Fix up x86 kexec to exclude memory on i686 kernels beyond 64GB limit We found a problem recently on x86 systems. If a 32 bit PAE enabled system contains more then 64GB of physical ram, the kernel will truncate the max_pfn value to 64GB. Unfortunately it still leaves all the physical memory regions present in /proc/iomem. Since kexec builds its elf headers based on /proc/iomem the elf headers indicate the size of memory is larger than what the kernel is willing to address. The result is that, during a copy of /proc/vmcore, a read will return -EFAULT when the requested offset is beyond the 64GB range, leaving the seemingly truncated vmcore useless, as the elf headers indicate memory beyond what the file contains. The fix for it is pretty straightforward, just ensure that, when on x86 systems, we don't record any entries in the memory_range array that cross the 64Gb mark. This keeps us in line with the kernel and lets the copy finish sucessfully, providing a workable core Tested successfully by myself Originally-authored-by: Dave Anderson <anderson at redhat.com> Signed-off-by: Neil Horman <nhorman at tuxdriver.com> diff --git a/kexec/arch/i386/crashdump-x86.c b/kexec/arch/i386/crashdump-x86.c index 9d37442..85879a9 100644 --- a/kexec/arch/i386/crashdump-x86.c +++ b/kexec/arch/i386/crashdump-x86.c @@ -114,6 +114,15 @@ static int get_crash_memory_ranges(struct memory_range **range, int *ranges, if (end <= 0x0009ffff) continue; + /* + * Exclude any segments starting at or beyond 64GB, and + * restrict any segments from ending at or beyond 64GB. + */ + if (start >= 0x1000000000) + continue; + if (end >= 0x1000000000) + end = 0xfffffffff; + crash_memory_range[memory_ranges].start = start; crash_memory_range[memory_ranges].end = end; crash_memory_range[memory_ranges].type = type;
