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[FREELDR] Adapt bootsectors and multiboot code for future base address change (#7785)

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See also PRs #8439 and #7530.
CORE-19882
This commit is contained in:
Daniel Victor
2025-11-08 16:40:01 -03:00
committed by GitHub
parent 0362651eb8
commit 9decadee83
9 changed files with 70 additions and 41 deletions
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2
boot/freeldr/bootsect/btrfs.S
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@@ -386,7 +386,7 @@ FreeLdrFound:
//mov dh, 0 // Load boot partition into DH (not needed, FreeLbr detects it itself) //mov dh, 0 // Load boot partition into DH (not needed, FreeLbr detects it itself)
/* Transfer execution to the bootloader */ /* Transfer execution to the bootloader */
ljmp16 0, FREELDR_BASE ljmp16 FREELDR_BASE / 16, 0
// Insert chunk into chunk map (located at DS:[CHUNK_MAP_OFFSET]) // Insert chunk into chunk map (located at DS:[CHUNK_MAP_OFFSET])

33
boot/freeldr/bootsect/fat.S
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@@ -48,10 +48,10 @@ DataAreaStartLow = 4
BiosCHSDriveSizeHigh = 6 BiosCHSDriveSizeHigh = 6
BiosCHSDriveSizeLow = 8 BiosCHSDriveSizeLow = 8
BiosCHSDriveSize = 8 BiosCHSDriveSize = 8
ReadSectorsOffset = 10 ReadSectorsOffset = 12
ReadClusterOffset = 12 ReadClusterOffset = 16
PutCharsOffset = 14 PutCharsOffset = 20
BootSectorStackTop = HEX(7c00) - 16 BootSectorStackTop = HEX(7c00) - 22
// org 7c00h // org 7c00h
@@ -218,9 +218,14 @@ FoundFreeLoader:
// Save the addresses of needed functions so // Save the addresses of needed functions so
// the helper code will know where to call them. // the helper code will know where to call them.
mov word ptr [bp-ReadSectorsOffset], offset ReadSectors // Save the address of ReadSectors xor bx, bx
mov word ptr [bp-ReadClusterOffset], offset ReadCluster // Save the address of ReadCluster mov word ptr [bp-(ReadSectorsOffset-2)], bx // Save the segment of ReadSectors
mov word ptr [bp-PutCharsOffset], offset PutChars // Save the address of PutChars mov word ptr [bp-(ReadClusterOffset-2)], bx // Save the segment of ReadCluster
mov word ptr [bp-(PutCharsOffset-2)], bx // Save the segment of PutChars
mov word ptr [bp-ReadSectorsOffset], offset ReadSectors // Save the address of ReadSectors
mov word ptr [bp-ReadClusterOffset], offset ReadCluster // Save the address of ReadCluster
mov word ptr [bp-PutCharsOffset], offset PutChars // Save the address of PutChars
mov byte ptr [PatchedRet], HEX(CB) // Patch 'ret' with 'retf'
// Now AX has start cluster of FreeLoader and we // Now AX has start cluster of FreeLoader and we
// have loaded the helper code in the first 512 bytes // have loaded the helper code in the first 512 bytes
@@ -228,7 +233,7 @@ FoundFreeLoader:
// to the helper code. Skip the first three bytes // to the helper code. Skip the first three bytes
// because they contain a jump instruction to skip // because they contain a jump instruction to skip
// over the helper code in the FreeLoader image. // over the helper code in the FreeLoader image.
ljmp16 0, FREELDR_BASE + 3 ljmp16 FREELDR_BASE / 16, 3
@@ -249,13 +254,11 @@ Reboot:
PutChars: PutChars:
lodsb lodsb
or al,al or al,al
jz short Done jz PatchedRet
mov ah, HEX(0e) mov ah, HEX(0e)
mov bx, 7 mov bx, 7
int HEX(10) int HEX(10)
jmp short PutChars jmp short PutChars
Done:
ret
// Displays a bad boot message // Displays a bad boot message
// And reboots // And reboots
@@ -265,7 +268,6 @@ BadBoot:
jmp short Reboot jmp short Reboot
// Reads cluster number in AX into [ES:0000] // Reads cluster number in AX into [ES:0000]
ReadCluster: ReadCluster:
// StartSector = ((Cluster - 2) * SectorsPerCluster) + ReservedSectors + HiddenSectors; // StartSector = ((Cluster - 2) * SectorsPerCluster) + ReservedSectors + HiddenSectors;
@@ -354,7 +356,7 @@ ReadSectorsLBALoop:
loop ReadSectorsLBALoop // Read next sector loop ReadSectorsLBALoop // Read next sector
ret jmp PatchedRet
// Reads logical sectors into [ES:BX] // Reads logical sectors into [ES:BX]
@@ -403,11 +405,12 @@ NoCarryCHS:
// Increment read buffer for next sector // Increment read buffer for next sector
loop ReadSectorsCHSLoop // Read next sector loop ReadSectorsCHSLoop // Read next sector
PatchedRet:
ret ret
msgDiskError: msgDiskError:
.ascii "Disk error", CR, LF, NUL // .ascii "Disk error", CR, LF, NUL
.ascii "ERR", CR, LF, NUL
msgFreeLdr: msgFreeLdr:
.ascii "Ldr not found", CR, LF, NUL .ascii "Ldr not found", CR, LF, NUL
// Sorry, need the space... // Sorry, need the space...

2
boot/freeldr/bootsect/fat32.S
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@@ -425,7 +425,7 @@ LoadFileDone:
mov dh, byte ptr ds:[BootPartition] // Load boot partition into DH mov dh, byte ptr ds:[BootPartition] // Load boot partition into DH
/* Transfer execution to the bootloader */ /* Transfer execution to the bootloader */
ljmp16 0, FREELDR_BASE ljmp16 FREELDR_BASE / 16, 0
// Returns the FAT entry for a given cluster number // Returns the FAT entry for a given cluster number
// On entry EAX has cluster number // On entry EAX has cluster number

2
boot/freeldr/bootsect/faty.S
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@@ -400,7 +400,7 @@ main:
/* Now the complete freeldr imag is loaded. /* Now the complete freeldr imag is loaded.
Jump to the realmode entry point. */ Jump to the realmode entry point. */
ljmp16 0, FREELDR_BASE ljmp16 FREELDR_BASE / 16, 0

2
boot/freeldr/bootsect/isoboot.S
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@@ -303,7 +303,7 @@ found_drive:
.jump_to_freeldr: .jump_to_freeldr:
// Transfer execution to the bootloader. // Transfer execution to the bootloader.
ljmp16 0, FREELDR_BASE ljmp16 FREELDR_BASE / 16, 0
/* FUNCTIONS *****************************************************************/ /* FUNCTIONS *****************************************************************/

2
boot/freeldr/bootsect/ntfs.S
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@@ -417,7 +417,7 @@ StartSearch:
mov dl, byte ptr [BootDrive] mov dl, byte ptr [BootDrive]
mov dh, byte ptr [BootPartition] mov dh, byte ptr [BootPartition]
ljmp16 0, FREELDR_BASE ljmp16 FREELDR_BASE / 16, 0
// Error message if Freeldr is compressed, encrypted or sparse // Error message if Freeldr is compressed, encrypted or sparse
CompressedFreeldr: CompressedFreeldr:

30
boot/freeldr/bootsect/pc98/fat12fdd.S
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@@ -25,10 +25,10 @@ DataAreaStartLow = 4
BiosCHSDriveSizeHigh = 6 BiosCHSDriveSizeHigh = 6
BiosCHSDriveSizeLow = 8 BiosCHSDriveSizeLow = 8
BiosCHSDriveSize = 8 BiosCHSDriveSize = 8
ReadSectorsOffset = 10 ReadSectorsOffset = 12
ReadClusterOffset = 12 ReadClusterOffset = 16
PutCharsOffset = 14 PutCharsOffset = 20
BootSectorStackTop = HEX(7C00) - 16 BootSectorStackTop = HEX(7C00) - 22
if 0 if 0
.macro DEBUG_STOP .macro DEBUG_STOP
@@ -242,9 +242,14 @@ FoundFreeLoader:
* Save the addresses of needed functions so * Save the addresses of needed functions so
* the helper code will know where to call them * the helper code will know where to call them
*/ */
mov word ptr [bp - ReadSectorsOffset], offset ReadSectors // Save the address of ReadSectors xor bx, bx
mov word ptr [bp - ReadClusterOffset], offset ReadCluster // Save the address of ReadCluster mov word ptr [bp-(ReadSectorsOffset-2)], bx // Save the segment of ReadSectors
mov word ptr [bp - PutCharsOffset], offset PrintString // Save the address of PrintString mov word ptr [bp-(ReadClusterOffset-2)], bx // Save the segment of ReadCluster
mov word ptr [bp-(PutCharsOffset-2)], bx // Save the segment of PrintString
mov word ptr [bp-ReadSectorsOffset], offset ReadSectors // Save the address of ReadSectors
mov word ptr [bp-ReadClusterOffset], offset ReadCluster // Save the address of ReadCluster
mov word ptr [bp-PutCharsOffset], offset PrintString // Save the address of PrintString
mov byte ptr [PatchedRet], HEX(CB) // Patch 'ret' with 'retf'
/* /*
* Now AX has start cluster of FreeLoader and we * Now AX has start cluster of FreeLoader and we
@@ -254,7 +259,7 @@ FoundFreeLoader:
* because they contain a jump instruction to skip * because they contain a jump instruction to skip
* over the helper code in the FreeLoader image * over the helper code in the FreeLoader image
*/ */
ljmp16 0, FREELDR_BASE + 3 ljmp16 FREELDR_BASE / 16, 3
/* /*
* Reads cluster number in AX into [ES:BX] * Reads cluster number in AX into [ES:BX]
@@ -345,7 +350,7 @@ ReadSectors:
pop bx pop bx
loop .ReadSectorsLoop // Increment read buffer for next sector, read next sector loop .ReadSectorsLoop // Increment read buffer for next sector, read next sector
ret jmp PatchedRet
/* /*
* Prints a character * Prints a character
@@ -380,7 +385,7 @@ PrintString:
lodsb // Get a single char from a ptr lodsb // Get a single char from a ptr
or al, al or al, al
jz short .PrintEnd // Found NULL jz short PatchedRet // Found NULL
cmp al, HEX(0D) cmp al, HEX(0D)
jz short .PrintStringHandleCR // Found CR jz short .PrintStringHandleCR // Found CR
@@ -398,7 +403,7 @@ PrintString:
inc si // Skip the next LF character inc si // Skip the next LF character
jmp short PrintString jmp short PrintString
.PrintEnd: PatchedRet:
ret ret
if 0 if 0
@@ -476,7 +481,8 @@ msgDiskError:
msgNotFoundError: msgNotFoundError:
.ascii "NFE", CR, LF, NUL .ascii "NFE", CR, LF, NUL
msgAnyKey: msgAnyKey:
.ascii "Press any key", NUL // .ascii "Press any key", NUL
.ascii "Press key", NULL
filename: filename:
.ascii "FREELDR SYS" .ascii "FREELDR SYS"

4
boot/freeldr/freeldr/arch/i386/multiboot.S
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@@ -3,7 +3,7 @@
* LICENSE: GPL-2.0-or-later (https://spdx.org/licenses/GPL-2.0-or-later) * LICENSE: GPL-2.0-or-later (https://spdx.org/licenses/GPL-2.0-or-later)
* PURPOSE: Support for the Multiboot v1 specification. * PURPOSE: Support for the Multiboot v1 specification.
* COPYRIGHT: Copyright 1998-2002 Brian Palmer <brianp@sginet.com> * COPYRIGHT: Copyright 1998-2002 Brian Palmer <brianp@sginet.com>
* Copyright 2024 Daniel Victor <ilauncherdeveloper@gmail.com> * Copyright 2024-2025 Daniel Victor <ilauncherdeveloper@gmail.com>
*/ */
#include <asm.inc> #include <asm.inc>
@@ -190,7 +190,7 @@ mb4:
mov cr0, rax mov cr0, rax
/* Jump to real entry point */ /* Jump to real entry point */
ljmp16 0, FREELDR_BASE ljmp16 FREELDR_BASE / 16, 0
/* Force 8-byte alignment */ /* Force 8-byte alignment */

34
boot/freeldr/freeldr/arch/realmode/fathelp.inc
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@@ -14,9 +14,13 @@
#define BiosCHSDriveSizeHigh 6 #define BiosCHSDriveSizeHigh 6
#define BiosCHSDriveSizeLow 8 #define BiosCHSDriveSizeLow 8
#define BiosCHSDriveSize 8 #define BiosCHSDriveSize 8
#define ReadSectorsOffset 10 #define ReadSectorsOffset 12
#define ReadClusterOffset 12 #define ReadClusterOffset 16
#define PutCharsOffset 14 #define PutCharsOffset 20
#define ReadSectors dword ptr ss:[bp-ReadSectorsOffset]
#define ReadCluster dword ptr ss:[bp-ReadClusterOffset]
#define PutChars dword ptr ss:[bp-PutCharsOffset]
#define OEMName 3 #define OEMName 3
#define BytesPerSector 11 #define BytesPerSector 11
@@ -65,8 +69,8 @@ FatHelperEntryPoint:
push ax push ax
/* Display "Loading FreeLoader..." message */ /* Display "Loading FreeLoader..." message */
mov si, offset msgLoading mov si, offset msgLoading - FREELDR_BASE
call word ptr [bp-PutCharsOffset] call CS_PutChars
call ReadFatIntoMemory call ReadFatIntoMemory
@@ -92,7 +96,7 @@ LoadFile3:
push ax push ax
xor bx,bx // Load ROSLDR starting at 0000:8000h xor bx,bx // Load ROSLDR starting at 0000:8000h
push es push es
call word ptr [bp-ReadClusterOffset] call ReadCluster
pop es pop es
xor bx,bx xor bx,bx
@@ -133,7 +137,7 @@ ReadFatIntoMemory:
mov bx, HEX(7000) mov bx, HEX(7000)
mov es,bx mov es,bx
xor bx,bx xor bx,bx
call word ptr [bp-ReadSectorsOffset] call ReadSectors
ret ret
@@ -216,6 +220,22 @@ IsFat12_2:
IsFat12_Done: IsFat12_Done:
ret ret
CS_PutChars:
/* Save necessary registers */
push ax
push ds
/* Prepare ds before PutChars call */
mov ax, cs
mov ds, ax
/* Display the message */
call PutChars
/* Restore necessary registers and return */
pop ds
pop ax
ret
msgLoading: msgLoading:
.ascii "Loading FreeLoader...", CR, LF, NUL .ascii "Loading FreeLoader...", CR, LF, NUL