Commit a331c6d7 authored by Alex Bennée's avatar Alex Bennée
Browse files

semihosting: implement a semihosting console 



This provides two functions for handling console output that handle
the common backend behaviour for semihosting.

Signed-off-by: default avatarAlex Bennée <alex.bennee@linaro.org>
parent 16932bb7

hw/semihosting/Makefile.objs

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obj-$(CONFIG_SEMIHOSTING) += config.o

obj-$(CONFIG_SEMIHOSTING) += console.o

hw/semihosting/console.c

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/*

 * Semihosting Console Support

 *

 * Copyright (c) 2015 Imagination Technologies

 * Copyright (c) 2019 Linaro Ltd

 *

 * This provides support for outputting to a semihosting console.

 *

 * While most semihosting implementations support reading and writing

 * to arbitrary file descriptors we treat the console as something

 * specifically for debugging interaction. This means messages can be

 * re-directed to gdb (if currently being used to debug) or even

 * re-directed elsewhere.

 *

 * SPDX-License-Identifier: GPL-2.0-or-later

 */



#include "qemu/osdep.h"

#include "cpu.h"

#include "hw/semihosting/console.h"

#include "exec/gdbstub.h"

#include "qemu/log.h"



int qemu_semihosting_log_out(const char *s, int len)

{

    return write(STDERR_FILENO, s, len);

}



/*

 * A re-implementation of lock_user_string that we can use locally

 * instead of relying on softmmu-semi. Hopefully we can deprecate that

 * in time. We either copy len bytes if specified or until we find a NULL.

 */

static GString *copy_user_string(CPUArchState *env, target_ulong addr, int len)

{

    CPUState *cpu = ENV_GET_CPU(env);

    GString *s = g_string_sized_new(len ? len : 128);

    uint8_t c;

    bool done;



    do {

        if (cpu_memory_rw_debug(cpu, addr++, &c, 1, 0) == 0) {

            s = g_string_append_c(s, c);

            done = len ? s->len == len : c == 0;

        } else {

            qemu_log_mask(LOG_GUEST_ERROR,

                          "%s: passed inaccessible address " TARGET_FMT_lx,

                          __func__, addr);

            done = true;

        }

    } while (!done);



    return s;

}



static void semihosting_cb(CPUState *cs, target_ulong ret, target_ulong err)

{

    if (ret == (target_ulong) -1) {

        qemu_log("%s: gdb console output failed ("TARGET_FMT_ld")",

                 __func__, err);

    }

}



int qemu_semihosting_console_out(CPUArchState *env, target_ulong addr, int len)

{

    GString *s = copy_user_string(env, addr, len);

    int out = s->len;



    if (use_gdb_syscalls()) {

        gdb_do_syscall(semihosting_cb, "write,2,%x,%x", addr, s->len);

    } else {

        out = qemu_semihosting_log_out(s->str, s->len);

    }



    g_string_free(s, true);

    return out;

}

include/hw/semihosting/console.h

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/*

 * Semihosting Console

 *

 * Copyright (c) 2019 Linaro Ltd

 *

 * SPDX-License-Identifier: GPL-2.0-or-later

 */



#ifndef _SEMIHOST_CONSOLE_H_

#define _SEMIHOST_CONSOLE_H_



/**

 * qemu_semihosting_console_out:

 * @env: CPUArchState

 * @s: host address of guest string

 * @len: length of string or 0 (string is null terminated)

 *

 * Send a guest string to the debug console. This may be the remote

 * gdb session if a softmmu guest is currently being debugged.

 *

 * Returns: number of bytes written.

 */

int qemu_semihosting_console_out(CPUArchState *env, target_ulong s, int len);



/**

 * qemu_semihosting_log_out:

 * @s: pointer to string

 * @len: length of string

 *

 * Send a string to the debug output. Unlike console_out these strings

 * can't be sent to a remote gdb instance as they don't exist in guest

 * memory.

 *

 * Returns: number of bytes written

 */

int qemu_semihosting_log_out(const char *s, int len);



#endif /* _SEMIHOST_CONSOLE_H_ */