asm - Inline x86 port I/O and CPU-control helpers

Header: kernel/include/kernel/asm.h

All functions in this header are declared inline and consist of a single asm volatile statement. They compile to one or two instructions with no function-call overhead.

Functions

outb

void outb(uint16_t port, uint8_t val);

Write byte val to I/O port port using the x86 OUT instruction. Marked volatile to prevent the compiler from reordering or eliminating the write.

inb

uint8_t inb(uint16_t port);

Read and return one byte from I/O port port using the x86 IN instruction.

enable_interrupts

void enable_interrupts(void);

Execute STI - sets the CPU interrupt-enable flag, allowing hardware interrupts to be delivered. Call only after the IDT is fully configured.

disable_interrupts

void disable_interrupts(void);

Execute CLI - clears the CPU interrupt-enable flag, masking all maskable hardware interrupts. Used in critical sections and panic handlers.

invlpg

void invlpg(void *m);

Invalidate the TLB entry for the virtual address m using the INVLPG instruction. Must be called whenever a page-directory or page-table entry is modified while paging is active, to ensure the CPU does not use a stale cached mapping.