xref: /openbmc/qemu/semihosting/console.c (revision 6c187695)
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     int ret;
47     g_assert(qemu_mutex_iothread_locked());
48     ret = (int) fifo8_num_free(&c->fifo);
49     return ret;
50 }
51 
52 static void console_wake_up(gpointer data, gpointer user_data)
53 {
54     CPUState *cs = (CPUState *) data;
55     /* cpu_handle_halt won't know we have work so just unbung here */
56     cs->halted = 0;
57     qemu_cpu_kick(cs);
58 }
59 
60 static void console_read(void *opaque, const uint8_t *buf, int size)
61 {
62     SemihostingConsole *c = opaque;
63     g_assert(qemu_mutex_iothread_locked());
64     while (size-- && !fifo8_is_full(&c->fifo)) {
65         fifo8_push(&c->fifo, *buf++);
66     }
67     g_slist_foreach(c->sleeping_cpus, console_wake_up, NULL);
68     c->sleeping_cpus = NULL;
69 }
70 
71 bool qemu_semihosting_console_ready(void)
72 {
73     SemihostingConsole *c = &console;
74 
75     g_assert(qemu_mutex_iothread_locked());
76     return !fifo8_is_empty(&c->fifo);
77 }
78 
79 void qemu_semihosting_console_block_until_ready(CPUState *cs)
80 {
81     SemihostingConsole *c = &console;
82 
83     g_assert(qemu_mutex_iothread_locked());
84 
85     /* Block if the fifo is completely empty. */
86     if (fifo8_is_empty(&c->fifo)) {
87         c->sleeping_cpus = g_slist_prepend(c->sleeping_cpus, cs);
88         cs->halted = 1;
89         cs->exception_index = EXCP_HALTED;
90         cpu_loop_exit(cs);
91         /* never returns */
92     }
93 }
94 
95 int qemu_semihosting_console_read(CPUState *cs, void *buf, int len)
96 {
97     SemihostingConsole *c = &console;
98     int ret = 0;
99 
100     qemu_semihosting_console_block_until_ready(cs);
101 
102     /* Read until buffer full or fifo exhausted. */
103     do {
104         *(char *)(buf + ret) = fifo8_pop(&c->fifo);
105         ret++;
106     } while (ret < len && !fifo8_is_empty(&c->fifo));
107 
108     return ret;
109 }
110 
111 int qemu_semihosting_console_write(void *buf, int len)
112 {
113     if (console.chr) {
114         int r = qemu_chr_write_all(console.chr, (uint8_t *)buf, len);
115         return r < 0 ? 0 : r;
116     } else {
117         return fwrite(buf, 1, len, stderr);
118     }
119 }
120 
121 void qemu_semihosting_console_init(Chardev *chr)
122 {
123     console.chr = chr;
124     if  (chr) {
125         fifo8_create(&console.fifo, FIFO_SIZE);
126         qemu_chr_fe_init(&console.backend, chr, &error_abort);
127         qemu_chr_fe_set_handlers(&console.backend,
128                                  console_can_read,
129                                  console_read,
130                                  NULL, NULL, &console,
131                                  NULL, true);
132     }
133 
134     qemu_semihosting_guestfd_init();
135 }
136