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Re: [patch] Fix resolving ELF symbols for live PIDs with deleted files
- From: Mark Wielaard <mjw at redhat dot com>
- To: elfutils-devel at lists dot fedorahosted dot org
- Date: Fri, 29 Aug 2014 11:55:32 +0200
- Subject: Re: [patch] Fix resolving ELF symbols for live PIDs with deleted files
On Thu, 2014-08-28 at 22:12 +0200, Jan Kratochvil wrote:
> Formerly shared libraries did not get resolved properly:
> #2 0x00007fc4d86c56d6
> #3 0x0000000000400938 main
>
> Fixed elfutils produce:
> #2 0x00007f61094876d6 libfunc
> #3 0x0000000000400938 main
>
> Signed-off-by: Jan Kratochvil <jan.kratochvil@redhat.com>
Nice, thanks. I would add the why to the commit message. "For deleted
shared library files the offsets to the symbol table were calculated
wrongly from the phdrs because the main_bias wasn't taken into account."
+2014-08-28 Jan Kratochvil <jan.kratochvil@redhat.com>
> +
> + * dwfl_module_getdwarf.c (find_offsets): Add parameter main_bias, use
> + it.
> + (find_dynsym): Pass the new parameter main_bias.
>
Looks good.
+# Older Linux (such as 2.6.32) required PTRACE_ATTACH to read /proc/PID/mem.
> +sleep 60 & p=$!; sleep 0.1
> +addr=0x$(cat /proc/$p/maps|sed -n 's#^\([0-9a-f]*\)-[0-9a-f]* r[^ ]* 00* .*/sleep$#\1#p'|head -n1)
> +supported=$[$(dd if=/proc/$p/mem bs=1 skip=$[$addr] count=1|wc -c)]
> +kill -9 $p
> +if [ $supported -eq 0 ]; then
> + exit 77
> +fi
I don't think this check is needed. eu-stack needs to be attached to get
the register values and dwfl_linux_proc_find_elf makes sure the process
is attached before calling elf_from_remote_memory.
Cheers,
Mark