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