On 2014/5/20 3:41, Dave Anderson wrote: > > > ----- Original Message ----- >> >> Hi Atsushi and Simon, >> >> I find a problem about VMSPLIT on arm plarform, related to kexec and >> makedumpfile. >> >> When CONFIG_VMSPLIT_1G/2G is selected by kernel, PAGE_OFFSET is actually >> 0x40000000 or 0x80000000. However, kexec hard codes PAGE_OFFSET to >> 0xc0000000 (in kexec/arch/arm/crashdump-arm.h), which is incorrect in >> these situations. For example, on realview-pbx board with 1G/3G VMSPLIT, >> PHDRs in generated /proc/vmcore is as follow: >> >> Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align >> NOTE 0x001000 0x00000000 0x00000000 0x00690 0x00690 0 >> LOAD 0x002000 0xc0000000 0x00000000 0x10000000 0x10000000 RWE 0 >> LOAD 0x10002000 0xe0000000 0x20000000 0x8000000 0x8000000 RWE 0 >> LOAD 0x18002000 0xf0000000 0x30000000 0x10000000 0x10000000 RWE 0 >> LOAD 0x28002000 0x40000000 0x80000000 0x10000000 0x10000000 RWE 0 >> >> Which should be: >> >> Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align >> ... >> LOAD ... 0x40000000 0x00000000 0x10000000 0x10000000 RWE 0 >> LOAD ... 0x60000000 0x20000000 0x8000000 0x8000000 RWE 0 >> LOAD ... 0x70000000 0x30000000 0x10000000 0x10000000 RWE 0 >> LOAD ... 0xc0000000 0x80000000 0x10000000 0x10000000 RWE 0 >> >> I don't know why crash utility can deal with it without problem, > > For ARM the crash utility masks the symbol value of "_stext" with 0x1fffffff > to determine the PAGE_OFFSET value, which was basically copied from the way > it was done for i386. > kexec-tools can do the same thing by reading /proc/kallsyms (crashdump-x86.c has already done this). However, KALLSYMS and KALLSYMS_ALL are turned off on some embedded systems with memory limitation, which is common on ARM. >> but in makedumpfile such VMSPLIT setting causes segfault: >> >> $ ./makedumpfile -c -d 31 /proc/vmcore ./out -f >> The kernel version is not supported. >> The created dumpfile may be incomplete. >> Excluding unnecessary pages : [ 0.0 %] /Segmentation fault >> >> There are many ways to deal with it, I want discuss them in the maillist and >> make a decision: >> >> 1. Kexec changes, detect PAGE_OFFSET dynamically. However, I don't know >> whether there is a reliably way for this purpose, here I suggest >> kernel to export PAGE_OFFSET through sysfs, such as >> /sys/kernel/page_offset. >> >> 2. Or, kexec accepts PAGE_OFFSET as a command line arguments, let user >> provide correct information. >> >> 3. Or, makedumpfile changes, don't trust EHDR anymore. Kernel should >> export PAGE_OFFSET through VMCOREINFO. >> >> How do you feel? >> >> Thank you! >>
