linux-kernel - Re: [RESEND PATCH v5 06/11] ppc64/kexec_file: restrict memory usage of kdump kernel

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Message-ID: <23c4e7a2-6fbc-8007-5e9a-35c3a4d3898b@linux.ibm.com>
Date:   Wed, 29 Jul 2020 01:04:22 +0530
From:   Hari Bathini <hbathini@...ux.ibm.com>
To:     Michael Ellerman <mpe@...erman.id.au>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     Pingfan Liu <piliu@...hat.com>,
        Kexec-ml <kexec@...ts.infradead.org>,
        Mimi Zohar <zohar@...ux.ibm.com>,
        Nayna Jain <nayna@...ux.ibm.com>,
        Petr Tesarik <ptesarik@...e.cz>,
        Mahesh J Salgaonkar <mahesh@...ux.ibm.com>,
        Sourabh Jain <sourabhjain@...ux.ibm.com>,
        lkml <linux-kernel@...r.kernel.org>,
        linuxppc-dev <linuxppc-dev@...abs.org>,
        Eric Biederman <ebiederm@...ssion.com>,
        Thiago Jung Bauermann <bauerman@...ux.ibm.com>,
        Dave Young <dyoung@...hat.com>, Vivek Goyal <vgoyal@...hat.com>
Subject: Re: [RESEND PATCH v5 06/11] ppc64/kexec_file: restrict memory usage
 of kdump kernel



On 28/07/20 7:14 pm, Michael Ellerman wrote:
> Hari Bathini <hbathini@...ux.ibm.com> writes:
>> diff --git a/arch/powerpc/kexec/file_load_64.c b/arch/powerpc/kexec/file_load_64.c
>> index 2df6f4273ddd..8df085a22fd7 100644
>> --- a/arch/powerpc/kexec/file_load_64.c
>> +++ b/arch/powerpc/kexec/file_load_64.c
>> @@ -17,9 +17,21 @@
>>   #include <linux/kexec.h>
>>   #include <linux/of_fdt.h>
>>   #include <linux/libfdt.h>
>> +#include <linux/of_device.h>
>>   #include <linux/memblock.h>
>> +#include <linux/slab.h>
>> +#include <asm/drmem.h>
>>   #include <asm/kexec_ranges.h>
>>   
>> +struct umem_info {
>> +	uint64_t *buf; /* data buffer for usable-memory property */
>> +	uint32_t idx;  /* current index */
>> +	uint32_t size; /* size allocated for the data buffer */
> 
> Use kernel types please, u64, u32.
> 
>> +	/* usable memory ranges to look up */
>> +	const struct crash_mem *umrngs;
> 
> "umrngs".
> 
> Given it's part of the umem_info struct could it just be "ranges"?

True. Actually, having crash_mem_range *ranges + u32 nr_ranges and 
populating them seems better. Will do that..

>> +		return NULL;
>> +	}
> 
> 	um_info->size = new_size;
> 
>> +
>> +	memset(tbuf + um_info->idx, 0, MEM_RANGE_CHUNK_SZ);
> 
> Just pass __GFP_ZERO to krealloc?

There are patches submitted to stable fixing a few modules that use 
krealloc with __GFP_ZERO. Also, this zeroing is not really needed.
I will drop the memset instead..

Thanks
Hari