arch/s390/mm/extable.c

Source file repositories/reference/linux-study-clean/arch/s390/mm/extable.c

File Facts

System
Linux kernel
Corpus path
arch/s390/mm/extable.c
Extension
.c
Size
3673 bytes
Lines
130
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

struct insn_ssf {
	u64	opc1 : 8;
	u64	r3   : 4;
	u64	opc2 : 4;
	u64	b1   : 4;
	u64	d1   : 12;
	u64	b2   : 4;
	u64	d2   : 12;
} __packed;

static bool ex_handler_ua_mvcos(const struct exception_table_entry *ex,
				bool from, struct pt_regs *regs)
{
	unsigned long uaddr, remainder;
	struct insn_ssf *insn;

	/*
	 * If the faulting user space access crossed a page boundary retry by
	 * limiting the access to the first page (adjust length accordingly).
	 * Then the mvcos instruction will either complete with condition code
	 * zero, or generate another fault where the user space access did not
	 * cross a page boundary.
	 * If the faulting user space access did not cross a page boundary set
	 * length to zero and retry. In this case no user space access will
	 * happen, and the mvcos instruction will complete with condition code
	 * zero.
	 * In both cases the instruction will complete with condition code
	 * zero (copying finished), and the register which contains the
	 * length, indicates the number of bytes copied.
	 */
	regs->psw.addr = extable_fixup(ex);
	insn = (struct insn_ssf *)regs->psw.addr;
	if (from)
		uaddr = regs->gprs[insn->b2] + insn->d2;
	else
		uaddr = regs->gprs[insn->b1] + insn->d1;
	remainder = PAGE_SIZE - (uaddr & (PAGE_SIZE - 1));
	if (regs->gprs[insn->r3] <= remainder)
		remainder = 0;
	regs->gprs[insn->r3] = remainder;
	return true;
}

bool fixup_exception(struct pt_regs *regs)
{
	const struct exception_table_entry *ex;

	ex = s390_search_extables(instruction_pointer(regs));
	if (!ex)
		return false;
	switch (ex->type) {
	case EX_TYPE_FIXUP:
		return ex_handler_fixup(ex, regs);
	case EX_TYPE_BPF:
		return ex_handler_bpf(ex, regs);
	case EX_TYPE_UA_FAULT:
		return ex_handler_ua_fault(ex, regs);
	case EX_TYPE_UA_LOAD_REG:
		return ex_handler_ua_load_reg(ex, false, regs);
	case EX_TYPE_UA_LOAD_REGPAIR:
		return ex_handler_ua_load_reg(ex, true, regs);
	case EX_TYPE_FPC:
		return ex_handler_fpc(ex, regs);
	case EX_TYPE_UA_MVCOS_TO:
		return ex_handler_ua_mvcos(ex, false, regs);
	case EX_TYPE_UA_MVCOS_FROM:
		return ex_handler_ua_mvcos(ex, true, regs);
	}
	panic("invalid exception table entry");
}

Annotation

Implementation Notes