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[ Upstream commit3dc709e518] When CONFIG_FSL_PMC is set to n, no value is assigned to cpu_up_prepare in the mpc85xx_pm_ops structure. As a result, oops is triggered in smp_85xx_start_cpu(). smp: Bringing up secondary CPUs ... kernel tried to execute user page (0) - exploit attempt? (uid: 0) BUG: Unable to handle kernel instruction fetch (NULL pointer?) Faulting instruction address: 0x00000000 Oops: Kernel access of bad area, sig: 11 [#1] ... NIP [00000000] 0x0 LR [c0021d2c] smp_85xx_kick_cpu+0xe8/0x568 Call Trace: [c1051da8] [c0021cb8] smp_85xx_kick_cpu+0x74/0x568 (unreliable) [c1051de8] [c0011460] __cpu_up+0xc0/0x228 [c1051e18] [c0031bbc] bringup_cpu+0x30/0x224 [c1051e48] [c0031f3c] cpu_up.constprop.0+0x180/0x33c [c1051e88] [c00322e8] bringup_nonboot_cpus+0x88/0xc8 [c1051eb8] [c07e67bc] smp_init+0x30/0x78 [c1051ed8] [c07d9e28] kernel_init_freeable+0x118/0x2a8 [c1051f18] [c00032d8] kernel_init+0x14/0x124 [c1051f38] [c0010278] ret_from_kernel_thread+0x14/0x1c Fixes:c45361abb9("powerpc/85xx: fix timebase sync issue when CONFIG_HOTPLUG_CPU=n") Reported-by: Martin Kennedy <hurricos@gmail.com> Signed-off-by: Xiaoming Ni <nixiaoming@huawei.com> Tested-by: Martin Kennedy <hurricos@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20211126041153.16926-1-nixiaoming@huawei.com Signed-off-by: Sasha Levin <sashal@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
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.