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Re: [PATCH] ARM: Add pointer guard support.


On 09/25/2013 05:06 AM, Will Newton wrote:
> 
> Add support for pointer mangling in glibc internal structures in C
> and assembler code.
> 
> Tested on armv7 with hard and soft thread pointers.

Have you measured the performance versus using the existing
global variable? 

TLS access on ARM is quite slow and it looks to me like it 
may be faster to use the global variable. Keep in mind that
the pointer guard and stack guard do not vary by thread.

32-bit ARM is currently using a global variable e.g.
__pointer_chk_guard, all you need to do to make it work
is adjust the definitions of PTR_MANGLE and PTR_DEMANGLE
to reference the global symbol.

This is the second proposal for ARM (first was [1] for
AArch64) to support storing the a guard in the TCB, but
nobody has responded yet to my question about performance.

Cheers,
Carlos.

[1] https://sourceware.org/ml/libc-ports/2013-08/msg00052.html


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