diff options
Diffstat (limited to 'source/a/lilo/lilo.ignore.usable.memory.above.4G.diff')
| -rw-r--r-- | source/a/lilo/lilo.ignore.usable.memory.above.4G.diff | 42 |
1 files changed, 42 insertions, 0 deletions
diff --git a/source/a/lilo/lilo.ignore.usable.memory.above.4G.diff b/source/a/lilo/lilo.ignore.usable.memory.above.4G.diff new file mode 100644 index 000000000..ee5ad8bca --- /dev/null +++ b/source/a/lilo/lilo.ignore.usable.memory.above.4G.diff @@ -0,0 +1,42 @@ +From Sl4ck3ver on LQ: +http://www.linuxquestions.org/questions/slackware-14/[patch]-found-a-nasty-lilo-bug-with-a-2-line-fix-for-14-2-a-4175577969/ + +Every BIOS-e820 entry contains start and size of the area as 64-bit value +and is shifted right 10 bits (1024) with "shrd" while searching for the +largest "usable" memory range entry. + + +Finally the found values are converted back into real addresses by shifting +left 10 bits... + +BUT this is done the wrong only using a 32-bit register so the high dword is lost!!! + +0x000000027fffffff gets 0x000000007fffffff :-( + +Every EXISTING system which happens to work fine just happens to +have an entry which just contains "usable" memory at that address. +Often in the form of an entry like: + +BIOS-e820: [mem 0x0000000000100000-0x00000000fxxxxxxx] usable + +Virtually all systems have "usable" memory at that position, so until +now this bug was not noticed! + + +HERE IS THE FIX, A 2-LINER: +=========================== + +Ignore any usable memory range not starting below 4GB and +so avoid the truncation, really just a work around :-) + +--- ./src/second.S.orig 2016-04-21 15:12:57.155456806 -0500 ++++ ./src/second.S 2016-04-21 15:15:08.918466313 -0500 +@@ -2975,6 +2975,8 @@ + shrd memmap+8,eax,#10 ; convert to 1k + cmp dword memmap,#1024 ; below 1M + jb e8go2 ; below 1M, no interest ++ cmp dword memmap,#4*1024*1024 ; above 4G ++ jae e8go2 ; above 4G, no interest + cmp esi,memmap+8 ; check size + ja e8go2 ; want largest + mov edx,memmap ; start (in 1k) |