67556d7a85
Allocating the crashkernel region outside lowmem causes the kernel to oops while trying to kexec into the new kernel: Loading crashdump kernel... Unable to handle kernel NULL pointer dereference at virtual address 00000000 pgd = edd70000 [00000000] *pgd=de19e835 Internal error: Oops: 817 [#2] SMP ARM Modules linked in: ... CPU: 0 PID: 689 Comm: sh Not tainted 4.12.0-rc3-next-20170601-04015-gc3a5a20 Hardware name: Generic DRA74X (Flattened Device Tree) task: edb32f00 task.stack: edf18000 PC is at memcpy+0x50/0x330 LR is at 0xe3c34001 pc : [<c04baf30>] lr : [<e3c34001>] psr: 800c0193 sp : edf19c2c ip : 0a000001 fp : c0553170 r10: c055316e r9 : 00000001 r8 : e3130001 r7 : e4903004 r6 : 0a000014 r5 : e3500000 r4 : e59f106c r3 : e59f0074 r2 : ffffffe8 r1 : c010fb88 r0 : 00000000 Flags: Nzcv IRQs off FIQs on Mode SVC_32 ISA ARM Segment none Control: 10c5387d Table: add7006a DAC: 00000051 Process sh (pid: 689, stack limit = 0xedf18218) Stack: (0xedf19c2c to 0xedf1a000) ... [<c04baf30>] (memcpy) from [<c010fae0>] (machine_kexec+0xa8/0x12c) [<c010fae0>] (machine_kexec) from [<c01e4104>] (__crash_kexec+0x5c/0x98) [<c01e4104>] (__crash_kexec) from [<c01e419c>] (crash_kexec+0x5c/0x68) [<c01e419c>] (crash_kexec) from [<c010c5c0>] (die+0x228/0x490) [<c010c5c0>] (die) from [<c011e520>] (__do_kernel_fault.part.0+0x54/0x1e4) [<c011e520>] (__do_kernel_fault.part.0) from [<c082412c>] (do_page_fault+0x1e8/0x400) [<c082412c>] (do_page_fault) from [<c010135c>] (do_DataAbort+0x38/0xb8) [<c010135c>] (do_DataAbort) from [<c0823584>] (__dabt_svc+0x64/0xa0) This is caused by image->control_code_page being a highmem page, so page_address(image->control_code_page) returns NULL. In any case, we don't want the control page to be a highmem page. We already limit the crash kernel region to the top of 32-bit physical memory space. Also limit it to the top of lowmem in physical space. Reported-by: Keerthy <j-keerthy@ti.com> Tested-by: Keerthy <j-keerthy@ti.com> Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
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.