Re: nios2 crash/hang in mainline due to 'lib: update LZ4 compressor module'

[Guenter Roeck <linux@roeck-us.net>]

On Thu, Mar 09, 2017 at 03:43:40PM +0100, Tobias Klauser wrote:
> On 2017-03-09 at 14:20:51 +0100, Guenter Roeck <linux@roeck-us.net> wrote:
> > On 03/07/2017 04:46 AM, Tobias Klauser wrote:
> > [ ... ]
> > 
> > >
> > >Linux version 4.11.0-rc1-dirty (tobiask@ziws08) (gcc version 7.0.1 20170226 (experimental) (GCC) ) #46 Tue Mar 7 13:40:53 CET 2017
> > >bootconsole [early0] enabled
> > >Early console on uart16650 initialized at 0xf8001600
> > >OF: fdt: Error -11 processing FDT
> > >Kernel panic - not syncing: setup_cpuinfo: No CPU found in devicetree!
> > >
> > >---[ end Kernel panic - not syncing: setup_cpuinfo: No CPU found in devicetree!
> > >
> > >Looks like the in-memory device tree somehow gets corrupted. Not sure
> > >yet why and how this is linked to the Kconfig options selected but at
> > >least we now have a possibility to use debug messages earlier on.
> > >
> > 
> > I think I found the problem. In unflatten_and_copy_device_tree(), with added
> > debug information:
> > 
> > OF: fdt: initial_boot_params=c861e400, dt=c861f000 size=28874 (0x70ca)
> > 
> > ... and then initial_boot_params is copied to dt, which results in corrupted
> > fdt since the memory overlaps. Looks like the initial_boot_params memory
> > is not reserved and (re-)allocated by early_init_dt_alloc_memory_arch().
> 
> Thanks for the analysis. That certainly explains the issue. The
> following patch solves the issue for me. Though I'm not entirely sure if
> it is correct and that is all that is needed. Do we need to retain the
> memory for initial_boot_params after bootmem is freed?
> 

I don't know if it is correct either, but it matches what I came up with,
and it does work for me as well. Feel free to add

Tested-by: Guenter Roeck <linux@roeck-us.net>

when you submit the patch for real.

Thanks,
Guenter

> diff --git a/arch/nios2/kernel/prom.c b/arch/nios2/kernel/prom.c
> index 099f5ce1f3cb..6869fe03f3ff 100644
> --- a/arch/nios2/kernel/prom.c
> +++ b/arch/nios2/kernel/prom.c
> @@ -48,6 +48,13 @@ void * __init early_init_dt_alloc_memory_arch(u64 size, u64 align)
>  	return alloc_bootmem_align(size, align);
>  }
>  
> +int __init early_init_dt_reserve_memory_arch(phys_addr_t base,
> +					phys_addr_t size, bool nomap)
> +{
> +	reserve_bootmem(base, size, BOOTMEM_DEFAULT);
> +	return 0;
> +}
> +
>  void __init early_init_devtree(void *params)
>  {
>  	__be32 *dtb = (u32 *)__dtb_start;
> diff --git a/arch/nios2/kernel/setup.c b/arch/nios2/kernel/setup.c
> index 6e57ffa5db27..6044d9be28b4 100644
> --- a/arch/nios2/kernel/setup.c
> +++ b/arch/nios2/kernel/setup.c
> @@ -201,6 +201,9 @@ void __init setup_arch(char **cmdline_p)
>  	}
>  #endif /* CONFIG_BLK_DEV_INITRD */
>  
> +	early_init_fdt_reserve_self();
> +	early_init_fdt_scan_reserved_mem();
> +
>  	unflatten_and_copy_device_tree();
>  
>  	setup_cpuinfo();