From mboxrd@z Thu Jan 1 00:00:00 1970 From: takahiro.akashi@linaro.org (AKASHI Takahiro) Date: Thu, 18 Aug 2016 16:32:24 +0900 Subject: [PATCH] fixup! arm64: kdump: add kdump support In-Reply-To: <1471448011-20386-1-git-send-email-james.morse@arm.com> References: <57B2E759.201@arm.com> <1471448011-20386-1-git-send-email-james.morse@arm.com> Message-ID: <20160818073223.GD20080@linaro.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Wed, Aug 17, 2016 at 04:33:31PM +0100, James Morse wrote: > copy_oldmem_page() and mmap_vmcore() provide two ways for userspace to read > from /proc/vmcore. Neither of these check with memblock to see if the page > they are accessing is nomap. On Seattle this causes: > > [ 174.393875] Unhandled fault: synchronous external abort (0x96000210) at > 0xffffff80096b6000 > [ 174.402158] Internal error: : 96000210 [#1] PREEMPT SMP > [ 174.407370] Modules linked in: > [ 174.410417] CPU: 6 PID: 2059 Comm: cp Tainted: G S W I 4.8.0-rc1+ #4708 > [ 174.417799] Hardware name: AMD Overdrive/Supercharger/Default string, BIOS > ROD1002C 04/08/2016 > [ 174.426396] task: ffffffc0fdec5780 task.stack: ffffffc0f34bc000 > [ 174.432313] PC is at __arch_copy_to_user+0x180/0x280 > [ 174.437274] LR is at copy_oldmem_page+0xac/0xf0 > [ 174.441791] pc : [] lr : [] pstate: 20000145 > [ 174.449173] sp : ffffffc0f34bfc90 > [ 174.452474] x29: ffffffc0f34bfc90 x28: 0000000000000000 > [ 174.457776] x27: 0000000008000000 x26: 000000000000d000 > [ 174.463077] x25: 0000000000000001 x24: ffffff8008eb5000 > [ 174.468378] x23: 0000000000000000 x22: ffffff80096b6000 > [ 174.473679] x21: 0000000000000001 x20: 0000000030127000 > [ 174.478979] x19: 0000000000001000 x18: 0000007ff7085d60 > [ 174.484279] x17: 0000000000429358 x16: ffffff80081d9e88 > [ 174.489579] x15: 0000007fae377590 x14: 0000000000000000 > > [ 174.494880] x13: 0000000000000000 x12: ffffff8008dd1000 > [ 174.500180] x11: ffffff80096b6fff x10: ffffff80096b6fff > [ 174.505480] x9 : 0000000040000000 x8 : ffffff8008db6000 > [ 174.510781] x7 : ffffff80096b7000 x6 : 0000000030127000 > [ 174.516082] x5 : 0000000030128000 x4 : 0000000000000000 > [ 174.521382] x3 : 00e8000000000713 x2 : 0000000000000f80 > [ 174.526682] x1 : ffffff80096b6000 x0 : 0000000030127000 > [ 174.531982] > [ 174.533461] Process cp (pid: 2059, stack limit = 0xffffffc0f34bc020) > > [ 174.848448] [] __arch_copy_to_user+0x180/0x280 > [ 174.854448] [] read_from_oldmem.part.4+0xb4/0xf4 > [ 174.860615] [] read_vmcore+0x100/0x22c > [ 174.865919] [] proc_reg_read+0x64/0x90 > [ 174.871223] [] __vfs_read+0x28/0x108 > [ 174.876348] [] vfs_read+0x84/0x144 > [ 174.881301] [] SyS_read+0x44/0xa0 > [ 174.886167] [] el0_svc_naked+0x24/0x28 > [ 174.891466] Code: 00000000 00000000 00000000 00000000 (a8c12027) > [ 174.897562] ---[ end trace 00801b2e35b0cd1f ]--- > > When reading /proc/vmcore with cat/cp or or mmap()ing it with makedumpfile. > > The fs/proc/vmcore.c code provides a hook to indicate whether oldmem pages > are ram or not. Use this to look for our earlier handiwork in memblock. I'm not quite sure about the background that oldmem_pfn_is_ram() was originally introduced on x86, but I think that this feature be deserved for fixing an issue on Xen. See: commit 997c136 Author: Olaf Hering Date: Thu May 26 16:25:54 2011 -0700 fs/proc/vmcore.c: add hook to read_from_oldmem() to check for non-ram pages Thanks, -Takahiro AKASHI > > Signed-off-by: James Morse > --- > > Hi Pratyush, > > I couldn't get makedumpfile to build, or rather it depends on elfutils which > wouldn't build for autotools reasons. Does implementing this hook solve your > makedumpfile issue? > > With this patch I can extract a usable vmcore file using read or mmap, > avoiding the earlier splat. > > Akashi, if you agree this is the right thing to do, please consider folding > this into patch 5. (no need to keep the commit mesage or anything). > > Thanks, > > James > > arch/arm64/kernel/crash_dump.c | 28 ++++++++++++++++++++++++++++ > 1 file changed, 28 insertions(+) > > diff --git a/arch/arm64/kernel/crash_dump.c b/arch/arm64/kernel/crash_dump.c > index 2dc54d129be1..76c71ab42994 100644 > --- a/arch/arm64/kernel/crash_dump.c > +++ b/arch/arm64/kernel/crash_dump.c > @@ -12,10 +12,38 @@ > #include > #include > #include > +#include > #include > #include > #include > > +#ifdef CONFIG_PROC_VMCORE > +static int oldmem_pfn_is_ram(unsigned long pfn) > +{ > + unsigned long addr = pfn << PAGE_SHIFT; > + > + /* > + * We removed oldmem from memblock.memory, then re-added some regions > + * which are reserved by/for firmware as memory and nomap. > + * If an address exists as memory, but is marked nomap, return false. > + */ > + if (memblock_is_memory(addr) && !memblock_is_map_memory(addr)) > + return 0; > + > + return 1; > +} > + > +static int __init do_register_oldmem_pfn_is_ram(void) > +{ > + return register_oldmem_pfn_is_ram(&oldmem_pfn_is_ram); > +} > +/* > + * vmcore_init() is called via fs_initcall, ensure we register > + * oldmem_pfn_is_ram() before then. > + */ > +arch_initcall(do_register_oldmem_pfn_is_ram); > +#endif > + > /** > * copy_oldmem_page() - copy one page from old kernel memory > * @pfn: page frame number to be copied > -- > 2.8.0.rc3 >