semihosting/guestfd.c

   1 /*
   2  * Hosted file support for semihosting syscalls.
   3  *
   4  * Copyright (c) 2005, 2007 CodeSourcery.
   5  * Copyright (c) 2019 Linaro
   6  * Copyright © 2020 by Keith Packard <keithp@keithp.com>
   7  *
   8  * SPDX-License-Identifier: GPL-2.0-or-later
   9  */
  10
  11 #include "qemu/osdep.h"
  12 #include "gdbstub/syscalls.h"
  13 #include "semihosting/semihost.h"
  14 #include "semihosting/guestfd.h"
  15 #ifdef CONFIG_USER_ONLY
  16 #include "qemu.h"
  17 #else
  18 #include "semihosting/uaccess.h"
  19 #include CONFIG_DEVICES
  20 #endif
  21
  22 static GArray *guestfd_array;
  23
  24 #ifdef CONFIG_ARM_COMPATIBLE_SEMIHOSTING
  25 GuestFD console_in_gf;
  26 GuestFD console_out_gf;
  27 #endif
  28
  29 void qemu_semihosting_guestfd_init(void)
  30 {
  31     /* New entries zero-initialized, i.e. type GuestFDUnused */
  32     guestfd_array = g_array_new(FALSE, TRUE, sizeof(GuestFD));
  33
  34 #ifdef CONFIG_ARM_COMPATIBLE_SEMIHOSTING
  35     /* For ARM-compat, the console is in a separate namespace. */
  36     if (use_gdb_syscalls()) {
  37         console_in_gf.type = GuestFDGDB;
  38         console_in_gf.hostfd = 0;
  39         console_out_gf.type = GuestFDGDB;
  40         console_out_gf.hostfd = 2;
  41     } else {
  42         console_in_gf.type = GuestFDConsole;
  43         console_out_gf.type = GuestFDConsole;
  44     }
  45 #else
  46     /* Otherwise, the stdio file descriptors apply. */
  47     guestfd_array = g_array_set_size(guestfd_array, 3);
  48 #ifndef CONFIG_USER_ONLY
  49     if (!use_gdb_syscalls()) {
  50         GuestFD *gf = &g_array_index(guestfd_array, GuestFD, 0);
  51         gf[0].type = GuestFDConsole;
  52         gf[1].type = GuestFDConsole;
  53         gf[2].type = GuestFDConsole;
  54         return;
  55     }
  56 #endif
  57     associate_guestfd(0, 0);
  58     associate_guestfd(1, 1);
  59     associate_guestfd(2, 2);
  60 #endif
  61 }
  62
  63 /*
  64  * Allocate a new guest file descriptor and return it; if we
  65  * couldn't allocate a new fd then return -1.
  66  * This is a fairly simplistic implementation because we don't
  67  * expect that most semihosting guest programs will make very
  68  * heavy use of opening and closing fds.
  69  */
  70 int alloc_guestfd(void)
  71 {
  72     guint i;
  73
  74     /* SYS_OPEN should return nonzero handle on success. Start guestfd from 1 */
  75     for (i = 1; i < guestfd_array->len; i++) {
  76         GuestFD *gf = &g_array_index(guestfd_array, GuestFD, i);
  77
  78         if (gf->type == GuestFDUnused) {
  79             return i;
  80         }
  81     }
  82
  83     /* All elements already in use: expand the array */
  84     g_array_set_size(guestfd_array, i + 1);
  85     return i;
  86 }
  87
  88 static void do_dealloc_guestfd(GuestFD *gf)
  89 {
  90     gf->type = GuestFDUnused;
  91 }
  92
  93 /*
  94  * Look up the guestfd in the data structure; return NULL
  95  * for out of bounds, but don't check whether the slot is unused.
  96  * This is used internally by the other guestfd functions.
  97  */
  98 static GuestFD *do_get_guestfd(int guestfd)
  99 {
 100     if (guestfd < 0 || guestfd >= guestfd_array->len) {
 101         return NULL;
 102     }
 103
 104     return &g_array_index(guestfd_array, GuestFD, guestfd);
 105 }
 106
 107 /*
 108  * Given a guest file descriptor, get the associated struct.
 109  * If the fd is not valid, return NULL. This is the function
 110  * used by the various semihosting calls to validate a handle
 111  * from the guest.
 112  * Note: calling alloc_guestfd() or dealloc_guestfd() will
 113  * invalidate any GuestFD* obtained by calling this function.
 114  */
 115 GuestFD *get_guestfd(int guestfd)
 116 {
 117     GuestFD *gf = do_get_guestfd(guestfd);
 118
 119     if (!gf || gf->type == GuestFDUnused) {
 120         return NULL;
 121     }
 122     return gf;
 123 }
 124
 125 /*
 126  * Associate the specified guest fd (which must have been
 127  * allocated via alloc_fd() and not previously used) with
 128  * the specified host/gdb fd.
 129  */
 130 void associate_guestfd(int guestfd, int hostfd)
 131 {
 132     GuestFD *gf = do_get_guestfd(guestfd);
 133
 134     assert(gf);
 135     gf->type = use_gdb_syscalls() ? GuestFDGDB : GuestFDHost;
 136     gf->hostfd = hostfd;
 137 }
 138
 139 void staticfile_guestfd(int guestfd, const uint8_t *data, size_t len)
 140 {
 141     GuestFD *gf = do_get_guestfd(guestfd);
 142
 143     assert(gf);
 144     gf->type = GuestFDStatic;
 145     gf->staticfile.data = data;
 146     gf->staticfile.len = len;
 147     gf->staticfile.off = 0;
 148 }
 149
 150 /*
 151  * Deallocate the specified guest file descriptor. This doesn't
 152  * close the host fd, it merely undoes the work of alloc_fd().
 153  */
 154 void dealloc_guestfd(int guestfd)
 155 {
 156     GuestFD *gf = do_get_guestfd(guestfd);
 157
 158     assert(gf);
 159     do_dealloc_guestfd(gf);
 160 }