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, 209 insertions, 0 deletions

diff --git a/linux-user/riscv/signal.c b/linux-user/riscv/signal.c
new file mode 100644
index 000000000..a0f9542ce
--- /dev/null
+++ b/linux-user/riscv/signal.c
@@ -0,0 +1,209 @@
+/*
+ *  Emulation of Linux signals
+ *
+ *  Copyright (c) 2003 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.h"
+#include "user-internals.h"
+#include "signal-common.h"
+#include "linux-user/trace.h"
+
+/* Signal handler invocation must be transparent for the code being
+   interrupted. Complete CPU (hart) state is saved on entry and restored
+   before returning from the handler. Process sigmask is also saved to block
+   signals while the handler is running. The handler gets its own stack,
+   which also doubles as storage for the CPU state and sigmask.
+
+   The code below is qemu re-implementation of arch/riscv/kernel/signal.c */
+
+struct target_sigcontext {
+    abi_long pc;
+    abi_long gpr[31]; /* x0 is not present, so all offsets must be -1 */
+    uint64_t fpr[32];
+    uint32_t fcsr;
+}; /* cf. riscv-linux:arch/riscv/include/uapi/asm/ptrace.h */
+
+struct target_ucontext {
+    unsigned long uc_flags;
+    struct target_ucontext *uc_link;
+    target_stack_t uc_stack;
+    target_sigset_t uc_sigmask;
+    uint8_t   __unused[1024 / 8 - sizeof(target_sigset_t)];
+    struct target_sigcontext uc_mcontext QEMU_ALIGNED(16);
+};
+
+struct target_rt_sigframe {
+    struct target_siginfo info;
+    struct target_ucontext uc;
+};
+
+static abi_ulong get_sigframe(struct target_sigaction *ka,
+                              CPURISCVState *regs, size_t framesize)
+{
+    abi_ulong sp = get_sp_from_cpustate(regs);
+
+    /* If we are on the alternate signal stack and would overflow it, don't.
+       Return an always-bogus address instead so we will die with SIGSEGV. */
+    if (on_sig_stack(sp) && !likely(on_sig_stack(sp - framesize))) {
+        return -1L;
+    }
+
+    /* This is the X/Open sanctioned signal stack switching.  */
+    sp = target_sigsp(sp, ka) - framesize;
+
+    /* XXX: kernel aligns with 0xf ? */
+    sp &= ~3UL; /* align sp on 4-byte boundary */
+
+    return sp;
+}
+
+static void setup_sigcontext(struct target_sigcontext *sc, CPURISCVState *env)
+{
+    int i;
+
+    __put_user(env->pc, &sc->pc);
+
+    for (i = 1; i < 32; i++) {
+        __put_user(env->gpr[i], &sc->gpr[i - 1]);
+    }
+    for (i = 0; i < 32; i++) {
+        __put_user(env->fpr[i], &sc->fpr[i]);
+    }
+
+    uint32_t fcsr = riscv_csr_read(env, CSR_FCSR);
+    __put_user(fcsr, &sc->fcsr);
+}
+
+static void setup_ucontext(struct target_ucontext *uc,
+                           CPURISCVState *env, target_sigset_t *set)
+{
+    __put_user(0,    &(uc->uc_flags));
+    __put_user(0,    &(uc->uc_link));
+
+    target_save_altstack(&uc->uc_stack, env);
+
+    int i;
+    for (i = 0; i < TARGET_NSIG_WORDS; i++) {
+        __put_user(set->sig[i], &(uc->uc_sigmask.sig[i]));
+    }
+
+    setup_sigcontext(&uc->uc_mcontext, env);
+}
+
+void setup_rt_frame(int sig, struct target_sigaction *ka,
+                    target_siginfo_t *info,
+                    target_sigset_t *set, CPURISCVState *env)
+{
+    abi_ulong frame_addr;
+    struct target_rt_sigframe *frame;
+
+    frame_addr = get_sigframe(ka, env, sizeof(*frame));
+    trace_user_setup_rt_frame(env, frame_addr);
+
+    if (!lock_user_struct(VERIFY_WRITE, frame, frame_addr, 0)) {
+        goto badframe;
+    }
+
+    setup_ucontext(&frame->uc, env, set);
+    tswap_siginfo(&frame->info, info);
+
+    env->pc = ka->_sa_handler;
+    env->gpr[xSP] = frame_addr;
+    env->gpr[xA0] = sig;
+    env->gpr[xA1] = frame_addr + offsetof(struct target_rt_sigframe, info);
+    env->gpr[xA2] = frame_addr + offsetof(struct target_rt_sigframe, uc);
+    env->gpr[xRA] = default_rt_sigreturn;
+
+    return;
+
+badframe:
+    unlock_user_struct(frame, frame_addr, 1);
+    if (sig == TARGET_SIGSEGV) {
+        ka->_sa_handler = TARGET_SIG_DFL;
+    }
+    force_sig(TARGET_SIGSEGV);
+}
+
+static void restore_sigcontext(CPURISCVState *env, struct target_sigcontext *sc)
+{
+    int i;
+
+    __get_user(env->pc, &sc->pc);
+
+    for (i = 1; i < 32; ++i) {
+        __get_user(env->gpr[i], &sc->gpr[i - 1]);
+    }
+    for (i = 0; i < 32; ++i) {
+        __get_user(env->fpr[i], &sc->fpr[i]);
+    }
+
+    uint32_t fcsr;
+    __get_user(fcsr, &sc->fcsr);
+    riscv_csr_write(env, CSR_FCSR, fcsr);
+}
+
+static void restore_ucontext(CPURISCVState *env, struct target_ucontext *uc)
+{
+    sigset_t blocked;
+    target_sigset_t target_set;
+    int i;
+
+    target_sigemptyset(&target_set);
+    for (i = 0; i < TARGET_NSIG_WORDS; i++) {
+        __get_user(target_set.sig[i], &(uc->uc_sigmask.sig[i]));
+    }
+
+    target_to_host_sigset_internal(&blocked, &target_set);
+    set_sigmask(&blocked);
+
+    restore_sigcontext(env, &uc->uc_mcontext);
+}
+
+long do_rt_sigreturn(CPURISCVState *env)
+{
+    struct target_rt_sigframe *frame;
+    abi_ulong frame_addr;
+
+    frame_addr = env->gpr[xSP];
+    trace_user_do_sigreturn(env, frame_addr);
+    if (!lock_user_struct(VERIFY_READ, frame, frame_addr, 1)) {
+        goto badframe;
+    }
+
+    restore_ucontext(env, &frame->uc);
+    target_restore_altstack(&frame->uc.uc_stack, env);
+
+    unlock_user_struct(frame, frame_addr, 0);
+    return -TARGET_QEMU_ESIGRETURN;
+
+badframe:
+    unlock_user_struct(frame, frame_addr, 0);
+    force_sig(TARGET_SIGSEGV);
+    return 0;
+}
+
+void setup_sigtramp(abi_ulong sigtramp_page)
+{
+    uint32_t *tramp = lock_user(VERIFY_WRITE, sigtramp_page, 8, 0);
+    assert(tramp != NULL);
+
+    __put_user(0x08b00893, tramp + 0);  /* li a7, 139 = __NR_rt_sigreturn */
+    __put_user(0x00000073, tramp + 1);  /* ecall */
+
+    default_rt_sigreturn = sigtramp_page;
+    unlock_user(tramp, sigtramp_page, 8);
+}