linux-kernel - Re: [linux-next][0692229e] next-20171106 fails to boot on Power 7

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Date:   Fri, 10 Nov 2017 13:30:26 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Abdul Haleem <abdhalee@...ux.vnet.ibm.com>
Cc:     linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        linux-next <linux-next@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        sachinp <sachinp@...ux.vnet.ibm.com>
Subject: Re: [linux-next][0692229e] next-20171106 fails to boot on Power 7

Hi Abdul,

On Tue 07-11-17 11:28:54, Michal Hocko wrote:
> On Tue 07-11-17 15:20:29, Abdul Haleem wrote:
> > Hi,
> > 
> > Today's next kernel fails to boot on Power 7 Machine with below errors
> > in boot log messages.
> > 
> > 'Uhuuh, elf segement at 0000000010040000 requested but the memory is
> > mapped already'
> > 
> > It was introduced with commit:
> > 
> > 0692229e : fs/binfmt_elf.c: drop MAP_FIXED usage from elf_map
> 
> Weird. Clashes shouldn't really happen. Maybe power is doing something
> different from other platforms. Could you apply the following debugging
> patch to see what is going on there?

Did you have chance to test with this debugging patch, please?

> ---
> diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
> index 0abc30d681ae..f098aaf60039 100644
> --- a/fs/binfmt_elf.c
> +++ b/fs/binfmt_elf.c
> @@ -361,8 +361,28 @@ static unsigned long elf_vm_mmap(struct file *filep, unsigned long addr,
>  		return map_addr;
>  
>  	if ((type & MAP_FIXED) && map_addr != addr) {
> -		pr_info("Uhuuh, elf segement at %p requested but the memory is mapped already\n",
> -				(void*)addr);
> +		struct mm_struct *mm = current->mm;
> +		struct vm_area_struct *vma;
> +		pr_info("Uhuuh, elf segement at %p requested but the memory is mapped already, got %p\n",
> +				(void*)addr, (void*)map_addr);
> +		down_read(&mm->mmap_sem);
> +		vma = find_vma(mm, addr);
> +		if (vma) {
> +			const char *name;
> +			pr_info("Clashing vma [%lx, %lx] flags:%lx", vma->vm_start, vma->vm_end, vma->vm_flags);
> +			name = arch_vma_name(vma);
> +			if (!name) {
> +				if (vma->vm_start <= mm->brk &&
> +				    vma->vm_end >= mm->start_brk)
> +					name = "[heap]";
> +				else if (vma->vm_start <= vma->vm_mm->start_stack &&
> +						vma->vm_end >= vma->vm_mm->start_stack)
> +					name = "[stack]";
> +			}
> +			pr_cont(" name:%s\n", name);
> +		} else
> +			pr_info("Uhm, no clashing VMA\n");
> +		up_read(&mm->mmap_sem);
>  		return -EAGAIN;
>  	}
>  
> 
> -- 
> Michal Hocko
> SUSE Labs

-- 
Michal Hocko
SUSE Labs