linux-kernel - Re: [PATCH] nios2: reserve boot memory for device tree

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Date:   Mon, 03 Apr 2017 06:19:21 -0700
From:   Ley Foon Tan <ley.foon.tan@...el.com>
To:     Tobias Klauser <tklauser@...tanz.ch>,
        nios2-dev@...ts.rocketboards.org
Cc:     Guenter Roeck <linux@...ck-us.net>, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org,
        "lftan.linux@...il.com" <lftan.linux@...il.com>
Subject: Re: [PATCH] nios2: reserve boot memory for device tree

On Fri, 2017-03-31 at 11:40 +0200, Tobias Klauser wrote:
> Make sure to reserve the boot memory for the flattened device tree.
> Otherwise it might get overwritten, e.g. when initial_boot_params is
> copied, leading to a corrupted FDT and a boot hang/crash:
> 
>   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!
> 
> Guenter Roeck says:
> 
> > 
> > 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().
> Cc: stable@...r.kernel.org
> Reported-by: Guenter Roeck <linux@...ck-us.net>
> Reference: http://lkml.kernel.org/r/20170226210338.GA19476@roeck-us.n
> et
> Tested-by: Guenter Roeck <linux@...ck-us.net>
> Signed-off-by: Tobias Klauser <tklauser@...tanz.ch>

Acked-by: Ley Foon Tan <ley.foon.tan@...el.com>

Thanks for the fix. Will add this for 4.11.

Regards
Ley Foon

> ---
>  arch/nios2/kernel/prom.c  | 7 +++++++
>  arch/nios2/kernel/setup.c | 3 +++
>  2 files changed, 10 insertions(+)
> 
> diff --git a/arch/nios2/kernel/prom.c b/arch/nios2/kernel/prom.c
> index 367c5426157b..3901b80d4420 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();
> --
> 2.12.2.399.g034667a45805
> 
> 
> 
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