hidemem.c File Reference

#include <string.h>
#include <assert.h>
#include <realmode.h>
#include <biosint.h>
#include <basemem.h>
#include <fakee820.h>
#include <ipxe/init.h>
#include <ipxe/io.h>
#include <ipxe/uheap.h>
#include <ipxe/memmap.h>

Go to the source code of this file.

Data Structures
struct	hidden_region
	A hidden region of iPXE. More...

Macros
#define	FAKE_E820   0
	Set to true if you want to test a fake E820 map. More...
#define	ALIGN_HIDDEN   4096 /* 4kB page alignment should be enough */
	Alignment for hidden memory regions. More...
#define	hidemem_base   __use_data16 ( hidemem_base )
#define	hidemem_umalloc   __use_data16 ( hidemem_umalloc )
#define	hidemem_textdata   __use_data16 ( hidemem_textdata )
#define	int15_vector   __use_text16 ( int15_vector )
#define	int15_intercept_flag   __use_text16 ( int15_intercept_flag )
#define	_text16_memsz   ABS_VALUE ( _text16_memsz )
#define	_data16_memsz   ABS_VALUE ( _data16_memsz )

Functions
	FILE_LICENCE (GPL2_OR_LATER_OR_UBDL)
struct hidden_region	__data16 (hidemem_base)
	Hidden base memory. More...
struct hidden_region	__data16 (hidemem_umalloc)
	Hidden umalloc memory. More...
struct hidden_region	__data16 (hidemem_textdata)
	Hidden text memory. More...
void	int15 ()
	Assembly routine in e820mangler.S. More...
struct segoff	__text16 (int15_vector)
	Vector for storing original INT 15 handler. More...
uint8_t	__text16 (int15_intercept_flag)
	INT 15 interception flag. More...
size_t	ABS_SYMBOL (_text16_memsz)
size_t	ABS_SYMBOL (_data16_memsz)
static void	hide_region (struct hidden_region *region, physaddr_t start, physaddr_t end)
	Hide region of memory from system memory map. More...
void	hide_basemem (void)
	Hide used base memory. More...
void	hide_textdata (void)
	Hide .text and .data. More...
static void	int15_sync (void)
	Synchronise in-use regions with the externally visible system memory map. More...
void	int15_intercept (int intercept)
	Set INT 15 interception flag. More...
static void	hide_etherboot (void)
	Hide Etherboot. More...
static void	unhide_etherboot (int flags __unused)
	Unhide Etherboot. More...
struct startup_fn hide_etherboot_startup_fn	__startup_fn (STARTUP_EARLY)
	Hide Etherboot startup function. More...
	PROVIDE_MEMMAP (int15, memmap_sync, int15_sync)

Variables
struct hidden_region	__attribute__
char	_textdata []
char	_etextdata []

Macro Definition Documentation

FAKE_E820

#define FAKE_E820   0

Set to true if you want to test a fake E820 map.

Definition at line 37 of file hidemem.c.

ALIGN_HIDDEN

#define ALIGN_HIDDEN   4096 /* 4kB page alignment should be enough */

Alignment for hidden memory regions.

Definition at line 40 of file hidemem.c.

hidemem_base

#define hidemem_base   __use_data16 ( hidemem_base )

Definition at line 60 of file hidemem.c.

hidemem_umalloc

#define hidemem_umalloc   __use_data16 ( hidemem_umalloc )

Definition at line 64 of file hidemem.c.

hidemem_textdata

#define hidemem_textdata   __use_data16 ( hidemem_textdata )

Definition at line 68 of file hidemem.c.

int15_vector

#define int15_vector   __use_text16 ( int15_vector )

Definition at line 75 of file hidemem.c.

int15_intercept_flag

#define int15_intercept_flag   __use_text16 ( int15_intercept_flag )

Definition at line 79 of file hidemem.c.

_text16_memsz

#define _text16_memsz   ABS_VALUE ( _text16_memsz )

Definition at line 85 of file hidemem.c.

_data16_memsz

#define _data16_memsz   ABS_VALUE ( _data16_memsz )

Definition at line 87 of file hidemem.c.

Function Documentation

FILE_LICENCE()

FILE_LICENCE

(

GPL2_OR_LATER_OR_UBDL

)

__data16() [1/3]

struct hidden_region __data16

(

hidemem_base

)

Hidden base memory.

__data16() [2/3]

struct hidden_region __data16

(

hidemem_umalloc

)

Hidden umalloc memory.

__data16() [3/3]

struct hidden_region __data16

(

hidemem_textdata

)

Hidden text memory.

int15()

void int15

(

)

Assembly routine in e820mangler.S.

Referenced by hide_etherboot(), and unhide_etherboot().

__text16() [1/2]

struct segoff __text16

(

int15_vector

)

Vector for storing original INT 15 handler.

__text16() [2/2]

uint8_t __text16

(

int15_intercept_flag

)

INT 15 interception flag.

ABS_SYMBOL() [1/2]

size_t ABS_SYMBOL

(

_text16_memsz

)

ABS_SYMBOL() [2/2]

size_t ABS_SYMBOL

(

_data16_memsz

)

hide_region()

static void hide_region ( struct hidden_region *  region, physaddr_t  start, physaddr_t  end  )

static

Hide region of memory from system memory map.

Parameters

region	Hidden memory region
start	Start of region
end	End of region

Definition at line 96 of file hidemem.c.

                                                             {

        /* Some operating systems get a nasty shock if a region of the
         * E820 map seems to start on a non-page boundary.  Make life
         * safer by rounding out our edited region.
         */
        region->start = ( start & ~( ALIGN_HIDDEN - 1 ) );
        region->end = ( ( end + ALIGN_HIDDEN - 1 ) & ~( ALIGN_HIDDEN - 1 ) );

        DBG ( "Hiding region [%llx,%llx)\n", region->start, region->end );
}

References ALIGN_HIDDEN, DBG, end, hidden_region::end, start, and hidden_region::start.

Referenced by hide_textdata(), and int15_sync().

hide_basemem()

void hide_basemem

(

void

)

Hide used base memory.

Definition at line 113 of file hidemem.c.

                           {
        /* Hide from the top of free base memory to 640kB.  Don't use
         * hide_region(), because we don't want this rounded to the
         * nearest page boundary.
         */
        hidemem_base.start = ( get_fbms() * 1024 );
}

References get_fbms(), and hidemem_base.

Referenced by hide_etherboot(), and set_fbms().

hide_textdata()

void hide_textdata

(

void

)

Hide .text and .data.

Definition at line 125 of file hidemem.c.

                            {
        hide_region ( &hidemem_textdata, virt_to_phys ( _textdata ),
                      virt_to_phys ( _etextdata ) );
}

References _etextdata, _textdata, hide_region(), and hidemem_textdata.

Referenced by hide_etherboot().

int15_sync()

static void int15_sync ( void  )

static

Synchronise in-use regions with the externally visible system memory map.

Definition at line 134 of file hidemem.c.

                                {
        physaddr_t start;
        physaddr_t end;

        /* Besides our fixed base memory and textdata regions, we
         * support hiding only a single in-use memory region (the
         * umalloc region), which must be placed before the hidden
         * textdata region (even if zero-length).
         */
        start = uheap_start;
        end = uheap_end;
        if ( start == end )
                start = end = virt_to_phys ( _textdata );
        hide_region ( &hidemem_umalloc, start, end );
}

References _textdata, end, hide_region(), hidemem_umalloc, start, uheap_end, and uheap_start.

Referenced by hide_etherboot().

int15_intercept()

void int15_intercept

(

int

intercept

)

Set INT 15 interception flag.

Parameters

intercept

Intercept INT 15 calls to modify memory map

Definition at line 155 of file hidemem.c.

                                       {

        /* Set flag for INT 15 handler */
        int15_intercept_flag = intercept;
}

References int15_intercept_flag.

Referenced by int15_describe().

hide_etherboot()

static void hide_etherboot ( void  )

static

Hide Etherboot.

Installs an INT 15 handler to edit Etherboot out of the memory map returned by the BIOS.

Definition at line 167 of file hidemem.c.

                                    {
        unsigned int rm_ds_top;
        unsigned int rm_cs_top;
        unsigned int fbms;

        /* Dump memory map before mangling */
        DBG ( "Hiding iPXE from system memory map\n" );
        memmap_dump_all ( 1 );

        /* Hook in fake E820 map, if we're testing one */
        if ( FAKE_E820 ) {
                DBG ( "Hooking in fake E820 map\n" );
                fake_e820();
                memmap_dump_all ( 1 );
        }

        /* Initialise the hidden regions */
        hide_basemem();
        hide_textdata();
        int15_sync();

        /* Some really moronic BIOSes bring up the PXE stack via the
         * UNDI loader entry point and then don't bother to unload it
         * before overwriting the code and data segments.  If this
         * happens, we really don't want to leave INT 15 hooked,
         * because that will cause any loaded OS to die horribly as
         * soon as it attempts to fetch the system memory map.
         *
         * We use a heuristic to guess whether or not we are being
         * loaded sensibly.
         */
        rm_cs_top = ( ( ( rm_cs << 4 ) + _text16_memsz + 1024 - 1 ) >> 10 );
        rm_ds_top = ( ( ( rm_ds << 4 ) + _data16_memsz + 1024 - 1 ) >> 10 );
        fbms = get_fbms();
        if ( ( rm_cs_top < fbms ) && ( rm_ds_top < fbms ) ) {
                DBG ( "Detected potentially unsafe UNDI load at CS=%04x "
                      "DS=%04x FBMS=%dkB\n", rm_cs, rm_ds, fbms );
                DBG ( "Disabling INT 15 memory hiding\n" );
                return;
        }

        /* Hook INT 15 */
        hook_bios_interrupt ( 0x15, ( intptr_t ) int15, &int15_vector );

        /* Dump memory map after mangling */
        DBG ( "Hidden iPXE from system memory map\n" );
        memmap_dump_all ( 1 );
}

References _data16_memsz, _text16_memsz, DBG, FAKE_E820, fake_e820(), get_fbms(), hide_basemem(), hide_textdata(), hook_bios_interrupt(), int15(), int15_sync(), int15_vector, memmap_dump_all(), rm_cs, and rm_ds.

unhide_etherboot()

static void unhide_etherboot ( int flags  __unused )

static

Unhide Etherboot.

Uninstalls the INT 15 handler installed by hide_etherboot(), if possible.

Definition at line 222 of file hidemem.c.

                                                    {
        int rc;

        /* If we have more than one hooked interrupt at this point, it
         * means that some other vector is still hooked, in which case
         * we can't safely unhook INT 15 because we need to keep our
         * memory protected.  (We expect there to be at least one
         * hooked interrupt, because INT 15 itself is still hooked).
         */
        if ( hooked_bios_interrupts > 1 ) {
                DBG ( "Cannot unhide: %d interrupt vectors still hooked\n",
                      hooked_bios_interrupts );
                return;
        }

        /* Try to unhook INT 15 */
        if ( ( rc = unhook_bios_interrupt ( 0x15, ( intptr_t ) int15,
                                            &int15_vector ) ) != 0 ) {
                DBG ( "Cannot unhook INT15: %s\n", strerror ( rc ) );
                /* Leave it hooked; there's nothing else we can do,
                 * and it should be intrinsically safe (though
                 * wasteful of RAM).
                 */
        }

        /* Unhook fake E820 map, if used */
        if ( FAKE_E820 )
                unfake_e820();

        /* Dump memory map after unhiding */
        DBG ( "Unhidden iPXE from system memory map\n" );
        memmap_dump_all ( 1 );
}

References DBG, FAKE_E820, hooked_bios_interrupts, int15(), int15_vector, memmap_dump_all(), rc, strerror(), unfake_e820(), and unhook_bios_interrupt().

__startup_fn()

struct startup_fn hide_etherboot_startup_fn __startup_fn

(

STARTUP_EARLY

)

Hide Etherboot startup function.

PROVIDE_MEMMAP()

PROVIDE_MEMMAP	(	int15	,
		memmap_sync	,
		int15_sync
	)

Variable Documentation

__attribute__

struct hidden_region __attribute__

_textdata

char _textdata[]

Referenced by hide_textdata(), and int15_sync().

_etextdata

char _etextdata[]

Referenced by hide_textdata().