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Date: Wed, 9 Sep 2015 05:14:28 +0200 From: Sedat Dilek <sedat.dilek@...il.com> To: Baoquan He <bhe@...hat.com>, Denys Vlasenko <dvlasenk@...hat.com> Cc: Tejun Heo <tj@...nel.org>, Christoph Lameter <cl@...ux.com>, LKML <linux-kernel@...r.kernel.org>, Andrew Morton <akpm@...ux-foundation.org>, David Rientjes <rientjes@...gle.com>, Linus Torvalds <torvalds@...ux-foundation.org>, Peter Zijlstra <peterz@...radead.org>, Thomas Gleixner <tglx@...utronix.de>, Thomas Graf <tgraf@...g.ch>, Ingo Molnar <mingo@...nel.org>, "the arch/x86 maintainers" <x86@...nel.org> Subject: Re: [llvmlinux] percpu | bitmap issue? (Cannot boot on bare metal due to a kernel NULL pointer dereference) On Wed, Sep 9, 2015 at 5:04 AM, Sedat Dilek <sedat.dilek@...il.com> wrote: > On Wed, Sep 9, 2015 at 4:51 AM, Sedat Dilek <sedat.dilek@...il.com> wrote: >> On Wed, Sep 9, 2015 at 4:29 AM, Baoquan He <bhe@...hat.com> wrote: >>> >>> Seems it happened when call num_possible_cpus() which is a inline >>> function to call __bitmap_weight(). So did you check >>> lib/bitmap.c:__bitmap_weight() by objdump? >>> >>> setup_percpu: NR_CPUS:256 nr_cpumask_bits:256 nr_cpu_ids:1 nr_node_ids:1 >>> >> >> [ CC->TO Denys ] >> >> Hi Boaquan, >> >> Thanks for your reply. >> >> I tried a lot in the meantime :-). >> >> For example I applied a patch from Denys Vlasenko <dvlasenk@...hat.com>... >> >> commit 1a1d48a4a8fde49aedc045d894efe67173d59fe0 >> "linux/bitmap: Force inlining of bitmap weight functions" >> >> ...on top of Linux v4.2. >> >> This resulted in the same call-trace in QEMU. >> >> I hacked around to only re-build mm/percpu.c with GCC (rest with >> CLANG) with some guidance from Linus (compiler warapper-script) etc. >> >> What do you need for outputs? >> objdump of lib/bitmap.o? >> From both builds - with GCC and CLANG? >> >> Please give me clear instructions, Thanks! >> >> Regards, >> - Sedat - >> >> [1] http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=1a1d48a4a8fde49aedc045d894efe67173d59fe0 > > Below snippets against Linux v4.2 and Linux v4.2 plus llvmlinux-fixes > (see file-attachment)... > ( The patch "linux/bitmap: Force inlining of bitmap weight functions" > from Denys was not applied. ) > > [ lib-bitmap_o-objdump-drw_CLANG-3-7.txt ] > > 0000000000000670 <__bitmap_weight>: > 670: 49 89 f8 mov %rdi,%r8 > 673: 31 d2 xor %edx,%edx > 675: 41 89 f1 mov %esi,%r9d > 678: 41 c1 e9 06 shr $0x6,%r9d > 67c: b8 00 00 00 00 mov $0x0,%eax > 681: 74 26 je 6a9 <__bitmap_weight+0x39> > 683: 31 d2 xor %edx,%edx > 685: 45 89 ca mov %r9d,%r10d > 688: 4c 89 c1 mov %r8,%rcx > 68b: 0f 1f 44 00 00 nopl 0x0(%rax,%rax,1) > 690: 48 8b 39 mov (%rcx),%rdi > 693: e8 00 00 00 00 callq 698 > <__bitmap_weight+0x28> 694: R_X86_64_PC32 > __sw_hweight64-0x4 > 698: 89 d2 mov %edx,%edx > 69a: 48 01 c2 add %rax,%rdx > 69d: 48 83 c1 08 add $0x8,%rcx > 6a1: 41 ff ca dec %r10d > 6a4: 75 ea jne 690 <__bitmap_weight+0x20> > 6a6: 44 89 c8 mov %r9d,%eax > 6a9: 40 f6 c6 3f test $0x3f,%sil > 6ad: 74 1c je 6cb <__bitmap_weight+0x5b> > 6af: f7 de neg %esi > 6b1: 48 c7 c7 ff ff ff ff mov $0xffffffffffffffff,%rdi > 6b8: 40 88 f1 mov %sil,%cl > 6bb: 48 d3 ef shr %cl,%rdi > 6be: 49 23 3c c0 and (%r8,%rax,8),%rdi > 6c2: e8 00 00 00 00 callq 6c7 > <__bitmap_weight+0x57> 6c3: R_X86_64_PC32 > __sw_hweight64-0x4 > 6c7: 01 d0 add %edx,%eax > 6c9: 89 c2 mov %eax,%edx > 6cb: 89 d0 mov %edx,%eax > 6cd: c3 retq > 6ce: 66 90 xchg %ax,%ax > > [ lib-bitmap_o-objdump-drw_GCC-4-9.txt ] > > 0000000000000d60 <__bitmap_weight>: > d60: 89 f1 mov %esi,%ecx > d62: 55 push %rbp > d63: 49 89 fa mov %rdi,%r10 > d66: c1 e9 06 shr $0x6,%ecx > d69: 85 c9 test %ecx,%ecx > d6b: 48 89 e5 mov %rsp,%rbp > d6e: 74 52 je dc2 <__bitmap_weight+0x62> > d70: 8d 41 ff lea -0x1(%rcx),%eax > d73: 48 89 fa mov %rdi,%rdx > d76: 45 31 c0 xor %r8d,%r8d > d79: 4c 8d 0c c5 08 00 00 00 lea 0x8(,%rax,8),%r9 > d81: 49 01 f9 add %rdi,%r9 > d84: 48 8b 3a mov (%rdx),%rdi > d87: 48 83 c2 08 add $0x8,%rdx > d8b: e8 00 00 00 00 callq d90 <__bitmap_weight+0x30> > d8c: R_X86_64_PC32 __sw_hweight64-0x4 > d90: 41 01 c0 add %eax,%r8d > d93: 4c 39 ca cmp %r9,%rdx > d96: 75 ec jne d84 <__bitmap_weight+0x24> > d98: 40 f6 c6 3f test $0x3f,%sil > d9c: 44 89 c0 mov %r8d,%eax > d9f: 74 1f je dc0 <__bitmap_weight+0x60> > da1: f7 de neg %esi > da3: 89 ca mov %ecx,%edx > da5: 48 c7 c0 ff ff ff ff mov $0xffffffffffffffff,%rax > dac: 89 f1 mov %esi,%ecx > dae: 48 d3 e8 shr %cl,%rax > db1: 49 23 04 d2 and (%r10,%rdx,8),%rax > db5: 48 89 c7 mov %rax,%rdi > db8: e8 00 00 00 00 callq dbd <__bitmap_weight+0x5d> > db9: R_X86_64_PC32 __sw_hweight64-0x4 > dbd: 44 01 c0 add %r8d,%eax > dc0: 5d pop %rbp > dc1: c3 retq > dc2: 85 f6 test %esi,%esi > dc4: 74 19 je ddf <__bitmap_weight+0x7f> > dc6: f7 de neg %esi > dc8: 48 c7 c0 ff ff ff ff mov $0xffffffffffffffff,%rax > dcf: 45 31 c0 xor %r8d,%r8d > dd2: 89 f1 mov %esi,%ecx > dd4: 48 d3 e8 shr %cl,%rax > dd7: 49 23 02 and (%r10),%rax > dda: 48 89 c7 mov %rax,%rdi > ddd: eb d9 jmp db8 <__bitmap_weight+0x58> > ddf: 31 c0 xor %eax,%eax > de1: 5d pop %rbp > de2: c3 retq > de3: 66 66 66 66 2e 0f 1f 84 00 00 00 00 00 data32 data32 data32 > nopw %cs:0x0(%rax,%rax,1) > Looking at the GCC bug-report [1] mentionned in [2] I have set here... CONFIG_OPTIMIZE_INLINING=y - Sedat - [1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66122 [2] http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=1a1d48a4a8fde49aedc045d894efe67173d59fe0 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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