В Sat, 30 Dec 2017 11:57:46 -0600 Josh Poimboeuf <jpoimboe@xxxxxxxxxx> пишет: > On Sat, Dec 30, 2017 at 11:09:46AM -0600, Josh Poimboeuf wrote: > > On Sat, Dec 30, 2017 at 11:45:13AM +0300, Alexander Tsoy wrote: > > > В Пт, 29/12/2017 в 21:49 -0600, Josh Poimboeuf пишет: > > > > On Fri, Dec 29, 2017 at 05:10:35PM -0700, Andy Lutomirski > > > > wrote: > > > > > (Also, Josh, the oops code should have printed the contents > > > > > of the struct pt_regs at the top of the DF stack. Any idea > > > > > why it didn't?) > > > > > > > > Looking at one of the dumps: > > > > > > > > [ 392.774879] NMI backtrace for cpu 0 > > > > [ 392.774881] CPU: 0 PID: 1 Comm: init Not tainted > > > > 4.14.9-gentoo #1 > > > > [ 392.774881] Hardware name: Red Hat KVM, BIOS 0.5.1 > > > > 01/01/2011 [ 392.774882] task: ffff8802368b8000 task.stack: > > > > ffffc9000000c000 [ 392.774885] RIP: 0010:double_fault+0x0/0x30 > > > > [ 392.774886] RSP: 0000:ffffffffff527fd0 EFLAGS: 00000086 > > > > [ 392.774887] RAX: 000000003fc00000 RBX: 0000000000000001 > > > > RCX: 00000000c0000101 > > > > [ 392.774887] RDX: 00000000ffff8802 RSI: 0000000000000000 > > > > RDI: ffffffffff527f58 > > > > [ 392.774887] RBP: 0000000000000000 R08: 0000000000000000 > > > > R09: 0000000000000000 > > > > [ 392.774888] R10: 0000000000000000 R11: 0000000000000000 > > > > R12: ffffffff816ae726 > > > > [ 392.774888] R13: 0000000000000000 R14: 0000000000000000 > > > > R15: 0000000000000000 > > > > [ 392.774889] FS: 0000000000000000(0000) > > > > GS:ffff88023fc00000(0000) knlGS:0000000000000000 > > > > [ 392.774889] CS: 0010 DS: 0000 ES: 0000 CR0: > > > > 0000000080050033 [ 392.774890] CR2: ffffffffff526f08 CR3: > > > > 0000000235b48002 CR4: 00000000001606f0 > > > > [ 392.774892] Call Trace: > > > > [ 392.774894] <#DF> > > > > [ 392.774897] do_double_fault+0xb/0x140 > > > > [ 392.774898] </#DF> > > > > > > > > It should have at least printed the #DF iret frame registers, > > > > which I recently added support for in "x86/unwinder: Handle > > > > stack overflows more > > > > gracefully", which is in both 4.14.9 and 4.15-rc5. > > > > > > > > I think the missing iret regs are due to a bug in > > > > show_trace_log_lvl(), > > > > where if the unwind starts with two regs frames in a row, the > > > > second regs don't get printed. > > > > > > > > Alexander, would you mind reproducing again with the below > > > > patch? It should still fail, but this time it should hopefully > > > > show another RIP/RSP/EFLAGS instead of the > > > > "do_double_fault+0xb/0x140" line. > > > > > > Yes, it works: > > > > > > [ 23.058064] NMI backtrace for cpu 2 > > > [ 23.058068] CPU: 2 PID: 1 Comm: init Not tainted 4.15.0-rc5+ #1 > > > [ 23.058069] Hardware name: QEMU Standard PC (i440FX + PIIX, > > > 1996), BIOS 1.10.2-1.fc27 04/01/2014 > > > [ 23.058074] RIP: 0010:double_fault+0x0/0x30 > > > [ 23.058075] RSP: 0000:fffffe800005ffd0 EFLAGS: 00000086 > > > [ 23.058077] RAX: 000000003fd00000 RBX: 0000000000000001 RCX: > > > 00000000c0000101 > > > [ 23.058077] RDX: 00000000ffff9681 RSI: 0000000000000000 RDI: > > > fffffe800005ff58 > > > [ 23.058078] RBP: 0000000000000000 R08: 0000000000000000 R09: > > > 0000000000000000 > > > [ 23.058079] R10: 0000000000000000 R11: 0000000000000000 R12: > > > ffffffff92001426 > > > [ 23.058080] R13: 0000000000000000 R14: 0000000000000000 R15: > > > 0000000000000000 > > > [ 23.058083] FS: 0000000000000000(0000) > > > GS:ffff96813fd00000(0000) knlGS:0000000000000000 > > > [ 23.058084] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > > > [ 23.058085] CR2: fffffe800005ef08 CR3: 0000000137a09000 CR4: > > > 00000000000406a0 > > > [ 23.058089] Call Trace: > > > [ 23.058101] <#DF> > > > [ 23.058104] RIP: 0010:do_double_fault+0xb/0x140 > > > [ 23.058105] RSP: 0000:fffffe800005ef18 EFLAGS: 00010086 > > > ORIG_RAX: 0000000000000000 > > > [ 23.058106] RAX: 000000003fd00000 RBX: 0000000000000001 RCX: > > > 00000000c0000101 > > > [ 23.058107] RDX: 00000000ffff9681 RSI: 0000000000000000 RDI: > > > fffffe800005ff58 > > > [ 23.058107] RBP: 0000000000000000 R08: 0000000000000000 R09: > > > 0000000000000000 > > > [ 23.058108] R10: 0000000000000000 R11: 0000000000000000 R12: > > > ffffffff92001426 > > > [ 23.058108] R13: 0000000000000000 R14: 0000000000000000 R15: > > > 0000000000000000 > > > [ 23.058111] </#DF> > > > [ 23.058111] Code: 05 00 00 48 89 e7 31 f6 e8 2e 8c 61 ff e9 69 > > > 06 00 00 e8 94 05 00 00 48 89 e7 31 f6 e8 1a 8c 61 ff e9 55 06 00 > > > 00 0f 1f 44 00 00 <0f> 1f 00 48 83 c4 88 e8 e4 04 00 00 48 89 e7 > > > 48 8b 74 24 78 48 > > > > That's better indeed, though still not quite right. It should have > > only shown a subset of those registers. One more bug to fix > > there... > > Turns out my previous code to print iret frames was a bit ... > misguided, to put it nicely. Not sure what I was smoking. > > Hopefully the below patch should fix it (in place of the previous > patch). Would you mind testing again? > With that patch I get: [ 2.160017] NMI backtrace for cpu 0 [ 2.160017] CPU: 0 PID: 1 Comm: init Not tainted 4.15.0-rc5 #1 [ 2.160017] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1.fc27 04/01/2014 [ 2.160017] RIP: 0010:double_fault+0x0/0x30 [ 2.160017] RSP: 0000:fffffe8000007fd0 EFLAGS: 00010086 [ 2.160017] RAX: 00000000ffc00000 RBX: 0000000000000001 RCX: 00000000c0000101 [ 2.160017] RDX: 00000000ffff8edc RSI: 0000000000000000 RDI: fffffe8000007f58 [ 2.160017] RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 [ 2.160017] R10: 0000000000000000 R11: 0000000000000000 R12: ffffffffa3c01426 [ 2.160017] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000 [ 2.160017] FS: 0000000000000000(0000) GS:ffff8edcffc00000(0000) knlGS:0000000000000000 [ 2.160017] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 2.160017] CR2: fffffe8000006f08 CR3: 000000007c153000 CR4: 00000000000006b0 [ 2.160017] Call Trace: [ 2.160017] <#DF> [ 2.160017] RIP: 0010:do_double_fault+0xb/0x140 [ 2.160017] RSP: 0000:fffffe8000006f18 EFLAGS: 00010086 [ 2.160017] </#DF> -- Best regards, Alexander Tsoy