From e7897de9471e1d94ad79e2b03fcb8afc685760f1 Mon Sep 17 00:00:00 2001
From: Regia König
Date: Thu, 25 Aug 2022 15:08:09 +0200
Subject: Setup.S documentation and new command in create_debug.sh

---
 .../24_08_22_memtest_build_process                 | 39 ++++++++++++++++++++++
 1 file changed, 39 insertions(+)

(limited to 'documentation')

diff --git a/documentation/memtest86_build_process/24_08_22_memtest_build_process b/documentation/memtest86_build_process/24_08_22_memtest_build_process
index 9847a5b..fc8f33c 100644
--- a/documentation/memtest86_build_process/24_08_22_memtest_build_process
+++ b/documentation/memtest86_build_process/24_08_22_memtest_build_process
@@ -203,3 +203,42 @@ coff_header:
 #
 #	setup.S
 #
+Collects memory map information from the BIOS, disables APM, enables A20 and performs
+the switch from real mode to protected mode before jumping to the main program entry
+point.
+
+The memory map information is stored in the 4KB block of memory immediately following
+the setup code. The layout of the information matches the Linux boot_params struct.
+A pointer to this block is passed to the main program, for compatibility with the Linux
+32-bit boot protocol.
+
+. # define BOOT_PARAMS_START	(SETUP_SECS * 512)	|| SETUP_SEC is defined in boot.h
+. # define BOOT_PARAMS_END	(BOOT_PARAMS_START + 4096)  <--- here are the 4K
+
+	.section ".setup",  "ax", @progbits
+	.code16
+
+Emulate the Linux boot header, to allow loading by other boot loaders. Indicate that the
+main program code should be loaded in high memory.
+
+	.globl setup
+setup: jmp do_setup
+
+101: do_setup:
+	Reload the segment registers, except for the stack
+	Get the memory map and disable APM
+	Disable interrupts
+	Enable A20
+	...
+
+179: flush:
+	Reload the segment registers and jump to the main test program <------------!!!!
+
+	...
+188: jump:
+	data32 ljmp $KERNEL_CS, $0
+
+
+
+389: Pad to the declared size
+	.org	(ESTUP_SECS*512)
-- 
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