[PATCH 30/30] bsd-user/signal.c: do_sigaltstack

[Warner Losh <imp@bsdimp.com>]

Implement the meat of the sigaltstack(2) system call with do_sigaltstack.

Signed-off-by: Stacey Son <sson@FreeBSD.org>
Signed-off-by: Kyle Evans <kevans@freebsd.org>
Signed-off-by: Warner Losh <imp@bsdimp.com>
---
 bsd-user/qemu.h   |  1 +
 bsd-user/signal.c | 66 +++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 67 insertions(+)

diff --git a/bsd-user/qemu.h b/bsd-user/qemu.h
index c643d6ba246..fcdea460ed2 100644
--- a/bsd-user/qemu.h
+++ b/bsd-user/qemu.h
@@ -226,6 +226,7 @@ int host_to_target_signal(int sig);
 void host_to_target_sigset(target_sigset_t *d, const sigset_t *s);
 void target_to_host_sigset(sigset_t *d, const target_sigset_t *s);
 long do_sigreturn(CPUArchState *regs, abi_ulong addr);
+abi_long do_sigaltstack(abi_ulong uss_addr, abi_ulong uoss_addr, abi_ulong sp);
 int do_sigaction(int sig, const struct target_sigaction *act,
                 struct target_sigaction *oact);
 void QEMU_NORETURN force_sig(int target_sig);
diff --git a/bsd-user/signal.c b/bsd-user/signal.c
index f055d1db407..e5e5e28c60c 100644
--- a/bsd-user/signal.c
+++ b/bsd-user/signal.c
@@ -528,6 +528,72 @@ static void host_signal_handler(int host_sig, siginfo_t *info, void *puc)
     cpu_exit(thread_cpu);
 }
 
+/* do_sigaltstack() returns target values and errnos. */
+/* compare to kern/kern_sig.c sys_sigaltstack() and kern_sigaltstack() */
+abi_long do_sigaltstack(abi_ulong uss_addr, abi_ulong uoss_addr, abi_ulong sp)
+{
+    int ret;
+    target_stack_t oss;
+
+    if (uoss_addr) {
+        /* Save current signal stack params */
+        oss.ss_sp = tswapl(target_sigaltstack_used.ss_sp);
+        oss.ss_size = tswapl(target_sigaltstack_used.ss_size);
+        oss.ss_flags = tswapl(sas_ss_flags(sp));
+    }
+
+    if (uss_addr) {
+        target_stack_t *uss;
+        target_stack_t ss;
+        size_t minstacksize = TARGET_MINSIGSTKSZ;
+
+        ret = -TARGET_EFAULT;
+        if (!lock_user_struct(VERIFY_READ, uss, uss_addr, 1)) {
+            goto out;
+        }
+        __get_user(ss.ss_sp, &uss->ss_sp);
+        __get_user(ss.ss_size, &uss->ss_size);
+        __get_user(ss.ss_flags, &uss->ss_flags);
+        unlock_user_struct(uss, uss_addr, 0);
+
+        ret = -TARGET_EPERM;
+        if (on_sig_stack(sp)) {
+            goto out;
+        }
+
+        ret = -TARGET_EINVAL;
+        if (ss.ss_flags != TARGET_SS_DISABLE
+            && ss.ss_flags != TARGET_SS_ONSTACK
+            && ss.ss_flags != 0) {
+            goto out;
+        }
+
+        if (ss.ss_flags == TARGET_SS_DISABLE) {
+            ss.ss_size = 0;
+            ss.ss_sp = 0;
+        } else {
+            ret = -TARGET_ENOMEM;
+            if (ss.ss_size < minstacksize) {
+                goto out;
+            }
+        }
+
+        target_sigaltstack_used.ss_sp = ss.ss_sp;
+        target_sigaltstack_used.ss_size = ss.ss_size;
+    }
+
+    if (uoss_addr) {
+        ret = -TARGET_EFAULT;
+        if (copy_to_user(uoss_addr, &oss, sizeof(oss))) {
+            goto out;
+        }
+    }
+
+    ret = 0;
+out:
+    return ret;
+}
+
 static int fatal_signal(int sig)
 {
 
-- 
2.33.1