Introduce Virtio-loopback epsilon release:

Epsilon release introduces a new compatibility layer which make virtio-loopback
design to work with QEMU and rust-vmm vhost-user backend without require any
changes.

Signed-off-by: Timos Ampelikiotis <t.ampelikiotis@virtualopensystems.com>
Change-Id: I52e57563e08a7d0bdc002f8e928ee61ba0c53dd9

1 files changed, 138 insertions, 0 deletions

diff --git a/linux-user/riscv/cpu_loop.c b/linux-user/riscv/cpu_loop.c
new file mode 100644
index 000000000..b301dac80
--- /dev/null
+++ b/linux-user/riscv/cpu_loop.c
@@ -0,0 +1,138 @@
+/*
+ *  qemu user cpu loop
+ *
+ *  Copyright (c) 2003-2008 Fabrice Bellard
+ *
+ *  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-common.h"
+#include "qemu/error-report.h"
+#include "qemu.h"
+#include "user-internals.h"
+#include "cpu_loop-common.h"
+#include "signal-common.h"
+#include "elf.h"
+#include "semihosting/common-semi.h"
+
+void cpu_loop(CPURISCVState *env)
+{
+    CPUState *cs = env_cpu(env);
+    int trapnr, signum, sigcode;
+    target_ulong sigaddr;
+    target_ulong ret;
+
+    for (;;) {
+        cpu_exec_start(cs);
+        trapnr = cpu_exec(cs);
+        cpu_exec_end(cs);
+        process_queued_cpu_work(cs);
+
+        signum = 0;
+        sigcode = 0;
+        sigaddr = 0;
+
+        switch (trapnr) {
+        case EXCP_INTERRUPT:
+            /* just indicate that signals should be handled asap */
+            break;
+        case EXCP_ATOMIC:
+            cpu_exec_step_atomic(cs);
+            break;
+        case RISCV_EXCP_U_ECALL:
+            env->pc += 4;
+            if (env->gpr[xA7] == TARGET_NR_arch_specific_syscall + 15) {
+                /* riscv_flush_icache_syscall is a no-op in QEMU as
+                   self-modifying code is automatically detected */
+                ret = 0;
+            } else {
+                ret = do_syscall(env,
+                                 env->gpr[(env->elf_flags & EF_RISCV_RVE)
+                                    ? xT0 : xA7],
+                                 env->gpr[xA0],
+                                 env->gpr[xA1],
+                                 env->gpr[xA2],
+                                 env->gpr[xA3],
+                                 env->gpr[xA4],
+                                 env->gpr[xA5],
+                                 0, 0);
+            }
+            if (ret == -TARGET_ERESTARTSYS) {
+                env->pc -= 4;
+            } else if (ret != -TARGET_QEMU_ESIGRETURN) {
+                env->gpr[xA0] = ret;
+            }
+            if (cs->singlestep_enabled) {
+                goto gdbstep;
+            }
+            break;
+        case RISCV_EXCP_ILLEGAL_INST:
+            signum = TARGET_SIGILL;
+            sigcode = TARGET_ILL_ILLOPC;
+            break;
+        case RISCV_EXCP_BREAKPOINT:
+            signum = TARGET_SIGTRAP;
+            sigcode = TARGET_TRAP_BRKPT;
+            sigaddr = env->pc;
+            break;
+        case RISCV_EXCP_SEMIHOST:
+            env->gpr[xA0] = do_common_semihosting(cs);
+            env->pc += 4;
+            break;
+        case EXCP_DEBUG:
+        gdbstep:
+            signum = TARGET_SIGTRAP;
+            sigcode = TARGET_TRAP_BRKPT;
+            break;
+        default:
+            EXCP_DUMP(env, "\nqemu: unhandled CPU exception %#x - aborting\n",
+                     trapnr);
+            exit(EXIT_FAILURE);
+        }
+
+        if (signum) {
+            target_siginfo_t info = {
+                .si_signo = signum,
+                .si_errno = 0,
+                .si_code = sigcode,
+                ._sifields._sigfault._addr = sigaddr
+            };
+            queue_signal(env, info.si_signo, QEMU_SI_FAULT, &info);
+        }
+
+        process_pending_signals(env);
+    }
+}
+
+void target_cpu_copy_regs(CPUArchState *env, struct target_pt_regs *regs)
+{
+    CPUState *cpu = env_cpu(env);
+    TaskState *ts = cpu->opaque;
+    struct image_info *info = ts->info;
+
+    env->pc = regs->sepc;
+    env->gpr[xSP] = regs->sp;
+    env->elf_flags = info->elf_flags;
+
+    if ((env->misa_ext & RVE) && !(env->elf_flags & EF_RISCV_RVE)) {
+        error_report("Incompatible ELF: RVE cpu requires RVE ABI binary");
+        exit(EXIT_FAILURE);
+    }
+
+    ts->stack_base = info->start_stack;
+    ts->heap_base = info->brk;
+    /* This will be filled in on the first SYS_HEAPINFO call.  */
+    ts->heap_limit = 0;
+}