From: Dave Hansen This was reported because someone was getting oopses reading /proc/iomem. It was tracked down to a zero-sized 'struct resource' entry which was located right at 4GB. You need two conditions to hit this bug: a BIOS E820_RAM area starting at exactly the boundary where you specify mem= (to get a zero-sized entry), and for the legacy_init_iomem_resources() loop to skip that resource (which only happens at exactly 4G). I think the killing zero-sized e820 entry is the easiest way to fix this. Signed-off-by: Dave Hansen Signed-off-by: Andrew Morton --- arch/i386/kernel/setup.c | 24 +++++++++++++++++------- 1 files changed, 17 insertions(+), 7 deletions(-) diff -puN arch/i386/kernel/setup.c~fixup-bogus-e820-entry-with-mem= arch/i386/kernel/setup.c --- devel/arch/i386/kernel/setup.c~fixup-bogus-e820-entry-with-mem= 2005-09-27 19:54:30.000000000 -0700 +++ devel-akpm/arch/i386/kernel/setup.c 2005-09-27 19:54:30.000000000 -0700 @@ -389,14 +389,24 @@ static void __init limit_regions(unsigne } } for (i = 0; i < e820.nr_map; i++) { - if (e820.map[i].type == E820_RAM) { - current_addr = e820.map[i].addr + e820.map[i].size; - if (current_addr >= size) { - e820.map[i].size -= current_addr-size; - e820.nr_map = i + 1; - return; - } + current_addr = e820.map[i].addr + e820.map[i].size; + if (current_addr < size) + continue; + + if (e820.map[i].type != E820_RAM) + continue; + + if (e820.map[i].addr >= size) { + /* + * This region starts past the end of the + * requested size, skip it completely. + */ + e820.nr_map = i; + } else { + e820.nr_map = i + 1; + e820.map[i].size -= current_addr - size; } + return; } } _