lwn.git/arch/x86/kernel/dumpstack_32.c, branch v3.0.56

x86, dumpstack: Correct stack dump info when frame pointer is available

2011-03-18T09:51:42+00:00

Current stack dump code scans entire stack and check each entry contains a pointer to kernel code. If CONFIG_FRAME_POINTER=y it could mark whether the pointer is valid or not based on value of the frame pointer. Invalid entries could be preceded by '?' sign. However this was not going to happen because scan start point was always higher than the frame pointer so that they could not meet. Commit 9c0729dc8062 ("x86: Eliminate bp argument from the stack tracing routines") delayed bp acquisition point, so the bp was read in lower frame, thus all of the entries were marked invalid. This patch fixes this by reverting above commit while retaining stack_frame() helper as suggested by Frederic Weisbecker. End result looks like below: before: [ 3.508329] Call Trace: [ 3.508551] [] ? panic+0x91/0x199 [ 3.508662] [] ? printk+0x68/0x6a [ 3.508770] [] ? mount_block_root+0x257/0x26e [ 3.508876] [] ? mount_root+0x56/0x5a [ 3.508975] [] ? prepare_namespace+0x170/0x1a9 [ 3.509216] [] ? kernel_init+0x1d2/0x1e2 [ 3.509335] [] ? kernel_thread_helper+0x4/0x10 [ 3.509442] [] ? restore_args+0x0/0x30 [ 3.509542] [] ? kernel_init+0x0/0x1e2 [ 3.509641] [] ? kernel_thread_helper+0x0/0x10 after: [ 3.522991] Call Trace: [ 3.523351] [] panic+0x91/0x199 [ 3.523468] [] ? printk+0x68/0x6a [ 3.523576] [] mount_block_root+0x257/0x26e [ 3.523681] [] mount_root+0x56/0x5a [ 3.523780] [] prepare_namespace+0x170/0x1a9 [ 3.523885] [] kernel_init+0x1d2/0x1e2 [ 3.523987] [] kernel_thread_helper+0x4/0x10 [ 3.524228] [] ? restore_args+0x0/0x30 [ 3.524345] [] ? kernel_init+0x0/0x1e2 [ 3.524445] [] ? kernel_thread_helper+0x0/0x10 -v5: * fix build breakage with oprofile -v4: * use 0 instead of regs->bp * separate out printk changes -v3: * apply comment from Frederic * add a couple of printk fixes Signed-off-by: Namhyung Kim Acked-by: Peter Zijlstra Acked-by: Frederic Weisbecker Cc: Soren Sandmann Cc: Paul Mackerras Cc: Arnaldo Carvalho de Melo Cc: Robert Richter LKML-Reference: <1300416006-3163-1-git-send-email-namhyung@gmail.com> Signed-off-by: Ingo Molnar

x86: Eliminate bp argument from the stack tracing routines

2010-11-18T13:37:34+00:00

The various stack tracing routines take a 'bp' argument in which the caller is supposed to provide the base pointer to use, or 0 if doesn't have one. Since bp is garbage whenever CONFIG_FRAME_POINTER is not defined, this means all callers in principle should either always pass 0, or be conditional on CONFIG_FRAME_POINTER. However, there are only really three use cases for stack tracing: (a) Trace the current task, including IRQ stack if any (b) Trace the current task, but skip IRQ stack (c) Trace some other task In all cases, if CONFIG_FRAME_POINTER is not defined, bp should just be 0. If it _is_ defined, then - in case (a) bp should be gotten directly from the CPU's register, so the caller should pass NULL for regs, - in case (b) the caller should should pass the IRQ registers to dump_trace(), - in case (c) bp should be gotten from the top of the task's stack, so the caller should pass NULL for regs. Hence, the bp argument is not necessary because the combination of task and regs is sufficient to determine an appropriate value for bp. This patch introduces a new inline function stack_frame(task, regs) that computes the desired bp. This function is then called from the two versions of dump_stack(). Signed-off-by: Soren Sandmann Acked-by: Steven Rostedt Cc: Thomas Gleixner Cc: Ingo Molnar Cc: H. Peter Anvin Cc: Peter Zijlstra Cc: Arjan van de Ven , Cc: Frederic Weisbecker , Cc: Arnaldo Carvalho de Melo , LKML-Reference: > Signed-off-by: Frederic Weisbecker

x86, printk: Get rid of <0> from stack output

2010-10-23T18:03:03+00:00

The stack output currently looks like this: 7fffffffffffffff 0000000a00000000 ffffffff81093341 0000000000000046 <0> ffff88003a545fd8 0000000000000000 0000000000000000 00007fffa39769c0 <0> ffff88003e403f58 ffffffff8102fc4c ffff88003e403f58 ffff88003e403f78 The superfluous <0> are caused by recent printk KERN_CONT change. <*> is now ignored in printk unless some text follows the level and even then it still has to be the first in the format message. Note that the log_lvl parameter is now completely ignored in show_stack_log_lvl and the stack is dumped with the default level (like for quite some time already). It behaves the same as the rest of the dump, function traces are dumped in the very same manner. Only Code and maybe some lines are printed with EMERG level. Unfortunately I see no way how to fix this conceptually to have the whole oops/BUG/panic output with the same level, so this removed only the superfluous characters for the time being. Just for illustration: <4>Process kworker/0:0 (pid: 0, threadinfo ffff88003c8a6000, task ffff88003c85c100) <0>Stack: <4> ffffffff818022c0 0000000a00000001 0000000000000001 0000000000000046 <4> ffff88003c8a7fd8 0000000000000001 ffff88003c8a7e58 0000000000000000 <4> ffff88003e503f48 ffffffff8102fc4c ffff88003e503f48 ffff88003e503f68 <0>Call Trace: <0> <4> [] ? call_softirq+0x1c/0x30 ... <0>Code: 00 01 00 00 65 8b 04 25 80 c5 00 00 c7 45 ... Signed-off-by: Jiri Slaby Cc: jirislaby@gmail.com Cc: Linus Torvalds Cc: Andrew Morton LKML-Reference: <1287586131-16222-1-git-send-email-jslaby@suse.cz> Signed-off-by: Ingo Molnar

x86: Unify dumpstack.h and stacktrace.h

2010-06-08T21:29:52+00:00

arch/x86/include/asm/stacktrace.h and arch/x86/kernel/dumpstack.h declare headers of objects that deal with the same topic. Actually most of the files that include stacktrace.h also include dumpstack.h Although dumpstack.h seems more reserved for internals of stack traces, those are quite often needed to define specialized stack trace operations. And perf event arch headers are going to need access to such low level operations anyway. So don't continue to bother with dumpstack.h as it's not anymore about isolated deep internals. v2: fix struct stack_frame definition conflict in sysprof Signed-off-by: Frederic Weisbecker Cc: Ingo Molnar Cc: H. Peter Anvin Cc: Thomas Gleixner Cc: Soeren Sandmann

perf: Drop useless check for ignored frame

2010-01-13T09:09:08+00:00

The check that ignores the debug and nmi stack frames is useless now that we have a frame pointer that makes us start at the right place. We don't anymore have to deal with these. Signed-off-by: Frederic Weisbecker Cc: Peter Zijlstra Cc: Arnaldo Carvalho de Melo Cc: Paul Mackerras LKML-Reference: <1262235183-5320-2-git-send-regression-fweisbec@gmail.com> Signed-off-by: Ingo Molnar

perf events, x86/stacktrace: Make stack walking optional

2009-12-17T08:56:19+00:00

The current print_context_stack helper that does the stack walking job is good for usual stacktraces as it walks through all the stack and reports even addresses that look unreliable, which is nice when we don't have frame pointers for example. But we have users like perf that only require reliable stacktraces, and those may want a more adapted stack walker, so lets make this function a callback in stacktrace_ops that users can tune for their needs. Signed-off-by: Frederic Weisbecker Cc: Peter Zijlstra Cc: Arnaldo Carvalho de Melo Cc: Paul Mackerras LKML-Reference: <1261024834-5336-1-git-send-regression-fweisbec@gmail.com> Signed-off-by: Ingo Molnar

x86: dumpstack: Clean up the x86_stack_ids[][] initalization and other details

2009-11-26T07:24:33+00:00

Make the initialization more readable, plus tidy up a few small visual details as well. No change in functionality. LKML-Reference: Signed-off-by: Ingo Molnar

headers: utsname.h redux

2009-09-24T01:13:10+00:00

* remove asm/atomic.h inclusion from linux/utsname.h -- not needed after kref conversion * remove linux/utsname.h inclusion from files which do not need it NOTE: it looks like fs/binfmt_elf.c do not need utsname.h, however due to some personality stuff it _is_ needed -- cowardly leave ELF-related headers and files alone. Signed-off-by: Alexey Dobriyan Signed-off-by: Linus Torvalds

perf_counter: Ignore the nmi call frames in the x86-64 backtraces

2009-07-01T20:37:23+00:00

About every callchains recorded with perf record are filled up including the internal perfcounter nmi frame: perf_callchain perf_counter_overflow intel_pmu_handle_irq perf_counter_nmi_handler notifier_call_chain atomic_notifier_call_chain notify_die do_nmi nmi We want ignore this frame as it's not interesting for instrumentation. To solve this, we simply ignore every frames from nmi context. New example of "perf report -s sym -c" after this patch: 9.59% [k] search_by_key 4.88% search_by_key reiserfs_read_locked_inode reiserfs_iget reiserfs_lookup do_lookup __link_path_walk path_walk do_path_lookup user_path_at vfs_fstatat vfs_lstat sys_newlstat system_call_fastpath __lxstat 0x406fb1 3.19% search_by_key search_by_entry_key reiserfs_find_entry reiserfs_lookup do_lookup __link_path_walk path_walk do_path_lookup user_path_at vfs_fstatat vfs_lstat sys_newlstat system_call_fastpath __lxstat 0x406fb1 [...] For now this patch only solves the problem in x86-64. Signed-off-by: Frederic Weisbecker Cc: Peter Zijlstra Cc: Mike Galbraith Cc: Paul Mackerras Cc: Anton Blanchard Cc: Arnaldo Carvalho de Melo LKML-Reference: <1246474930-6088-1-git-send-email-fweisbec@gmail.com> Signed-off-by: Ingo Molnar

ftrace: print real return in dumpstack for function graph

2008-12-03T07:56:25+00:00

Impact: better dumpstack output I noticed in my crash dumps and even in the stack tracer that a lot of functions listed in the stack trace are simply return_to_handler which is ftrace graphs way to insert its own call into the return of a function. But we lose out where the actually function was called from. This patch adds in hooks to the dumpstack mechanism that detects this and finds the real function to print. Both are printed to let the user know that a hook is still in place. This does give a funny side effect in the stack tracer output: Depth Size Location (80 entries) ----- ---- -------- 0) 4144 48 save_stack_trace+0x2f/0x4d 1) 4096 128 ftrace_call+0x5/0x2b 2) 3968 16 mempool_alloc_slab+0x16/0x18 3) 3952 384 return_to_handler+0x0/0x73 4) 3568 -240 stack_trace_call+0x11d/0x209 5) 3808 144 return_to_handler+0x0/0x73 6) 3664 -128 mempool_alloc+0x4d/0xfe 7) 3792 128 return_to_handler+0x0/0x73 8) 3664 -32 scsi_sg_alloc+0x48/0x4a [scsi_mod] As you can see, the real functions are now negative. This is due to them not being found inside the stack. Signed-off-by: Steven Rostedt Signed-off-by: Ingo Molnar