linux-kernel - Re: [PATCH v16 11/12] powerpc: Use OF alloc and free for FDT

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Date:   Mon, 08 Feb 2021 15:12:59 +1100
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Rob Herring <robh@...nel.org>,
        Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>
Cc:     Mimi Zohar <zohar@...ux.ibm.com>,
        Thiago Jung Bauermann <bauerman@...ux.ibm.com>,
        "AKASHI, Takahiro" <takahiro.akashi@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Will Deacon <will@...nel.org>, Joe Perches <joe@...ches.com>,
        Catalin Marinas <catalin.marinas@....com>,
        James Morse <james.morse@....com>,
        Sasha Levin <sashal@...nel.org>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Frank Rowand <frowand.list@...il.com>,
        vincenzo.frascino@....com, Mark Rutland <mark.rutland@....com>,
        dmitry.kasatkin@...il.com, James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Pavel Tatashin <pasha.tatashin@...een.com>,
        Allison Randal <allison@...utok.net>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Bhupesh Sharma <bhsharma@...hat.com>,
        Matthias Brugger <mbrugger@...e.com>,
        Hsin-Yi Wang <hsinyi@...omium.org>, tao.li@...o.com,
        Christophe Leroy <christophe.leroy@....fr>,
        Prakhar Srivastava <prsriva@...ux.microsoft.com>,
        balajib@...ux.microsoft.com, linux-integrity@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        devicetree@...r.kernel.org,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>
Subject: Re: [PATCH v16 11/12] powerpc: Use OF alloc and free for FDT

Rob Herring <robh@...nel.org> writes:
> On Thu, Feb 4, 2021 at 10:42 AM Lakshmi Ramasubramanian
> <nramas@...ux.microsoft.com> wrote:
...
>> diff --git a/arch/powerpc/kexec/elf_64.c b/arch/powerpc/kexec/elf_64.c
>> index d0e459bb2f05..51d2d8eb6c1b 100644
>> --- a/arch/powerpc/kexec/elf_64.c
>> +++ b/arch/powerpc/kexec/elf_64.c
>> @@ -19,6 +19,7 @@
>>  #include <linux/kexec.h>
>>  #include <linux/libfdt.h>
>>  #include <linux/module.h>
>> +#include <linux/of.h>
>>  #include <linux/of_fdt.h>
>>  #include <linux/slab.h>
>>  #include <linux/types.h>
>> @@ -32,7 +33,7 @@ static void *elf64_load(struct kimage *image, char *kernel_buf,
>>         unsigned int fdt_size;
>>         unsigned long kernel_load_addr;
>>         unsigned long initrd_load_addr = 0, fdt_load_addr;
>> -       void *fdt;
>> +       void *fdt = NULL;
>>         const void *slave_code;
>>         struct elfhdr ehdr;
>>         char *modified_cmdline = NULL;
>> @@ -103,18 +104,12 @@ static void *elf64_load(struct kimage *image, char *kernel_buf,
>>         }
>>
>>         fdt_size = fdt_totalsize(initial_boot_params) * 2;
>> -       fdt = kmalloc(fdt_size, GFP_KERNEL);
>> +       fdt = of_alloc_and_init_fdt(fdt_size);
>>         if (!fdt) {
>>                 pr_err("Not enough memory for the device tree.\n");
>>                 ret = -ENOMEM;
>>                 goto out;
>>         }
>> -       ret = fdt_open_into(initial_boot_params, fdt, fdt_size);
>> -       if (ret < 0) {
>> -               pr_err("Error setting up the new device tree.\n");
>> -               ret = -EINVAL;
>> -               goto out;
>> -       }
>>
>>         ret = setup_new_fdt_ppc64(image, fdt, initrd_load_addr,
>
> The first thing this function does is call setup_new_fdt() which first
> calls of_kexec_setup_new_fdt(). (Note, I really don't understand the
> PPC code split. It looks like there's a 32-bit and 64-bit split, but
> 32-bit looks broken to me. Nothing ever calls setup_new_fdt() except
> setup_new_fdt_ppc64()).

I think that's because 32-bit doesn't support kexec_file_load().

cheers