fr;
     abi_ulong frame_addr, return_addr;
@@ -1641,7 +1686,14 @@ static void target_setup_frame(int usig, struct 
target_sigaction *ka,
 
     target_setup_general_frame(frame, env, set);
     target_setup_fpsimd_record((void *)frame + fpsimd_ofs, env);
+    if (extra_ofs) {
+        target_setup_extra_record((void *)frame + extra_ofs,
+                                  frame_addr + extra_base, extra_size);
+    }
     target_setup_end_record((void *)frame + end1_ofs);
+    if (end2_ofs) {
+        target_setup_end_record((void *)frame + end2_ofs);
+    }
 
     /* Set up the stack frame for unwinding.  */
     fr = (void *)frame + fr_ofs;
-- 
2.14.3