arch/arm64/include/asm/daifflags.h

Source file repositories/reference/linux-study-clean/arch/arm64/include/asm/daifflags.h

File Facts

System
Linux kernel
Corpus path
arch/arm64/include/asm/daifflags.h
Extension
.h
Size
3574 bytes
Lines
145
Domain
Architecture Layer
Bucket
arch/arm64
Inferred role
Architecture Layer: implementation source
Status
source implementation candidate

Why This File Exists

CPU and platform-specific kernel glue: boot entry, traps, syscall entry, interrupts, page tables, context switch, and low-level barriers.

Dependency Surface

Detected Declarations

Annotated Snippet

if (system_uses_irq_prio_masking()) {
			gic_write_pmr(GIC_PRIO_IRQON);
			pmr_sync();
		}
	} else if (system_uses_irq_prio_masking()) {
		u64 pmr;

		if (!(flags & PSR_A_BIT)) {
			/*
			 * If interrupts are disabled but we can take
			 * asynchronous errors, we can take NMIs
			 */
			flags &= ~(PSR_I_BIT | PSR_F_BIT);
			pmr = GIC_PRIO_IRQOFF;
		} else {
			pmr = GIC_PRIO_IRQON | GIC_PRIO_PSR_I_SET;
		}

		/*
		 * There has been concern that the write to daif
		 * might be reordered before this write to PMR.
		 * From the ARM ARM DDI 0487D.a, section D1.7.1
		 * "Accessing PSTATE fields":
		 *   Writes to the PSTATE fields have side-effects on
		 *   various aspects of the PE operation. All of these
		 *   side-effects are guaranteed:
		 *     - Not to be visible to earlier instructions in
		 *       the execution stream.
		 *     - To be visible to later instructions in the
		 *       execution stream
		 *
		 * Also, writes to PMR are self-synchronizing, so no
		 * interrupts with a lower priority than PMR is signaled
		 * to the PE after the write.
		 *
		 * So we don't need additional synchronization here.
		 */
		gic_write_pmr(pmr);
	}

	write_sysreg(flags, daif);

	if (irq_disabled)
		trace_hardirqs_off();
}

/*
 * Called by synchronous exception handlers to restore the DAIF bits that were
 * modified by taking an exception.
 */
static __always_inline void local_daif_inherit(struct pt_regs *regs)
{
	unsigned long flags = regs->pstate & DAIF_MASK;

	if (!regs_irqs_disabled(regs))
		trace_hardirqs_on();

	if (system_uses_irq_prio_masking())
		gic_write_pmr(regs->pmr);

	/*
	 * We can't use local_daif_restore(regs->pstate) here as
	 * system_has_prio_mask_debugging() won't restore the I bit if it can
	 * use the pmr instead.
	 */
	write_sysreg(flags, daif);
}
#endif

Annotation

Implementation Notes