Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]
Groups > linux.kernel > #1678093
| From | Josh Poimboeuf <jpoimboe@redhat.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH v2 6/8] x86/entry: add unwind hint annotations |
| Date | 2017-06-29 21:10 +0200 |
| Message-ID | <tXMZd-354-49@gated-at.bofh.it> (permalink) |
| References | <tXmV4-8uj-15@gated-at.bofh.it> <tXmV4-8uj-23@gated-at.bofh.it> <tXLTs-2de-23@gated-at.bofh.it> <tXMPw-2Ms-23@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On Thu, Jun 29, 2017 at 11:50:18AM -0700, Andy Lutomirski wrote: > On Thu, Jun 29, 2017 at 10:53 AM, Josh Poimboeuf <jpoimboe@redhat.com> wrote: > > There's a bug here that will need a small change to the entry code. > > > > Mike Galbraith reported: > > > > WARNING: can't dereference registers at ffffc900089d7e08 for ip ffffffff81740bbb > > > > After some looking I found that it's caused by the following code > > snippet in the 'interrupt' macro in entry_64.S: > > > > /* > > * Save previous stack pointer, optionally switch to interrupt stack. > > * irq_count is used to check if a CPU is already on an interrupt stack > > * or not. While this is essentially redundant with preempt_count it is > > * a little cheaper to use a separate counter in the PDA (short of > > * moving irq_enter into assembly, which would be too much work) > > */ > > movq %rsp, %rdi > > incl PER_CPU_VAR(irq_count) > > cmovzq PER_CPU_VAR(irq_stack_ptr), %rsp > > UNWIND_HINT_REGS base=rdi > > pushq %rdi > > UNWIND_HINT_REGS indirect=1 > > > > The problem is that it's changing the stack pointer *before* writing the > > previous stack pointer (push %rdi). So when unwinding from an NMI which > > hit between the rsp write and the rdi push, the unwinder tries to access > > the regs on the previous stack (by reading rdi), but the previous stack > > pointer isn't there yet, so the access is considered out of bounds. > > Ugh, that code. Does this problem go away with this patch applied: > > https://git.kernel.org/pub/scm/linux/kernel/git/luto/linux.git/commit/?h=x86/entry_ist&id=2231ec7e0bcc1a2bc94a17081511ab54cc6badd1 > > If so, want to update the patch for new kernels (shouldn't conflict > with anything except your unwind hints)? I don't think that patch will fix it, because it still updates rsp *before* writing the old rsp on the new stack. So there's still a window where the "previous stack" pointer is missing. -- Josh
Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread
[PATCH v2 0/8] x86: undwarf unwinder Josh Poimboeuf <jpoimboe@redhat.com> - 2017-06-28 17:20 +0200
[PATCH v2 4/8] objtool: add undwarf debuginfo generation Josh Poimboeuf <jpoimboe@redhat.com> - 2017-06-28 17:20 +0200
Re: [PATCH v2 4/8] objtool: add undwarf debuginfo generation Ingo Molnar <mingo@kernel.org> - 2017-06-29 09:20 +0200
Re: [PATCH v2 4/8] objtool: add undwarf debuginfo generation Josh Poimboeuf <jpoimboe@redhat.com> - 2017-06-29 15:50 +0200
Re: [PATCH v2 4/8] objtool: add undwarf debuginfo generation Ingo Molnar <mingo@kernel.org> - 2017-06-29 09:30 +0200
Re: [PATCH v2 4/8] objtool: add undwarf debuginfo generation Josh Poimboeuf <jpoimboe@redhat.com> - 2017-06-29 16:10 +0200
Re: [PATCH v2 4/8] objtool: add undwarf debuginfo generation Ingo Molnar <mingo@kernel.org> - 2017-06-29 16:50 +0200
Re: [PATCH v2 4/8] objtool: add undwarf debuginfo generation Josh Poimboeuf <jpoimboe@redhat.com> - 2017-06-29 17:10 +0200
[PATCH v2 7/8] x86/asm: add unwind hint annotations to sync_core() Josh Poimboeuf <jpoimboe@redhat.com> - 2017-06-28 17:20 +0200
[PATCH v2 2/8] objtool, x86: add several functions and files to the objtool whitelist Josh Poimboeuf <jpoimboe@redhat.com> - 2017-06-28 17:20 +0200
[tip:core/objtool] objtool, x86: Add several functions and files to the objtool whitelist tip-bot for Josh Poimboeuf <tipbot@zytor.com> - 2017-06-30 15:20 +0200
[PATCH v2 6/8] x86/entry: add unwind hint annotations Josh Poimboeuf <jpoimboe@redhat.com> - 2017-06-28 17:20 +0200
Re: [PATCH v2 6/8] x86/entry: add unwind hint annotations Josh Poimboeuf <jpoimboe@redhat.com> - 2017-06-29 20:00 +0200
Re: [PATCH v2 6/8] x86/entry: add unwind hint annotations Andy Lutomirski <luto@kernel.org> - 2017-06-29 21:00 +0200
Re: [PATCH v2 6/8] x86/entry: add unwind hint annotations Josh Poimboeuf <jpoimboe@redhat.com> - 2017-06-29 21:10 +0200
Re: [PATCH v2 6/8] x86/entry: add unwind hint annotations Andy Lutomirski <luto@kernel.org> - 2017-06-29 23:20 +0200
Re: [PATCH v2 6/8] x86/entry: add unwind hint annotations Josh Poimboeuf <jpoimboe@redhat.com> - 2017-06-29 23:50 +0200
Re: [PATCH v2 6/8] x86/entry: add unwind hint annotations Andy Lutomirski <luto@amacapital.net> - 2017-06-30 01:00 +0200
Re: [PATCH v2 6/8] x86/entry: add unwind hint annotations Josh Poimboeuf <jpoimboe@redhat.com> - 2017-06-30 04:20 +0200
Re: [PATCH v2 6/8] x86/entry: add unwind hint annotations Andy Lutomirski <luto@kernel.org> - 2017-06-30 07:10 +0200
Re: [PATCH v2 6/8] x86/entry: add unwind hint annotations Andy Lutomirski <luto@kernel.org> - 2017-06-30 07:50 +0200
Re: [PATCH v2 6/8] x86/entry: add unwind hint annotations Josh Poimboeuf <jpoimboe@redhat.com> - 2017-06-30 15:20 +0200
Re: [PATCH v2 6/8] x86/entry: add unwind hint annotations Andy Lutomirski <luto@kernel.org> - 2017-06-30 17:50 +0200
Re: [PATCH v2 6/8] x86/entry: add unwind hint annotations Josh Poimboeuf <jpoimboe@redhat.com> - 2017-06-30 18:00 +0200
Re: [PATCH v2 6/8] x86/entry: add unwind hint annotations Andy Lutomirski <luto@kernel.org> - 2017-06-30 18:00 +0200
Re: [PATCH v2 6/8] x86/entry: add unwind hint annotations Josh Poimboeuf <jpoimboe@redhat.com> - 2017-06-30 18:20 +0200
[PATCH v2 1/8] objtool: move checking code to check.c Josh Poimboeuf <jpoimboe@redhat.com> - 2017-06-28 17:20 +0200
Re: [PATCH v2 0/8] x86: undwarf unwinder Ingo Molnar <mingo@kernel.org> - 2017-06-29 10:00 +0200
Re: [PATCH v2 0/8] x86: undwarf unwinder Josh Poimboeuf <jpoimboe@redhat.com> - 2017-06-29 16:20 +0200
Re: [PATCH v2 0/8] x86: undwarf unwinder Josh Poimboeuf <jpoimboe@redhat.com> - 2017-06-29 21:20 +0200
Re: [PATCH v2 3/8] objtool: stack validation 2.0 Ingo Molnar <mingo@kernel.org> - 2017-06-30 10:40 +0200
Re: [PATCH v2 3/8] objtool: stack validation 2.0 Josh Poimboeuf <jpoimboe@redhat.com> - 2017-06-30 15:30 +0200
Re: [PATCH v2 3/8] objtool: stack validation 2.0 Josh Poimboeuf <jpoimboe@redhat.com> - 2017-06-30 15:30 +0200
[PATCH] objtool: silence warnings for functions which use iret Josh Poimboeuf <jpoimboe@redhat.com> - 2017-06-30 16:10 +0200
[tip:core/objtool] objtool: Silence warnings for functions which use IRET tip-bot for Josh Poimboeuf <tipbot@zytor.com> - 2017-06-30 20:00 +0200
csiph-web