semihosting/console.c

   1 /*
   2  * Semihosting Console Support
   3  *
   4  * Copyright (c) 2015 Imagination Technologies
   5  * Copyright (c) 2019 Linaro Ltd
   6  *
   7  * This provides support for outputting to a semihosting console.
   8  *
   9  * While most semihosting implementations support reading and writing
  10  * to arbitrary file descriptors we treat the console as something
  11  * specifically for debugging interaction. This means messages can be
  12  * re-directed to gdb (if currently being used to debug) or even
  13  * re-directed elsewhere.
  14  *
  15  * SPDX-License-Identifier: GPL-2.0-or-later
  16  */
  17
  18 #include "qemu/osdep.h"
  19 #include "semihosting/semihost.h"
  20 #include "semihosting/console.h"
  21 #include "exec/gdbstub.h"
  22 #include "exec/exec-all.h"
  23 #include "qemu/log.h"
  24 #include "chardev/char.h"
  25 #include "chardev/char-fe.h"
  26 #include "qemu/main-loop.h"
  27 #include "qapi/error.h"
  28 #include "qemu/fifo8.h"
  29
  30 /* Access to this structure is protected by the BQL */
  31 typedef struct SemihostingConsole {
  32     CharBackend         backend;
  33     Chardev             *chr;
  34     GSList              *sleeping_cpus;
  35     bool                got;
  36     Fifo8               fifo;
  37 } SemihostingConsole;
  38
  39 static SemihostingConsole console;
  40
  41 #define FIFO_SIZE   1024
  42
  43 static int console_can_read(void *opaque)
  44 {
  45     SemihostingConsole *c = opaque;
  46     g_assert(bql_locked());
  47     return (int)fifo8_num_free(&c->fifo);
  48 }
  49
  50 static void console_wake_up(gpointer data, gpointer user_data)
  51 {
  52     CPUState *cs = (CPUState *) data;
  53     /* cpu_handle_halt won't know we have work so just unbung here */
  54     cs->halted = 0;
  55     qemu_cpu_kick(cs);
  56 }
  57
  58 static void console_read(void *opaque, const uint8_t *buf, int size)
  59 {
  60     SemihostingConsole *c = opaque;
  61     g_assert(bql_locked());
  62     while (size-- && !fifo8_is_full(&c->fifo)) {
  63         fifo8_push(&c->fifo, *buf++);
  64     }
  65     g_slist_foreach(c->sleeping_cpus, console_wake_up, NULL);
  66     c->sleeping_cpus = NULL;
  67 }
  68
  69 bool qemu_semihosting_console_ready(void)
  70 {
  71     SemihostingConsole *c = &console;
  72
  73     g_assert(bql_locked());
  74     return !fifo8_is_empty(&c->fifo);
  75 }
  76
  77 void qemu_semihosting_console_block_until_ready(CPUState *cs)
  78 {
  79     SemihostingConsole *c = &console;
  80
  81     g_assert(bql_locked());
  82
  83     /* Block if the fifo is completely empty. */
  84     if (fifo8_is_empty(&c->fifo)) {
  85         c->sleeping_cpus = g_slist_prepend(c->sleeping_cpus, cs);
  86         cs->halted = 1;
  87         cs->exception_index = EXCP_HALTED;
  88         cpu_loop_exit(cs);
  89         /* never returns */
  90     }
  91 }
  92
  93 int qemu_semihosting_console_read(CPUState *cs, void *buf, int len)
  94 {
  95     SemihostingConsole *c = &console;
  96     int ret = 0;
  97
  98     qemu_semihosting_console_block_until_ready(cs);
  99
 100     /* Read until buffer full or fifo exhausted. */
 101     do {
 102         *(char *)(buf + ret) = fifo8_pop(&c->fifo);
 103         ret++;
 104     } while (ret < len && !fifo8_is_empty(&c->fifo));
 105
 106     return ret;
 107 }
 108
 109 int qemu_semihosting_console_write(void *buf, int len)
 110 {
 111     if (console.chr) {
 112         int r = qemu_chr_write_all(console.chr, (uint8_t *)buf, len);
 113         return r < 0 ? 0 : r;
 114     } else {
 115         return fwrite(buf, 1, len, stderr);
 116     }
 117 }
 118
 119 void qemu_semihosting_console_init(Chardev *chr)
 120 {
 121     console.chr = chr;
 122     if  (chr) {
 123         fifo8_create(&console.fifo, FIFO_SIZE);
 124         qemu_chr_fe_init(&console.backend, chr, &error_abort);
 125         qemu_chr_fe_set_handlers(&console.backend,
 126                                  console_can_read,
 127                                  console_read,
 128                                  NULL, NULL, &console,
 129                                  NULL, true);
 130     }
 131
 132     qemu_semihosting_guestfd_init();
 133 }