bsd-user/arm/signal.c: arm set_sigtramp_args

Implement set_sigtramp_args to setup the arguments to the sigtramp
calls.

Signed-off-by: Stacey Son <sson@FreeBSD.org>
Signed-off-by: Warner Losh <imp@bsdimp.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

bsd-user/arm/signal.c

+/*
+ *  arm signal functions
+ *
+ *  Copyright (c) 2013 Stacey D. Son
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or
+ *  (at your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "qemu.h"
+
+/*
+ * Compare to arm/arm/machdep.c sendsig()
+ * Assumes that target stack frame memory is locked.
+ */
+abi_long set_sigtramp_args(CPUARMState *env, int sig,
+                           struct target_sigframe *frame,
+                           abi_ulong frame_addr,
+                           struct target_sigaction *ka)
+{
+    /*
+     * Arguments to signal handler:
+     *  r0 = signal number
+     *  r1 = siginfo pointer
+     *  r2 = ucontext pointer
+     *  r5 = ucontext pointer
+     *  pc = signal handler pointer
+     *  sp = sigframe struct pointer
+     *  lr = sigtramp at base of user stack
+     */
+
+    env->regs[0] = sig;
+    env->regs[1] = frame_addr +
+        offsetof(struct target_sigframe, sf_si);
+    env->regs[2] = frame_addr +
+        offsetof(struct target_sigframe, sf_uc);
+
+    /* the trampoline uses r5 as the uc address */
+    env->regs[5] = frame_addr +
+        offsetof(struct target_sigframe, sf_uc);
+    env->regs[TARGET_REG_PC] = ka->_sa_handler & ~1;
+    env->regs[TARGET_REG_SP] = frame_addr;
+    env->regs[TARGET_REG_LR] = TARGET_PS_STRINGS - TARGET_SZSIGCODE;
+    /*
+     * Low bit indicates whether or not we're entering thumb mode.
+     */
+    cpsr_write(env, (ka->_sa_handler & 1) * CPSR_T, CPSR_T, CPSRWriteByInstr);
+
+    return 0;
+}