powerpc/32: Change the stack protector canary value per task
Partially copied from commit df0698be ("ARM: stack protector: change the canary value per task") A new random value for the canary is stored in the task struct whenever a new task is forked. This is meant to allow for different canary values per task. On powerpc, GCC expects the canary value to be found in a global variable called __stack_chk_guard. So this variable has to be updated with the value stored in the task struct whenever a task switch occurs. Because the variable GCC expects is global, this cannot work on SMP unfortunately. So, on SMP, the same initial canary value is kept throughout, making this feature a bit less effective although it is still useful. Signed-off-by: NChristophe Leroy <christophe.leroy@c-s.fr> Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>
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