linux-kernel - Re: [PATCH v15 09/10] arm64: Call kmalloc() to allocate DTB buffer

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Date:   Sun, 17 Jan 2021 08:23:53 -0500
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>,
        bauerman@...ux.ibm.com, robh@...nel.org,
        takahiro.akashi@...aro.org, gregkh@...uxfoundation.org,
        will@...nel.org, catalin.marinas@....com, mpe@...erman.id.au,
        Arnd Bergmann <arnd@...db.de>
Cc:     james.morse@....com, sashal@...nel.org, benh@...nel.crashing.org,
        paulus@...ba.org, frowand.list@...il.com,
        vincenzo.frascino@....com, mark.rutland@....com,
        dmitry.kasatkin@...il.com, jmorris@...ei.org, serge@...lyn.com,
        pasha.tatashin@...een.com, allison@...utok.net,
        masahiroy@...nel.org, bhsharma@...hat.com, mbrugger@...e.com,
        hsinyi@...omium.org, tao.li@...o.com, christophe.leroy@....fr,
        prsriva@...ux.microsoft.com, balajib@...ux.microsoft.com,
        linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v15 09/10] arm64: Call kmalloc() to allocate DTB buffer

Hi Ard,

On Fri, 2021-01-15 at 09:30 -0800, Lakshmi Ramasubramanian wrote:
> create_dtb() function allocates kernel virtual memory for
> the device tree blob (DTB).  This is not consistent with other
> architectures, such as powerpc, which calls kmalloc() for allocating
> memory for the DTB.
> 
> Call kmalloc() to allocate memory for the DTB, and kfree() to free
> the allocated memory.

The vmalloc() function description says, "vmalloc - allocate virtually
contiguous memory".  I'd appreciate your reviewing this patch, in
particular, which replaces vmalloc() with kmalloc().

thanks,

Mimi

> 
> Co-developed-by: Prakhar Srivastava <prsriva@...ux.microsoft.com>
> Signed-off-by: Prakhar Srivastava <prsriva@...ux.microsoft.com>
> Signed-off-by: Lakshmi Ramasubramanian <nramas@...ux.microsoft.com>
> ---
>  arch/arm64/kernel/machine_kexec_file.c | 12 +++++++-----
>  1 file changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/arm64/kernel/machine_kexec_file.c b/arch/arm64/kernel/machine_kexec_file.c
> index 7de9c47dee7c..51c40143d6fa 100644
> --- a/arch/arm64/kernel/machine_kexec_file.c
> +++ b/arch/arm64/kernel/machine_kexec_file.c
> @@ -29,7 +29,7 @@ const struct kexec_file_ops * const kexec_file_loaders[] = {
>  
>  int arch_kimage_file_post_load_cleanup(struct kimage *image)
>  {
> -	vfree(image->arch.dtb);
> +	kfree(image->arch.dtb);
>  	image->arch.dtb = NULL;
>  
>  	vfree(image->arch.elf_headers);
> @@ -59,19 +59,21 @@ static int create_dtb(struct kimage *image,
>  			+ cmdline_len + DTB_EXTRA_SPACE;
>  
>  	for (;;) {
> -		buf = vmalloc(buf_size);
> +		buf = kmalloc(buf_size, GFP_KERNEL);
>  		if (!buf)
>  			return -ENOMEM;
>  
>  		/* duplicate a device tree blob */
>  		ret = fdt_open_into(initial_boot_params, buf, buf_size);
> -		if (ret)
> +		if (ret) {
> +			kfree(buf);
>  			return -EINVAL;
> +		}
>  
>  		ret = of_kexec_setup_new_fdt(image, buf, initrd_load_addr,
>  					     initrd_len, cmdline);
>  		if (ret) {
> -			vfree(buf);
> +			kfree(buf);
>  			if (ret == -ENOMEM) {
>  				/* unlikely, but just in case */
>  				buf_size += DTB_EXTRA_SPACE;
> @@ -217,6 +219,6 @@ int load_other_segments(struct kimage *image,
>  	return 0;
>  
>  out_err:
> -	vfree(dtb);
> +	kfree(dtb);
>  	return ret;
>  }