Re: [PATCH] [20/20] x86: Print which shared library/executable faulted in segfault etc. messages

Eric Dumazet
2008-01-03T06:28:46Z

Andi Kleen a écrit :
> They now look like
>
> hal-resmgr[13791]: segfault at 3c rip 2b9c8caec182 rsp 7fff1e825d30 error 4 in libacl.so.1.1.0[2b9c8caea000+6000]
>
> This makes it easier to pinpoint bugs to specific libraries.
>
> And printing the offset into a mapping also always allows to find the
> correct fault point in a library even with randomized mappings. Previously
> there was no way to actually find the correct code address inside
> the randomized mapping.
>
> Relies on earlier patch to shorten the printk formats.
>
> They are often now longer than 80 characters, but I think that's worth
> it.
>
> Patch for i386 and x86-64.
>
> Signed-off-by: Andi Kleen <ak@suse.de>
>
> ---
> arch/x86/kernel/signal_32.c | 7 +++++--
> arch/x86/kernel/signal_64.c | 7 +++++--
> arch/x86/kernel/traps_32.c | 7 +++++--
> arch/x86/mm/fault_32.c | 4 +++-
> include/linux/mm.h | 1 +
> mm/memory.c | 27 +++++++++++++++++++++++++++
> 6 files changed, 46 insertions(+), 7 deletions(-)
>
> Index: linux/include/linux/mm.h
> ===================================================================
> --- linux.orig/include/linux/mm.h
> +++ linux/include/linux/mm.h
> @@ -1145,6 +1145,7 @@ extern int randomize_va_space;
> #endif
>
> const char * arch_vma_name(struct vm_area_struct *vma);
> +void print_vma_addr(char *prefix, unsigned long rip);
>
> struct page *sparse_mem_map_populate(unsigned long pnum, int nid);
> pgd_t *vmemmap_pgd_populate(unsigned long addr, int node);
> Index: linux/mm/memory.c
> ===================================================================
> --- linux.orig/mm/memory.c
> +++ linux/mm/memory.c
> @@ -2746,3 +2746,30 @@ int access_process_vm(struct task_struct
>
> return buf - old_buf;
> }
> +
> +/*
> + * Print the name of a VMA.
> + */
> +void print_vma_addr(char *prefix, unsigned long ip)
> +{
> + struct mm_struct *mm = current->mm;
> + struct vm_area_struct *vma;
> + down_read(&mm->mmap_sem);
> + vma = find_vma(mm, ip);
> + if (vma && vma->vm_file) {
> + struct file *f = vma->vm_file;
> + char *buf = (char *)__get_free_page(GFP_KERNEL);
> + if (buf) {
> + char *p, *s;
> + p = d_path(f->f_dentry, f->f_vfsmnt, buf, PAGE_SIZE);

d_path() can returns an error. You should add :

if (IS_ERR(p))
p = "?";

> + s = strrchr(p, '/');
> + if (s)
> + p = s+1;
> + printk("%s%s[%lx+%lx]", prefix, p,
> + vma->vm_start,
> + vma->vm_end - vma->vm_start);
> + free_page((unsigned long)buf);
> + }
> + }
> + up_read(&current->mm->mmap_sem);
> +}

Thank you