pathbased: clean up diskstart address numbers, 256 byte subvols

Clean up the uses of hard-coded addresses in diskstart.inc.
Furthermore, the btrfs spec allows 255 characters for a subvolume, so
we might as well allocate that much.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

diff --git a/core/diskstart.inc b/core/diskstart.inc
index ca627b1..566feed 100644 (file)
--- a/core/diskstart.inc
+++ b/core/diskstart.inc
@@ -471,7 +471,7 @@ bootsignature       dw kaboom.again-bootsec
 ;  Start of LDLINUX.SYS
 ; ===========================================================================
 
-LDLINUX_SYS equ        0x7e00
+LDLINUX_SYS    equ ($-$$)+TEXT_START
 ldlinux_sys:
 
 syslinux_banner        db 0Dh, 0Ah
@@ -486,6 +486,9 @@ ldlinux_magic       dd LDLINUX_MAGIC
 ; This area is patched by the installer.  It is found by looking for
 ; LDLINUX_MAGIC, plus 8 bytes.
 ;
+SUBVOL_MAX     equ 256
+CURRENTDIR_MAX equ FILENAME_MAX
+
 patch_area:
 DataSectors    dw 0            ; Number of sectors (not including bootsec)
 ADVSectors     dw 0            ; Additional sectors for ADVs
@@ -493,12 +496,23 @@ LDLDwords dd 0            ; Total dwords starting at ldlinux_sys,
 CheckSum       dd 0            ; Checksum starting at ldlinux_sys
                                ; value = LDLINUX_MAGIC - [sum of dwords]
 CurrentDirPtr  dw CurrentDirName-LDLINUX_SYS   ; Current directory name string
-CurrentDirLen  dw FILENAME_MAX
-SubvolPtr      dw SubvolName - LDLINUX_SYS
-SubvolLen      dw 64           ; Should be enough
-SecPtrOffset   dw SectorPtrs - LDLINUX_SYS
+CurrentDirLen  dw CURRENTDIR_MAX
+SubvolPtr      dw SubvolName-LDLINUX_SYS
+SubvolLen      dw SUBVOL_MAX
+SecPtrOffset   dw SectorPtrs-LDLINUX_SYS
 SecPtrCnt      dw (SectorPtrsEnd - SectorPtrs) >> 2
 
+;
+; Installer pokes the base directory here.  This is in .data16 so it
+; isn't actually located in the first sector.
+;
+%define HAVE_CURRENTDIRNAME
+               section .data16
+               global CurrentDirName, SubvolName
+CurrentDirName times CURRENTDIR_MAX db 0
+SubvolName     times SUBVOL_MAX db 0
+               section .init
+
 ldlinux_ent:
 ;
 ; Note that some BIOSes are buggy and run the boot sector at 07C0:0000
@@ -540,7 +554,7 @@ BIOSName    resw 1
 ;
 load_rest:
                lea esi,[SectorPtrs]
-               mov ebx,7C00h+2*SECTOR_SIZE     ; Where we start loading
+               mov ebx,TEXT_START+2*SECTOR_SIZE ; Where we start loading
                mov cx,[DataSectors]
                dec cx                          ; Minus this sector
 
@@ -683,7 +697,7 @@ rl_checkpt_off      equ ($-$$)
 ; Sector pointers
                alignz 4
 MaxInitDataSize        equ 96 << 10
-MaxLMA         equ 0x7c00+SECTOR_SIZE+MaxInitDataSize
+MaxLMA         equ TEXT_START+SECTOR_SIZE+MaxInitDataSize
 SectorPtrs     times MaxInitDataSize >> SECTOR_SHIFT dd 0
 SectorPtrsEnd  equ $
 
@@ -691,15 +705,6 @@ SectorPtrsEnd      equ $
 ;  End of code and data that have to be in the first sector
 ; ----------------------------------------------------------------------------
 
-;
-; Installer pokes the base directory here, needs to be in .text16 so the pointer
-; address can be calculated by the assembler.
-;
-%define HAVE_CURRENTDIRNAME
-               section .data16
-               global CurrentDirName, SubvolName
-CurrentDirName times FILENAME_MAX db 0
-SubvolName     times 64 db 0
                section .text16
 all_read:
 ;

diff --git a/extlinux/main.c b/extlinux/main.c
index c29e3b0..b02cfe2 100644 (file)
--- a/extlinux/main.c
+++ b/extlinux/main.c
@@ -140,7 +140,8 @@ static const char short_options[] = "iUuzS:H:rvho:O";
    boot image, the boot sector is from 0~512, the boot image starts at 2K */
 #define BTRFS_EXTLINUX_OFFSET (2*1024)
 #define BTRFS_SUBVOL_OPT "subvol="
-static char subvol[64];
+#define BTRFS_SUBVOL_MAX 256   /* By btrfs specification */
+static char subvol[BTRFS_SUBVOL_MAX];
 /*
  * Boot block
  */