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

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Date:   Tue, 7 Nov 2017 11:28:54 +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

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?
---
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