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Linux kernel for uConsole
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Naveen N. Rao c179ea2701 powerpc/kprobes: Fix warnings from __this_cpu_read() on preempt kernels 
Kamalesh pointed out that we are getting the below call traces with
livepatched functions when we enable CONFIG_PREEMPT:

[  495.470721] BUG: using __this_cpu_read() in preemptible [00000000] code: cat/8394
[  495.471167] caller is is_current_kprobe_addr+0x30/0x90
[  495.471171] CPU: 4 PID: 8394 Comm: cat Tainted: G              K 4.13.0-rc7-nnr+ #95
[  495.471173] Call Trace:
[  495.471178] [c00000008fd9b960] [c0000000009f039c] dump_stack+0xec/0x160 (unreliable)
[  495.471184] [c00000008fd9b9a0] [c00000000059169c] check_preemption_disabled+0x15c/0x170
[  495.471187] [c00000008fd9ba30] [c000000000046460] is_current_kprobe_addr+0x30/0x90
[  495.471191] [c00000008fd9ba60] [c00000000004e9a0] ftrace_call+0x1c/0xb8
[  495.471195] [c00000008fd9bc30] [c000000000376fd8] seq_read+0x238/0x5c0
[  495.471199] [c00000008fd9bcd0] [c0000000003cfd78] proc_reg_read+0x88/0xd0
[  495.471203] [c00000008fd9bd00] [c00000000033e5d4] __vfs_read+0x44/0x1b0
[  495.471206] [c00000008fd9bd90] [c0000000003402ec] vfs_read+0xbc/0x1b0
[  495.471210] [c00000008fd9bde0] [c000000000342138] SyS_read+0x68/0x110
[  495.471214] [c00000008fd9be30] [c00000000000bc6c] system_call+0x58/0x6c

Commit c05b8c4474 ("powerpc/kprobes: Skip livepatch_handler() for
jprobes") introduced a helper is_current_kprobe_addr() to help determine
if the current function has been livepatched or if it has a jprobe
installed, both of which modify the NIP. This was subsequently renamed
to __is_active_jprobe().

In the case of a jprobe, kprobe_ftrace_handler() disables pre-emption
before calling into setjmp_pre_handler() which returns without disabling
pre-emption. This is done to ensure that the jprobe handler won't
disappear beneath us if the jprobe is unregistered between the
setjmp_pre_handler() and the subsequent longjmp_break_handler() called
from the jprobe handler. Due to this, we can use __this_cpu_read() in
__is_active_jprobe() with the pre-emption check as we know that
pre-emption will be disabled.

However, if this function has been livepatched, we are still doing this
check and when we do so, pre-emption won't necessarily be disabled. This
results in the call trace shown above.

Fix this by only invoking __is_active_jprobe() when pre-emption is
disabled. And since we now guard this within a pre-emption check, we can
instead use raw_cpu_read() to get the current_kprobe value skipping the
check done by __this_cpu_read().

Fixes: c05b8c4474 ("powerpc/kprobes: Skip livepatch_handler() for jprobes")
Reported-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
Tested-by: Kamalesh Babulal <kamalesh@linux.vnet.ibm.com>
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
2017-10-04 23:42:20 +11:00
arch powerpc/kprobes: Fix warnings from __this_cpu_read() on preempt kernels 2017-10-04 23:42:20 +11:00
block block: directly insert blk-mq request from blk_insert_cloned_request() 2017-09-11 16:43:57 -06:00
certs modsign: add markers to endif-statements in certs/Makefile 2017-07-14 11:01:37 +10:00
crypto crypto: af_alg - update correct dst SGL entry 2017-09-20 17:42:42 +08:00
Documentation DeviceTree fixes for 4.14: 2017-09-24 16:04:12 -07:00
drivers cxl: Set the valid bit in PE for dedicated mode 2017-10-03 16:03:46 +11:00
firmware firmware: Restore support for built-in firmware 2017-09-16 10:58:48 -07:00
fs Various SMB3 fixes for stable and security improvements from the recently completed SMB3/Samba test events 2017-09-22 16:11:48 -10:00
include DeviceTree fixes for 4.14: 2017-09-24 16:04:12 -07:00
init Merge branch 'work.mount' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2017-09-14 18:54:01 -07:00
ipc ipc/shm: Fix order of parameters when calling copy_compat_shmid_to_user 2017-09-20 23:27:48 -04:00
kernel Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2017-09-23 05:41:27 -10:00
lib Merge branch 'parisc-4.14-2' of git://git.kernel.org/pub/scm/linux/kernel/git/deller/parisc-linux 2017-09-23 06:14:06 -10:00
mm Merge branch 'work.read_write' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2017-09-14 19:29:55 -07:00
net Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2017-09-23 05:41:27 -10:00
samples media updates for v4.14-rc1 2017-09-07 12:53:14 -07:00
scripts DeviceTree fixes for 4.14: 2017-09-24 16:04:12 -07:00
security Merge branch 'next-general' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security 2017-09-24 11:40:41 -07:00
sound vfs: constify path argument to kernel_read_file_from_path 2017-09-14 20:18:45 -07:00
tools Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2017-09-24 12:33:58 -07:00
usr ramfs: clarify help text that compression applies to ramfs as well as legacy ramdisk. 2017-07-06 16:24:30 -07:00
virt Revert "KVM: Don't accept obviously wrong gsi values via KVM_IRQFD" 2017-09-19 08:37:17 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore kbuild: Add support to generate LLVM assembly files 2017-04-25 08:13:52 +09:00
.mailmap power supply and reset changes for the v4.12 series (part 2) 2017-05-12 12:02:21 -07:00
COPYING
CREDITS selinux/stable-4.14 PR 20170831 2017-09-12 13:21:00 -07:00
Kbuild kbuild: Consolidate header generation from ASM offset information 2017-04-13 05:43:37 +09:00
Kconfig
MAINTAINERS Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2017-09-23 05:41:27 -10:00
Makefile Linux 4.14-rc2 2017-09-24 16:38:56 -07:00
README README: add a new README file, pointing to the Documentation/ 2016-10-24 08:12:35 -02:00

README 

Linux kernel
============

This file was moved to Documentation/admin-guide/README.rst

Please notice that there are several guides for kernel developers and users.
These guides can be rendered in a number of formats, like HTML and PDF.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.