Subject: [PATCH v22 2/8] arm64: limit memory regions based on DT property, usable-memory-range

From: [email-masked] (James Morse)
Date: Mon, 18 Jul 2016 19:04:33 +0100

Hi!

(CC: Dennis Chen)

On 12/07/16 06:05, AKASHI Takahiro wrote:
> Crash dump kernel will be run with a limited range of memory as System
> RAM.
> 
> On arm64, we will use a device-tree property under /chosen,
>    linux,usable-memory-range = <BASE SIZE>
> in order for primary kernel either on uefi or non-uefi (device tree only)
> system to hand over the information about usable memory region to crash
> dump kernel. This property will supercede entries in uefi memory map table
> and "memory" nodes in a device tree.

> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> index 51b1302..d8b296f 100644
> --- a/arch/arm64/mm/init.c
> +++ b/arch/arm64/mm/init.c
> @@ -300,10 +300,48 @@ static int __init early_mem(char *p)
>  }
>  early_param("mem", early_mem);
>  
> +static int __init early_init_dt_scan_usablemem(unsigned long node,
> +		const char *uname, int depth, void *data)
> +{
> +	struct memblock_region *usablemem = (struct memblock_region *)data;
> +	const __be32 *reg;
> +	int len;
> +
> +	usablemem->size = 0;
> +
> +	if (depth != 1 || strcmp(uname, "chosen") != 0)
> +		return 0;
> +
> +	reg = of_get_flat_dt_prop(node, "linux,usable-memory-range", &len);
> +	if (!reg || (len < (dt_root_addr_cells + dt_root_size_cells)))
> +		return 1;
> +
> +	usablemem->base = dt_mem_next_cell(dt_root_addr_cells, &reg);
> +	usablemem->size = dt_mem_next_cell(dt_root_size_cells, &reg);
> +
> +	return 1;
> +}
> +
> +static void __init fdt_enforce_memory_region(void)
> +{
> +	struct memblock_region reg;
> +
> +	of_scan_flat_dt(early_init_dt_scan_usablemem, &reg);
> +
> +	if (reg.size) {
> +		memblock_remove(0, PAGE_ALIGN(reg.base));
> +		memblock_remove(round_down(reg.base + reg.size, PAGE_SIZE),
> +				ULLONG_MAX);

I think this is a new way to trip the problem Dennis Chen has been working on
[0]. If I kdump with --reuse-cmdline on a kernel booted with 'acpi=on', I get
the panic below [1]...

It looks like Dennis's fix involves changes in mm/memblock.c, maybe they can be
extended to support a range instead of just a limit?

(It looks like x86 explicitly adds the acpi regions to the crash-kernels memory
map in crash_setup_memmap_entries()).

Is it possible for the kernel text to be outside this range? (a bug in
kexec-tools, or another user of the DT property) If we haven't already failed in
this case, it may be worth printing a warning, or refusing to
restrict-memory/expose-vmcore.

Thanks,

James

[0] http://lists.infradead.org/pipermail/linux-arm-kernel/2016-July/443356.html
[1]
[    0.000000] efi: Getting EFI parameters from FDT:
[    0.000000] efi: EFI v2.50 by ARM Juno EFI Nov 24 2015 12:36:35
[    0.000000] efi:  ACPI=0xf95b0000  ACPI 2.0=0xf95b0014  PROP=0xfe8db4d8
[    0.000000] Reserving 1KB of memory at 0x9fffff000 for elfcorehdr
[    0.000000] cma: Reserved 16 MiB at 0x00000009fec00000
[    0.000000] ACPI: Early table checksum verification disabled
[    0.000000] ACPI: RSDP 0x00000000F95B0014 000024 (v02 ARMLTD)
[    0.000000] ACPI: XSDT 0x00000000F95A00E8 00004C (v01 ARMLTD ARM-JUNO 2014072
7      01000013)
[    0.000000] ACPI: FACP 0x00000000F9500000 00010C (v05 ARMLTD ARM-JUNO 2014072
7 ARM  00000099)
[    0.000000] ACPI: DSDT 0x00000000F94C0000 000396 (v01 ARMLTD ARM-JUNO 2014072
7 INTL 20150619)
[    0.000000] ACPI: GTDT 0x00000000F94F0000 000060 (v02 ARMLTD ARM-JUNO 2014072
7 ARM  00000099)
[    0.000000] ACPI: APIC 0x00000000F94E0000 000224 (v03 ARMLTD ARM-JUNO 2014072
7 ARM  00000099)
[    0.000000] ACPI: SSDT 0x00000000F94D0000 0001E3 (v01 ARMLTD ARM-JUNO 2014072
7 INTL 20150619)
[    0.000000] ACPI: MCFG 0x00000000F94B0000 00003C (v01 ARMLTD ARM-JUNO 2014072
7 ARM  00000099)
...
[    0.737577] Serial: AMBA PL011 UART driver
[    0.786086] HugeTLB registered 2 MB page size, pre-allocated 0 pages
[    0.794203] ACPI: Added _OSI(Module Device)
[    0.798659] ACPI: Added _OSI(Processor Device)
[    0.803190] ACPI: Added _OSI(3.0 _SCP Extensions)
[    0.807973] ACPI: Added _OSI(Processor Aggregator Device)
[    0.813653] Unable to handle kernel paging request at virtual address ffff000
00804e027
[    0.821704] pgd = ffff000008cce000
[    0.825155] [ffff00000804e027] *pgd=00000009ffffd003, *pud=00000009ffffc003,
*pmd=00000009ffffb003, *pte=00e80000f94c0707
[    0.836319] Internal error: Oops: 96000021 [#1] PREEMPT SMP
[    0.841972] Modules linked in:
[    0.845073] CPU: 2 PID: 1 Comm: swapper/0 Tainted: G S              4.7.0-rc4
+ #4569
[    0.852927] Hardware name: ARM Juno development board (r1) (DT)
[    0.858936] task: ffff80003d898000 ti: ffff80003d894000 task.ti: ffff80003d89
4000
[    0.866537] PC is at acpi_ns_lookup+0x23c/0x378
[    0.871131] LR is at acpi_ds_load1_begin_op+0x88/0x260
[    0.876340] pc : [<ffff0000084061a4>] lr : [<ffff0000083fc08c>] pstate: 60000
045
[    0.883846] sp : ffff80003d8979b0
[    0.887206] x29: ffff80003d8979b0 x28: 0000000000000000
[    0.892596] x27: 000000000000001b x26: ffff000008a80a07
[    0.897986] x25: ffff80003d897a48 x24: 0000000000000001
[    0.903377] x23: 0000000000000001 x22: ffff00000804e027
[    0.908769] x21: 000000000000001b x20: 0000000000000001
[    0.914158] x19: 0000000000000000 x18: ffff00000804efff
[    0.919547] x17: 00000000000038ff x16: 0000000000000002
[    0.924937] x15: ffff00000804efff x14: 0000008000000000
[    0.930326] x13: ffff000008c942b2 x12: ffff00000804efff
[    0.935717] x11: ffff000008bf0000 x10: 00000000ffffff76
[    0.941107] x9 : 0000000000000000 x8 : ffff000008cb6000
[    0.946498] x7 : 0000000000000000 x6 : ffff80003d897aa8
[    0.951891] x5 : ffff80003d028400 x4 : 0000000000000001
[    0.957281] x3 : 0000000000000003 x2 : ffff000008cb6090
[    0.962673] x1 : 000000000000005f x0 : 0000000000000000
[    0.968063]
[    0.969569] Process swapper/0 (pid: 1, stack limit = 0xffff80003d894020)
[    1.387661] Call trace:
...
[    1.473172] [<ffff0000084061a4>] acpi_ns_lookup+0x23c/0x378
[    1.478832] [<ffff0000083fc08c>] acpi_ds_load1_begin_op+0x88/0x260
[    1.485105] [<ffff00000840c0e8>] acpi_ps_build_named_op+0xa8/0x170
[    1.491378] [<ffff00000840c2e0>] acpi_ps_create_op+0x130/0x230
[    1.497299] [<ffff00000840bc28>] acpi_ps_parse_loop+0x168/0x580
[    1.503302] [<ffff00000840cb44>] acpi_ps_parse_aml+0xa0/0x278
[    1.509135] [<ffff0000084081d0>] acpi_ns_one_complete_parse+0x128/0x150
[    1.515852] [<ffff00000840821c>] acpi_ns_parse_table+0x24/0x44
[    1.521775] [<ffff0000084079e8>] acpi_ns_load_table+0x54/0xdc
[    1.527612] [<ffff000008411038>] acpi_tb_load_namespace+0xd0/0x230
[    1.533887] [<ffff000008b2695c>] acpi_load_tables+0x3c/0xa8
[    1.539542] [<ffff000008b25974>] acpi_init+0x88/0x2b0
[    1.544670] [<ffff000008081a08>] do_one_initcall+0x38/0x128
[    1.550325] [<ffff000008b00cc0>] kernel_init_freeable+0x14c/0x1f0
[    1.556517] [<ffff0000087d2088>] kernel_init+0x10/0x100
[    1.561823] [<ffff000008084e10>] ret_from_fork+0x10/0x40
[    1.567216] Code: b9008fbb 2a000318 36380054 32190318 (b94002c0)
[    1.573451] ---[ end trace dec6cecdcba673b7 ]---
[    1.578158] Kernel panic - not syncing: Attempted to kill init! exitcode=0x00
00000b
[    1.578158]
[    1.587428] SMP: stopping secondary CPUs
[    1.591411] ---[ end Kernel panic - not syncing: Attempted to kill init! exit
code=0x0000000b
[    0.969225] Process swapper/0 (pid: 1, stack limit = 0xffff80003d894020)