[llvm-dev] Allocating shadow tables at the bottom of memory on Linux.

[Carter Cheng via llvm-dev]

Great, thanks for the info!

On Fri, Jul 5, 2019 at 4:25 PM Tim Northover <t.p.northover at gmail.com>
wrote:

> Hi Carter,
>
> On Fri, 5 Jul 2019 at 09:05, Carter Cheng via llvm-dev
> <llvm-dev at lists.llvm.org> wrote:
> > I have been working on a llvm instrumentation pass as an exercise to get
> up to speed on how llvm operates. I am curious about what the best way
> would be to create a shadow table at a fixed address in low memory starting
> at 0x10000 and extending upwards.
>
> Normally you'd put your data into a custom named section and then tell
> the linker to put that section at a specific address through either
> command-line options or a linker script.
>
> > I am uncertain how the code ensures that the runtime metadata doesnt get
> overwritten by alloca calls for the stack.
>
> If the value is a global it'll pretty much automatically be handled by
> the linker and OS. The stack is usually pretty small and can be placed
> out of the way of any allocation the OS knows about (and it knows
> about all of them because it has to actually do the allocation at the
> end of the day).
>
> I think some sanitizers have a runtime that takes over the stack and
> heap though and allocate both the "real" memory and its shadow
> together. See compiler-rt/lib/asan for example.
>
> Cheers.
>
> Tim.
> >
> > Thanks in advance,
> >
> > Carter.
> > _______________________________________________
> > LLVM Developers mailing list
> > llvm-dev at lists.llvm.org
> > https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
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