On Tue, Apr 06, 2010 at 11:44:54AM +0900, Daisuke Nishimura wrote: > In !SPARSEMEM_EX case, the symbol mem_section points a array of struct mem_section, > doesn't point a array of pointer to mem_section[], so I think the check: > > if ((mem_sec[SECTION_NR_TO_ROOT(nr)] == 0) || > !IS_KVADDR(mem_sec[SECTION_NR_TO_ROOT(nr)])) > return 0; > > in nr_to_section() is not a valid check in this case. > > To make the matters worse, if CONFIG_CGROUP_MEM_RES_CTLR is enabled, the end of > struct mem_section is padded with 0. > > So, reading mem_section by "rd" will look like: > > crash> rd mem_section 128 > c08b71e0: c9002003 c9001200 f7000000 00000000 . .............. > c08b71f0: c9002003 c9001260 f6980000 00000000 . ..`........... > c08b7200: c9002003 c90012c0 f6300000 00000000 . ........0..... > c08b7210: c9002003 c9001320 f5c80000 00000000 . .. ........... > ... > > This means nr_to_section() will return 0 when "nr" is 3,7,11,... because it meets > the condition(mem_sec[SECTION_NR_TO_ROOT(nr)] == mem_sec[nr] == 0). > > As a result, mem_map for section 3,7,11,... cannot be handled properly. > Actually, "kmem -n" doesn't show a mem_map for them. > > crash> kmem -n > ... > NR SECTION CODED_MEM_MAP MEM_MAP PFN > 0 c08b71e0 c9002000 c9002000 0 > 1 c08b71f0 c9002000 c9402000 131072 > 2 c08b7200 c9002000 c9802000 262144 > 4 c08b7220 c9002000 ca002000 524288 > 5 c08b7230 c9002000 ca402000 655360 > 6 c08b7240 c9002000 ca802000 786432 > 8 c08b7260 c8c02000 cac02000 1048576 > 9 c08b7270 c8c02000 cb002000 1179648 > 10 c08b7280 c8c02000 cb402000 1310720 > 12 c08b72a0 c8c02000 cbc02000 1572864 > ... > > This patch is a fix for this problem. nr_to_section() will check "addr" by > IS_KVADDR() later anyway, so this patch just removes the problematic check. > > Signed-off-by: Daisuke Nishimura <nishimura at mxp.nes.nec.co.jp> > --- > diff -uprN crash-5.0.2.orig/memory.c crash-5.0.2/memory.c > --- crash-5.0.2.orig/memory.c 2010-04-05 16:08:52.000000000 +0900 > +++ crash-5.0.2/memory.c 2010-04-06 09:56:43.000000000 +0900 > @@ -13030,10 +13030,6 @@ nr_to_section(ulong nr) > } > } > > - if ((mem_sec[SECTION_NR_TO_ROOT(nr)] == 0) || > - !IS_KVADDR(mem_sec[SECTION_NR_TO_ROOT(nr)])) > - return 0; > - > if (IS_SPARSEMEM_EX()) > addr = mem_sec[SECTION_NR_TO_ROOT(nr)] + > (nr & SECTION_ROOT_MASK()) * SIZE(mem_section); This has been successfully tested here. Thanks! Neil
