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grub/grub-core/loader/i386/pc/linux.c
Peter Jones d5a32255de misc: Make grub_strtol() "end" pointers have safer const qualifiers 
Currently the string functions grub_strtol(), grub_strtoul(), and
grub_strtoull() don't declare the "end" pointer in such a way as to
require the pointer itself or the character array to be immutable to the
implementation, nor does the C standard do so in its similar functions,
though it does require us not to change any of it.

The typical declarations of these functions follow this pattern:

long
strtol(const char * restrict nptr, char ** restrict endptr, int base);

Much of the reason for this is historic, and a discussion of that
follows below, after the explanation of this change.  (GRUB currently
does not include the "restrict" qualifiers, and we name the arguments a
bit differently.)

The implementation is semantically required to treat the character array
as immutable, but such accidental modifications aren't stopped by the
compiler, and the semantics for both the callers and the implementation
of these functions are sometimes also helped by adding that requirement.

This patch changes these declarations to follow this pattern instead:

long
strtol(const char * restrict nptr,
       const char ** const restrict endptr,
       int base);

This means that if any modification to these functions accidentally
introduces either an errant modification to the underlying character
array, or an accidental assignment to endptr rather than *endptr, the
compiler should generate an error.  (The two uses of "restrict" in this
case basically mean strtol() isn't allowed to modify the character array
by going through *endptr, and endptr isn't allowed to point inside the
array.)

It also means the typical use case changes to:

  char *s = ...;
  const char *end;
  long l;

  l = strtol(s, &end, 10);

Or even:

  const char *p = str;
  while (p && *p) {
	  long l = strtol(p, &p, 10);
	  ...
  }

This fixes 26 places where we discard our attempts at treating the data
safely by doing:

  const char *p = str;
  long l;

  l = strtol(p, (char **)&ptr, 10);

It also adds 5 places where we do:

  char *p = str;
  while (p && *p) {
	  long l = strtol(p, (const char ** const)&p, 10);
	  ...
	  /* more calls that need p not to be pointer-to-const */
  }

While moderately distasteful, this is a better problem to have.

With one minor exception, I have tested that all of this compiles
without relevant warnings or errors, and that /much/ of it behaves
correctly, with gcc 9 using 'gcc -W -Wall -Wextra'.  The one exception
is the changes in grub-core/osdep/aros/hostdisk.c , which I have no idea
how to build.

Because the C standard defined type-qualifiers in a way that can be
confusing, in the past there's been a slow but fairly regular stream of
churn within our patches, which add and remove the const qualifier in many
of the users of these functions.  This change should help avoid that in
the future, and in order to help ensure this, I've added an explanation
in misc.h so that when someone does get a compiler warning about a type
error, they have the fix at hand.

The reason we don't have "const" in these calls in the standard is
purely anachronistic: C78 (de facto) did not have type qualifiers in the
syntax, and the "const" type qualifier was added for C89 (I think; it
may have been later).  strtol() appears to date from 4.3BSD in 1986,
which means it could not be added to those functions in the standard
without breaking compatibility, which is usually avoided.

The syntax chosen for type qualifiers is what has led to the churn
regarding usage of const, and is especially confusing on string
functions due to the lack of a string type.  Quoting from C99, the
syntax is:

 declarator:
  pointer[opt] direct-declarator
 direct-declarator:
  identifier
  ( declarator )
  direct-declarator [ type-qualifier-list[opt] assignment-expression[opt] ]
  ...
  direct-declarator [ type-qualifier-list[opt] * ]
  ...
 pointer:
  * type-qualifier-list[opt]
  * type-qualifier-list[opt] pointer
 type-qualifier-list:
  type-qualifier
  type-qualifier-list type-qualifier
 ...
 type-qualifier:
  const
  restrict
  volatile

So the examples go like:

const char foo;			// immutable object
const char *foo;		// mutable pointer to object
char * const foo;		// immutable pointer to mutable object
const char * const foo;		// immutable pointer to immutable object
const char const * const foo; 	// XXX extra const keyword in the middle
const char * const * const foo; // immutable pointer to immutable
				//   pointer to immutable object
const char ** const foo;	// immutable pointer to mutable pointer
				//   to immutable object

Making const left-associative for * and right-associative for everything
else may not have been the best choice ever, but here we are, and the
inevitable result is people using trying to use const (as they should!),
putting it at the wrong place, fighting with the compiler for a bit, and
then either removing it or typecasting something in a bad way.  I won't
go into describing restrict, but its syntax has exactly the same issue
as with const.

Anyway, the last example above actually represents the *behavior* that's
required of strtol()-like functions, so that's our choice for the "end"
pointer.

Signed-off-by: Peter Jones <pjones@redhat.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
2020-02-28 12:41:29 +01:00

490 lines
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/* linux.c - boot Linux zImage or bzImage */
/*
* GRUB -- GRand Unified Bootloader
* Copyright (C) 1999,2000,2001,2002,2003,2004,2005,2007,2008,2009,2010 Free Software Foundation, Inc.
*
* GRUB is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* GRUB is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with GRUB. If not, see <http://www.gnu.org/licenses/>.
*/
#include <grub/loader.h>
#include <grub/file.h>
#include <grub/err.h>
#include <grub/device.h>
#include <grub/disk.h>
#include <grub/misc.h>
#include <grub/types.h>
#include <grub/memory.h>
#include <grub/dl.h>
#include <grub/cpu/linux.h>
#include <grub/command.h>
#include <grub/i18n.h>
#include <grub/mm.h>
#include <grub/cpu/relocator.h>
#include <grub/video.h>
#include <grub/i386/floppy.h>
#include <grub/lib/cmdline.h>
#include <grub/linux.h>
GRUB_MOD_LICENSE ("GPLv3+");
#define GRUB_LINUX_CL_OFFSET 0x9000
static grub_dl_t my_mod;
static grub_size_t linux_mem_size;
static int loaded;
static struct grub_relocator *relocator = NULL;
static grub_addr_t grub_linux_real_target;
static char *grub_linux_real_chunk;
static grub_size_t grub_linux16_prot_size;
static grub_size_t maximal_cmdline_size;
static grub_err_t
grub_linux16_boot (void)
{
grub_uint16_t segment;
struct grub_relocator16_state state;
segment = grub_linux_real_target >> 4;
state.gs = state.fs = state.es = state.ds = state.ss = segment;
state.sp = GRUB_LINUX_SETUP_STACK;
state.cs = segment + 0x20;
state.ip = 0;
state.a20 = 1;
grub_video_set_mode ("text", 0, 0);
grub_stop_floppy ();
return grub_relocator16_boot (relocator, state);
}
static grub_err_t
grub_linux_unload (void)
{
grub_dl_unref (my_mod);
loaded = 0;
grub_relocator_unload (relocator);
relocator = NULL;
return GRUB_ERR_NONE;
}
static int
target_hook (grub_uint64_t addr, grub_uint64_t size, grub_memory_type_t type,
void *data)
{
grub_uint64_t *result = data;
grub_uint64_t candidate;
if (type != GRUB_MEMORY_AVAILABLE)
return 0;
if (addr >= 0xa0000)
return 0;
if (addr + size >= 0xa0000)
size = 0xa0000 - addr;
/* Put the real mode part at as a high location as possible. */
candidate = addr + size - (GRUB_LINUX_CL_OFFSET + maximal_cmdline_size);
/* But it must not exceed the traditional area. */
if (candidate > GRUB_LINUX_OLD_REAL_MODE_ADDR)
candidate = GRUB_LINUX_OLD_REAL_MODE_ADDR;
if (candidate < addr)
return 0;
if (candidate > *result || *result == (grub_uint64_t) -1)
*result = candidate;
return 0;
}
static grub_addr_t
grub_find_real_target (void)
{
grub_uint64_t result = (grub_uint64_t) -1;
grub_mmap_iterate (target_hook, &result);
return result;
}
static grub_err_t
grub_cmd_linux (grub_command_t cmd __attribute__ ((unused)),
int argc, char *argv[])
{
grub_file_t file = 0;
struct linux_i386_kernel_header lh;
grub_uint8_t setup_sects;
grub_size_t real_size;
grub_ssize_t len;
int i;
char *grub_linux_prot_chunk;
int grub_linux_is_bzimage;
grub_addr_t grub_linux_prot_target;
grub_err_t err;
grub_dl_ref (my_mod);
if (argc == 0)
{
grub_error (GRUB_ERR_BAD_ARGUMENT, N_("filename expected"));
goto fail;
}
file = grub_file_open (argv[0], GRUB_FILE_TYPE_LINUX_KERNEL);
if (! file)
goto fail;
if (grub_file_read (file, &lh, sizeof (lh)) != sizeof (lh))
{
if (!grub_errno)
grub_error (GRUB_ERR_BAD_OS, N_("premature end of file %s"),
argv[0]);
goto fail;
}
if (lh.boot_flag != grub_cpu_to_le16_compile_time (0xaa55))
{
grub_error (GRUB_ERR_BAD_OS, "invalid magic number");
goto fail;
}
if (lh.setup_sects > GRUB_LINUX_MAX_SETUP_SECTS)
{
grub_error (GRUB_ERR_BAD_OS, "too many setup sectors");
goto fail;
}
grub_linux_is_bzimage = 0;
setup_sects = lh.setup_sects;
linux_mem_size = 0;
maximal_cmdline_size = 256;
if (lh.header == grub_cpu_to_le32_compile_time (GRUB_LINUX_I386_MAGIC_SIGNATURE)
&& grub_le_to_cpu16 (lh.version) >= 0x0200)
{
grub_linux_is_bzimage = (lh.loadflags & GRUB_LINUX_FLAG_BIG_KERNEL);
lh.type_of_loader = GRUB_LINUX_BOOT_LOADER_TYPE;
if (grub_le_to_cpu16 (lh.version) >= 0x0206)
maximal_cmdline_size = grub_le_to_cpu32 (lh.cmdline_size) + 1;
grub_linux_real_target = grub_find_real_target ();
if (grub_linux_real_target == (grub_addr_t)-1)
{
grub_error (GRUB_ERR_OUT_OF_RANGE,
"no appropriate low memory found");
goto fail;
}
if (grub_le_to_cpu16 (lh.version) >= 0x0201)
{
lh.heap_end_ptr = grub_cpu_to_le16_compile_time (GRUB_LINUX_HEAP_END_OFFSET);
lh.loadflags |= GRUB_LINUX_FLAG_CAN_USE_HEAP;
}
if (grub_le_to_cpu16 (lh.version) >= 0x0202)
lh.cmd_line_ptr = grub_linux_real_target + GRUB_LINUX_CL_OFFSET;
else
{
lh.cl_magic = grub_cpu_to_le16_compile_time (GRUB_LINUX_CL_MAGIC);
lh.cl_offset = grub_cpu_to_le16_compile_time (GRUB_LINUX_CL_OFFSET);
lh.setup_move_size = grub_cpu_to_le16_compile_time (GRUB_LINUX_CL_OFFSET
+ maximal_cmdline_size);
}
}
else
{
/* Your kernel is quite old... */
lh.cl_magic = grub_cpu_to_le16_compile_time (GRUB_LINUX_CL_MAGIC);
lh.cl_offset = grub_cpu_to_le16_compile_time (GRUB_LINUX_CL_OFFSET);
setup_sects = GRUB_LINUX_DEFAULT_SETUP_SECTS;
grub_linux_real_target = GRUB_LINUX_OLD_REAL_MODE_ADDR;
}
/* If SETUP_SECTS is not set, set it to the default (4). */
if (! setup_sects)
setup_sects = GRUB_LINUX_DEFAULT_SETUP_SECTS;
real_size = setup_sects << GRUB_DISK_SECTOR_BITS;
grub_linux16_prot_size = grub_file_size (file)
- real_size - GRUB_DISK_SECTOR_SIZE;
if (! grub_linux_is_bzimage
&& GRUB_LINUX_ZIMAGE_ADDR + grub_linux16_prot_size
> grub_linux_real_target)
{
grub_error (GRUB_ERR_BAD_OS, "too big zImage (0x%x > 0x%x), use bzImage instead",
(char *) GRUB_LINUX_ZIMAGE_ADDR + grub_linux16_prot_size,
(grub_size_t) grub_linux_real_target);
goto fail;
}
grub_dprintf ("linux", "[Linux-%s, setup=0x%x, size=0x%x]\n",
grub_linux_is_bzimage ? "bzImage" : "zImage",
(unsigned) real_size,
(unsigned) grub_linux16_prot_size);
for (i = 1; i < argc; i++)
if (grub_memcmp (argv[i], "vga=", 4) == 0)
{
/* Video mode selection support. */
grub_uint16_t vid_mode;
char *val = argv[i] + 4;
if (grub_strcmp (val, "normal") == 0)
vid_mode = GRUB_LINUX_VID_MODE_NORMAL;
else if (grub_strcmp (val, "ext") == 0)
vid_mode = GRUB_LINUX_VID_MODE_EXTENDED;
else if (grub_strcmp (val, "ask") == 0)
vid_mode = GRUB_LINUX_VID_MODE_ASK;
else
vid_mode = (grub_uint16_t) grub_strtoul (val, 0, 0);
if (grub_errno)
goto fail;
lh.vid_mode = grub_cpu_to_le16 (vid_mode);
}
else if (grub_memcmp (argv[i], "mem=", 4) == 0)
{
const char *val = argv[i] + 4;
linux_mem_size = grub_strtoul (val, &val, 0);
if (grub_errno)
{
grub_errno = GRUB_ERR_NONE;
linux_mem_size = 0;
}
else
{
int shift = 0;
switch (grub_tolower (val[0]))
{
case 'g':
shift += 10;
/* Fallthrough. */
case 'm':
shift += 10;
/* Fallthrough. */
case 'k':
shift += 10;
/* Fallthrough. */
default:
break;
}
/* Check an overflow. */
if (linux_mem_size > (~0UL >> shift))
linux_mem_size = 0;
else
linux_mem_size <<= shift;
}
}
relocator = grub_relocator_new ();
if (!relocator)
goto fail;
{
grub_relocator_chunk_t ch;
err = grub_relocator_alloc_chunk_addr (relocator, &ch,
grub_linux_real_target,
GRUB_LINUX_CL_OFFSET
+ maximal_cmdline_size);
if (err)
return err;
grub_linux_real_chunk = get_virtual_current_address (ch);
}
/* Put the real mode code at the temporary address. */
grub_memmove (grub_linux_real_chunk, &lh, sizeof (lh));
len = real_size + GRUB_DISK_SECTOR_SIZE - sizeof (lh);
if (grub_file_read (file, grub_linux_real_chunk + sizeof (lh), len) != len)
{
if (!grub_errno)
grub_error (GRUB_ERR_BAD_OS, N_("premature end of file %s"),
argv[0]);
goto fail;
}
if (lh.header != grub_cpu_to_le32_compile_time (GRUB_LINUX_I386_MAGIC_SIGNATURE)
|| grub_le_to_cpu16 (lh.version) < 0x0200)
/* Clear the heap space. */
grub_memset (grub_linux_real_chunk
+ ((setup_sects + 1) << GRUB_DISK_SECTOR_BITS),
0,
((GRUB_LINUX_MAX_SETUP_SECTS - setup_sects - 1)
<< GRUB_DISK_SECTOR_BITS));
/* Create kernel command line. */
grub_memcpy ((char *)grub_linux_real_chunk + GRUB_LINUX_CL_OFFSET,
LINUX_IMAGE, sizeof (LINUX_IMAGE));
err = grub_create_loader_cmdline (argc, argv,
(char *)grub_linux_real_chunk
+ GRUB_LINUX_CL_OFFSET + sizeof (LINUX_IMAGE) - 1,
maximal_cmdline_size
- (sizeof (LINUX_IMAGE) - 1),
GRUB_VERIFY_KERNEL_CMDLINE);
if (err)
goto fail;
if (grub_linux_is_bzimage)
grub_linux_prot_target = GRUB_LINUX_BZIMAGE_ADDR;
else
grub_linux_prot_target = GRUB_LINUX_ZIMAGE_ADDR;
{
grub_relocator_chunk_t ch;
err = grub_relocator_alloc_chunk_addr (relocator, &ch,
grub_linux_prot_target,
grub_linux16_prot_size);
if (err)
return err;
grub_linux_prot_chunk = get_virtual_current_address (ch);
}
len = grub_linux16_prot_size;
if (grub_file_read (file, grub_linux_prot_chunk, len) != len && !grub_errno)
grub_error (GRUB_ERR_BAD_OS, N_("premature end of file %s"),
argv[0]);
if (grub_errno == GRUB_ERR_NONE)
{
grub_loader_set (grub_linux16_boot, grub_linux_unload, 0);
loaded = 1;
}
fail:
if (file)
grub_file_close (file);
if (grub_errno != GRUB_ERR_NONE)
{
grub_dl_unref (my_mod);
loaded = 0;
grub_relocator_unload (relocator);
}
return grub_errno;
}
static grub_err_t
grub_cmd_initrd (grub_command_t cmd __attribute__ ((unused)),
int argc, char *argv[])
{
grub_size_t size = 0;
grub_addr_t addr_max, addr_min;
struct linux_i386_kernel_header *lh;
grub_uint8_t *initrd_chunk;
grub_addr_t initrd_addr;
grub_err_t err;
struct grub_linux_initrd_context initrd_ctx = { 0, 0, 0 };
if (argc == 0)
{
grub_error (GRUB_ERR_BAD_ARGUMENT, N_("filename expected"));
goto fail;
}
if (!loaded)
{
grub_error (GRUB_ERR_BAD_ARGUMENT, N_("you need to load the kernel first"));
goto fail;
}
lh = (struct linux_i386_kernel_header *) grub_linux_real_chunk;
if (!(lh->header == grub_cpu_to_le32_compile_time (GRUB_LINUX_I386_MAGIC_SIGNATURE)
&& grub_le_to_cpu16 (lh->version) >= 0x0200))
{
grub_error (GRUB_ERR_BAD_OS, "the kernel is too old for initrd");
goto fail;
}
/* Get the highest address available for the initrd. */
if (grub_le_to_cpu16 (lh->version) >= 0x0203)
{
addr_max = grub_cpu_to_le32 (lh->initrd_addr_max);
/* XXX in reality, Linux specifies a bogus value, so
it is necessary to make sure that ADDR_MAX does not exceed
0x3fffffff. */
if (addr_max > GRUB_LINUX_INITRD_MAX_ADDRESS)
addr_max = GRUB_LINUX_INITRD_MAX_ADDRESS;
}
else
addr_max = GRUB_LINUX_INITRD_MAX_ADDRESS;
if (linux_mem_size != 0 && linux_mem_size < addr_max)
addr_max = linux_mem_size;
/* Linux 2.3.xx has a bug in the memory range check, so avoid
the last page.
Linux 2.2.xx has a bug in the memory range check, which is
worse than that of Linux 2.3.xx, so avoid the last 64kb. */
addr_max -= 0x10000;
addr_min = GRUB_LINUX_BZIMAGE_ADDR + grub_linux16_prot_size;
if (grub_initrd_init (argc, argv, &initrd_ctx))
goto fail;
size = grub_get_initrd_size (&initrd_ctx);
{
grub_relocator_chunk_t ch;
err = grub_relocator_alloc_chunk_align (relocator, &ch,
addr_min, addr_max - size,
size, 0x1000,
GRUB_RELOCATOR_PREFERENCE_HIGH, 0);
if (err)
return err;
initrd_chunk = get_virtual_current_address (ch);
initrd_addr = get_physical_target_address (ch);
}
if (grub_initrd_load (&initrd_ctx, argv, initrd_chunk))
goto fail;
lh->ramdisk_image = initrd_addr;
lh->ramdisk_size = size;
fail:
grub_initrd_close (&initrd_ctx);
return grub_errno;
}
static grub_command_t cmd_linux, cmd_initrd;
GRUB_MOD_INIT(linux16)
{
cmd_linux =
grub_register_command ("linux16", grub_cmd_linux,
0, N_("Load Linux."));
cmd_initrd =
grub_register_command ("initrd16", grub_cmd_initrd,
0, N_("Load initrd."));
my_mod = mod;
}
GRUB_MOD_FINI(linux16)
{
grub_unregister_command (cmd_linux);
grub_unregister_command (cmd_initrd);
}
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