/* Native debugging support for Intel x86 running DJGPP.
- Copyright 1997, 1999, 2000, 2001 Free Software Foundation, Inc.
+ Copyright (C) 1997, 1999, 2000, 2001, 2005, 2006, 2007
+ Free Software Foundation, Inc.
Written by Robert Hoehne.
This file is part of GDB.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
- Foundation, Inc., 59 Temple Place - Suite 330,
- Boston, MA 02111-1307, USA. */
+ Foundation, Inc., 51 Franklin Street, Fifth Floor,
+ Boston, MA 02110-1301, USA. */
#include <fcntl.h>
#include "gdbcmd.h"
#include "floatformat.h"
#include "buildsym.h"
-#include "i387-nat.h"
+#include "i387-tdep.h"
+#include "i386-tdep.h"
#include "value.h"
#include "regcache.h"
#include "gdb_string.h"
+#include "top.h"
#include <stdio.h> /* might be required for __DJGPP_MINOR__ */
#include <stdlib.h>
#include <unistd.h>
#include <sys/utsname.h>
#include <io.h>
-/* breakpoint.h defines `disable' which is an enum member. */
-#define disable interrup_disable
#include <dos.h>
-#undef disable
#include <dpmi.h>
#include <go32.h>
+#include <sys/farptr.h>
#include <debug/v2load.h>
#include <debug/dbgcom.h>
#if __DJGPP_MINOR__ > 2
static void
save_npx (void)
{
- asm ("inb $0xa0, %%al
- testb $0x20, %%al
- jz 1f
- xorb %% al, %%al
- outb %% al, $0xf0
- movb $0x20, %%al
- outb %% al, $0xa0
- outb %% al, $0x20
-1:
- fnsave % 0
+ asm ("inb $0xa0, %%al \n\
+ testb $0x20, %%al \n\
+ jz 1f \n\
+ xorb %%al, %%al \n\
+ outb %%al, $0xf0 \n\
+ movb $0x20, %%al \n\
+ outb %%al, $0xa0 \n\
+ outb %%al, $0x20 \n\
+1: \n\
+ fnsave %0 \n\
fwait "
: "=m" (npx)
: /* No input */
/* *INDENT-ON* */
-
-
-
/* ------------------------------------------------------------------------- */
/* Reload the contents of the NPX from the global variable `npx'. */
enum target_signal siggnal);
static ptid_t go32_wait (ptid_t ptid,
struct target_waitstatus *status);
-static void go32_fetch_registers (int regno);
-static void store_register (int regno);
-static void go32_store_registers (int regno);
-static void go32_prepare_to_store (void);
+static void go32_fetch_registers (struct regcache *, int regno);
+static void store_register (const struct regcache *, int regno);
+static void go32_store_registers (struct regcache *, int regno);
+static void go32_prepare_to_store (struct regcache *);
static int go32_xfer_memory (CORE_ADDR memaddr, char *myaddr, int len,
int write,
struct mem_attrib *attrib,
static void go32_files_info (struct target_ops *target);
static void go32_stop (void);
static void go32_kill_inferior (void);
-static void go32_create_inferior (char *exec_file, char *args, char **env);
+static void go32_create_inferior (char *exec_file, char *args, char **env, int from_tty);
static void go32_mourn_inferior (void);
static int go32_can_run (void);
static void
go32_attach (char *args, int from_tty)
{
- error ("\
+ error (_("\
You cannot attach to a running program on this platform.\n\
-Use the `run' command to run DJGPP programs.");
+Use the `run' command to run DJGPP programs."));
}
static void
}
static void
-fetch_register (int regno)
+fetch_register (struct regcache *regcache, int regno)
{
if (regno < FP0_REGNUM)
- supply_register (regno, (char *) &a_tss + regno_mapping[regno].tss_ofs);
- else if (regno <= LAST_FPU_CTRL_REGNUM)
- i387_supply_register (regno, (char *) &npx);
+ regcache_raw_supply (regcache, regno,
+ (char *) &a_tss + regno_mapping[regno].tss_ofs);
+ else if (i386_fp_regnum_p (regno) || i386_fpc_regnum_p (regno))
+ i387_supply_fsave (regcache, regno, &npx);
else
internal_error (__FILE__, __LINE__,
- "Invalid register no. %d in fetch_register.", regno);
+ _("Invalid register no. %d in fetch_register."), regno);
}
static void
-go32_fetch_registers (int regno)
+go32_fetch_registers (struct regcache *regcache, int regno)
{
if (regno >= 0)
- fetch_register (regno);
+ fetch_register (regcache, regno);
else
{
for (regno = 0; regno < FP0_REGNUM; regno++)
- fetch_register (regno);
- i387_supply_fsave ((char *) &npx);
+ fetch_register (regcache, regno);
+ i387_supply_fsave (regcache, -1, &npx);
}
}
static void
-store_register (int regno)
+store_register (const struct regcache *regcache, int regno)
{
- void *rp;
- void *v = (void *) register_buffer (regno);
-
if (regno < FP0_REGNUM)
- memcpy ((char *) &a_tss + regno_mapping[regno].tss_ofs,
- v, regno_mapping[regno].size);
- else if (regno <= LAST_FPU_CTRL_REGNUM)
- i387_fill_fsave ((char *)&npx, regno);
+ regcache_raw_collect (regcache, regno,
+ (char *) &a_tss + regno_mapping[regno].tss_ofs);
+ else if (i386_fp_regnum_p (regno) || i386_fpc_regnum_p (regno))
+ i387_collect_fsave (regcache, regno, &npx);
else
internal_error (__FILE__, __LINE__,
- "Invalid register no. %d in store_register.", regno);
+ _("Invalid register no. %d in store_register."), regno);
}
static void
-go32_store_registers (int regno)
+go32_store_registers (struct regcache *regcache, int regno)
{
unsigned r;
if (regno >= 0)
- store_register (regno);
+ store_register (regcache, regno);
else
{
for (r = 0; r < FP0_REGNUM; r++)
- store_register (r);
- i387_fill_fsave ((char *) &npx, -1);
+ store_register (regcache, r);
+ i387_collect_fsave (regcache, -1, &npx);
}
}
static void
-go32_prepare_to_store (void)
+go32_prepare_to_store (struct regcache *regcache)
{
}
}
static void
-go32_create_inferior (char *exec_file, char *args, char **env)
+go32_create_inferior (char *exec_file, char *args, char **env, int from_tty)
{
extern char **environ;
jmp_buf start_state;
/* Init command line storage. */
if (redir_debug_init (&child_cmd) == -1)
internal_error (__FILE__, __LINE__,
- "Cannot allocate redirection storage: not enough memory.\n");
+ _("Cannot allocate redirection storage: not enough memory.\n"));
/* Parse the command line and create redirections. */
if (strpbrk (args, "<>"))
if (redir_cmdline_parse (args, &child_cmd) == 0)
args = child_cmd.command;
else
- error ("Syntax error in command line.");
+ error (_("Syntax error in command line."));
}
else
child_cmd.command = xstrdup (args);
/* v2loadimage passes command lines via DOS memory, so it cannot
possibly handle commands longer than 1MB. */
if (cmdlen > 1024*1024)
- error ("Command line too long.");
+ error (_("Command line too long."));
cmdline = xmalloc (cmdlen + 4);
strcpy (cmdline + 1, args);
exit (1);
}
environ = env_save;
- free (cmdline);
+ xfree (cmdline);
edi_init (start_state);
#if __DJGPP_MINOR__ < 3
push_target (&go32_ops);
clear_proceed_status ();
insert_breakpoints ();
- proceed ((CORE_ADDR) -1, TARGET_SIGNAL_0, 0);
prog_has_started = 1;
}
{
if (i < 0 || i > 3)
internal_error (__FILE__, __LINE__,
- "Invalid register %d in go32_set_dr.\n", i);
+ _("Invalid register %d in go32_set_dr.\n"), i);
D_REGS[i] = addr;
}
if (redir_to_child (&child_cmd) == -1)
{
redir_to_debugger (&child_cmd);
- error ("Cannot redirect standard handles for program: %s.",
- strerror (errno));
+ error (_("Cannot redirect standard handles for program: %s."),
+ safe_strerror (errno));
}
/* set the console device of the inferior to whatever mode
(raw or cooked) we found it last time */
if (redir_to_debugger (&child_cmd) == -1)
{
redir_to_child (&child_cmd);
- error ("Cannot redirect standard handles for debugger: %s.",
- strerror (errno));
+ error (_("Cannot redirect standard handles for debugger: %s."),
+ safe_strerror (errno));
}
}
}
go32_ops.to_fetch_registers = go32_fetch_registers;
go32_ops.to_store_registers = go32_store_registers;
go32_ops.to_prepare_to_store = go32_prepare_to_store;
- go32_ops.to_xfer_memory = go32_xfer_memory;
+ go32_ops.deprecated_xfer_memory = go32_xfer_memory;
go32_ops.to_files_info = go32_files_info;
go32_ops.to_insert_breakpoint = memory_insert_breakpoint;
go32_ops.to_remove_breakpoint = memory_remove_breakpoint;
/* Initialize child's command line storage. */
if (redir_debug_init (&child_cmd) == -1)
internal_error (__FILE__, __LINE__,
- "Cannot allocate redirection storage: not enough memory.\n");
+ _("Cannot allocate redirection storage: not enough memory.\n"));
/* We are always processing GCC-compiled programs. */
processing_gcc_compilation = 2;
+
+ /* Override the default name of the GDB init file. */
+ strcpy (gdbinit, "gdb.ini");
}
unsigned short windows_major, windows_minor;
read_memory_region (unsigned long addr, void *dest, size_t len)
{
unsigned long dos_ds_limit = __dpmi_get_segment_limit (_dos_ds);
+ int retval = 1;
/* For the low memory, we can simply use _dos_ds. */
if (addr <= dos_ds_limit - len)
be able to access that memory. */
int sel = __dpmi_allocate_ldt_descriptors (1);
- if (sel <= 0
- || __dpmi_set_segment_base_address (sel, addr) == -1
- || __dpmi_set_segment_limit (sel, len - 1) == -1)
- return 0;
- movedata (sel, 0, _my_ds (), (unsigned)dest, len);
- __dpmi_free_ldt_descriptor (sel);
+ if (sel <= 0)
+ retval = 0;
+ else
+ {
+ int access_rights = __dpmi_get_descriptor_access_rights (sel);
+ size_t segment_limit = len - 1;
+
+ /* Make sure the crucial bits in the descriptor access
+ rights are set correctly. Some DPMI providers might barf
+ if we set the segment limit to something that is not an
+ integral multiple of 4KB pages if the granularity bit is
+ not set to byte-granular, even though the DPMI spec says
+ it's the host's responsibility to set that bit correctly. */
+ if (len > 1024 * 1024)
+ {
+ access_rights |= 0x8000;
+ /* Page-granular segments should have the low 12 bits of
+ the limit set. */
+ segment_limit |= 0xfff;
+ }
+ else
+ access_rights &= ~0x8000;
+
+ if (__dpmi_set_segment_base_address (sel, addr) != -1
+ && __dpmi_set_descriptor_access_rights (sel, access_rights) != -1
+ && __dpmi_set_segment_limit (sel, segment_limit) != -1
+ /* W2K silently fails to set the segment limit, leaving
+ it at zero; this test avoids the resulting crash. */
+ && __dpmi_get_segment_limit (sel) >= segment_limit)
+ movedata (sel, 0, _my_ds (), (unsigned)dest, len);
+ else
+ retval = 0;
+
+ __dpmi_free_ldt_descriptor (sel);
+ }
}
- return 1;
+ return retval;
}
/* Get a segment descriptor stored at index IDX in the descriptor
if (ldt_entry < 0
|| (ldt_entry & 4) == 0
|| (ldt_entry & 3) != (cpl & 3))
- error ("Invalid LDT entry 0x%03x.", ldt_entry);
+ error (_("Invalid LDT entry 0x%03lx."), (unsigned long)ldt_entry);
}
}
if (ldt_entry >= 0)
{
if (ldt_entry > limit)
- error ("Invalid LDT entry %#x: outside valid limits [0..%#x]",
- ldt_entry, limit);
+ error (_("Invalid LDT entry %#lx: outside valid limits [0..%#x]"),
+ (unsigned long)ldt_entry, limit);
display_descriptor (ldt_descr.stype, base, ldt_entry / 8, 1);
}
{
gdt_entry = parse_and_eval_long (arg);
if (gdt_entry < 0 || (gdt_entry & 7) != 0)
- error ("Invalid GDT entry 0x%03x: not an integral multiple of 8.",
- gdt_entry);
+ error (_("Invalid GDT entry 0x%03lx: not an integral multiple of 8."),
+ (unsigned long)gdt_entry);
}
}
if (gdt_entry >= 0)
{
if (gdt_entry > gdtr.limit)
- error ("Invalid GDT entry %#x: outside valid limits [0..%#x]",
- gdt_entry, gdtr.limit);
+ error (_("Invalid GDT entry %#lx: outside valid limits [0..%#x]"),
+ (unsigned long)gdt_entry, gdtr.limit);
display_descriptor (0, gdtr.base, gdt_entry / 8, 1);
}
{
idt_entry = parse_and_eval_long (arg);
if (idt_entry < 0)
- error ("Invalid (negative) IDT entry 0x%03x.", idt_entry);
+ error (_("Invalid (negative) IDT entry %ld."), idt_entry);
}
}
if (idt_entry >= 0)
{
if (idt_entry > idtr.limit)
- error ("Invalid IDT entry %#x: outside valid limits [0..%#x]",
- idt_entry, idtr.limit);
+ error (_("Invalid IDT entry %#lx: outside valid limits [0..%#x]"),
+ (unsigned long)idt_entry, idtr.limit);
display_descriptor (1, idtr.base, idt_entry, 1);
}
}
}
+/* Cached linear address of the base of the page directory. For
+ now, available only under CWSDPMI. Code based on ideas and
+ suggestions from Charles Sandmann <sandmann@clio.rice.edu>. */
+static unsigned long pdbr;
+
+static unsigned long
+get_cr3 (void)
+{
+ unsigned offset;
+ unsigned taskreg;
+ unsigned long taskbase, cr3;
+ struct dtr_reg gdtr;
+
+ if (pdbr > 0 && pdbr <= 0xfffff)
+ return pdbr;
+
+ /* Get the linear address of GDT and the Task Register. */
+ __asm__ __volatile__ ("sgdt %0" : "=m" (gdtr) : /* no inputs */ );
+ __asm__ __volatile__ ("str %0" : "=m" (taskreg) : /* no inputs */ );
+
+ /* Task Register is a segment selector for the TSS of the current
+ task. Therefore, it can be used as an index into the GDT to get
+ at the segment descriptor for the TSS. To get the index, reset
+ the low 3 bits of the selector (which give the CPL). Add 2 to the
+ offset to point to the 3 low bytes of the base address. */
+ offset = gdtr.base + (taskreg & 0xfff8) + 2;
+
+
+ /* CWSDPMI's task base is always under the 1MB mark. */
+ if (offset > 0xfffff)
+ return 0;
+
+ _farsetsel (_dos_ds);
+ taskbase = _farnspeekl (offset) & 0xffffffU;
+ taskbase += _farnspeekl (offset + 2) & 0xff000000U;
+ if (taskbase > 0xfffff)
+ return 0;
+
+ /* CR3 (a.k.a. PDBR, the Page Directory Base Register) is stored at
+ offset 1Ch in the TSS. */
+ cr3 = _farnspeekl (taskbase + 0x1c) & ~0xfff;
+ if (cr3 > 0xfffff)
+ {
+#if 0 /* not fullly supported yet */
+ /* The Page Directory is in UMBs. In that case, CWSDPMI puts
+ the first Page Table right below the Page Directory. Thus,
+ the first Page Table's entry for its own address and the Page
+ Directory entry for that Page Table will hold the same
+ physical address. The loop below searches the entire UMB
+ range of addresses for such an occurence. */
+ unsigned long addr, pte_idx;
+
+ for (addr = 0xb0000, pte_idx = 0xb0;
+ pte_idx < 0xff;
+ addr += 0x1000, pte_idx++)
+ {
+ if (((_farnspeekl (addr + 4 * pte_idx) & 0xfffff027) ==
+ (_farnspeekl (addr + 0x1000) & 0xfffff027))
+ && ((_farnspeekl (addr + 4 * pte_idx + 4) & 0xfffff000) == cr3))
+ {
+ cr3 = addr + 0x1000;
+ break;
+ }
+ }
+#endif
+
+ if (cr3 > 0xfffff)
+ cr3 = 0;
+ }
+
+ return cr3;
+}
+
+/* Return the N'th Page Directory entry. */
+static unsigned long
+get_pde (int n)
+{
+ unsigned long pde = 0;
+
+ if (pdbr && n >= 0 && n < 1024)
+ {
+ pde = _farpeekl (_dos_ds, pdbr + 4*n);
+ }
+ return pde;
+}
+
+/* Return the N'th entry of the Page Table whose Page Directory entry
+ is PDE. */
+static unsigned long
+get_pte (unsigned long pde, int n)
+{
+ unsigned long pte = 0;
+
+ /* pde & 0x80 tests the 4MB page bit. We don't support 4MB
+ page tables, for now. */
+ if ((pde & 1) && !(pde & 0x80) && n >= 0 && n < 1024)
+ {
+ pde &= ~0xfff; /* clear non-address bits */
+ pte = _farpeekl (_dos_ds, pde + 4*n);
+ }
+ return pte;
+}
+
+/* Display a Page Directory or Page Table entry. IS_DIR, if non-zero,
+ says this is a Page Directory entry. If FORCE is non-zero, display
+ the entry even if its Present flag is off. OFF is the offset of the
+ address from the page's base address. */
+static void
+display_ptable_entry (unsigned long entry, int is_dir, int force, unsigned off)
+{
+ if ((entry & 1) != 0)
+ {
+ printf_filtered ("Base=0x%05lx000", entry >> 12);
+ if ((entry & 0x100) && !is_dir)
+ puts_filtered (" Global");
+ if ((entry & 0x40) && !is_dir)
+ puts_filtered (" Dirty");
+ printf_filtered (" %sAcc.", (entry & 0x20) ? "" : "Not-");
+ printf_filtered (" %sCached", (entry & 0x10) ? "" : "Not-");
+ printf_filtered (" Write-%s", (entry & 8) ? "Thru" : "Back");
+ printf_filtered (" %s", (entry & 4) ? "Usr" : "Sup");
+ printf_filtered (" Read-%s", (entry & 2) ? "Write" : "Only");
+ if (off)
+ printf_filtered (" +0x%x", off);
+ puts_filtered ("\n");
+ }
+ else if (force)
+ printf_filtered ("Page%s not present or not supported; value=0x%lx.\n",
+ is_dir ? " Table" : "", entry >> 1);
+}
+
+static void
+go32_pde (char *arg, int from_tty)
+{
+ long pde_idx = -1, i;
+
+ if (arg && *arg)
+ {
+ while (*arg && isspace(*arg))
+ arg++;
+
+ if (*arg)
+ {
+ pde_idx = parse_and_eval_long (arg);
+ if (pde_idx < 0 || pde_idx >= 1024)
+ error (_("Entry %ld is outside valid limits [0..1023]."), pde_idx);
+ }
+ }
+
+ pdbr = get_cr3 ();
+ if (!pdbr)
+ puts_filtered ("Access to Page Directories is not supported on this system.\n");
+ else if (pde_idx >= 0)
+ display_ptable_entry (get_pde (pde_idx), 1, 1, 0);
+ else
+ for (i = 0; i < 1024; i++)
+ display_ptable_entry (get_pde (i), 1, 0, 0);
+}
+
+/* A helper function to display entries in a Page Table pointed to by
+ the N'th entry in the Page Directory. If FORCE is non-zero, say
+ something even if the Page Table is not accessible. */
+static void
+display_page_table (long n, int force)
+{
+ unsigned long pde = get_pde (n);
+
+ if ((pde & 1) != 0)
+ {
+ int i;
+
+ printf_filtered ("Page Table pointed to by Page Directory entry 0x%lx:\n", n);
+ for (i = 0; i < 1024; i++)
+ display_ptable_entry (get_pte (pde, i), 0, 0, 0);
+ puts_filtered ("\n");
+ }
+ else if (force)
+ printf_filtered ("Page Table not present; value=0x%lx.\n", pde >> 1);
+}
+
+static void
+go32_pte (char *arg, int from_tty)
+{
+ long pde_idx = -1L, i;
+
+ if (arg && *arg)
+ {
+ while (*arg && isspace(*arg))
+ arg++;
+
+ if (*arg)
+ {
+ pde_idx = parse_and_eval_long (arg);
+ if (pde_idx < 0 || pde_idx >= 1024)
+ error (_("Entry %ld is outside valid limits [0..1023]."), pde_idx);
+ }
+ }
+
+ pdbr = get_cr3 ();
+ if (!pdbr)
+ puts_filtered ("Access to Page Tables is not supported on this system.\n");
+ else if (pde_idx >= 0)
+ display_page_table (pde_idx, 1);
+ else
+ for (i = 0; i < 1024; i++)
+ display_page_table (i, 0);
+}
+
+static void
+go32_pte_for_address (char *arg, int from_tty)
+{
+ CORE_ADDR addr = 0, i;
+
+ if (arg && *arg)
+ {
+ while (*arg && isspace(*arg))
+ arg++;
+
+ if (*arg)
+ addr = parse_and_eval_address (arg);
+ }
+ if (!addr)
+ error_no_arg (_("linear address"));
+
+ pdbr = get_cr3 ();
+ if (!pdbr)
+ puts_filtered ("Access to Page Tables is not supported on this system.\n");
+ else
+ {
+ int pde_idx = (addr >> 22) & 0x3ff;
+ int pte_idx = (addr >> 12) & 0x3ff;
+ unsigned offs = addr & 0xfff;
+
+ printf_filtered ("Page Table entry for address 0x%llx:\n",
+ (unsigned long long)addr);
+ display_ptable_entry (get_pte (get_pde (pde_idx), pte_idx), 0, 1, offs);
+ }
+}
+
static struct cmd_list_element *info_dos_cmdlist = NULL;
static void
init_go32_ops ();
add_target (&go32_ops);
- add_prefix_cmd ("dos", class_info, go32_info_dos_command,
- "Print information specific to DJGPP (a.k.a. MS-DOS) debugging.",
+ add_prefix_cmd ("dos", class_info, go32_info_dos_command, _("\
+Print information specific to DJGPP (aka MS-DOS) debugging."),
&info_dos_cmdlist, "info dos ", 0, &infolist);
- add_cmd ("sysinfo", class_info, go32_sysinfo,
- "Display information about the target system, including CPU, OS, DPMI, etc.",
+ add_cmd ("sysinfo", class_info, go32_sysinfo, _("\
+Display information about the target system, including CPU, OS, DPMI, etc."),
+ &info_dos_cmdlist);
+ add_cmd ("ldt", class_info, go32_sldt, _("\
+Display entries in the LDT (Local Descriptor Table).\n\
+Entry number (an expression) as an argument means display only that entry."),
+ &info_dos_cmdlist);
+ add_cmd ("gdt", class_info, go32_sgdt, _("\
+Display entries in the GDT (Global Descriptor Table).\n\
+Entry number (an expression) as an argument means display only that entry."),
+ &info_dos_cmdlist);
+ add_cmd ("idt", class_info, go32_sidt, _("\
+Display entries in the IDT (Interrupt Descriptor Table).\n\
+Entry number (an expression) as an argument means display only that entry."),
&info_dos_cmdlist);
- add_cmd ("ldt", class_info, go32_sldt,
- "Display entries in the LDT (Local Descriptor Table).\n"
- "Entry number (an expression) as an argument means display only that entry.",
+ add_cmd ("pde", class_info, go32_pde, _("\
+Display entries in the Page Directory.\n\
+Entry number (an expression) as an argument means display only that entry."),
&info_dos_cmdlist);
- add_cmd ("gdt", class_info, go32_sgdt,
- "Display entries in the GDT (Global Descriptor Table).\n"
- "Entry number (an expression) as an argument means display only that entry.",
+ add_cmd ("pte", class_info, go32_pte, _("\
+Display entries in Page Tables.\n\
+Entry number (an expression) as an argument means display only entries\n\
+from the Page Table pointed to by the specified Page Directory entry."),
&info_dos_cmdlist);
- add_cmd ("idt", class_info, go32_sidt,
- "Display entries in the IDT (Interrupt Descriptor Table).\n"
- "Entry number (an expression) as an argument means display only that entry.",
+ add_cmd ("address-pte", class_info, go32_pte_for_address, _("\
+Display a Page Table entry for a linear address.\n\
+The address argument must be a linear address, after adding to\n\
+it the base address of the appropriate segment.\n\
+The base address of variables and functions in the debuggee's data\n\
+or code segment is stored in the variable __djgpp_base_address,\n\
+so use `__djgpp_base_address + (char *)&var' as the argument.\n\
+For other segments, look up their base address in the output of\n\
+the `info dos ldt' command."),
&info_dos_cmdlist);
}