[PATCH v3 11/11] bsd-user: implement sysctlbyname(2)

[Warner Losh <imp@bsdimp.com>]

From: Kyle Evans <kevans@FreeBSD.org>

do_freebsd_sysctlbyname needs to translate the 'name' back down to a OID
so we can intercept the special ones. Do that and call the common wrapper
do_freebsd_sysctl_oid.

Signed-off-by: Kyle Evans <kevans@FreeBSD.org>
Reviewed-by: Warner Losh <imp@bsdimp.com>
Signed-off-by: Warner Losh <imp@bsdimp.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
---
 bsd-user/freebsd/os-sys.c     | 67 +++++++++++++++++++++++++++++++++++
 bsd-user/freebsd/os-syscall.c |  4 +++
 bsd-user/qemu.h               |  3 ++
 3 files changed, 74 insertions(+)

diff --git a/bsd-user/freebsd/os-sys.c b/bsd-user/freebsd/os-sys.c
index f07ae7da740..d9386d3e7ef 100644
--- a/bsd-user/freebsd/os-sys.c
+++ b/bsd-user/freebsd/os-sys.c
@@ -472,6 +472,73 @@ out:
     return ret;
 }
 
+/*
+ * This syscall was created to make sysctlbyname(3) more efficient, but we can't
+ * really provide it in bsd-user.  Notably, we must always translate the names
+ * independently since some sysctl values have to be faked for the target
+ * environment, so it still has to break down to two syscalls for the underlying
+ * implementation.
+ */
+abi_long do_freebsd_sysctlbyname(CPUArchState *env, abi_ulong namep,
+        int32_t namelen, abi_ulong oldp, abi_ulong oldlenp, abi_ulong newp,
+        abi_ulong newlen)
+{
+    abi_long ret = -TARGET_EFAULT;
+    void *holdp = NULL, *hnewp = NULL;
+    char *snamep = NULL;
+    int oid[CTL_MAXNAME + 2];
+    size_t holdlen, oidplen;
+    abi_ulong oldlen = 0;
+
+    /* oldlenp is read/write, pre-check here for write */
+    if (oldlenp) {
+        if (!access_ok(VERIFY_WRITE, oldlenp, sizeof(abi_ulong)) ||
+            get_user_ual(oldlen, oldlenp)) {
+            goto out;
+        }
+    }
+    snamep = lock_user_string(namep);
+    if (snamep == NULL) {
+        goto out;
+    }
+    if (newp) {
+        hnewp = lock_user(VERIFY_READ, newp, newlen, 1);
+        if (hnewp == NULL) {
+            goto out;
+        }
+    }
+    if (oldp) {
+        holdp = lock_user(VERIFY_WRITE, oldp, oldlen, 0);
+        if (holdp == NULL) {
+            goto out;
+        }
+    }
+    holdlen = oldlen;
+
+    oidplen = ARRAY_SIZE(oid);
+    if (sysctlnametomib(snamep, oid, &oidplen) != 0) {
+        ret = -TARGET_EINVAL;
+        goto out;
+    }
+
+    ret = do_freebsd_sysctl_oid(env, oid, oidplen, holdp, &holdlen, hnewp,
+        newlen);
+
+    /*
+     * writeability pre-checked above. __sysctl(2) returns ENOMEM and updates
+     * oldlenp for the proper size to use.
+     */
+    if (oldlenp && (ret == 0 || ret == -TARGET_ENOMEM)) {
+        put_user_ual(holdlen, oldlenp);
+    }
+out:
+    unlock_user(snamep, namep, 0);
+    unlock_user(holdp, oldp, ret == 0 ? holdlen : 0);
+    unlock_user(hnewp, newp, 0);
+
+    return ret;
+}
+
 abi_long do_freebsd_sysctl(CPUArchState *env, abi_ulong namep, int32_t namelen,
         abi_ulong oldp, abi_ulong oldlenp, abi_ulong newp, abi_ulong newlen)
 {
diff --git a/bsd-user/freebsd/os-syscall.c b/bsd-user/freebsd/os-syscall.c
index 20ab3d4d9a1..179a20c304b 100644
--- a/bsd-user/freebsd/os-syscall.c
+++ b/bsd-user/freebsd/os-syscall.c
@@ -498,6 +498,10 @@ static abi_long freebsd_syscall(void *cpu_env, int num, abi_long arg1,
         ret = do_freebsd_sysctl(cpu_env, arg1, arg2, arg3, arg4, arg5, arg6);
         break;
 
+    case TARGET_FREEBSD_NR___sysctlbyname: /* sysctlbyname(2) */
+        ret = do_freebsd_sysctlbyname(cpu_env, arg1, arg2, arg3, arg4, arg5, arg6);
+        break;
+
     case TARGET_FREEBSD_NR_sysarch: /* sysarch(2) */
         ret = do_freebsd_sysarch(cpu_env, arg1, arg2);
         break;
diff --git a/bsd-user/qemu.h b/bsd-user/qemu.h
index c7248cfde6f..e24a8cfcfb1 100644
--- a/bsd-user/qemu.h
+++ b/bsd-user/qemu.h
@@ -254,6 +254,9 @@ int host_to_target_errno(int err);
 /* os-sys.c */
 abi_long do_freebsd_sysctl(CPUArchState *env, abi_ulong namep, int32_t namelen,
         abi_ulong oldp, abi_ulong oldlenp, abi_ulong newp, abi_ulong newlen);
+abi_long do_freebsd_sysctlbyname(CPUArchState *env, abi_ulong namep,
+        int32_t namelen, abi_ulong oldp, abi_ulong oldlenp, abi_ulong newp,
+        abi_ulong newlen);
 abi_long do_freebsd_sysarch(void *cpu_env, abi_long arg1, abi_long arg2);
 
 /* user access */
-- 
2.39.1