Bob Montgomery wrote: > On Fri, 2006-12-01 at 08:41 +0800, Zou, Nanhai wrote: > > Yes, I intent to put duplicate mapping for kernel code and data in > > kexec-tools to help both region 5 and region 7 trace on kernel text and > > data works. > > > > I see the discussion that Dave mentioned, but it was never really > spelled out that by providing that extra 40-byte PT_LOAD header so crash > can obtain the mapping of 0xa000000100000000 to 0x0000000004000000, it > would also throw in an extra 13918208 bytes of redundant data. That's a > lot of overhead to pick up 16 bytes of useful information. > > But I'm picking nits, I guess. It's only an extra 13 Mbytes in a vmcore > file that might be 1 Gb or larger in size. Still it seems wasteful. > Could the two aliased headers point to a single copy of the data? Would > that violate an elf rule?
It's not "16 bytes of useful information", and it wasn't put there so "crash can obtain the mapping". It's primarily a gdb requirement, because gdb only deals with kernel virtual addresses, so the region 5 segment is required for gdb to work at all. The crash utility only deals with physical addresses with respect to the vmcore, and simply takes advantage of the region 5 PT_LOAD segment to determine the base physical address where the kernel was loaded. That being said, if the region 5 and region 7 segments shared a common "file_offset" value in their respective PT_LOAD segments, I would presume that gdb wouldn't much care... Dave _______________________________________________ fastboot mailing list [email protected] https://lists.osdl.org/mailman/listinfo/fastboot
