bsd-user: Implement shmat(2) and shmdt(2)

Use `WITH_MMAP_LOCK_GUARD` instead of mmap_lock() and mmap_unlock(),
to match linux-user implementation, according to the following commits:

69fa2708a2 linux-user: Use WITH_MMAP_LOCK_GUARD in target_{shmat,shmdt}
ceda5688b6 linux-user: Fix shmdt

Signed-off-by: Stacey Son <sson@FreeBSD.org>
Signed-off-by: Karim Taha <kariem.taha2.7@gmail.com>
Message-Id: <20230925182709.4834-23-kariem.taha2.7@gmail.com>

bsd-user/bsd-mem.h

@@ -344,4 +344,91 @@ static inline abi_long do_bsd_shmctl(abi_long shmid, abi_long cmd,
     return ret;
 }
 
+/* shmat(2) */
+static inline abi_long do_bsd_shmat(int shmid, abi_ulong shmaddr, int shmflg)
+{
+    abi_ulong raddr;
+    abi_long ret;
+    struct shmid_ds shm_info;
+
+    /* Find out the length of the shared memory segment. */
+    ret = get_errno(shmctl(shmid, IPC_STAT, &shm_info));
+    if (is_error(ret)) {
+        /* Can't get the length */
+        return ret;
+    }
+
+    if (!guest_range_valid_untagged(shmaddr, shm_info.shm_segsz)) {
+        return -TARGET_EINVAL;
+    }
+
+    WITH_MMAP_LOCK_GUARD() {
+        void *host_raddr;
+
+        if (shmaddr) {
+            host_raddr = shmat(shmid, (void *)g2h_untagged(shmaddr), shmflg);
+        } else {
+            abi_ulong mmap_start;
+
+            mmap_start = mmap_find_vma(0, shm_info.shm_segsz);
+
+            if (mmap_start == -1) {
+                return -TARGET_ENOMEM;
+            }
+            host_raddr = shmat(shmid, g2h_untagged(mmap_start),
+                               shmflg | SHM_REMAP);
+        }
+
+        if (host_raddr == (void *)-1) {
+            return get_errno(-1);
+        }
+        raddr = h2g(host_raddr);
+
+        page_set_flags(raddr, raddr + shm_info.shm_segsz - 1,
+                       PAGE_VALID | PAGE_RESET | PAGE_READ |
+                       (shmflg & SHM_RDONLY ? 0 : PAGE_WRITE));
+
+        for (int i = 0; i < N_BSD_SHM_REGIONS; i++) {
+            if (bsd_shm_regions[i].start == 0) {
+                bsd_shm_regions[i].start = raddr;
+                bsd_shm_regions[i].size = shm_info.shm_segsz;
+                break;
+            }
+        }
+    }
+
+    return raddr;
+}
+
+/* shmdt(2) */
+static inline abi_long do_bsd_shmdt(abi_ulong shmaddr)
+{
+    abi_long ret;
+
+    WITH_MMAP_LOCK_GUARD() {
+        int i;
+
+        for (i = 0; i < N_BSD_SHM_REGIONS; ++i) {
+            if (bsd_shm_regions[i].start == shmaddr) {
+                break;
+            }
+        }
+
+        if (i == N_BSD_SHM_REGIONS) {
+            return -TARGET_EINVAL;
+        }
+
+        ret = get_errno(shmdt(g2h_untagged(shmaddr)));
+        if (ret == 0) {
+            abi_ulong size = bsd_shm_regions[i].size;
+
+            bsd_shm_regions[i].start = 0;
+            page_set_flags(shmaddr, shmaddr + size - 1, 0);
+            mmap_reserve(shmaddr, size);
+        }
+    }
+
+    return ret;
+}
+
 #endif /* BSD_USER_BSD_MEM_H */

bsd-user/freebsd/os-syscall.c

@@ -871,6 +871,14 @@ static abi_long freebsd_syscall(void *cpu_env, int num, abi_long arg1,
         ret = do_bsd_shmctl(arg1, arg2, arg3);
         break;
 
+    case TARGET_FREEBSD_NR_shmat: /* shmat(2) */
+        ret = do_bsd_shmat(arg1, arg2, arg3);
+        break;
+
+    case TARGET_FREEBSD_NR_shmdt: /* shmdt(2) */
+        ret = do_bsd_shmdt(arg1);
+        break;
+
         /*
          * Misc
          */

bsd-user/mmap.c

@@ -636,7 +636,7 @@ fail:
     return -1;
 }
 
-static void mmap_reserve(abi_ulong start, abi_ulong size)
+void mmap_reserve(abi_ulong start, abi_ulong size)
 {
     abi_ulong real_start;
     abi_ulong real_end;

bsd-user/qemu.h

@@ -233,6 +233,7 @@ abi_long target_mremap(abi_ulong old_addr, abi_ulong old_size,
 int target_msync(abi_ulong start, abi_ulong len, int flags);
 extern abi_ulong mmap_next_start;
 abi_ulong mmap_find_vma(abi_ulong start, abi_ulong size);
+void mmap_reserve(abi_ulong start, abi_ulong size);
 void TSA_NO_TSA mmap_fork_start(void);
 void TSA_NO_TSA mmap_fork_end(int child);