On Thu, Jul 21, 2016 at 2:21 PM, Josh Poimboeuf <jpoim...@redhat.com> wrote: > Now that we can find pt_regs registers in the middle of the stack due to > an interrupt or exception, we can print them. Here's what it looks > like: > > ... > [<ffffffff8106f7dc>] do_async_page_fault+0x2c/0xa0 > [<ffffffff8189f558>] async_page_fault+0x28/0x30 > RIP: 0010:[<ffffffff814529e2>] [<ffffffff814529e2>] __clear_user+0x42/0x70 > RSP: 0018:ffff88007876fd38 EFLAGS: 00010202 > RAX: 0000000000000000 RBX: 0000000000000138 RCX: 0000000000000138 > RDX: 0000000000000000 RSI: 0000000000000008 RDI: 000000000061b640 > RBP: ffff88007876fd48 R08: 0000000dc2ced0d0 R09: 0000000000000000 > R10: 0000000000000001 R11: 0000000000000000 R12: 000000000061b640 > R13: 0000000000000000 R14: ffff880078770000 R15: ffff880079947200 > [<ffffffff814529e2>] ? __clear_user+0x42/0x70 > [<ffffffff814529c3>] ? __clear_user+0x23/0x70 > [<ffffffff81452a7b>] clear_user+0x2b/0x40 > ...
This looks wrong. Here are some theories: (a) __clear_user is a reliable address that is indicated by RIP: .... Then it's found again as an unreliable address as "? __clear_user+0x42/0x70" by scanning the stack. "? __clear_user+0x23/0x70" is a genuine leftover artifact on the stack. In this case, shouldn't "? __clear_user+0x42/0x70" have been suppressed because it matched a reliable address? (b) You actually intended for all the addresses to be printed, in which case "? __clear_user+0x42/0x70" should have been "__clear_user+0x42/0x70" and you have a bug. In this case, it's plausible that your state machine got a bit lost leading to "? __clear_user+0x23/0x70" as well (i.e. it's not just an artifact -- it's a real frame and you didn't find it). (c) Something else and I'm confused. --Andy
