349941 di_notify_mmap might create wrong start/size DebugInfoMapping

Use seg->start instead of a as DebugInfoMapping avma. Normally seg->start
equals a. But when it is not then the size of the map might extend beyond
the segment (and not actually cover the start of the segment). When another
ELF file is them mapped right after this then it triggers an overlap purge
of the DebugInfo. In the case the mapping was for libc or ld.so this then
removes all intercepts causing "bad things".

git-svn-id: svn://svn.valgrind.org/valgrind/trunk@15398 a5019735-40e9-0310-863c-91ae7b9d1cf9
2 files changed