linux-kernel - Re: [PATCH v4 2/3] powerpc/fadump: Use the correct VMCOREINFO_NOTE

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Message-ID: <58F95887.3090404@redhat.com>
Date:   Fri, 21 Apr 2017 08:55:35 +0800
From:   Xunlei Pang <xpang@...hat.com>
To:     Xunlei Pang <xlpang@...hat.com>, linux-kernel@...r.kernel.org,
        kexec@...ts.infradead.org
Cc:     Baoquan He <bhe@...hat.com>, Petr Tesarik <ptesarik@...e.cz>,
        Eric Biederman <ebiederm@...ssion.com>,
        Hari Bathini <hbathini@...ux.vnet.ibm.com>,
        akpm@...ux-foundation.org, Dave Young <dyoung@...hat.com>,
        Michael Holzheu <holzheu@...ux.vnet.ibm.com>
Subject: Re: [PATCH v4 2/3] powerpc/fadump: Use the correct
 VMCOREINFO_NOTE_SIZE for phdr

Cc "Michael Holzheu"

On 04/20/2017 at 07:39 PM, Xunlei Pang wrote:
> vmcoreinfo_max_size stands for the vmcoreinfo_data, the
> correct one we should use is vmcoreinfo_note whose total
> size is VMCOREINFO_NOTE_SIZE.
>
> Like explained in commit 77019967f06b ("kdump: fix exported
> size of vmcoreinfo note"), it should not affect the actual
> function, but we better fix it, also this change should be
> safe and backward compatible.
>
> After this, we can get rid of variable vmcoreinfo_max_size,
> let's use the corresponding macros directly, fewer variables
> means more safety for vmcoreinfo operation.
>
> Cc: Mahesh Salgaonkar <mahesh@...ux.vnet.ibm.com>
> Cc: Hari Bathini <hbathini@...ux.vnet.ibm.com>
> Signed-off-by: Xunlei Pang <xlpang@...hat.com>
> ---
> v3->v4:
> -Rebased on the latest linux-next
>
>  arch/powerpc/kernel/fadump.c | 3 +--
>  include/linux/crash_core.h   | 1 -
>  kernel/crash_core.c          | 3 +--
>  3 files changed, 2 insertions(+), 5 deletions(-)
>
> diff --git a/arch/powerpc/kernel/fadump.c b/arch/powerpc/kernel/fadump.c
> index 466569e..7bd6cd0 100644
> --- a/arch/powerpc/kernel/fadump.c
> +++ b/arch/powerpc/kernel/fadump.c
> @@ -893,8 +893,7 @@ static int fadump_create_elfcore_headers(char *bufp)
>  
>  	phdr->p_paddr	= fadump_relocate(paddr_vmcoreinfo_note());
>  	phdr->p_offset	= phdr->p_paddr;
> -	phdr->p_memsz	= vmcoreinfo_max_size;
> -	phdr->p_filesz	= vmcoreinfo_max_size;
> +	phdr->p_memsz	= phdr->p_filesz = VMCOREINFO_NOTE_SIZE;
>  
>  	/* Increment number of program headers. */
>  	(elf->e_phnum)++;
> diff --git a/include/linux/crash_core.h b/include/linux/crash_core.h
> index ba283a2..7d6bc7b 100644
> --- a/include/linux/crash_core.h
> +++ b/include/linux/crash_core.h
> @@ -55,7 +55,6 @@
>  
>  extern u32 *vmcoreinfo_note;
>  extern size_t vmcoreinfo_size;
> -extern size_t vmcoreinfo_max_size;
>  
>  Elf_Word *append_elf_note(Elf_Word *buf, char *name, unsigned int type,
>  			  void *data, size_t data_len);
> diff --git a/kernel/crash_core.c b/kernel/crash_core.c
> index 0321f04..43cdb00 100644
> --- a/kernel/crash_core.c
> +++ b/kernel/crash_core.c
> @@ -16,7 +16,6 @@
>  /* vmcoreinfo stuff */
>  static unsigned char *vmcoreinfo_data;
>  size_t vmcoreinfo_size;
> -size_t vmcoreinfo_max_size = VMCOREINFO_BYTES;
>  u32 *vmcoreinfo_note;
>  
>  /*
> @@ -343,7 +342,7 @@ void vmcoreinfo_append_str(const char *fmt, ...)
>  	r = vscnprintf(buf, sizeof(buf), fmt, args);
>  	va_end(args);
>  
> -	r = min(r, vmcoreinfo_max_size - vmcoreinfo_size);
> +	r = min(r, VMCOREINFO_BYTES - vmcoreinfo_size);
>  
>  	memcpy(&vmcoreinfo_data[vmcoreinfo_size], buf, r);
>