Re: [PATCH v7 17/21] LoongArch Linux User Emulation

[WANG Xuerui <i.qemu@xen0n.name>]

Hi Song,

Sorry for the late review; I only became aware of this work and 
subscribed to qemu-devel after you sent v6, so I wasn't able to reply to 
that thread I didn't receive earlier.

On 10/18/21 20:47, Song Gao wrote:
> Implementation of linux user emulation for LoongArch.
>
> Signed-off-by: Song Gao <gaosong@loongson.cn>
> Signed-off-by: Xiaojuan Yang <yangxiaojuan@loongson.cn>
> ---
>   accel/tcg/user-exec.c                      |  15 ++
>   configure                                  |   5 +
>   include/elf.h                              |   2 +
>   linux-user/elfload.c                       |  58 ++++++
>   linux-user/host/loongarch/hostdep.h        |  11 +
>   linux-user/loongarch64/cpu_loop.c          |  98 +++++++++
>   linux-user/loongarch64/signal.c            | 163 +++++++++++++++
>   linux-user/loongarch64/sockbits.h          |   1 +
>   linux-user/loongarch64/syscall_nr.h        | 312 +++++++++++++++++++++++++++++
>   linux-user/loongarch64/target_cpu.h        |  35 ++++
>   linux-user/loongarch64/target_elf.h        |  14 ++
>   linux-user/loongarch64/target_errno_defs.h |   7 +
>   linux-user/loongarch64/target_fcntl.h      |  12 ++
>   linux-user/loongarch64/target_signal.h     |  30 +++
>   linux-user/loongarch64/target_structs.h    |  49 +++++
>   linux-user/loongarch64/target_syscall.h    |  46 +++++
>   linux-user/loongarch64/termbits.h          |   1 +
>   linux-user/syscall_defs.h                  |  10 +-
>   scripts/gensyscalls.sh                     |   1 +
>   19 files changed, 866 insertions(+), 4 deletions(-)
>   create mode 100644 linux-user/host/loongarch/hostdep.h
>   create mode 100644 linux-user/loongarch64/cpu_loop.c
>   create mode 100644 linux-user/loongarch64/signal.c
>   create mode 100644 linux-user/loongarch64/sockbits.h
>   create mode 100644 linux-user/loongarch64/syscall_nr.h
>   create mode 100644 linux-user/loongarch64/target_cpu.h
>   create mode 100644 linux-user/loongarch64/target_elf.h
>   create mode 100644 linux-user/loongarch64/target_errno_defs.h
>   create mode 100644 linux-user/loongarch64/target_fcntl.h
>   create mode 100644 linux-user/loongarch64/target_signal.h
>   create mode 100644 linux-user/loongarch64/target_structs.h
>   create mode 100644 linux-user/loongarch64/target_syscall.h
>   create mode 100644 linux-user/loongarch64/termbits.h
Overall I think this patch could use some further splitting. For example 
(1) splitting out the header additions except the syscall bits, (2) 
adding to gensyscalls.sh, (3) add the generated syscall_nr.h, and 
finally the other wiring-ups. This way the commit message could be more 
descriptive too.
>
> diff --git a/accel/tcg/user-exec.c b/accel/tcg/user-exec.c
> index e6bb29b..714eeb4 100644
> --- a/accel/tcg/user-exec.c
> +++ b/accel/tcg/user-exec.c
> @@ -803,6 +803,21 @@ int cpu_signal_handler(int host_signum, void *pinfo,
>       return handle_cpu_signal(pc, info, is_write, &uc->uc_sigmask);
>   }
>   
> +#elif defined(__loongarch__)
> +
> +int cpu_signal_handler(int host_signum, void *pinfo,
> +                       void *puc)
> +{
> +    siginfo_t *info = pinfo;
> +    ucontext_t *uc = puc;
> +    greg_t pc = uc->uc_mcontext.__pc;
> +    int is_write;
> +
> +    /* XXX: compute is_write */
> +    is_write = 0;

FYI this part is already covered by my patch [1], you may base your 
series on mine to avoid conflicts.

[1]: 
https://patchew.org/QEMU/20210925173032.2434906-1-git@xen0n.name/20210925173032.2434906-30-git@xen0n.name/

> +    return handle_cpu_signal(pc, info, is_write, &uc->uc_sigmask);
> +}
> +
>   #elif defined(__riscv)
>   
>   int cpu_signal_handler(int host_signum, void *pinfo,
> diff --git a/configure b/configure
> index 039467c..8d3cd59 100755
> --- a/configure
> +++ b/configure
> @@ -579,6 +579,8 @@ elif check_define __arm__ ; then
>     cpu="arm"
>   elif check_define __aarch64__ ; then
>     cpu="aarch64"
> +elif check_define __loongarch__ ; then
> +  cpu="loongarch"
>   else
>     cpu=$(uname -m)
>   fi
> @@ -610,6 +612,9 @@ case "$cpu" in
>     sparc|sun4[cdmuv])
>       cpu="sparc"
>     ;;
> +  loongarch)
> +    cpu="loongarch"
> +  ;;

And this [2]...

[2]: 
https://patchew.org/QEMU/20210925173032.2434906-1-git@xen0n.name/20210925173032.2434906-31-git@xen0n.name/

>     *)
>       # This will result in either an error or falling back to TCI later
>       ARCH=unknown
> diff --git a/include/elf.h b/include/elf.h
> index 811bf4a..3a4bcb6 100644
> --- a/include/elf.h
> +++ b/include/elf.h
> @@ -182,6 +182,8 @@ typedef struct mips_elf_abiflags_v0 {
>   
>   #define EM_NANOMIPS     249     /* Wave Computing nanoMIPS */
>   
> +#define EM_LOONGARCH    258     /* LoongArch */
> +

And this [3].

[3]: 
https://patchew.org/QEMU/20210925173032.2434906-1-git@xen0n.name/20210925173032.2434906-2-git@xen0n.name/

>   /*
>    * This is an interim value that we will use until the committee comes
>    * up with a final number.
> diff --git a/linux-user/elfload.c b/linux-user/elfload.c
> index 2404d48..9036f0a 100644
> --- a/linux-user/elfload.c
> +++ b/linux-user/elfload.c
> @@ -914,6 +914,64 @@ static void elf_core_copy_regs(target_elf_gregset_t *regs, const CPUPPCState *en
>   
>   #endif
>   
> +#ifdef TARGET_LOONGARCH64
> +
> +#define ELF_START_MMAP 0x80000000
> +
> +#define ELF_CLASS   ELFCLASS64
> +#define ELF_ARCH    EM_LOONGARCH
> +
> +#define elf_check_arch(x) ((x) == EM_LOONGARCH)
> +static inline void init_thread(struct target_pt_regs *regs,
> +                               struct image_info *infop)
> +{
> +    regs->csr_crmd = 2 << 3;
> +    regs->csr_era = infop->entry;
> +    regs->regs[3] = infop->start_stack;
> +}
> +
> +/* See linux kernel: arch/loongarch/include/asm/elf.h.  */
> +#define ELF_NREG 45
> +typedef target_elf_greg_t target_elf_gregset_t[ELF_NREG];
> +
> +/* See linux kernel: arch/loongarch/include/asm/reg.h.  */
> +enum {
> +    TARGET_EF_R0 = 0,
> +    TARGET_EF_CSR_ERA = TARGET_EF_R0 + 32,
> +    TARGET_EF_CSR_BADVADDR = TARGET_EF_R0 + 33,
> +};
> +
> +/* See linux kernel: arch/loongarch/kernel/process.c:loongarch_dump_regs64. */
> +static void elf_core_copy_regs(target_elf_gregset_t *regs,
> +                               const CPULoongArchState *env)
> +{
> +    int i;
> +
> +    for (i = 0; i < TARGET_EF_R0; i++) {
> +        (*regs)[i] = 0;
> +    }
> +    (*regs)[TARGET_EF_R0] = 0;
> +
> +    for (i = 1; i < ARRAY_SIZE(env->gpr); i++) {
> +        (*regs)[TARGET_EF_R0 + i] = tswapreg(env->gpr[i]);
> +    }
> +
> +    (*regs)[TARGET_EF_CSR_ERA] = tswapreg(env->pc);
> +    (*regs)[TARGET_EF_CSR_BADVADDR] = tswapreg(env->badaddr);
> +}
> +
> +#define USE_ELF_CORE_DUMP
> +#define ELF_EXEC_PAGESIZE        4096
> +
> +#define ELF_HWCAP get_elf_hwcap()
> +
> +static uint32_t get_elf_hwcap(void)
> +{
> +    return 0;
> +}
> +
> +#endif /* TARGET_LOONGARCH64 */
> +
>   #ifdef TARGET_MIPS
>   
>   #define ELF_START_MMAP 0x80000000
> diff --git a/linux-user/host/loongarch/hostdep.h b/linux-user/host/loongarch/hostdep.h
> new file mode 100644
> index 0000000..c1b1537
> --- /dev/null
> +++ b/linux-user/host/loongarch/hostdep.h
> @@ -0,0 +1,11 @@
> +/*
> + * hostdep.h : things which are dependent on the host architecture
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> + * See the COPYING file in the top-level directory.
> + */
> +
> +#ifndef LOONGARCH_HOSTDEP_H
> +#define LOONGARCH_HOSTDEP_H
> +
> +#endif

And this file [4].

[4]: 
https://patchew.org/QEMU/20210925173032.2434906-1-git@xen0n.name/20210925173032.2434906-29-git@xen0n.name/

> diff --git a/linux-user/loongarch64/cpu_loop.c b/linux-user/loongarch64/cpu_loop.c
> new file mode 100644
> index 0000000..6fba2ec
> --- /dev/null
> +++ b/linux-user/loongarch64/cpu_loop.c
> @@ -0,0 +1,98 @@
> +/*
> + * QEMU LoongArch user cpu loop.
> + *
> + * Copyright (c) 2021 Loongson Technology Corporation Limited
> + *
> + * SPDX-License-Identifier: LGPL-2.1+
> + */
> +
> +#include "qemu/osdep.h"
> +#include "qemu.h"
> +#include "qemu-common.h"
> +#include "user-internals.h"
> +#include "cpu_loop-common.h"
> +#include "signal-common.h"
> +
> +void cpu_loop(CPULoongArchState *env)
> +{
> +    CPUState *cs = env_cpu(env);
> +    int trapnr, si_code;
> +    abi_long ret;
> +
> +    for (;;) {
> +        cpu_exec_start(cs);
> +        trapnr = cpu_exec(cs);
> +        cpu_exec_end(cs);
> +        process_queued_cpu_work(cs);
> +
> +        switch (trapnr) {
> +        case EXCP_INTERRUPT:
> +            /* just indicate that signals should be handled asap */
> +            break;
> +        case EXCP_SYSCALL:
> +            env->pc += 4;
> +            ret = do_syscall(env, env->gpr[11],
> +                             env->gpr[4], env->gpr[5],
> +                             env->gpr[6], env->gpr[7],
> +                             env->gpr[8], env->gpr[9],
> +                             -1, -1);
> +            if (ret == -TARGET_ERESTARTSYS) {
> +                env->pc -= 4;
> +                break;
> +            }
> +            if (ret == -TARGET_QEMU_ESIGRETURN) {
> +                /*
> +                 * Returning from a successful sigreturn syscall.
> +                 * Avoid clobbering register state.
> +                 */
> +                break;
> +            }
> +            env->gpr[4] = ret;
> +            break;
> +        case EXCP_ADE:
> +            force_sig_fault(TARGET_SIGSEGV, TARGET_SEGV_MAPERR, env->badaddr);
> +            break;
> +        case EXCP_INE:
> +            force_sig_fault(TARGET_SIGILL, 0, env->pc);
> +            break;
> +        case EXCP_FPE:
> +            si_code = TARGET_FPE_FLTUNK;
> +            if (GET_FP_CAUSE(env->fcsr0) & FP_INVALID) {
> +                si_code = TARGET_FPE_FLTINV;
> +            } else if (GET_FP_CAUSE(env->fcsr0) & FP_DIV0) {
> +                si_code = TARGET_FPE_FLTDIV;
> +            } else if (GET_FP_CAUSE(env->fcsr0) & FP_OVERFLOW) {
> +                si_code = TARGET_FPE_FLTOVF;
> +            } else if (GET_FP_CAUSE(env->fcsr0) & FP_UNDERFLOW) {
> +                si_code = TARGET_FPE_FLTUND;
> +            } else if (GET_FP_CAUSE(env->fcsr0) & FP_INEXACT) {
> +                si_code = TARGET_FPE_FLTRES;
> +            }
> +            force_sig_fault(TARGET_SIGFPE, si_code, env->pc);
> +            break;
> +        case EXCP_DEBUG:
> +        case EXCP_BREAK:
> +            force_sig_fault(TARGET_SIGTRAP, TARGET_TRAP_BRKPT, env->pc);
> +            break;
> +        case EXCP_ATOMIC:
> +            cpu_exec_step_atomic(cs);
> +            break;
> +        default:
> +            EXCP_DUMP(env, "qemu: unhandled CPU exception 0x%x - aborting\n",
> +                      trapnr);
> +            exit(EXIT_FAILURE);
> +        }
> +        process_pending_signals(env);
> +    }
> +}
> +
> +void target_cpu_copy_regs(CPUArchState *env, struct target_pt_regs *regs)
> +{
> +    int i;
> +
> +    for (i = 0; i < 32; i++) {
> +        env->gpr[i] = regs->regs[i];
> +    }
> +    env->pc = regs->csr_era;
> +
> +}
> diff --git a/linux-user/loongarch64/signal.c b/linux-user/loongarch64/signal.c
> new file mode 100644
> index 0000000..f3d61de
> --- /dev/null
> +++ b/linux-user/loongarch64/signal.c
> @@ -0,0 +1,163 @@
> +/*
> + * LoongArch emulation of Linux signals
> + *
> + * Copyright (c) 2021 Loongson Technology Corporation Limited
> + *
> + * SPDX-License-Identifier: LGPL-2.1+
> + */
> +
> +#include "qemu/osdep.h"
> +#include "qemu.h"
> +#include "signal-common.h"
> +#include "user-internals.h"
> +#include "linux-user/trace.h"
> +
> +struct target_sigcontext {
> +    uint64_t   sc_pc;
> +    uint64_t   sc_gpr[32];
> +    uint64_t   sc_fpr[32];
> +    uint64_t   sc_fcc;
> +    uint32_t   sc_fcsr;
> +    uint32_t   sc_flags;
> +};
> +
> +struct target_ucontext {
> +    target_ulong tuc_flags;
> +    target_ulong tuc_link;
> +    target_stack_t tuc_stack;
> +    target_ulong pad0;
> +    struct target_sigcontext tuc_mcontext;
> +    target_sigset_t tuc_sigmask;
> +};
> +
> +struct target_rt_sigframe {
> +    struct target_siginfo rs_info;
> +    struct target_ucontext rs_uc;
> +};
> +
> +static inline void setup_sigcontext(CPULoongArchState *env,
> +                                    struct target_sigcontext *sc)
> +{
> +    int i;
> +
> +    __put_user(env->pc, &sc->sc_pc);
> +
> +    __put_user(0, &sc->sc_gpr[0]);
> +    for (i = 1; i < 32; ++i) {
> +        __put_user(env->gpr[i], &sc->sc_gpr[i]);
> +    }
> +
> +    for (i = 0; i < 32; ++i) {
> +        __put_user(env->fpr[i], &sc->sc_fpr[i]);
> +    }
> +}
> +
> +static inline void
> +restore_sigcontext(CPULoongArchState *env, struct target_sigcontext *sc)
> +{
> +    int i;
> +
> +    __get_user(env->pc, &sc->sc_pc);
> +
> +    for (i = 1; i < 32; ++i) {
> +        __get_user(env->gpr[i], &sc->sc_gpr[i]);
> +    }
> +
> +    for (i = 0; i < 32; ++i) {
> +        __get_user(env->fpr[i], &sc->sc_fpr[i]);
> +    }
> +}
> +
> +/*
> + * Determine which stack to use..
> + */
> +static inline abi_ulong
> +get_sigframe(struct target_sigaction *ka, CPULoongArchState *env,
> +             size_t frame_size)
> +{
> +    unsigned long sp;
> +
> +    sp = target_sigsp(get_sp_from_cpustate(env) - 32, ka);
> +
> +    return (sp - frame_size) & ~7;
> +}
> +
> +void setup_rt_frame(int sig, struct target_sigaction *ka,
> +                    target_siginfo_t *info,
> +                    target_sigset_t *set, CPULoongArchState *env)
> +{
> +    struct target_rt_sigframe *frame;
> +    abi_ulong frame_addr;
> +    int i;
> +
> +    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 give_sigsegv;
> +    }
> +
> +    tswap_siginfo(&frame->rs_info, info);
> +
> +    __put_user(0, &frame->rs_uc.tuc_flags);
> +    __put_user(0, &frame->rs_uc.tuc_link);
> +    target_save_altstack(&frame->rs_uc.tuc_stack, env);
> +
> +    setup_sigcontext(env, &frame->rs_uc.tuc_mcontext);
> +
> +    for (i = 0; i < TARGET_NSIG_WORDS; i++) {
> +        __put_user(set->sig[i], &frame->rs_uc.tuc_sigmask.sig[i]);
> +    }
> +
> +    env->gpr[4] = sig;
> +    env->gpr[5] = frame_addr + offsetof(struct target_rt_sigframe, rs_info);
> +    env->gpr[6] = frame_addr + offsetof(struct target_rt_sigframe, rs_uc);
> +    env->gpr[3] = frame_addr;
> +    env->gpr[1] = default_rt_sigreturn;
> +
> +    env->pc = env->gpr[20] = ka->_sa_handler;
> +    unlock_user_struct(frame, frame_addr, 1);
> +    return;
> +
> +give_sigsegv:
> +    unlock_user_struct(frame, frame_addr, 1);
> +    force_sigsegv(sig);
> +}
> +
> +long do_rt_sigreturn(CPULoongArchState *env)
> +{
> +    struct target_rt_sigframe *frame;
> +    abi_ulong frame_addr;
> +    sigset_t blocked;
> +
> +    frame_addr = env->gpr[3];
> +    trace_user_do_rt_sigreturn(env, frame_addr);
> +    if (!lock_user_struct(VERIFY_READ, frame, frame_addr, 1)) {
> +        goto badframe;
> +    }
> +
> +    target_to_host_sigset(&blocked, &frame->rs_uc.tuc_sigmask);
> +    set_sigmask(&blocked);
> +
> +    restore_sigcontext(env, &frame->rs_uc.tuc_mcontext);
> +    target_restore_altstack(&frame->rs_uc.tuc_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 -TARGET_QEMU_ESIGRETURN;
> +}
> +
> +void setup_sigtramp(abi_ulong sigtramp_page)
> +{
> +    uint32_t *tramp = lock_user(VERIFY_WRITE, sigtramp_page, 8, 0);
> +    assert(tramp != NULL);
> +
> +    __put_user(0x03822c0b, tramp + 0);  /* ori  a7, a7, 0x8b */
Nit: two spaces after "ori" which is neither alignment to "syscall" 
below, nor ordinary 1-space separation.
> +    __put_user(0x002b0000, tramp + 1);  /* syscall 0 */
> +
> +    default_rt_sigreturn = sigtramp_page;
> +    unlock_user(tramp, sigtramp_page, 8);
> +}
> diff --git a/linux-user/loongarch64/sockbits.h b/linux-user/loongarch64/sockbits.h
> new file mode 100644
> index 0000000..0e4c8f0
> --- /dev/null
> +++ b/linux-user/loongarch64/sockbits.h
> @@ -0,0 +1 @@
> +#include "../generic/sockbits.h"
> diff --git a/linux-user/loongarch64/syscall_nr.h b/linux-user/loongarch64/syscall_nr.h
> new file mode 100644
> index 0000000..8fbf287
> --- /dev/null
> +++ b/linux-user/loongarch64/syscall_nr.h
> @@ -0,0 +1,312 @@
> +/*
> + * This file contains the system call numbers.
> + * Do not modify.
> + * This file is generated by scripts/gensyscalls.sh
> + */
> +#ifndef LINUX_USER_LOONGARCH_SYSCALL_NR_H
> +#define LINUX_USER_LOONGARCH_SYSCALL_NR_H
> +
> +#define TARGET_NR_io_setup 0
> +#define TARGET_NR_io_destroy 1
> +#define TARGET_NR_io_submit 2
> +#define TARGET_NR_io_cancel 3
> +#define TARGET_NR_io_getevents 4
> +#define TARGET_NR_setxattr 5
> +#define TARGET_NR_lsetxattr 6
> +#define TARGET_NR_fsetxattr 7
> +#define TARGET_NR_getxattr 8
> +#define TARGET_NR_lgetxattr 9
> +#define TARGET_NR_fgetxattr 10
> +#define TARGET_NR_listxattr 11
> +#define TARGET_NR_llistxattr 12
> +#define TARGET_NR_flistxattr 13
> +#define TARGET_NR_removexattr 14
> +#define TARGET_NR_lremovexattr 15
> +#define TARGET_NR_fremovexattr 16
> +#define TARGET_NR_getcwd 17
> +#define TARGET_NR_lookup_dcookie 18
> +#define TARGET_NR_eventfd2 19
> +#define TARGET_NR_epoll_create1 20
> +#define TARGET_NR_epoll_ctl 21
> +#define TARGET_NR_epoll_pwait 22
> +#define TARGET_NR_dup 23
> +#define TARGET_NR_dup3 24
> +#define TARGET_NR_fcntl 25
> +#define TARGET_NR_inotify_init1 26
> +#define TARGET_NR_inotify_add_watch 27
> +#define TARGET_NR_inotify_rm_watch 28
> +#define TARGET_NR_ioctl 29
> +#define TARGET_NR_ioprio_set 30
> +#define TARGET_NR_ioprio_get 31
> +#define TARGET_NR_flock 32
> +#define TARGET_NR_mknodat 33
> +#define TARGET_NR_mkdirat 34
> +#define TARGET_NR_unlinkat 35
> +#define TARGET_NR_symlinkat 36
> +#define TARGET_NR_linkat 37
> +#define TARGET_NR_umount2 39
> +#define TARGET_NR_mount 40
> +#define TARGET_NR_pivot_root 41
> +#define TARGET_NR_nfsservctl 42
> +#define TARGET_NR_statfs 43
> +#define TARGET_NR_fstatfs 44
> +#define TARGET_NR_truncate 45
> +#define TARGET_NR_ftruncate 46
> +#define TARGET_NR_fallocate 47
> +#define TARGET_NR_faccessat 48
> +#define TARGET_NR_chdir 49
> +#define TARGET_NR_fchdir 50
> +#define TARGET_NR_chroot 51
> +#define TARGET_NR_fchmod 52
> +#define TARGET_NR_fchmodat 53
> +#define TARGET_NR_fchownat 54
> +#define TARGET_NR_fchown 55
> +#define TARGET_NR_openat 56
> +#define TARGET_NR_close 57
> +#define TARGET_NR_vhangup 58
> +#define TARGET_NR_pipe2 59
> +#define TARGET_NR_quotactl 60
> +#define TARGET_NR_getdents64 61
> +#define TARGET_NR_lseek 62
> +#define TARGET_NR_read 63
> +#define TARGET_NR_write 64
> +#define TARGET_NR_readv 65
> +#define TARGET_NR_writev 66
> +#define TARGET_NR_pread64 67
> +#define TARGET_NR_pwrite64 68
> +#define TARGET_NR_preadv 69
> +#define TARGET_NR_pwritev 70
> +#define TARGET_NR_sendfile 71
> +#define TARGET_NR_pselect6 72
> +#define TARGET_NR_ppoll 73
> +#define TARGET_NR_signalfd4 74
> +#define TARGET_NR_vmsplice 75
> +#define TARGET_NR_splice 76
> +#define TARGET_NR_tee 77
> +#define TARGET_NR_readlinkat 78
> +#define TARGET_NR_newfstatat 79
> +#define TARGET_NR_fstat 80
> +#define TARGET_NR_sync 81
> +#define TARGET_NR_fsync 82
> +#define TARGET_NR_fdatasync 83
> +#define TARGET_NR_sync_file_range 84
> +#define TARGET_NR_timerfd_create 85
> +#define TARGET_NR_timerfd_settime 86
> +#define TARGET_NR_timerfd_gettime 87
> +#define TARGET_NR_utimensat 88
> +#define TARGET_NR_acct 89
> +#define TARGET_NR_capget 90
> +#define TARGET_NR_capset 91
> +#define TARGET_NR_personality 92
> +#define TARGET_NR_exit 93
> +#define TARGET_NR_exit_group 94
> +#define TARGET_NR_waitid 95
> +#define TARGET_NR_set_tid_address 96
> +#define TARGET_NR_unshare 97
> +#define TARGET_NR_futex 98
> +#define TARGET_NR_set_robust_list 99
> +#define TARGET_NR_get_robust_list 100
> +#define TARGET_NR_nanosleep 101
> +#define TARGET_NR_getitimer 102
> +#define TARGET_NR_setitimer 103
> +#define TARGET_NR_kexec_load 104
> +#define TARGET_NR_init_module 105
> +#define TARGET_NR_delete_module 106
> +#define TARGET_NR_timer_create 107
> +#define TARGET_NR_timer_gettime 108
> +#define TARGET_NR_timer_getoverrun 109
> +#define TARGET_NR_timer_settime 110
> +#define TARGET_NR_timer_delete 111
> +#define TARGET_NR_clock_settime 112
> +#define TARGET_NR_clock_gettime 113
> +#define TARGET_NR_clock_getres 114
> +#define TARGET_NR_clock_nanosleep 115
> +#define TARGET_NR_syslog 116
> +#define TARGET_NR_ptrace 117
> +#define TARGET_NR_sched_setparam 118
> +#define TARGET_NR_sched_setscheduler 119
> +#define TARGET_NR_sched_getscheduler 120
> +#define TARGET_NR_sched_getparam 121
> +#define TARGET_NR_sched_setaffinity 122
> +#define TARGET_NR_sched_getaffinity 123
> +#define TARGET_NR_sched_yield 124
> +#define TARGET_NR_sched_get_priority_max 125
> +#define TARGET_NR_sched_get_priority_min 126
> +#define TARGET_NR_sched_rr_get_interval 127
> +#define TARGET_NR_restart_syscall 128
> +#define TARGET_NR_kill 129
> +#define TARGET_NR_tkill 130
> +#define TARGET_NR_tgkill 131
> +#define TARGET_NR_sigaltstack 132
> +#define TARGET_NR_rt_sigsuspend 133
> +#define TARGET_NR_rt_sigaction 134
> +#define TARGET_NR_rt_sigprocmask 135
> +#define TARGET_NR_rt_sigpending 136
> +#define TARGET_NR_rt_sigtimedwait 137
> +#define TARGET_NR_rt_sigqueueinfo 138
> +#define TARGET_NR_rt_sigreturn 139
> +#define TARGET_NR_setpriority 140
> +#define TARGET_NR_getpriority 141
> +#define TARGET_NR_reboot 142
> +#define TARGET_NR_setregid 143
> +#define TARGET_NR_setgid 144
> +#define TARGET_NR_setreuid 145
> +#define TARGET_NR_setuid 146
> +#define TARGET_NR_setresuid 147
> +#define TARGET_NR_getresuid 148
> +#define TARGET_NR_setresgid 149
> +#define TARGET_NR_getresgid 150
> +#define TARGET_NR_setfsuid 151
> +#define TARGET_NR_setfsgid 152
> +#define TARGET_NR_times 153
> +#define TARGET_NR_setpgid 154
> +#define TARGET_NR_getpgid 155
> +#define TARGET_NR_getsid 156
> +#define TARGET_NR_setsid 157
> +#define TARGET_NR_getgroups 158
> +#define TARGET_NR_setgroups 159
> +#define TARGET_NR_uname 160
> +#define TARGET_NR_sethostname 161
> +#define TARGET_NR_setdomainname 162
> +#define TARGET_NR_getrusage 165
> +#define TARGET_NR_umask 166
> +#define TARGET_NR_prctl 167
> +#define TARGET_NR_getcpu 168
> +#define TARGET_NR_gettimeofday 169
> +#define TARGET_NR_settimeofday 170
> +#define TARGET_NR_adjtimex 171
> +#define TARGET_NR_getpid 172
> +#define TARGET_NR_getppid 173
> +#define TARGET_NR_getuid 174
> +#define TARGET_NR_geteuid 175
> +#define TARGET_NR_getgid 176
> +#define TARGET_NR_getegid 177
> +#define TARGET_NR_gettid 178
> +#define TARGET_NR_sysinfo 179
> +#define TARGET_NR_mq_open 180
> +#define TARGET_NR_mq_unlink 181
> +#define TARGET_NR_mq_timedsend 182
> +#define TARGET_NR_mq_timedreceive 183
> +#define TARGET_NR_mq_notify 184
> +#define TARGET_NR_mq_getsetattr 185
> +#define TARGET_NR_msgget 186
> +#define TARGET_NR_msgctl 187
> +#define TARGET_NR_msgrcv 188
> +#define TARGET_NR_msgsnd 189
> +#define TARGET_NR_semget 190
> +#define TARGET_NR_semctl 191
> +#define TARGET_NR_semtimedop 192
> +#define TARGET_NR_semop 193
> +#define TARGET_NR_shmget 194
> +#define TARGET_NR_shmctl 195
> +#define TARGET_NR_shmat 196
> +#define TARGET_NR_shmdt 197
> +#define TARGET_NR_socket 198
> +#define TARGET_NR_socketpair 199
> +#define TARGET_NR_bind 200
> +#define TARGET_NR_listen 201
> +#define TARGET_NR_accept 202
> +#define TARGET_NR_connect 203
> +#define TARGET_NR_getsockname 204
> +#define TARGET_NR_getpeername 205
> +#define TARGET_NR_sendto 206
> +#define TARGET_NR_recvfrom 207
> +#define TARGET_NR_setsockopt 208
> +#define TARGET_NR_getsockopt 209
> +#define TARGET_NR_shutdown 210
> +#define TARGET_NR_sendmsg 211
> +#define TARGET_NR_recvmsg 212
> +#define TARGET_NR_readahead 213
> +#define TARGET_NR_brk 214
> +#define TARGET_NR_munmap 215
> +#define TARGET_NR_mremap 216
> +#define TARGET_NR_add_key 217
> +#define TARGET_NR_request_key 218
> +#define TARGET_NR_keyctl 219
> +#define TARGET_NR_clone 220
> +#define TARGET_NR_execve 221
> +#define TARGET_NR_mmap 222
> +#define TARGET_NR_fadvise64 223
> +#define TARGET_NR_swapon 224
> +#define TARGET_NR_swapoff 225
> +#define TARGET_NR_mprotect 226
> +#define TARGET_NR_msync 227
> +#define TARGET_NR_mlock 228
> +#define TARGET_NR_munlock 229
> +#define TARGET_NR_mlockall 230
> +#define TARGET_NR_munlockall 231
> +#define TARGET_NR_mincore 232
> +#define TARGET_NR_madvise 233
> +#define TARGET_NR_remap_file_pages 234
> +#define TARGET_NR_mbind 235
> +#define TARGET_NR_get_mempolicy 236
> +#define TARGET_NR_set_mempolicy 237
> +#define TARGET_NR_migrate_pages 238
> +#define TARGET_NR_move_pages 239
> +#define TARGET_NR_rt_tgsigqueueinfo 240
> +#define TARGET_NR_perf_event_open 241
> +#define TARGET_NR_accept4 242
> +#define TARGET_NR_recvmmsg 243
> +#define TARGET_NR_arch_specific_syscall 244
> +#define TARGET_NR_wait4 260
> +#define TARGET_NR_prlimit64 261
> +#define TARGET_NR_fanotify_init 262
> +#define TARGET_NR_fanotify_mark 263
> +#define TARGET_NR_name_to_handle_at 264
> +#define TARGET_NR_open_by_handle_at 265
> +#define TARGET_NR_clock_adjtime 266
> +#define TARGET_NR_syncfs 267
> +#define TARGET_NR_setns 268
> +#define TARGET_NR_sendmmsg 269
> +#define TARGET_NR_process_vm_readv 270
> +#define TARGET_NR_process_vm_writev 271
> +#define TARGET_NR_kcmp 272
> +#define TARGET_NR_finit_module 273
> +#define TARGET_NR_sched_setattr 274
> +#define TARGET_NR_sched_getattr 275
> +#define TARGET_NR_renameat2 276
> +#define TARGET_NR_seccomp 277
> +#define TARGET_NR_getrandom 278
> +#define TARGET_NR_memfd_create 279
> +#define TARGET_NR_bpf 280
> +#define TARGET_NR_execveat 281
> +#define TARGET_NR_userfaultfd 282
> +#define TARGET_NR_membarrier 283
> +#define TARGET_NR_mlock2 284
> +#define TARGET_NR_copy_file_range 285
> +#define TARGET_NR_preadv2 286
> +#define TARGET_NR_pwritev2 287
> +#define TARGET_NR_pkey_mprotect 288
> +#define TARGET_NR_pkey_alloc 289
> +#define TARGET_NR_pkey_free 290
> +#define TARGET_NR_statx 291
> +#define TARGET_NR_io_pgetevents 292
> +#define TARGET_NR_rseq 293
> +#define TARGET_NR_kexec_file_load 294
> +#define TARGET_NR_pidfd_send_signal 424
> +#define TARGET_NR_io_uring_setup 425
> +#define TARGET_NR_io_uring_enter 426
> +#define TARGET_NR_io_uring_register 427
> +#define TARGET_NR_open_tree 428
> +#define TARGET_NR_move_mount 429
> +#define TARGET_NR_fsopen 430
> +#define TARGET_NR_fsconfig 431
> +#define TARGET_NR_fsmount 432
> +#define TARGET_NR_fspick 433
> +#define TARGET_NR_pidfd_open 434
> +#define TARGET_NR_clone3 435
> +#define TARGET_NR_close_range 436
> +#define TARGET_NR_openat2 437
> +#define TARGET_NR_pidfd_getfd 438
> +#define TARGET_NR_faccessat2 439
> +#define TARGET_NR_process_madvise 440
> +#define TARGET_NR_epoll_pwait2 441
> +#define TARGET_NR_mount_setattr 442
> +#define TARGET_NR_quotactl_fd 443
> +#define TARGET_NR_landlock_create_ruleset 444
> +#define TARGET_NR_landlock_add_rule 445
> +#define TARGET_NR_landlock_restrict_self 446
> +#define TARGET_NR_process_mrelease 448
> +#define TARGET_NR_syscalls 449
> +
> +#endif /* LINUX_USER_LOONGARCH_SYSCALL_NR_H */
> diff --git a/linux-user/loongarch64/target_cpu.h b/linux-user/loongarch64/target_cpu.h
> new file mode 100644
> index 0000000..5bd13a7
> --- /dev/null
> +++ b/linux-user/loongarch64/target_cpu.h
> @@ -0,0 +1,35 @@
> +/*
> + * LoongArch specific CPU ABI and functions for linux-user
> + *
> + * Copyright (c) 2021 Loongson Technology Corporation Limited
> + *
> + * SPDX-License-Identifier: LGPL-2.1+
> + */
> +
> +#ifndef LOONGARCH_TARGET_CPU_H
> +#define LOONGARCH_TARGET_CPU_H
> +
> +static inline void cpu_clone_regs_child(CPULoongArchState *env,
> +                                        target_ulong newsp, unsigned flags)
> +{
> +    if (newsp) {
> +        env->gpr[3] = newsp;
> +    }
> +    env->gpr[4] = 0;
> +}
> +
> +static inline void cpu_clone_regs_parent(CPULoongArchState *env,
> +                                         unsigned flags)
> +{
> +}
> +
> +static inline void cpu_set_tls(CPULoongArchState *env, target_ulong newtls)
> +{
> +    env->gpr[2] = newtls;
> +}
> +
> +static inline abi_ulong get_sp_from_cpustate(CPULoongArchState *state)
> +{
> +    return state->gpr[3];
> +}
> +#endif
> diff --git a/linux-user/loongarch64/target_elf.h b/linux-user/loongarch64/target_elf.h
> new file mode 100644
> index 0000000..7c88394
> --- /dev/null
> +++ b/linux-user/loongarch64/target_elf.h
> @@ -0,0 +1,14 @@
> +/*
> + * Copyright (c) 2021 Loongson Technology Corporation Limited
> + *
> + * SPDX-License-Identifier: LGPL-2.1+
> + */
> +
> +
> +#ifndef LOONGARCH_TARGET_ELF_H
> +#define LOONGARCH_TARGET_ELF_H
> +static inline const char *cpu_get_model(uint32_t eflags)
> +{
> +    return "Loongson-3A5000";
> +}
> +#endif
> diff --git a/linux-user/loongarch64/target_errno_defs.h b/linux-user/loongarch64/target_errno_defs.h
> new file mode 100644
> index 0000000..17165c1
> --- /dev/null
> +++ b/linux-user/loongarch64/target_errno_defs.h
> @@ -0,0 +1,7 @@
> +#ifndef LOONGARCH_TARGET_ERRNO_DEFS_H
> +#define LOONGARCH_TARGET_ERRNO_DEFS_H
> +
> +/* Target uses generic errno */
> +#include "../generic/target_errno_defs.h"
> +
> +#endif
> diff --git a/linux-user/loongarch64/target_fcntl.h b/linux-user/loongarch64/target_fcntl.h
> new file mode 100644
> index 0000000..b810293
> --- /dev/null
> +++ b/linux-user/loongarch64/target_fcntl.h
> @@ -0,0 +1,12 @@
> +/*
> + * Copyright (c) 2021 Loongson Technology Corporation Limited
> + *
> + * SPDX-License-Identifier: LGPL-2.1+
> + */
> +
> +#ifndef LOONGARCH_TARGET_FCNTL_H
> +#define LOONGARCH_TARGET_FCNTL_H
> +
> +#include "../generic/fcntl.h"
> +
> +#endif  /* LOONGARCH_TARGET_FCNTL_H */
> diff --git a/linux-user/loongarch64/target_signal.h b/linux-user/loongarch64/target_signal.h
> new file mode 100644
> index 0000000..2deb88c
> --- /dev/null
> +++ b/linux-user/loongarch64/target_signal.h
> @@ -0,0 +1,30 @@
> +/*
> + * Copyright (c) 2021 Loongson Technology Corporation Limited
> + *
> + * SPDX-License-Identifier: LGPL-2.1+
> + */
> +
> +#ifndef LOONGARCH_TARGET_SIGNAL_H
> +#define LOONGARCH_TARGET_SIGNAL_H
> +
> +/* this struct defines a stack used during syscall handling */
> +typedef struct target_sigaltstack {
> +        abi_long ss_sp;
> +        abi_int ss_flags;
> +        abi_ulong ss_size;
> +} target_stack_t;
> +
> +/*
> + * sigaltstack controls
> + */
> +#define TARGET_SS_ONSTACK     1
> +#define TARGET_SS_DISABLE     2
> +
> +#define TARGET_MINSIGSTKSZ    2048
> +#define TARGET_SIGSTKSZ       8192
> +
> +#include "../generic/signal.h"
> +
> +#define TARGET_ARCH_HAS_SIGTRAMP_PAGE 1
> +
> +#endif /* LOONGARCH_TARGET_SIGNAL_H */
> diff --git a/linux-user/loongarch64/target_structs.h b/linux-user/loongarch64/target_structs.h
> new file mode 100644
> index 0000000..818e8d6
> --- /dev/null
> +++ b/linux-user/loongarch64/target_structs.h
> @@ -0,0 +1,49 @@
> +/*
> + * LoongArch specific structures for linux-user
> + *
> + * Copyright (c) 2021 Loongson Technology Corporation Limited
> + *
> + * SPDX-License-Identifier: LGPL-2.1+
> + */
> +
> +#ifndef LOONGARCH_TARGET_STRUCTS_H
> +#define LOONGARCH_TARGET_STRUCTS_H
> +
> +struct target_ipc_perm {
> +    abi_int __key;                      /* Key.  */
> +    abi_uint uid;                       /* Owner's user ID.  */
> +    abi_uint gid;                       /* Owner's group ID.  */
> +    abi_uint cuid;                      /* Creator's user ID.  */
> +    abi_uint cgid;                      /* Creator's group ID.  */
> +    abi_uint mode;                      /* Read/write permission.  */
> +    abi_ushort __seq;                   /* Sequence number.  */
> +    abi_ushort __pad1;
> +    abi_ulong __unused1;
> +    abi_ulong __unused2;
> +};
> +
> +struct target_shmid_ds {
> +    struct target_ipc_perm shm_perm;    /* operation permission struct */
> +    abi_long shm_segsz;                 /* size of segment in bytes */
> +    abi_ulong shm_atime;                /* time of last shmat() */
> +    abi_ulong shm_dtime;                /* time of last shmdt() */
> +    abi_ulong shm_ctime;                /* time of last change by shmctl() */
> +    abi_int shm_cpid;                   /* pid of creator */
> +    abi_int shm_lpid;                   /* pid of last shmop */
> +    abi_ulong shm_nattch;               /* number of current attaches */
> +    abi_ulong __unused1;
> +    abi_ulong __unused2;
> +};
> +
> +#define TARGET_SEMID64_DS
> +
> +struct target_semid64_ds {
> +    struct target_ipc_perm sem_perm;
> +    abi_ulong sem_otime;
> +    abi_ulong sem_ctime;
> +    abi_ulong sem_nsems;
> +    abi_ulong __unused1;
> +    abi_ulong __unused2;
> +};
> +
> +#endif
> diff --git a/linux-user/loongarch64/target_syscall.h b/linux-user/loongarch64/target_syscall.h
> new file mode 100644
> index 0000000..393160d
> --- /dev/null
> +++ b/linux-user/loongarch64/target_syscall.h
> @@ -0,0 +1,46 @@
> +/*
> + * Copyright (c) 2021 Loongson Technology Corporation Limited
> + *
> + * SPDX-License-Identifier: LGPL-2.1+
> + */
> +
> +#ifndef LOONGARCH_TARGET_SYSCALL_H
> +#define LOONGARCH_TARGET_SYSCALL_H
> +
> +/*
> + * this struct defines the way the registers are stored on the
> + * stack during a system call.
> + */
> +
> +struct target_pt_regs {
> +    /* Saved main processor registers. */
> +    target_ulong regs[32];
> +
> +    /* Saved special registers. */
> +    target_ulong csr_crmd;
> +    target_ulong csr_prmd;
> +    target_ulong csr_euen;
> +    target_ulong csr_ecfg;
> +    target_ulong csr_estat;
> +    target_ulong csr_era;
> +    target_ulong csr_badvaddr;
> +    target_ulong orig_a0;
> +    target_ulong __last[0];
> +};
> +
> +#define UNAME_MACHINE "loongarch64"
> +#define UNAME_MINIMUM_RELEASE "4.19.0"

The 4.19.x LoongArch kernel is not upstreamed, is not upstreamable, and 
AFAIK not even open-source (GPL violation, anyone?).

In addition to this, the kernel being upstreamed has NSIG=64 like almost 
every other architecture except MIPS, while AFAIK the shipped 4.19.x 
kernel blobs all have NSIG=128 like MIPS, so binaries compiled for that 
old kernel version are ABI-incompatible with this series. They are 
nearly impossible to work, since signal handling is present/required for 
nearly every non-trivial app.

So I'd suggest bumping this to at least the upcoming Linux version which 
is 5.16 at the moment; I personally think even this would need 
re-visiting because it seems not likely to have LoongArch accepted 
before end of 2021.

> +
> +#define TARGET_MINSIGSTKSZ 2048
> +#define TARGET_MCL_CURRENT 1
> +#define TARGET_MCL_FUTURE  2
> +#define TARGET_MCL_ONFAULT 4
> +
> +#define TARGET_FORCE_SHMLBA
> +
> +static inline abi_ulong target_shmlba(CPULoongArchState *env)
> +{
> +    return 0x40000;
> +}
> +
> +#endif
> diff --git a/linux-user/loongarch64/termbits.h b/linux-user/loongarch64/termbits.h
> new file mode 100644
> index 0000000..b1d4f4f
> --- /dev/null
> +++ b/linux-user/loongarch64/termbits.h
> @@ -0,0 +1 @@
> +#include "../generic/termbits.h"
> diff --git a/linux-user/syscall_defs.h b/linux-user/syscall_defs.h
> index a5ce487..bec125f 100644
> --- a/linux-user/syscall_defs.h
> +++ b/linux-user/syscall_defs.h
> @@ -74,7 +74,7 @@
>       || defined(TARGET_M68K) || defined(TARGET_CRIS) \
>       || defined(TARGET_S390X) || defined(TARGET_OPENRISC) \
>       || defined(TARGET_NIOS2) || defined(TARGET_RISCV) \
> -    || defined(TARGET_XTENSA)
> +    || defined(TARGET_XTENSA) || defined(TARGET_LOONGARCH64)
>   
>   #define TARGET_IOC_SIZEBITS	14
>   #define TARGET_IOC_DIRBITS	2
> @@ -2129,7 +2129,8 @@ struct target_stat64  {
>       abi_ulong __unused5;
>   };
>   
> -#elif defined(TARGET_OPENRISC) || defined(TARGET_NIOS2) || defined(TARGET_RISCV)
> +#elif defined(TARGET_OPENRISC) || defined(TARGET_NIOS2) || \
> +      defined(TARGET_RISCV) || defined(TARGET_LOONGARCH64)
>   
>   /* These are the asm-generic versions of the stat and stat64 structures */
>   
> @@ -2157,7 +2158,7 @@ struct target_stat {
>       unsigned int __unused5;
>   };
>   
> -#if !defined(TARGET_RISCV64)
> +#if !defined(TARGET_RISCV64) && !defined(TARGET_LOONGARCH64)
>   #define TARGET_HAS_STRUCT_STAT64
>   struct target_stat64 {
>       uint64_t st_dev;
> @@ -2327,7 +2328,8 @@ struct target_statfs64 {
>   };
>   #elif (defined(TARGET_PPC64) || defined(TARGET_X86_64) || \
>          defined(TARGET_SPARC64) || defined(TARGET_AARCH64) || \
> -       defined(TARGET_RISCV)) && !defined(TARGET_ABI32)
> +       defined(TARGET_RISCV) || defined(TARGET_LOONGARCH64)) && \
> +       !defined(TARGET_ABI32)
>   struct target_statfs {
>   	abi_long f_type;
>   	abi_long f_bsize;
> diff --git a/scripts/gensyscalls.sh b/scripts/gensyscalls.sh
> index 8fb450e..b69e193 100755
> --- a/scripts/gensyscalls.sh
> +++ b/scripts/gensyscalls.sh
> @@ -99,4 +99,5 @@ generate_syscall_nr openrisc 32 "$output/linux-user/openrisc/syscall_nr.h"
>   generate_syscall_nr riscv 32 "$output/linux-user/riscv/syscall32_nr.h"
>   generate_syscall_nr riscv 64 "$output/linux-user/riscv/syscall64_nr.h"
>   generate_syscall_nr hexagon 32 "$output/linux-user/hexagon/syscall_nr.h"
> +generate_syscall_nr loongarch 64 "$output/linux-user/loongarch64/syscall_nr.h"
>   rm -fr "$TMP"