arch/s390/include/asm/entry-percpu.h

Source file repositories/reference/linux-study-clean/arch/s390/include/asm/entry-percpu.h

File Facts

System
Linux kernel
Corpus path
arch/s390/include/asm/entry-percpu.h
Extension
.h
Size
2183 bytes
Lines
81
Domain
Architecture Layer
Bucket
arch/s390
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

#ifndef ARCH_S390_ENTRY_PERCPU_H
#define ARCH_S390_ENTRY_PERCPU_H

#include <linux/kprobes.h>
#include <linux/percpu.h>
#include <asm/lowcore.h>
#include <asm/ptrace.h>
#include <asm/asm-offsets.h>

static __always_inline void percpu_entry(struct pt_regs *regs)
{
	struct lowcore *lc = get_lowcore();

	if (user_mode(regs))
		return;
	regs->cpu = lc->cpu_nr;
	regs->percpu_register = lc->percpu_register;
	lc->percpu_register = 0;
}

static __always_inline bool percpu_code_check(struct pt_regs *regs)
{
	unsigned int insn, disp;
	struct kprobe *p;

	if (likely(user_mode(regs) || !regs->percpu_register))
		return false;
	/*
	 * Within a percpu code section - check if the percpu base register
	 * needs to be updated. This is the case if the PSW does not point to
	 * the ADD instruction within the section.
	 * - AG %rx,percpu_offset_in_lowcore(%r0,%r0)
	 * which adds the percpu offset to the percpu base register.
	 */
	lockdep_assert_preemption_disabled();
again:
	insn = READ_ONCE(*(u16 *)psw_bits(regs->psw).ia);
	if (unlikely(insn == BREAKPOINT_INSTRUCTION)) {
		p = get_kprobe((void *)psw_bits(regs->psw).ia);
		/*
		 * If the kprobe is concurrently removed on a different CPU
		 * it might not be found anymore. However text must have
		 * been restored - try again.
		 */
		if (!p)
			goto again;
		insn = p->opcode;
	}
	if ((insn & 0xff0f) != 0xe300)
		return true;
	disp = offsetof(struct lowcore, percpu_offset);
	if (machine_has_relocated_lowcore())
		disp += LOWCORE_ALT_ADDRESS;
	insn = (disp & 0xff000) >> 4 | (disp & 0x00fff) << 16 | 0x8;
	if (*(u32 *)(psw_bits(regs->psw).ia + 2) != insn)
		return true;
	return false;
}

static __always_inline void percpu_exit(struct pt_regs *regs, bool needs_fixup)
{
	struct lowcore *lc = get_lowcore();
	unsigned char reg;

	if (user_mode(regs))
		return;
	reg = regs->percpu_register;
	lc->percpu_register = reg;
	if (likely(!needs_fixup))
		return;
	/* Check if process has been migrated to a different CPU. */
	if (regs->cpu == lc->cpu_nr)
		return;
	/* Fixup percpu base register */
	regs->gprs[reg] -= __per_cpu_offset[regs->cpu];
	regs->gprs[reg] += lc->percpu_offset;
}

#endif

Annotation

Implementation Notes