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Kernel: Make use of interrupts as an entropy source

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Booting old computers without RDRAND/RDSEED and without a disk makes
the system severely starved for entropy. Uses interrupts as a source
to side-step that issue.

Also warn whenever the system is starved of entropy, because that's
a non-obvious failure mode.
This commit is contained in:
Jean-Baptiste Boric 2021-01-24 18:17:54 +01:00 • committed by Andreas Kling
parent cb89d3b780
commit 7eaefa5aa6
3 changed files with 16 additions and 2 deletions
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4
Kernel/Arch/i386/CPU.cpp
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@ -44,6 +44,7 @@
#include <Kernel/Interrupts/UnhandledInterruptHandler.h>
#include <Kernel/KSyms.h>
#include <Kernel/Process.h>
#include <Kernel/Random.h>
#include <Kernel/SpinLock.h>
#include <Kernel/Thread.h>
#include <Kernel/VM/MemoryManager.h>
@ -58,6 +59,8 @@ static Descriptor s_idt[256];
static GenericInterruptHandler* s_interrupt_handler[GENERIC_INTERRUPT_HANDLERS_COUNT];
static EntropySource s_entropy_source_interrupts{EntropySource::Static::Interrupts};
// The compiler can't see the calls to these functions inside assembly.
// Declare them, to avoid dead code warnings.
extern "C" void enter_thread_context(Thread* from_thread, Thread* to_thread);
@ -709,6 +712,7 @@ void handle_interrupt(TrapFrame* trap)
auto& regs = *trap->regs;
ASSERT(regs.isr_number >= IRQ_VECTOR_BASE && regs.isr_number <= (IRQ_VECTOR_BASE + GENERIC_INTERRUPT_HANDLERS_COUNT));
u8 irq = (u8)(regs.isr_number - 0x50);
s_entropy_source_interrupts.add_random_event(irq);
auto* handler = s_interrupt_handler[irq];
ASSERT(handler);
handler->increment_invoking_counter();