[syslinux] isolinux.bin checksum

[Ady Ady]

> man mkisofs paragraph "EL TORITO BOOT INFORMATION TABLE" says:
> -----------------------------------------------------------------------------
>    The  format  of  this  table is as follows; all integers are in section
>    7.3.1 ("little endian") format.
> 
>      Offset    Name           Size      Meaning
>       8        bi_pvd         4 bytes   LBA of primary volume descriptor
>      12        bi_file        4 bytes   LBA of boot file
>      16        bi_length      4 bytes   Boot file length in bytes
>      20        bi_csum        4 bytes   32-bit checksum
>      24        bi_reserved    40 bytes  Reserved
> 
>           The 32-bit checksum is the sum of all the 32-bit  words  in  the
>           boot  file  starting  at  byte  offset  64.   All  linear  block
>           addresses (LBAs) are given in CD sectors (normally 2048 bytes).
> -----------------------------------------------------------------------------
> 
> The "primary volume descriptor" of a first session on medium is always at
> Logical Block Address 16 = 0x10 0x00 0x00 0x00.
> "Boot file length" and "32-bit checksum" get filled in by prepcore and do
> not change by the -boot-info-table changes. Nevertheless the ISO producer
> programs set these values too.
 
 
With this info, I have re-checked all the isolinux.bin files that were involved 
in my tests, both before and after the creation of the ISO images, and those 
within the ISO images themselves.

Besides discovering a "brain fart" in my prior email ( 40 = 0x28 != 28, oops), 
all the above "fields" are correct in all the isolinux.bin files originated 
from the one that included Thomas' patch for '.lzo/prepcore.c':


diff --git a/lzo/prepcore.c b/lzo/prepcore.c
index 9147b2e4..b5ebe88b 100644
--- a/lzo/prepcore.c
+++ b/lzo/prepcore.c
@@ -331,7 +331,7 @@ int main(int argc, char *argv[])
 	unsigned int ptr;
 	outfile_len =
 	    ((offset - start + out_len + 2047) & ~2047) - (offset - start);
-	for (ptr = 64; ptr < offset; ptr += 4)
+	for (ptr = start + 64; ptr < offset; ptr += 4)
 	    csum += get_32((uint32_t *) (infile + ptr));
 	for (ptr = 0; ptr < outfile_len; ptr += 4)
 	    csum += get_32((uint32_t *) (out + ptr));




Is there any reason not to accept Thomas' patch immediately?

Regards,
Ady.