Make more space for the heap when doing so is possible

If we have a modern kernel which is loaded high, we can allow a lot
more space for the real-mode heap.

3 files changed, 63 insertions, 35 deletions

diff --git a/com32/lib/syslinux/load_linux.c b/com32/lib/syslinux/load_linux.c
index b8d5a732..d2ad2644 100644
--- a/com32/lib/syslinux/load_linux.c
+++ b/com32/lib/syslinux/load_linux.c
@@ -81,9 +81,6 @@ struct linux_header {
 #define LOAD_HIGH	0x01
 #define CAN_USE_HEAP	0x80
 
-/* Offset for the command line versus the real mode code */
-#define CMDLINE_OFFSET	0x9000
-
 /* Get the combined size of the initramfs */
 static addr_t initramfs_size(struct initramfs *initramfs)
 {
@@ -147,7 +144,7 @@ int syslinux_boot_linux(void *kernel_buf, size_t kernel_size,
   size_t real_mode_size, prot_mode_size;
   addr_t real_mode_base, prot_mode_base;
   addr_t irf_size;
-  size_t cmdline_size;
+  size_t cmdline_size, cmdline_offset;
   struct syslinux_rm_regs regs;
   struct syslinux_movelist *fraglist = NULL;
   struct syslinux_memmap *mmap = NULL;
@@ -159,8 +156,9 @@ int syslinux_boot_linux(void *kernel_buf, size_t kernel_size,
     goto bail;
 
   /* Copy the header into private storage */
+  /* Use whdr to modify the actual kernel header */
   memcpy(&hdr, kernel_buf, sizeof hdr);
-  whdr = (struct linux_header *)kernel_buf; /* Writable header */
+  whdr = (struct linux_header *)kernel_buf;
 
   if (hdr.boot_flag != BOOT_MAGIC)
     goto bail;
@@ -189,6 +187,11 @@ int syslinux_boot_linux(void *kernel_buf, size_t kernel_size,
     cmdline[cmdline_size-1] = '\0';
   }
 
+  if (hdr.version < 0x0202 || !(hdr.loadflags & 0x01))
+    cmdline_offset = (0x9ff0 - cmdline_size) & ~15;
+  else
+    cmdline_offset = (0xfff0 - cmdline_size) & ~15;
+
   real_mode_size = (hdr.setup_sects+1) << 9;
   real_mode_base = (hdr.loadflags & LOAD_HIGH) ? 0x10000 : 0x90000;
   prot_mode_base = (hdr.loadflags & LOAD_HIGH) ? 0x100000 : 0x10000;
@@ -203,16 +206,16 @@ int syslinux_boot_linux(void *kernel_buf, size_t kernel_size,
   if (hdr.version >= 0x0200) {
     whdr->type_of_loader = 0x30; /* SYSLINUX unknown module */
     if (hdr.version >= 0x0201) {
-      whdr->heap_end_ptr = CMDLINE_OFFSET - 0x0200;
+      whdr->heap_end_ptr = cmdline_offset - 0x0200;
       whdr->loadflags |= CAN_USE_HEAP;
     }
     if (hdr.version >= 0x0202) {
-      whdr->cmd_line_ptr = real_mode_base + CMDLINE_OFFSET;
+      whdr->cmd_line_ptr = real_mode_base+cmdline_offset;
     } else {
       whdr->old_cmd_line_magic  = OLD_CMDLINE_MAGIC;
-      whdr->old_cmd_line_offset = CMDLINE_OFFSET;
+      whdr->old_cmd_line_offset = cmdline_offset;
       /* Be paranoid and round up to a multiple of 16 */
-      whdr->setup_move_size = (CMDLINE_OFFSET+cmdline_size+15) & ~15;
+      whdr->setup_move_size = (cmdline_offset+cmdline_size+15) & ~15;
     }
   }
 
@@ -236,17 +239,17 @@ int syslinux_boot_linux(void *kernel_buf, size_t kernel_size,
   if (syslinux_add_movelist(&fraglist, real_mode_base, (addr_t)kernel_buf,
 			    real_mode_size))
     goto bail;
-  if (syslinux_add_memmap(&amap, real_mode_base, CMDLINE_OFFSET+cmdline_size,
+  if (syslinux_add_memmap(&amap, real_mode_base, cmdline_offset+cmdline_size,
 			  SMT_ALLOC))
     goto bail;
 
   /* Zero region between real mode code and cmdline */
   if (syslinux_add_memmap(&mmap, real_mode_base+real_mode_size,
-			  CMDLINE_OFFSET-real_mode_size, SMT_ZERO))
+			  cmdline_offset-real_mode_size, SMT_ZERO))
     goto bail;
 
   /* Command line */
-  if (syslinux_add_movelist(&fraglist, real_mode_base+CMDLINE_OFFSET,
+  if (syslinux_add_movelist(&fraglist, real_mode_base+cmdline_offset,
 			    (addr_t)cmdline, cmdline_size))
     goto bail;
 
@@ -296,7 +299,7 @@ int syslinux_boot_linux(void *kernel_buf, size_t kernel_size,
   regs.es = regs.ds = regs.ss = regs.fs = regs.gs = real_mode_base >> 4;
   regs.cs = (real_mode_base >> 4)+0x20;
   /* regs.ip = 0; */
-  regs.esp.w[0] = CMDLINE_OFFSET;
+  regs.esp.w[0] = cmdline_offset;
 
   syslinux_shuffle_boot_rm(fraglist, mmap, 0, &regs);
 
diff --git a/kernel.inc b/kernel.inc
index e4ff0219..d72ce2f3 100644
--- a/kernel.inc
+++ b/kernel.inc
@@ -1,6 +1,6 @@
 ;; -----------------------------------------------------------------------
 ;;
-;;   Copyright 1994-2002 H. Peter Anvin - All Rights Reserved
+;;   Copyright 1994-2007 H. Peter Anvin - All Rights Reserved
 ;;
 ;;   This program is free software; you can redistribute it and/or modify
 ;;   it under the terms of the GNU General Public License as published by
@@ -56,19 +56,26 @@ su_heapend	resw 1			; 0224
 su_pad1		resw 1			; 0226
 su_cmd_line_ptr	resd 1			; 0228
 su_ramdisk_max	resd 1			; 022C
-		resb (9000h-12)-($-$$)	; Were bootsect.S puts it...
-linux_stack	equ $			; 8FF4
-linux_fdctab	equ $
-		resb 9000h-($-$$)
-cmd_line_here	equ $			; 9000 Should be out of the way
+		resb (0e000h-12)-($-$$)	; Were bootsect.S puts it...
+linux_stack	equ $			; BFF4
+linux_fdctab	resb 12
+cmd_line_here	equ $			; C000 Should be out of the way
 		endstruc
 
 ;
-; Kernel command line signature
+; Old kernel command line signature
 ;
 CMD_MAGIC	equ 0A33Fh		; Command line magic
 
 ;
+; If we're loading the command line old-style, we need a smaller
+; heap.
+;
+old_cmd_line_here equ 9000h
+old_linux_fdctab  equ old_cmd_line_here-12
+old_linux_stack   equ old_linux_fdctab
+
+;
 ; Magic number of su_header field
 ;
 HEADER_ID       equ 'HdrS'		; HdrS (in littleendian hex)
diff --git a/runkernel.inc b/runkernel.inc
index aabbd86b..22e8e69c 100644
--- a/runkernel.inc
+++ b/runkernel.inc
@@ -1,6 +1,6 @@
 ;; -----------------------------------------------------------------------
 ;;
-;;   Copyright 1994-2006 H. Peter Anvin - All Rights Reserved
+;;   Copyright 1994-2007 H. Peter Anvin - All Rights Reserved
 ;;
 ;;   This program is free software; you can redistribute it and/or modify
 ;;   it under the terms of the GNU General Public License as published by
@@ -205,16 +205,18 @@ cmdline_end:
 ;
 ; Now check if we have a large kernel, which needs to be loaded high
 ;
+prepare_header:
 		mov dword [RamdiskMax], HIGHMEM_MAX	; Default initrd limit
 		cmp dword [es:su_header],HEADER_ID	; New setup code ID
 		jne old_kernel		; Old kernel, load low
-		cmp word [es:su_version],0200h	; Setup code version 2.0
-		jb old_kernel		; Old kernel, load low
-                cmp word [es:su_version],0201h	; Version 2.01+?
+		mov ax,[es:su_version]
+		cmp ax,0200h			; Setup code version 2.0
+		jb old_kernel			; Old kernel, load low
+		cmp ax,0201h			; Version 2.01+?
                 jb new_kernel                   ; If 2.00, skip this step
                 mov word [es:su_heapend],linux_stack	; Set up the heap
                 or byte [es:su_loadflags],80h	; Let the kernel know we care
-		cmp word [es:su_version],0203h	; Version 2.03+?
+		cmp ax,0203h			; Version 2.03+?
 		jb new_kernel			; Not 2.03+
 		mov eax,[es:su_ramdisk_max]
 		mov [RamdiskMax],eax		; Set the ramdisk limit
@@ -320,7 +322,7 @@ nk_noinitrd:
 		mov fs,ax
 
 ;
-; Copy command line.  Unfortunately, the kernel boot protocol requires
+; Copy command line.  Unfortunately, the old kernel boot protocol requires
 ; the command line to exist in the 9xxxxh range even if the rest of the
 ; setup doesn't.
 ;
@@ -332,26 +334,38 @@ nk_noinitrd:
 		; New cmdline protocol
 		; Store 32-bit (flat) pointer to command line
 		mov dword [fs:su_cmd_line_ptr],(real_mode_seg << 4) + cmd_line_here
-		jmp short in_proper_place
+		jmp in_proper_place
 
 need_high_cmdline:
 ;
-; Copy command line up to 90000h
+; Copy command line to 90000h (old style) -- this happens either if
+; we have a zImage kernel or the protocol is less than 2.02.
 ;
 		mov ax,9000h			; Note AL <- 0
 		mov es,ax
 		mov si,cmd_line_here
-		mov di,si
+		mov di,old_cmd_line_here
 		mov [fs:kern_cmd_magic],word CMD_MAGIC ; Store magic
 		mov [fs:kern_cmd_offset],di	; Store pointer
+		mov word [HeapEnd],old_linux_stack
+		mov ax,255			; Max cmdline limit
+		cmp word [fs:su_version],0201h
+		jb .adjusted
+		; Protocol 2.01+
+		mov word [fs:su_heapend],old_linux_stack
+		jbe .adjusted
+		; Protocol 2.02+
+		mov dword [fs:su_cmd_line_ptr],0x90000+old_cmd_line_here
+		mov ax,4095			; 2.02+ allow a higher limit
+.adjusted:
 
 		mov cx,[CmdLineLen]
-		cmp cx,255
+		cmp cx,ax
 		jna .len_ok
-		mov cx,255			; Protocol < 0x202 has 255 as hard limit
+		mov cx,ax			; Truncate the command line
 .len_ok:
 		fs rep movsb
-		stosb				; Final null, note AL == 0 already
+		stosb				; Final null, note AL=0 already
 
 		push fs
 		pop es
@@ -419,8 +433,8 @@ root_not_floppy:
 ;
 %if IS_SYSLINUX || IS_MDSLINUX
 		lgs si,[cs:fdctab]
-		mov di,linux_fdctab
-		mov cx,6			; 12 bytes
+		mov di,[cs:HeapEnd]
+		mov cx,6
 		gs rep movsw
 		mov [cs:fdctab],word linux_fdctab ; Save new floppy tab pos
 		mov [cs:fdctab+2],es
@@ -445,13 +459,15 @@ kill_motor:
 ; Set up segment registers and the Linux real-mode stack
 ; Note: es == the real mode segment
 ;
+
 		cli
 		mov bx,es
 		mov ds,bx
 		mov fs,bx
 		mov gs,bx
 		mov ss,bx
-		mov sp,linux_stack
+		mov sp,[cs:HeapEnd]
+
 ;
 ; We're done... now RUN THAT KERNEL!!!!
 ; Setup segment == real mode segment + 020h; we need to jump to offset
@@ -622,6 +638,8 @@ no_high_mem:					; Error routine
                 ret
 
 		section .data
+		alignb 2
+HeapEnd		dw linux_stack		; Default end of heap
 boot_image      db 'BOOT_IMAGE='
 boot_image_len  equ $-boot_image