bsd-user: Implement RISC-V signal trampoline setup functions

Added functions for setting up the RISC-V signal trampoline and signal
frame:

'set_sigtramp_args()': Configures the RISC-V CPU state with arguments
for the signal handler. It sets up the registers with the signal
number,pointers to the signal info and user context, the signal handler
address, and the signal frame pointer.

'setup_sigframe_arch()': Initializes the signal frame with the current
machine context.This function copies the context from the CPU state to
the signal frame, preparing it for the signal handler.

Signed-off-by: Mark Corbin <mark@dibsco.co.uk>
Signed-off-by: Ajeet Singh <itachis@FreeBSD.org>
Signed-off-by: Warner Losh <imp@bsdimp.com>
Co-authored-by: Warner Losh <imp@bsdimp.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-ID: <20240916155119.14610-15-itachis@FreeBSD.org>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

1 files changed, 63 insertions, 0 deletions

diff --git a/bsd-user/riscv/signal.c b/bsd-user/riscv/signal.c
new file mode 100644
index 0000000..2597fec
--- /dev/null
+++ b/bsd-user/riscv/signal.c
@@ -0,0 +1,63 @@
+/*
+ *  RISC-V signal definitions
+ *
+ *  Copyright (c) 2019 Mark Corbin
+ *
+ *  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/osdep.h"
+
+#include "qemu.h"
+
+/*
+ * Compare with sendsig() in riscv/riscv/exec_machdep.c
+ * Assumes that target stack frame memory is locked.
+ */
+abi_long
+set_sigtramp_args(CPURISCVState *regs, int sig, struct target_sigframe *frame,
+    abi_ulong frame_addr, struct target_sigaction *ka)
+{
+    /*
+     * Arguments to signal handler:
+     *  a0 (10) = signal number
+     *  a1 (11) = siginfo pointer
+     *  a2 (12) = ucontext pointer
+     *  pc      = signal pointer handler
+     *  sp (2)  = sigframe pointer
+     *  ra (1)  = sigtramp at base of user stack
+     */
+
+     regs->gpr[xA0] = sig;
+     regs->gpr[xA1] = frame_addr +
+         offsetof(struct target_sigframe, sf_si);
+     regs->gpr[xA2] = frame_addr +
+         offsetof(struct target_sigframe, sf_uc);
+     regs->pc = ka->_sa_handler;
+     regs->gpr[xSP] = frame_addr;
+     regs->gpr[xRA] = TARGET_PS_STRINGS - TARGET_SZSIGCODE;
+     return 0;
+}
+
+/*
+ * Compare to riscv/riscv/exec_machdep.c sendsig()
+ * Assumes that the memory is locked if frame points to user memory.
+ */
+abi_long setup_sigframe_arch(CPURISCVState *env, abi_ulong frame_addr,
+                             struct target_sigframe *frame, int flags)
+{
+    target_mcontext_t *mcp = &frame->sf_uc.uc_mcontext;
+
+    get_mcontext(env, mcp, flags);
+    return 0;
+}