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, 630 insertions, 0 deletions

diff --git a/linux-user/arm/signal.c b/linux-user/arm/signal.c
new file mode 100644
index 000000000..df9f8e8eb
--- /dev/null
+++ b/linux-user/arm/signal.c
@@ -0,0 +1,630 @@
+/*
+ *  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"
+
+struct target_sigcontext {
+    abi_ulong trap_no;
+    abi_ulong error_code;
+    abi_ulong oldmask;
+    abi_ulong arm_r0;
+    abi_ulong arm_r1;
+    abi_ulong arm_r2;
+    abi_ulong arm_r3;
+    abi_ulong arm_r4;
+    abi_ulong arm_r5;
+    abi_ulong arm_r6;
+    abi_ulong arm_r7;
+    abi_ulong arm_r8;
+    abi_ulong arm_r9;
+    abi_ulong arm_r10;
+    abi_ulong arm_fp;
+    abi_ulong arm_ip;
+    abi_ulong arm_sp;
+    abi_ulong arm_lr;
+    abi_ulong arm_pc;
+    abi_ulong arm_cpsr;
+    abi_ulong fault_address;
+};
+
+struct target_ucontext {
+    abi_ulong tuc_flags;
+    abi_ulong tuc_link;
+    target_stack_t tuc_stack;
+    struct target_sigcontext tuc_mcontext;
+    target_sigset_t  tuc_sigmask;       /* mask last for extensibility */
+    char __unused[128 - sizeof(target_sigset_t)];
+    abi_ulong tuc_regspace[128] __attribute__((__aligned__(8)));
+};
+
+struct target_user_vfp {
+    uint64_t fpregs[32];
+    abi_ulong fpscr;
+};
+
+struct target_user_vfp_exc {
+    abi_ulong fpexc;
+    abi_ulong fpinst;
+    abi_ulong fpinst2;
+};
+
+struct target_vfp_sigframe {
+    abi_ulong magic;
+    abi_ulong size;
+    struct target_user_vfp ufp;
+    struct target_user_vfp_exc ufp_exc;
+} __attribute__((__aligned__(8)));
+
+struct target_iwmmxt_sigframe {
+    abi_ulong magic;
+    abi_ulong size;
+    uint64_t regs[16];
+    /* Note that not all the coprocessor control registers are stored here */
+    uint32_t wcssf;
+    uint32_t wcasf;
+    uint32_t wcgr0;
+    uint32_t wcgr1;
+    uint32_t wcgr2;
+    uint32_t wcgr3;
+} __attribute__((__aligned__(8)));
+
+#define TARGET_VFP_MAGIC 0x56465001
+#define TARGET_IWMMXT_MAGIC 0x12ef842a
+
+struct sigframe
+{
+    struct target_ucontext uc;
+    abi_ulong retcode[4];
+};
+
+struct rt_sigframe
+{
+    struct target_siginfo info;
+    struct sigframe sig;
+};
+
+static abi_ptr sigreturn_fdpic_tramp;
+
+/*
+ * Up to 3 words of 'retcode' in the sigframe are code,
+ * with retcode[3] being used by fdpic for the function descriptor.
+ * This code is not actually executed, but is retained for ABI compat.
+ *
+ * We will create a table of 8 retcode variants in the sigtramp page.
+ * Let each table entry use 3 words.
+ */
+#define RETCODE_WORDS  3
+#define RETCODE_BYTES  (RETCODE_WORDS * 4)
+
+static inline int valid_user_regs(CPUARMState *regs)
+{
+    return 1;
+}
+
+static void
+setup_sigcontext(struct target_sigcontext *sc, /*struct _fpstate *fpstate,*/
+                 CPUARMState *env, abi_ulong mask)
+{
+    __put_user(env->regs[0], &sc->arm_r0);
+    __put_user(env->regs[1], &sc->arm_r1);
+    __put_user(env->regs[2], &sc->arm_r2);
+    __put_user(env->regs[3], &sc->arm_r3);
+    __put_user(env->regs[4], &sc->arm_r4);
+    __put_user(env->regs[5], &sc->arm_r5);
+    __put_user(env->regs[6], &sc->arm_r6);
+    __put_user(env->regs[7], &sc->arm_r7);
+    __put_user(env->regs[8], &sc->arm_r8);
+    __put_user(env->regs[9], &sc->arm_r9);
+    __put_user(env->regs[10], &sc->arm_r10);
+    __put_user(env->regs[11], &sc->arm_fp);
+    __put_user(env->regs[12], &sc->arm_ip);
+    __put_user(env->regs[13], &sc->arm_sp);
+    __put_user(env->regs[14], &sc->arm_lr);
+    __put_user(env->regs[15], &sc->arm_pc);
+    __put_user(cpsr_read(env), &sc->arm_cpsr);
+
+    __put_user(/* current->thread.trap_no */ 0, &sc->trap_no);
+    __put_user(/* current->thread.error_code */ 0, &sc->error_code);
+    __put_user(/* current->thread.address */ 0, &sc->fault_address);
+    __put_user(mask, &sc->oldmask);
+}
+
+static inline abi_ulong
+get_sigframe(struct target_sigaction *ka, CPUARMState *regs, int framesize)
+{
+    unsigned long sp;
+
+    sp = target_sigsp(get_sp_from_cpustate(regs), ka);
+    /*
+     * ATPCS B01 mandates 8-byte alignment
+     */
+    return (sp - framesize) & ~7;
+}
+
+static int
+setup_return(CPUARMState *env, struct target_sigaction *ka, int usig,
+             struct sigframe *frame, abi_ulong sp_addr)
+{
+    abi_ulong handler = 0;
+    abi_ulong handler_fdpic_GOT = 0;
+    abi_ulong retcode;
+    int thumb, retcode_idx;
+    int is_fdpic = info_is_fdpic(((TaskState *)thread_cpu->opaque)->info);
+    bool copy_retcode;
+
+    if (is_fdpic) {
+        /* In FDPIC mode, ka->_sa_handler points to a function
+         * descriptor (FD). The first word contains the address of the
+         * handler. The second word contains the value of the PIC
+         * register (r9).  */
+        abi_ulong funcdesc_ptr = ka->_sa_handler;
+        if (get_user_ual(handler, funcdesc_ptr)
+            || get_user_ual(handler_fdpic_GOT, funcdesc_ptr + 4)) {
+            return 1;
+        }
+    } else {
+        handler = ka->_sa_handler;
+    }
+
+    thumb = handler & 1;
+    retcode_idx = thumb + (ka->sa_flags & TARGET_SA_SIGINFO ? 2 : 0);
+
+    uint32_t cpsr = cpsr_read(env);
+
+    cpsr &= ~CPSR_IT;
+    if (thumb) {
+        cpsr |= CPSR_T;
+    } else {
+        cpsr &= ~CPSR_T;
+    }
+    if (env->cp15.sctlr_el[1] & SCTLR_E0E) {
+        cpsr |= CPSR_E;
+    } else {
+        cpsr &= ~CPSR_E;
+    }
+
+    if (ka->sa_flags & TARGET_SA_RESTORER) {
+        if (is_fdpic) {
+            __put_user((abi_ulong)ka->sa_restorer, &frame->retcode[3]);
+            retcode = (sigreturn_fdpic_tramp +
+                       retcode_idx * RETCODE_BYTES + thumb);
+            copy_retcode = true;
+        } else {
+            retcode = ka->sa_restorer;
+            copy_retcode = false;
+        }
+    } else {
+        retcode = default_sigreturn + retcode_idx * RETCODE_BYTES + thumb;
+        copy_retcode = true;
+    }
+
+    /* Copy the code to the stack slot for ABI compatibility. */
+    if (copy_retcode) {
+        memcpy(frame->retcode, g2h_untagged(retcode & ~1), RETCODE_BYTES);
+    }
+
+    env->regs[0] = usig;
+    if (is_fdpic) {
+        env->regs[9] = handler_fdpic_GOT;
+    }
+    env->regs[13] = sp_addr;
+    env->regs[14] = retcode;
+    env->regs[15] = handler & (thumb ? ~1 : ~3);
+    cpsr_write(env, cpsr, CPSR_IT | CPSR_T | CPSR_E, CPSRWriteByInstr);
+
+    return 0;
+}
+
+static abi_ulong *setup_sigframe_vfp(abi_ulong *regspace, CPUARMState *env)
+{
+    int i;
+    struct target_vfp_sigframe *vfpframe;
+    vfpframe = (struct target_vfp_sigframe *)regspace;
+    __put_user(TARGET_VFP_MAGIC, &vfpframe->magic);
+    __put_user(sizeof(*vfpframe), &vfpframe->size);
+    for (i = 0; i < 32; i++) {
+        __put_user(*aa32_vfp_dreg(env, i), &vfpframe->ufp.fpregs[i]);
+    }
+    __put_user(vfp_get_fpscr(env), &vfpframe->ufp.fpscr);
+    __put_user(env->vfp.xregs[ARM_VFP_FPEXC], &vfpframe->ufp_exc.fpexc);
+    __put_user(env->vfp.xregs[ARM_VFP_FPINST], &vfpframe->ufp_exc.fpinst);
+    __put_user(env->vfp.xregs[ARM_VFP_FPINST2], &vfpframe->ufp_exc.fpinst2);
+    return (abi_ulong*)(vfpframe+1);
+}
+
+static abi_ulong *setup_sigframe_iwmmxt(abi_ulong *regspace, CPUARMState *env)
+{
+    int i;
+    struct target_iwmmxt_sigframe *iwmmxtframe;
+    iwmmxtframe = (struct target_iwmmxt_sigframe *)regspace;
+    __put_user(TARGET_IWMMXT_MAGIC, &iwmmxtframe->magic);
+    __put_user(sizeof(*iwmmxtframe), &iwmmxtframe->size);
+    for (i = 0; i < 16; i++) {
+        __put_user(env->iwmmxt.regs[i], &iwmmxtframe->regs[i]);
+    }
+    __put_user(env->vfp.xregs[ARM_IWMMXT_wCSSF], &iwmmxtframe->wcssf);
+    __put_user(env->vfp.xregs[ARM_IWMMXT_wCASF], &iwmmxtframe->wcssf);
+    __put_user(env->vfp.xregs[ARM_IWMMXT_wCGR0], &iwmmxtframe->wcgr0);
+    __put_user(env->vfp.xregs[ARM_IWMMXT_wCGR1], &iwmmxtframe->wcgr1);
+    __put_user(env->vfp.xregs[ARM_IWMMXT_wCGR2], &iwmmxtframe->wcgr2);
+    __put_user(env->vfp.xregs[ARM_IWMMXT_wCGR3], &iwmmxtframe->wcgr3);
+    return (abi_ulong*)(iwmmxtframe+1);
+}
+
+static void setup_sigframe(struct target_ucontext *uc,
+                           target_sigset_t *set, CPUARMState *env)
+{
+    struct target_sigaltstack stack;
+    int i;
+    abi_ulong *regspace;
+
+    /* Clear all the bits of the ucontext we don't use.  */
+    memset(uc, 0, offsetof(struct target_ucontext, tuc_mcontext));
+
+    memset(&stack, 0, sizeof(stack));
+    target_save_altstack(&stack, env);
+    memcpy(&uc->tuc_stack, &stack, sizeof(stack));
+
+    setup_sigcontext(&uc->tuc_mcontext, env, set->sig[0]);
+    /* Save coprocessor signal frame.  */
+    regspace = uc->tuc_regspace;
+    if (cpu_isar_feature(aa32_vfp_simd, env_archcpu(env))) {
+        regspace = setup_sigframe_vfp(regspace, env);
+    }
+    if (arm_feature(env, ARM_FEATURE_IWMMXT)) {
+        regspace = setup_sigframe_iwmmxt(regspace, env);
+    }
+
+    /* Write terminating magic word */
+    __put_user(0, regspace);
+
+    for(i = 0; i < TARGET_NSIG_WORDS; i++) {
+        __put_user(set->sig[i], &uc->tuc_sigmask.sig[i]);
+    }
+}
+
+void setup_frame(int usig, struct target_sigaction *ka,
+                 target_sigset_t *set, CPUARMState *regs)
+{
+    struct sigframe *frame;
+    abi_ulong frame_addr = get_sigframe(ka, regs, sizeof(*frame));
+
+    trace_user_setup_frame(regs, frame_addr);
+    if (!lock_user_struct(VERIFY_WRITE, frame, frame_addr, 0)) {
+        goto sigsegv;
+    }
+
+    setup_sigframe(&frame->uc, set, regs);
+
+    if (setup_return(regs, ka, usig, frame, frame_addr)) {
+        goto sigsegv;
+    }
+
+    unlock_user_struct(frame, frame_addr, 1);
+    return;
+sigsegv:
+    unlock_user_struct(frame, frame_addr, 1);
+    force_sigsegv(usig);
+}
+
+void setup_rt_frame(int usig, struct target_sigaction *ka,
+                    target_siginfo_t *info,
+                    target_sigset_t *set, CPUARMState *env)
+{
+    struct rt_sigframe *frame;
+    abi_ulong frame_addr = get_sigframe(ka, env, sizeof(*frame));
+    abi_ulong info_addr, uc_addr;
+
+    trace_user_setup_rt_frame(env, frame_addr);
+    if (!lock_user_struct(VERIFY_WRITE, frame, frame_addr, 0)) {
+        goto sigsegv;
+    }
+
+    info_addr = frame_addr + offsetof(struct rt_sigframe, info);
+    uc_addr = frame_addr + offsetof(struct rt_sigframe, sig.uc);
+    tswap_siginfo(&frame->info, info);
+
+    setup_sigframe(&frame->sig.uc, set, env);
+
+    if (setup_return(env, ka, usig, &frame->sig, frame_addr)) {
+        goto sigsegv;
+    }
+
+    env->regs[1] = info_addr;
+    env->regs[2] = uc_addr;
+
+    unlock_user_struct(frame, frame_addr, 1);
+    return;
+sigsegv:
+    unlock_user_struct(frame, frame_addr, 1);
+    force_sigsegv(usig);
+}
+
+static int
+restore_sigcontext(CPUARMState *env, struct target_sigcontext *sc)
+{
+    int err = 0;
+    uint32_t cpsr;
+
+    __get_user(env->regs[0], &sc->arm_r0);
+    __get_user(env->regs[1], &sc->arm_r1);
+    __get_user(env->regs[2], &sc->arm_r2);
+    __get_user(env->regs[3], &sc->arm_r3);
+    __get_user(env->regs[4], &sc->arm_r4);
+    __get_user(env->regs[5], &sc->arm_r5);
+    __get_user(env->regs[6], &sc->arm_r6);
+    __get_user(env->regs[7], &sc->arm_r7);
+    __get_user(env->regs[8], &sc->arm_r8);
+    __get_user(env->regs[9], &sc->arm_r9);
+    __get_user(env->regs[10], &sc->arm_r10);
+    __get_user(env->regs[11], &sc->arm_fp);
+    __get_user(env->regs[12], &sc->arm_ip);
+    __get_user(env->regs[13], &sc->arm_sp);
+    __get_user(env->regs[14], &sc->arm_lr);
+    __get_user(env->regs[15], &sc->arm_pc);
+    __get_user(cpsr, &sc->arm_cpsr);
+    cpsr_write(env, cpsr, CPSR_USER | CPSR_EXEC, CPSRWriteByInstr);
+
+    err |= !valid_user_regs(env);
+
+    return err;
+}
+
+static abi_ulong *restore_sigframe_vfp(CPUARMState *env, abi_ulong *regspace)
+{
+    int i;
+    abi_ulong magic, sz;
+    uint32_t fpscr, fpexc;
+    struct target_vfp_sigframe *vfpframe;
+    vfpframe = (struct target_vfp_sigframe *)regspace;
+
+    __get_user(magic, &vfpframe->magic);
+    __get_user(sz, &vfpframe->size);
+    if (magic != TARGET_VFP_MAGIC || sz != sizeof(*vfpframe)) {
+        return 0;
+    }
+    for (i = 0; i < 32; i++) {
+        __get_user(*aa32_vfp_dreg(env, i), &vfpframe->ufp.fpregs[i]);
+    }
+    __get_user(fpscr, &vfpframe->ufp.fpscr);
+    vfp_set_fpscr(env, fpscr);
+    __get_user(fpexc, &vfpframe->ufp_exc.fpexc);
+    /* Sanitise FPEXC: ensure VFP is enabled, FPINST2 is invalid
+     * and the exception flag is cleared
+     */
+    fpexc |= (1 << 30);
+    fpexc &= ~((1 << 31) | (1 << 28));
+    env->vfp.xregs[ARM_VFP_FPEXC] = fpexc;
+    __get_user(env->vfp.xregs[ARM_VFP_FPINST], &vfpframe->ufp_exc.fpinst);
+    __get_user(env->vfp.xregs[ARM_VFP_FPINST2], &vfpframe->ufp_exc.fpinst2);
+    return (abi_ulong*)(vfpframe + 1);
+}
+
+static abi_ulong *restore_sigframe_iwmmxt(CPUARMState *env,
+                                          abi_ulong *regspace)
+{
+    int i;
+    abi_ulong magic, sz;
+    struct target_iwmmxt_sigframe *iwmmxtframe;
+    iwmmxtframe = (struct target_iwmmxt_sigframe *)regspace;
+
+    __get_user(magic, &iwmmxtframe->magic);
+    __get_user(sz, &iwmmxtframe->size);
+    if (magic != TARGET_IWMMXT_MAGIC || sz != sizeof(*iwmmxtframe)) {
+        return 0;
+    }
+    for (i = 0; i < 16; i++) {
+        __get_user(env->iwmmxt.regs[i], &iwmmxtframe->regs[i]);
+    }
+    __get_user(env->vfp.xregs[ARM_IWMMXT_wCSSF], &iwmmxtframe->wcssf);
+    __get_user(env->vfp.xregs[ARM_IWMMXT_wCASF], &iwmmxtframe->wcssf);
+    __get_user(env->vfp.xregs[ARM_IWMMXT_wCGR0], &iwmmxtframe->wcgr0);
+    __get_user(env->vfp.xregs[ARM_IWMMXT_wCGR1], &iwmmxtframe->wcgr1);
+    __get_user(env->vfp.xregs[ARM_IWMMXT_wCGR2], &iwmmxtframe->wcgr2);
+    __get_user(env->vfp.xregs[ARM_IWMMXT_wCGR3], &iwmmxtframe->wcgr3);
+    return (abi_ulong*)(iwmmxtframe + 1);
+}
+
+static int do_sigframe_return(CPUARMState *env,
+                              target_ulong context_addr,
+                              struct target_ucontext *uc)
+{
+    sigset_t host_set;
+    abi_ulong *regspace;
+
+    target_to_host_sigset(&host_set, &uc->tuc_sigmask);
+    set_sigmask(&host_set);
+
+    if (restore_sigcontext(env, &uc->tuc_mcontext)) {
+        return 1;
+    }
+
+    /* Restore coprocessor signal frame */
+    regspace = uc->tuc_regspace;
+    if (cpu_isar_feature(aa32_vfp_simd, env_archcpu(env))) {
+        regspace = restore_sigframe_vfp(env, regspace);
+        if (!regspace) {
+            return 1;
+        }
+    }
+    if (arm_feature(env, ARM_FEATURE_IWMMXT)) {
+        regspace = restore_sigframe_iwmmxt(env, regspace);
+        if (!regspace) {
+            return 1;
+        }
+    }
+
+    target_restore_altstack(&uc->tuc_stack, env);
+
+#if 0
+    /* Send SIGTRAP if we're single-stepping */
+    if (ptrace_cancel_bpt(current))
+        send_sig(SIGTRAP, current, 1);
+#endif
+
+    return 0;
+}
+
+long do_sigreturn(CPUARMState *env)
+{
+    abi_ulong frame_addr;
+    struct sigframe *frame = NULL;
+
+    /*
+     * Since we stacked the signal on a 64-bit boundary,
+     * then 'sp' should be word aligned here.  If it's
+     * not, then the user is trying to mess with us.
+     */
+    frame_addr = env->regs[13];
+    trace_user_do_sigreturn(env, frame_addr);
+    if (frame_addr & 7) {
+        goto badframe;
+    }
+
+    if (!lock_user_struct(VERIFY_READ, frame, frame_addr, 1)) {
+        goto badframe;
+    }
+
+    if (do_sigframe_return(env,
+                           frame_addr + offsetof(struct sigframe, uc),
+                           &frame->uc)) {
+        goto badframe;
+    }
+
+    unlock_user_struct(frame, frame_addr, 0);
+    return -TARGET_QEMU_ESIGRETURN;
+
+badframe:
+    unlock_user_struct(frame, frame_addr, 0);
+    force_sig(TARGET_SIGSEGV);
+    return -TARGET_QEMU_ESIGRETURN;
+}
+
+long do_rt_sigreturn(CPUARMState *env)
+{
+    abi_ulong frame_addr;
+    struct rt_sigframe *frame = NULL;
+
+    /*
+     * Since we stacked the signal on a 64-bit boundary,
+     * then 'sp' should be word aligned here.  If it's
+     * not, then the user is trying to mess with us.
+     */
+    frame_addr = env->regs[13];
+    trace_user_do_rt_sigreturn(env, frame_addr);
+    if (frame_addr & 7) {
+        goto badframe;
+    }
+
+    if (!lock_user_struct(VERIFY_READ, frame, frame_addr, 1)) {
+        goto badframe;
+    }
+
+    if (do_sigframe_return(env,
+                           frame_addr + offsetof(struct rt_sigframe, sig.uc),
+                           &frame->sig.uc)) {
+        goto badframe;
+    }
+
+    unlock_user_struct(frame, frame_addr, 0);
+    return -TARGET_QEMU_ESIGRETURN;
+
+badframe:
+    unlock_user_struct(frame, frame_addr, 0);
+    force_sig(TARGET_SIGSEGV);
+    return -TARGET_QEMU_ESIGRETURN;
+}
+
+/*
+ * EABI syscalls pass the number via r7.
+ * Note that the kernel still adds the OABI syscall number to the trap,
+ * presumably for backward ABI compatibility with unwinders.
+ */
+#define ARM_MOV_R7_IMM(X)       (0xe3a07000 | (X))
+#define ARM_SWI_SYS(X)          (0xef000000 | (X) | ARM_SYSCALL_BASE)
+
+#define THUMB_MOVS_R7_IMM(X)    (0x2700 | (X))
+#define THUMB_SWI_SYS           0xdf00
+
+static void write_arm_sigreturn(uint32_t *rc, int syscall)
+{
+    __put_user(ARM_MOV_R7_IMM(syscall), rc);
+    __put_user(ARM_SWI_SYS(syscall), rc + 1);
+    /* Wrote 8 of 12 bytes */
+}
+
+static void write_thm_sigreturn(uint32_t *rc, int syscall)
+{
+    __put_user(THUMB_SWI_SYS << 16 | THUMB_MOVS_R7_IMM(syscall), rc);
+    /* Wrote 4 of 12 bytes */
+}
+
+/*
+ * Stub needed to make sure the FD register (r9) contains the right value.
+ * Use the same instruction sequence as the kernel.
+ */
+static void write_arm_fdpic_sigreturn(uint32_t *rc, int ofs)
+{
+    assert(ofs <= 0xfff);
+    __put_user(0xe59d3000 | ofs, rc + 0);   /* ldr r3, [sp, #ofs] */
+    __put_user(0xe8930908, rc + 1);         /* ldm r3, { r3, r9 } */
+    __put_user(0xe12fff13, rc + 2);         /* bx  r3 */
+    /* Wrote 12 of 12 bytes */
+}
+
+static void write_thm_fdpic_sigreturn(void *vrc, int ofs)
+{
+    uint16_t *rc = vrc;
+
+    assert((ofs & ~0x3fc) == 0);
+    __put_user(0x9b00 | (ofs >> 2), rc + 0);      /* ldr r3, [sp, #ofs] */
+    __put_user(0xcb0c, rc + 1);                   /* ldm r3, { r2, r3 } */
+    __put_user(0x4699, rc + 2);                   /* mov r9, r3 */
+    __put_user(0x4710, rc + 3);                   /* bx  r2 */
+    /* Wrote 8 of 12 bytes */
+}
+
+void setup_sigtramp(abi_ulong sigtramp_page)
+{
+    uint32_t total_size = 8 * RETCODE_BYTES;
+    uint32_t *tramp = lock_user(VERIFY_WRITE, sigtramp_page, total_size, 0);
+
+    assert(tramp != NULL);
+
+    default_sigreturn = sigtramp_page;
+    write_arm_sigreturn(&tramp[0 * RETCODE_WORDS], TARGET_NR_sigreturn);
+    write_thm_sigreturn(&tramp[1 * RETCODE_WORDS], TARGET_NR_sigreturn);
+    write_arm_sigreturn(&tramp[2 * RETCODE_WORDS], TARGET_NR_rt_sigreturn);
+    write_thm_sigreturn(&tramp[3 * RETCODE_WORDS], TARGET_NR_rt_sigreturn);
+
+    sigreturn_fdpic_tramp = sigtramp_page + 4 * RETCODE_BYTES;
+    write_arm_fdpic_sigreturn(tramp + 4 * RETCODE_WORDS,
+                              offsetof(struct sigframe, retcode[3]));
+    write_thm_fdpic_sigreturn(tramp + 5 * RETCODE_WORDS,
+                                offsetof(struct sigframe, retcode[3]));
+    write_arm_fdpic_sigreturn(tramp + 6 * RETCODE_WORDS,
+                              offsetof(struct rt_sigframe, sig.retcode[3]));
+    write_thm_fdpic_sigreturn(tramp + 7 * RETCODE_WORDS,
+                              offsetof(struct rt_sigframe, sig.retcode[3]));
+
+    unlock_user(tramp, sigtramp_page, total_size);
+}