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Re: semantic error: not accessible at this address
- From: "Frank Ch. Eigler" <fche at redhat dot com>
- To: Vincent Bernat <bernat at luffy dot cx>
- Cc: systemtap at sourceware dot org
- Date: Fri, 27 Sep 2013 19:25:29 -0400
- Subject: Re: semantic error: not accessible at this address
- Authentication-results: sourceware.org; auth=none
- References: <87ioxmf2e9 dot fsf at guybrush dot luffy dot cx> <y0mvc1mt0k7 dot fsf at fche dot csb> <8738opg9ym dot fsf at guybrush dot luffy dot cx> <20130927230432 dot GA32221 at redhat dot com> <87wqm1etsz dot fsf at guybrush dot luffy dot cx>
Hi, Vincent -
> I also tried with a GCC 4.7.3 but ends up with even less symbols.
I wonder why. In any case, GCC 4.8 is more current, and we've had
fine luck with it.
> probe vfs_write@/home/bernat/src/linux-lts-saucy-3.11.0/fs/read_write.c:459 kernel reloc=.dynamic pc=0xffffffff811b42b0
> saveargs: examining 'vfs_write' (dieoffset: 0x1774208)
> saveargs: finding location for local 'file' (dieoffset: 0x177422e)
> saveargs: local 'file' (dieoffset: 0x177422e) is not available at this address (0xffffffff811b42b0)
> saveargs: finding location for local 'buf' (dieoffset: 0x177423e)
> saveargs: local 'buf' (dieoffset: 0x177423e) is not available at this address (0xffffffff811b42b0)
> saveargs: finding location for local 'count' (dieoffset: 0x177424e)
> [...]
The -mfentry-compensation code should cause you to be seeing some
messages like this:
retrying variable location-list lookup at address pc+5
> [...]
> > % readelf -w ../vmlinux # like you had, but focusing on location list item
> > # (offset) [5ec5ff] from .debug_loc
>
> [5ec5ff] member
> name (strp) "spin_lock"
> decl_file (data1) 18
> decl_line (data2) 333
> type (ref4) [5ec679]
> data_member_location (block1) [ 0] plus_uconst 16
That's an unrelated .debug_info tidbit. I'd like to see the
location_list entries associated with one of the sys_write variables.
That's far later in the readelf -w output, in the .debug_loc section,
specifically for the two offsets listed below:
frame_base (data4) location list [5ec58b]
"file" var location (data4) location list [5ec5ff]
- FChE