bsd-user/arm/target_arch_sigtramp.h: Signal Trampoline for arm

Copy of the signal trampoline code for arm, as well as setup_sigtramp to
write it to the stack.

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

bsd-user/arm/target_arch_sigtramp.h

+/*
+ *  arm sysarch() system call emulation
+ *
+ *  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/>.
+ */
+
+#ifndef _TARGET_ARCH_SIGTRAMP_H_
+#define _TARGET_ARCH_SIGTRAMP_H_
+
+/* Compare to arm/arm/locore.S ENTRY_NP(sigcode) */
+static inline abi_long setup_sigtramp(abi_ulong offset, unsigned sigf_uc,
+        unsigned sys_sigreturn)
+{
+    int i;
+    uint32_t sys_exit = TARGET_FREEBSD_NR_exit;
+    uint32_t sigtramp_code[] = {
+    /* 1 */ 0xE1A0000D,                  /* mov r0, sp */
+    /* 2 */ 0xE2800000 + sigf_uc,        /* add r0, r0, #SIGF_UC */
+    /* 3 */ 0xE59F700C,                  /* ldr r7, [pc, #12] */
+    /* 4 */ 0xEF000000 + sys_sigreturn,  /* swi (SYS_sigreturn) */
+    /* 5 */ 0xE59F7008,                  /* ldr r7, [pc, #8] */
+    /* 6 */ 0xEF000000 + sys_exit,       /* swi (SYS_exit)*/
+    /* 7 */ 0xEAFFFFFA,                  /* b . -16 */
+    /* 8 */ sys_sigreturn,
+    /* 9 */ sys_exit
+    };
+
+    G_STATIC_ASSERT(sizeof(sigtramp_code) == TARGET_SZSIGCODE);
+
+    for (i = 0; i < 9; i++) {
+        tswap32s(&sigtramp_code[i]);
+    }
+
+    return memcpy_to_target(offset, sigtramp_code, TARGET_SZSIGCODE);
+}
+#endif /* _TARGET_ARCH_SIGTRAMP_H_ */