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AK+LibC+LibPthread: Introduce NoAllocationGuard

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NoAllocationGuard is an RAII stack guard that prevents allocations
while it exists. This is done through a thread-local global flag which
causes malloc to crash on a VERIFY if it is false. The guard allows for
recursion.

The intended use case for this class is in real-time audio code. In such
code, allocations are really bad, and this is an easy way of dynamically
enforcing the no-allocations rule while giving the user good feedback if
it is violated. Before real-time audio code is executed, e.g. in LibDSP,
a NoAllocationGuard is instantiated. This is not done with this commit,
as currently some code in LibDSP may still incorrectly allocate in real-
time situations.

Other use cases for the Kernel have also been added, so this commit
builds on the previous to add the support both in Userland and in the
Kernel.
This commit is contained in:
kleines Filmröllchen 2022-01-09 13:01:27 +01:00 • committed by Linus Groh
parent e2c9578390
commit 2f50d8f4d3
4 changed files with 91 additions and 0 deletions
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6
Userland/Libraries/LibC/mallocdefs.h
View file

@ -19,6 +19,12 @@
static constexpr unsigned short size_classes[] = { 16, 32, 64, 128, 256, 496, 1008, 2032, 4080, 8176, 16368, 32752, 0 };
static constexpr size_t num_size_classes = (sizeof(size_classes) / sizeof(unsigned short)) - 1;
#ifndef NO_TLS
extern "C" {
extern __thread bool s_allocation_enabled;
}
#endif
consteval bool check_size_classes_alignment()
{
for (size_t i = 0; i < num_size_classes; i++) {