From 67556d7a851c20116923c23f1d49ecdec954e3a0 Mon Sep 17 00:00:00 2001 From: Russell King Date: Wed, 19 Jul 2017 23:01:38 +0100 Subject: [PATCH] ARM: kexec: avoid allocating crashkernel region outside lowmem 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 : [] lr : [] 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) ... [] (memcpy) from [] (machine_kexec+0xa8/0x12c) [] (machine_kexec) from [] (__crash_kexec+0x5c/0x98) [] (__crash_kexec) from [] (crash_kexec+0x5c/0x68) [] (crash_kexec) from [] (die+0x228/0x490) [] (die) from [] (__do_kernel_fault.part.0+0x54/0x1e4) [] (__do_kernel_fault.part.0) from [] (do_page_fault+0x1e8/0x400) [] (do_page_fault) from [] (do_DataAbort+0x38/0xb8) [] (do_DataAbort) from [] (__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 Tested-by: Keerthy Signed-off-by: Russell King --- arch/arm/kernel/setup.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c index 4e80bf7420d4..8e9a3e40d949 100644 --- a/arch/arm/kernel/setup.c +++ b/arch/arm/kernel/setup.c @@ -987,6 +987,9 @@ static void __init reserve_crashkernel(void) if (crash_base <= 0) { unsigned long long crash_max = idmap_to_phys((u32)~0); + unsigned long long lowmem_max = __pa(high_memory - 1) + 1; + if (crash_max > lowmem_max) + crash_max = lowmem_max; crash_base = memblock_find_in_range(CRASH_ALIGN, crash_max, crash_size, CRASH_ALIGN); if (!crash_base) { -- 2.11.0