Re: [Valgrind-developers] Capability of handling programs with large BSS and data segments

[Philippe W. <phi...@sk...>]

On Mon, 2019-08-19 at 23:31 +0200, Philippe Waroquiers wrote:
> Note that it just took me now about 1 minute and 5 lines of code to reproduce it
> in Ada (but I guess it can be done in whatever language: it is enough to just
> produce a very large BSS).
> 
> So, valgrind error message is correctly pointing at the problem of very large bss
> (as was already determined in 2017 IIUC).
> 
> Philippe
> 
> 
Reproducer:

package P is
  S : constant String (1 .. 1_800_000_000) := (others => 'a');
end P;
with P;
wit
h Text_Io; use Text_Io;
procedure Pm is
begin
  Put_Line (P.S (1..10) & P.S(100..110));
end;

A solution is to link the user executable at an address 'high enough'
above the valgrind address:

gnatmake -g pm
...
valgrind ./pm
valgrind: mmap(0x10e000, 1800007680) failed in UME with error 22 (Invalid argument).
valgrind: this can be caused by executables with very large text, data or bss segments.

rm ./pm
gnatmake -g pm -largs -Wl,-Ttext-segment=0x68000000
...
valgrind ./pm
...
==19326== Warning: set address range perms: large range [0x68006000, 0xd34a5000) (defined)
aaaaaaaaaaaaaaaaaaaaa
==19326== 
==19326== HEAP SUMMARY:
....

(valgrind itself is loaded at 0x58000000).

We might maybe improve the valgrind mmap error detection and error message
to indicate this solution.

Philippe