semantic error: not accessible at this address

[Frank Ch. Eigler]

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