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cap bss, clean up some padding issues and clean up sign section

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This commit is contained in:
Elaina Claus
2025-09-13 12:50:42 -04:00
parent a50af35abd
commit 721ff2e62d
2 changed files with 25 additions and 15 deletions
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2
include/config.inc
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@@ -15,7 +15,7 @@
%ifndef __INC_STEVIA_CONFIG %ifndef __INC_STEVIA_CONFIG
%define SECTOR_SIZE 512 %define SECTOR_SIZE 0x200
%define STAGE2_SECTOR_COUNT 0x20 %define STAGE2_SECTOR_COUNT 0x20
; 16 KiB ; 16 KiB
%define MAX_STAGE2_BYTES (SECTOR_SIZE * STAGE2_SECTOR_COUNT) %define MAX_STAGE2_BYTES (SECTOR_SIZE * STAGE2_SECTOR_COUNT)

38
src/stage2/stage2.nasm
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@@ -36,7 +36,7 @@
section .text section .text
begin_text: begin_text:
; dl = byte boot_drive ; dl = byte boot_drive
ALIGN 4, db 0x90 ALIGN 16, db 0x90
init: init:
cli ; We do not want to be interrupted cli ; We do not want to be interrupted
mov [boot_drive], dl ; copy boot_drive to globals mov [boot_drive], dl ; copy boot_drive to globals
@@ -375,7 +375,8 @@ EnterUnrealMode:
end_text: end_text:
section .data follows=.text section .data follows=.text
align 512 align 16, db 0
begin_data: begin_data:
; ############# ; #############
; ;
@@ -410,19 +411,15 @@ define_info MaybeFound_Boot, "Maybe found a file...checking..."
define_cstr BootTarget, "BOOT BIN" define_cstr BootTarget, "BOOT BIN"
align 16, db 0
BootTarget:
db 'BOOT BIN'
;
; pre-bss init globals
;
; set to boot_drive passed from BIOS almost first thing in init ; set to boot_drive passed from BIOS almost first thing in init
align 4, db 0 align 4, db 0
boot_drive: boot_drive:
db 0x00 db 0x00
align 16, db 0
BootTarget:
db 'BOOT BIN'
align 16, db 0 align 16, db 0
IntToHex_table: IntToHex_table:
db '0123456789ABCDEF' db '0123456789ABCDEF'
@@ -504,15 +501,20 @@ BUILD_GIT_HASH:
db __GIT_HASH__, 00h db __GIT_HASH__, 00h
end_data: end_data:
%assign bytes_remaining ((MAX_STAGE2_BYTES - 512) - (($ - $$) + (end_text - begin_text))) %define SIG_BYTES 0x4
%warning STAGE2 has bytes_remaining bytes remaining for code/data (MAX: MAX_STAGE2_BYTES)
; Optional: fail fast if we overflowed
%if ((MAX_STAGE2_BYTES - 512) - (($ - $$) + (end_text - begin_text))) < 0
%error "Stage2 overflow: code+data exceed MAX_STAGE2_BYTES - SIG_BYTES"
%endif
; section start location needs to be a 'critical expression' ; section start location needs to be a 'critical expression'
; i.e resolvable at build time, we are setting 0x0500 as the offset since ; i.e resolvable at build time, we are setting 0x0500 as the offset since
section .sign start=((MAX_STAGE2_BYTES - 512) + 0x0500) section .sign start=((MAX_STAGE2_BYTES - 512) + 0x0500)
times ((512 - 4) - ($ -$$) ) db 0x90 ; nop times ((512 - 4) - ($ -$$) ) db 0x90 ; nop
STAGE2_SIG: dd 0xDEADBEEF ; Signature to mark the end of the stage2 STAGE2_SIG: dd 0xDEADBEEF ; Signature to mark the end of the stage2
; !!! END Stage2 .text/.data !!!
align 16, resb 1
section .bss follows=.sign section .bss follows=.sign
begin_bss: begin_bss:
@@ -595,4 +597,12 @@ align 16, resb 1
stack_bottom: stack_bottom:
resb 1024 resb 1024
stack_top: stack_top:
end_bss: end_bss:
; Pad to the cap (emits nothing in the file; only increases .bss virtual size).
; If BSS_SIZE > BSS_MAX_BYTES, this becomes negative and NASM errors out.
%define BSS_MAX_BYTES 0x3000
resb (BSS_MAX_BYTES - (end_bss - begin_bss))
; Optional: keep a label for later math:
bss_cap_end: