x86/dumpstack: Remove kernel text addresses from stack dump

Printing kernel text addresses in stack dumps is of questionable value,
especially now that address randomization is becoming common.

It

x86/dumpstack: Remove kernel text addresses from stack dump

Printing kernel text addresses in stack dumps is of questionable value,
especially now that address randomization is becoming common.

It can be a security issue because it leaks kernel addresses. It also
affects the usefulness of the stack dump. Linus says:

"I actually spend time cleaning up commit messages in logs, because
useless data that isn't actually information (random hex numbers) is
actively detrimental.

It makes commit logs less legible.

It also makes it harder to parse dumps.

It's not useful. That makes it actively bad.

I probably look at more oops reports than most people. I have not
found the hex numbers useful for the last five years, because they are
just randomized crap.

The stack content thing just makes code scroll off the screen etc, for
example."

The only real downside to removing these addresses is that they can be
used to disambiguate duplicate symbol names. However such cases are
rare, and the context of the stack dump should be enough to be able to
figure it out.

There's now a 'faddr2line' script which can be used to convert a
function address to a file name and line:

$ ./scripts/faddr2line ~/k/vmlinux write_sysrq_trigger+0x51/0x60
write_sysrq_trigger+0x51/0x60:
write_sysrq_trigger at drivers/tty/sysrq.c:1098

Or gdb can be used:

$ echo "list *write_sysrq_trigger+0x51" |gdb ~/k/vmlinux |grep "is in"
(gdb) 0xffffffff815b5d83 is in driver_probe_device (/home/jpoimboe/git/linux/drivers/base/dd.c:378).

(But note that when there are duplicate symbol names, gdb will only show
the first symbol it finds. faddr2line is recommended over gdb because
it handles duplicates and it also does function size checking.)

Here's an example of what a stack dump looks like after this change:

BUG: unable to handle kernel NULL pointer dereference at (null)
IP: sysrq_handle_crash+0x45/0x80
PGD 36bfa067 [ 29.650644] PUD 7aca3067
Oops: 0002 [#1] PREEMPT SMP
Modules linked in: ...
CPU: 1 PID: 786 Comm: bash Tainted: G E 4.9.0-rc1+ #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.1-1.fc24 04/01/2014
task: ffff880078582a40 task.stack: ffffc90000ba8000
RIP: 0010:sysrq_handle_crash+0x45/0x80
RSP: 0018:ffffc90000babdc8 EFLAGS: 00010296
RAX: ffff880078582a40 RBX: 0000000000000063 RCX: 0000000000000001
RDX: 0000000000000001 RSI: 0000000000000000 RDI: 0000000000000292
RBP: ffffc90000babdc8 R08: 0000000b31866061 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000007 R14: ffffffff81ee8680 R15: 0000000000000000
FS: 00007ffb43869700(0000) GS:ffff88007d400000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000007a3e9000 CR4: 00000000001406e0
Stack:
ffffc90000babe00 ffffffff81572d08 ffffffff81572bd5 0000000000000002
0000000000000000 ffff880079606600 00007ffb4386e000 ffffc90000babe20
ffffffff81573201 ffff880036a3fd00 fffffffffffffffb ffffc90000babe40
Call Trace:
__handle_sysrq+0x138/0x220
? __handle_sysrq+0x5/0x220
write_sysrq_trigger+0x51/0x60
proc_reg_write+0x42/0x70
__vfs_write+0x37/0x140
? preempt_count_sub+0xa1/0x100
? __sb_start_write+0xf5/0x210
? vfs_write+0x183/0x1a0
vfs_write+0xb8/0x1a0
SyS_write+0x58/0xc0
entry_SYSCALL_64_fastpath+0x1f/0xc2
RIP: 0033:0x7ffb42f55940
RSP: 002b:00007ffd33bb6b18 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000046 RCX: 00007ffb42f55940
RDX: 0000000000000002 RSI: 00007ffb4386e000 RDI: 0000000000000001
RBP: 0000000000000011 R08: 00007ffb4321ea40 R09: 00007ffb43869700
R10: 00007ffb43869700 R11: 0000000000000246 R12: 0000000000778a10
R13: 00007ffd33bb5c00 R14: 0000000000000007 R15: 0000000000000010
Code: 34 e8 d0 34 bc ff 48 c7 c2 3b 2b 57 81 be 01 00 00 00 48 c7 c7 e0 dd e5 81 e8 a8 55 ba ff c7 05 0e 3f de 00 01 00 00 00 0f ae f8 <c6> 04 25 00 00 00 00 01 5d c3 e8 4c 49 bc ff 84 c0 75 c3 48 c7
RIP: sysrq_handle_crash+0x45/0x80 RSP: ffffc90000babdc8
CR2: 0000000000000000

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/69329cb29b8f324bb5fcea14d61d224807fb6488.1477405374.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

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Merge remote-tracking branch 'airlied/drm-next' into topic/drm-misc

Backmerge latest drm-next to have a baseline for the
s/fence/dma_fence/ patch from Chris.

Signed-off-by: Daniel Vetter <daniel.ve

Merge remote-tracking branch 'airlied/drm-next' into topic/drm-misc

Backmerge latest drm-next to have a baseline for the
s/fence/dma_fence/ patch from Chris.

Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>

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Merge remote-tracking branch 'airlied/drm-next' into drm-intel-next-queued

Backmerge because Chris Wilson needs the very latest&greates of
Gustavo Padovan's sync_file work, specifically the refcount

Merge remote-tracking branch 'airlied/drm-next' into drm-intel-next-queued

Backmerge because Chris Wilson needs the very latest&greates of
Gustavo Padovan's sync_file work, specifically the refcounting changes
from:

commit 30cd85dd6edc86ea8d8589efb813f1fad41ef233
Author: Gustavo Padovan <gustavo.padovan@collabora.co.uk>
Date: Wed Oct 19 15:48:32 2016 -0200

dma-buf/sync_file: hold reference to fence when creating sync_file

Also good to sync in general since git tends to get confused with the
cherry-picking going on.

Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>

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Merge tag 'v4.9-rc1' into patchwork

Linux 4.9-rc1

* tag 'v4.9-rc1': (13774 commits)
Linux 4.9-rc1
score: traps: Add missing include file to fix build error
fs/super.c: don't fool lockdep in f

Merge tag 'v4.9-rc1' into patchwork

Linux 4.9-rc1

* tag 'v4.9-rc1': (13774 commits)
Linux 4.9-rc1
score: traps: Add missing include file to fix build error
fs/super.c: don't fool lockdep in freeze_super() and thaw_super() paths
fs/super.c: fix race between freeze_super() and thaw_super()
overlayfs: Fix setting IOP_XATTR flag
iov_iter: kernel-doc import_iovec() and rw_copy_check_uvector()
CIFS: Retrieve uid and gid from special sid if enabled
CIFS: Add new mount option to set owner uid and gid from special sids in acl
qedr: Add events support and register IB device
qedr: Add GSI support
qedr: Add LL2 RoCE interface
qedr: Add support for data path
qedr: Add support for memory registeration verbs
qedr: Add support for QP verbs
qedr: Add support for PD,PKEY and CQ verbs
qedr: Add support for user context verbs
qedr: Add support for RoCE HW init
qedr: Add RoCE driver framework
pkeys: Remove easily triggered WARN
MIPS: Wire up new pkey_{mprotect,alloc,free} syscalls
...

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Merge tag 'v4.8' into next

Sync up with mainline to bring in I2C host notify changes and other
updates.

Merge branches 'pm-cpufreq-fixes' and 'pm-sleep-fixes'

* pm-cpufreq-fixes:
cpufreq: intel_pstate: Always set max P-state in performance mode
cpufreq: intel_pstate: Set P-state upfront in perform

Merge branches 'pm-cpufreq-fixes' and 'pm-sleep-fixes'

* pm-cpufreq-fixes:
cpufreq: intel_pstate: Always set max P-state in performance mode
cpufreq: intel_pstate: Set P-state upfront in performance mode

* pm-sleep-fixes:
PM / suspend: Fix missing KERN_CONT for suspend message

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Merge branch 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull low-level x86 updates from Ingo Molnar:
"In this cycle this topic tree has become one of those 'super

Merge branch 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull low-level x86 updates from Ingo Molnar:
"In this cycle this topic tree has become one of those 'super topics'
that accumulated a lot of changes:

- Add CONFIG_VMAP_STACK=y support to the core kernel and enable it on
x86 - preceded by an array of changes. v4.8 saw preparatory changes
in this area already - this is the rest of the work. Includes the
thread stack caching performance optimization. (Andy Lutomirski)

- switch_to() cleanups and all around enhancements. (Brian Gerst)

- A large number of dumpstack infrastructure enhancements and an
unwinder abstraction. The secret long term plan is safe(r) live
patching plus maybe another attempt at debuginfo based unwinding -
but all these current bits are standalone enhancements in a frame
pointer based debug environment as well. (Josh Poimboeuf)

- More __ro_after_init and const annotations. (Kees Cook)

- Enable KASLR for the vmemmap memory region. (Thomas Garnier)"

[ The virtually mapped stack changes are pretty fundamental, and not
x86-specific per se, even if they are only used on x86 right now. ]

* 'x86-asm-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (70 commits)
x86/asm: Get rid of __read_cr4_safe()
thread_info: Use unsigned long for flags
x86/alternatives: Add stack frame dependency to alternative_call_2()
x86/dumpstack: Fix show_stack() task pointer regression
x86/dumpstack: Remove dump_trace() and related callbacks
x86/dumpstack: Convert show_trace_log_lvl() to use the new unwinder
oprofile/x86: Convert x86_backtrace() to use the new unwinder
x86/stacktrace: Convert save_stack_trace_*() to use the new unwinder
perf/x86: Convert perf_callchain_kernel() to use the new unwinder
x86/unwind: Add new unwind interface and implementations
x86/dumpstack: Remove NULL task pointer convention
fork: Optimize task creation by caching two thread stacks per CPU if CONFIG_VMAP_STACK=y
sched/core: Free the stack early if CONFIG_THREAD_INFO_IN_TASK
lib/syscall: Pin the task stack in collect_syscall()
x86/process: Pin the target stack in get_wchan()
x86/dumpstack: Pin the target stack when dumping it
kthread: Pin the stack via try_get_task_stack()/put_task_stack() in to_live_kthread() function
sched/core: Add try_get_task_stack() and put_task_stack()
x86/entry/64: Fix a minor comment rebase error
iommu/amd: Don't put completion-wait semaphore on stack
...

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Merge tag 'irqchip-4.9-1' of git://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms into irq/core

Merge the first drop of irqchip updates for 4.9 from Marc Zyngier:

- ACPI IORT core code
-

Merge tag 'irqchip-4.9-1' of git://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms into irq/core

Merge the first drop of irqchip updates for 4.9 from Marc Zyngier:

- ACPI IORT core code
- IORT support for the GICv3 ITS
- A few of GIC cleanups

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x86/dumpstack: Remove show_trace()

There are a bewildering array of options for dumping the stack.
Simplify things a little by removing show_trace(), which is unused.

Signed-off-by: Josh Poimboeuf

x86/dumpstack: Remove show_trace()

There are a bewildering array of options for dumping the stack.
Simplify things a little by removing show_trace(), which is unused.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Byungchul Park <byungchul.park@lge.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Nilay Vaish <nilayvaish@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/fe02292eac9d409001ec0cf6d06f90ced242570d.1471535549.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

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Merge remote-tracking branch 'airlied/drm-next' into drm-intel-next-queued

Backmerge because too many conflicts, and also we need to get at the
latest struct fence patches from Gustavo. Requested by

Merge remote-tracking branch 'airlied/drm-next' into drm-intel-next-queued

Backmerge because too many conflicts, and also we need to get at the
latest struct fence patches from Gustavo. Requested by Chris Wilson.

Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>

show more ...

Merge branch 'linus' into x86/microcode, to pick up merge window changes

Signed-off-by: Ingo Molnar <mingo@kernel.org>

Merge branch 'x86-debug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 stackdump update from Ingo Molnar:
"A number of stackdump enhancements"

* 'x86-debug-for-linus'

Merge branch 'x86-debug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 stackdump update from Ingo Molnar:
"A number of stackdump enhancements"

* 'x86-debug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/dumpstack: Add show_stack_regs() and use it
printk: Make the printk*once() variants return a value
x86/dumpstack: Honor supplied @regs arg

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x86/dumpstack: Add show_stack_regs() and use it

Add a helper to dump supplied pt_regs and use it in the MSR exception
handling code to have precise stack traces pointing to the actual
function causi

x86/dumpstack: Add show_stack_regs() and use it

Add a helper to dump supplied pt_regs and use it in the MSR exception
handling code to have precise stack traces pointing to the actual
function causing the MSR access exception and not the stack frame of the
exception handler itself.

The new output looks like this:

unchecked MSR access error: RDMSR from 0xdeadbeef at rIP: 0xffffffff8102ddb6 (early_init_intel+0x16/0x3a0)
00000000756e6547 ffffffff81c03f68 ffffffff81dd0940 ffffffff81c03f10
ffffffff81d42e65 0000000001000000 ffffffff81c03f58 ffffffff81d3e5a3
0000800000000000 ffffffff81800080 ffffffffffffffff 0000000000000000
Call Trace:
[<ffffffff81d42e65>] early_cpu_init+0xe7/0x136
[<ffffffff81d3e5a3>] setup_arch+0xa5/0x9df
[<ffffffff81d38bb9>] start_kernel+0x9f/0x43a
[<ffffffff81d38294>] x86_64_start_reservations+0x2f/0x31
[<ffffffff81d383fe>] x86_64_start_kernel+0x168/0x176

Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1467671487-10344-4-git-send-email-bp@alien8.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

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Merge remote-tracking branch 'linusw-gpio/for-next' into devm_gpiochip

Base for demv_gpiochip_add_data() and devm_gpiochip_remove().

Merge tag 'v4.4'

Linux 4.4

Orangefs: Merge tag 'v4.4-rc1' into for-next

Linux 4.4-rc1

Merge branch 'next' into for-linus

Prepare first round of input updates for 4.5 merge window.

Merge back earlier 'pm-domains' material for v4.5.

Merge branches 'acpi-pci' and 'pm-pci'

* acpi-pci:
x86/PCI/ACPI: Fix regression caused by commit 4d6b4e69a245

* pm-pci:
PCI / PM: Tune down retryable runtime suspend error messages

Merge tag 'v4.4-rc3' into next

Merge with Linux 4.4-rc3 to bring in helpers for multiu-driver modules.

Merge tag 'asoc-fix-v4.4-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound into for-linus

ASoC: Fixes for v4.4

Quite a large batch of fixes have come in since the merge window, ma

Merge tag 'asoc-fix-v4.4-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/broonie/sound into for-linus

ASoC: Fixes for v4.4

Quite a large batch of fixes have come in since the merge window, mainly
driver specific ones but there's a couple of core ones:

- A fix for DAPM resume on active streams to ensure everything ends up
cleanly in the right state.
- Reset the DAPM cache when freeing widgets to fix a crash on driver
remove and reload.

The PM functions for nau8825 are new code which fix crashes on resume.

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Merge tag 'v4.4-rc1' into HEAD

Linux 4.4-rc1

Sync to Linus v4.4-rc2 for LSM developers.

Merge tag 'v4.4-rc2' into drm-intel-next-queued

Linux 4.4-rc2

Backmerge to get at

commit 1b0e3a049efe471c399674fd954500ce97438d30
Author: Imre Deak <imre.deak@intel.com>
Date: Thu Nov 5 23:04:11

Merge tag 'v4.4-rc2' into drm-intel-next-queued

Linux 4.4-rc2

Backmerge to get at

commit 1b0e3a049efe471c399674fd954500ce97438d30
Author: Imre Deak <imre.deak@intel.com>
Date: Thu Nov 5 23:04:11 2015 +0200

drm/i915/skl: disable display side power well support for now

so that we can proplery re-eanble skl power wells in -next.

Conflicts are just adjacent lines changed, except for intel_fbdev.c
where we need to interleave the changs. Nothing nefarious.

Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>

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Merge tag 'v4.4-rc1' into patchwork

Linux 4.4-rc1

* tag 'v4.4-rc1': (12900 commits)
Linux 4.4-rc1
ARC: Fix silly typo in MAINTAINERS file
ARC: cpu_relax() to be compiler barrier even for UP

Merge tag 'v4.4-rc1' into patchwork

Linux 4.4-rc1

* tag 'v4.4-rc1': (12900 commits)
Linux 4.4-rc1
ARC: Fix silly typo in MAINTAINERS file
ARC: cpu_relax() to be compiler barrier even for UP
ARC: use ASL assembler mnemonic
ARC: [arcompact] Handle bus error from userspace as Interrupt not exception
ARC: remove extraneous header include
f2fs: xattr simplifications
squashfs: xattr simplifications
9p: xattr simplifications
xattr handlers: Pass handler to operations instead of flags
jffs2: Add missing capability check for listing trusted xattrs
hfsplus: Remove unused xattr handler list operations
ubifs: Remove unused security xattr handler
vfs: Fix the posix_acl_xattr_list return value
vfs: Check attribute names in posix acl xattr handers
mpt3sas: fix inline markers on non inline function declarations
dax: fix __dax_pmd_fault crash
Revert "drm/rockchip: Convert the probe function to the generic drm_of_component_probe()"
drm: Don't oops in drm_calc_timestamping_constants() if drm_vblank_init() wasn't called
ALSA: pci: depend on ZONE_DMA
...

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