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[i386] Free allocated base memory on exit, if possible

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Code paths that automatically allocate memory from the FBMS at 40:13
should also free it, if possible.

Freeing this memory will not be possible if either

  1. The FBMS has been modified since our allocation, or

  2. We have not been able to unhook one or more BIOS interrupt vectors.
This commit is contained in:
Michael Brown 2008-11-18 19:43:13 +00:00
parent 85f82f09e9
commit 0a8a17e669
9 changed files with 133 additions and 29 deletions
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15
src/arch/i386/include/biosint.h
View File

@ -6,9 +6,22 @@
*
*/
#include <realmode.h>
struct segoff;
extern int hooked_bios_interrupts;
/**
* Hooked interrupt count
*
* At exit, after unhooking all possible interrupts, this counter
* should be examined. If it is non-zero, it means that we failed to
* unhook at least one interrupt vector, and so must not free up the
* memory we are using. (Note that this also implies that we should
* re-hook INT 15 in order to hide ourselves from the memory map).
*/
extern uint16_t __text16 ( hooked_bios_interrupts );
#define hooked_bios_interrupts __use_text16 ( hooked_bios_interrupts )
extern void hook_bios_interrupt ( unsigned int interrupt, unsigned int handler,
struct segoff *chain_vector );
extern int unhook_bios_interrupt ( unsigned int interrupt,

11
src/arch/i386/interface/pcbios/biosint.c
View File

@ -7,17 +7,6 @@
*
*/
/**
* Hooked interrupt count
*
* At exit, after unhooking all possible interrupts, this counter
* should be examined. If it is non-zero, it means that we failed to
* unhook at least one interrupt vector, and so must not free up the
* memory we are using. (Note that this also implies that we should
* re-hook INT 15 in order to hide ourselves from the memory map).
*/
int hooked_bios_interrupts = 0;
/**
* Hook INT vector
*

6
src/arch/i386/prefix/dskprefix.S
View File

@ -353,6 +353,7 @@ msg1end:
.word 0xAA55
start_runtime:
/* Install gPXE */
call install
/* Set up real-mode stack */
@ -368,7 +369,10 @@ start_runtime:
pushl $main
pushw %cs
call prot_call
popl %eax /* discard */
popl %ecx /* discard */
/* Uninstall gPXE */
call uninstall
/* Boot next device */
int $0x18

6
src/arch/i386/prefix/hdprefix.S
View File

@ -82,6 +82,7 @@ load_failed:
.byte 0x55, 0xaa
start_image:
/* Install gPXE */
call install
/* Set up real-mode stack */
@ -97,7 +98,10 @@ start_image:
pushl $main
pushw %cs
call prot_call
popl %eax /* discard */
popl %ecx /* discard */
/* Uninstall gPXE */
call uninstall
/* Boot next device */
int $0x18

91
src/arch/i386/prefix/libprefix.S
View File

@ -537,17 +537,20 @@ install_block:
.code16
.globl alloc_basemem
alloc_basemem:
/* Preserve registers */
pushw %fs
/* FBMS => %ax as segment address */
movw $0x40, %ax
movw %ax, %fs
pushw $0x40
popw %fs
movw %fs:0x13, %ax
shlw $6, %ax
/* .data16 segment address */
/* Calculate .data16 segment address */
subw $_data16_memsz_pgh, %ax
pushw %ax
/* .text16 segment address */
/* Calculate .text16 segment address */
subw $_text16_memsz_pgh, %ax
pushw %ax
@ -555,12 +558,67 @@ alloc_basemem:
shrw $6, %ax
movw %ax, %fs:0x13
/* Return */
/* Retrieve .text16 and .data16 segment addresses */
popw %ax
popw %bx
/* Restore registers and return */
popw %fs
ret
.size alloc_basemem, . - alloc_basemem
/****************************************************************************
* free_basemem (real-mode near call)
*
* Free space allocated with alloc_basemem.
*
* Parameters:
* %ax : .text16 segment address
* %bx : .data16 segment address
* Returns:
* %ax : 0 if successfully freed
* Corrupts:
* none
****************************************************************************
*/
.section ".text16"
.code16
.globl free_basemem
free_basemem:
/* Preserve registers */
pushw %fs
/* Check FBMS counter */
pushw %ax
shrw $6, %ax
pushw $0x40
popw %fs
cmpw %ax, %fs:0x13
popw %ax
jne 1f
/* Check hooked interrupt count */
cmpw $0, %cs:hooked_bios_interrupts
jne 1f
/* OK to free memory */
addw $_text16_memsz_pgh, %ax
addw $_data16_memsz_pgh, %ax
shrw $6, %ax
movw %ax, %fs:0x13
xorw %ax, %ax
1: /* Restore registers and return */
popw %fs
ret
.size free_basemem, . - free_basemem
.section ".text16.data"
.globl hooked_bios_interrupts
hooked_bios_interrupts:
.word 0
.size hooked_bios_interrupts, . - hooked_bios_interrupts
/****************************************************************************
* install (real-mode near call)
*
@ -709,6 +767,29 @@ prot_call_vector:
.size prot_call_vector, . - prot_call_vector
#endif
/****************************************************************************
* uninstall (real-mode near call)
*
* Uninstall all text and data segments.
*
* Parameters:
* %ax : .text16 segment address
* %bx : .data16 segment address
* Returns:
* none
* Corrupts:
* none
****************************************************************************
*/
.section ".text16"
.code16
.globl uninstall
uninstall:
call free_basemem
ret
.size uninstall, . - uninstall
/* File split information for the compressor */
#if COMPRESS

6
src/arch/i386/prefix/lkrnprefix.S
View File

@ -189,6 +189,7 @@ run_gpxe:
movw %ax, %ss
movw $0x7c00, %sp
/* Install gPXE */
call install
/* Set up real-mode stack */
@ -204,7 +205,10 @@ run_gpxe:
pushl $main
pushw %cs
call prot_call
popl %eax /* discard */
popl %ecx /* discard */
/* Uninstall gPXE */
call uninstall
/* Boot next device */
int $0x18

7
src/arch/i386/prefix/nbiprefix.S
View File

@ -52,7 +52,7 @@ memlen: .long _filesz - 512
*****************************************************************************
*/
entry:
/* Install low and high memory regions */
/* Install gPXE */
call install
/* Jump to .text16 segment */
@ -64,7 +64,10 @@ entry:
pushl $main
pushw %cs
call prot_call
popl %eax /* discard */
popl %ecx /* discard */
/* Uninstall gPXE */
call uninstall
/* Reboot system */
int $0x19

13
src/arch/i386/prefix/pxeprefix.S
View File

@ -318,7 +318,7 @@ print_free_basemem:
*****************************************************************************
*/
finished:
jmp run_etherboot
jmp run_gpxe
/*****************************************************************************
* Subroutine: print segment:offset address
@ -554,11 +554,11 @@ flags: .word UNDI_FL_STARTED
.equ undi_device_size, ( . - undi_device )
/*****************************************************************************
* Run Etherboot main code
* Run gPXE main code
*****************************************************************************
*/
run_etherboot:
/* Install Etherboot */
run_gpxe:
/* Install gPXE */
call install
/* Set up real-mode stack */
@ -585,7 +585,10 @@ run_etherboot:
pushl $main
pushw %cs
call prot_call
popl %eax /* discard */
popl %ecx /* discard */
/* Uninstall gPXE */
call uninstall
/* Boot next device */
int $0x18

7
src/arch/i386/prefix/romprefix.S
View File

@ -591,8 +591,11 @@ exec: /* Set %ds = %cs */
pushl $main
pushw %cs
call prot_call
/* No need to clean up stack; we are about to reload %ss:sp */
popl %ecx /* discard */
/* Uninstall gPXE */
call uninstall
/* Restore BIOS stack */
movw %dx, %ss
movw %bp, %sp