The function is used in VG_(client_syscall) to avoid extending the stack
when it is clear that the current value of the stack pointer does not
point into a segment that looks like a stack segment.
See the comments in the code there.
As a side effect of this we can now revert r15018 which increased
the stack size of the alternate stack in memcheck/tests/sigaltstack.c.
The reason is that the belief at the time: "alternate stack is too small"
was not correct. What instead happened was that VG_(client_syscall) called
VG_(extend_stack) without need (the syscall was tgkill) and the new stack
pointer happened to be in a file segment.
In other words: the current stack pointer was still within the alternate
stack, i.e. the alternate stack was (barely) large enough.
git-svn-id: svn://svn.valgrind.org/valgrind/trunk@15034
This was found by accident and there is no known way to detect
an overflow of an alternate stack in the general case.
git-svn-id: svn://svn.valgrind.org/valgrind/trunk@15018
Valgrind's dependency on the dynamic linker for getting started, and
instead takes things into its own hands.
This checkin doesn't add much in the way of new functionality, but it
is the basis for all future work on Valgrind. It allows us much more
flexibility in implementation, and well as increasing the reliability
of Valgrind by protecting it more from its clients.
This patch requires some changes to tools to update them to the changes
in the tool API, but they are straightforward. See the posting "Heads
up: Full Virtualization" on valgrind-developers for a more complete
description of this change and its effects on you.
git-svn-id: svn://svn.valgrind.org/valgrind/trunk@2118
