arch/mips/kernel/scall64-o32.S

Source file repositories/reference/linux-study-clean/arch/mips/kernel/scall64-o32.S

File Facts

System
Linux kernel
Corpus path
arch/mips/kernel/scall64-o32.S
Extension
.S
Size
5291 bytes
Lines
223
Domain
Architecture Layer
Bucket
arch/mips
Inferred role
Architecture Layer: arch/mips
Status
atlas-only

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

#include <linux/errno.h>
#include <asm/asm.h>
#include <asm/asmmacro.h>
#include <asm/irqflags.h>
#include <asm/mipsregs.h>
#include <asm/regdef.h>
#include <asm/stackframe.h>
#include <asm/thread_info.h>
#include <asm/unistd.h>
#include <asm/sysmips.h>

	.align	5
NESTED(handle_sys, PT_SIZE, sp)
	.set	noat
	SAVE_SOME
	TRACE_IRQS_ON_RELOAD
	STI
	.set	at
	ld	t1, PT_EPC(sp)		# skip syscall on return

	dsubu	t0, v0, __NR_O32_Linux	# check syscall number
	sltiu	t0, t0, __NR_O32_Linux_syscalls
	daddiu	t1, 4			# skip to next instruction
	sd	t1, PT_EPC(sp)
	beqz	t0, not_o32_scall
#if 0
 SAVE_ALL
 move a1, v0
 ASM_PRINT("Scall %ld\n")
 RESTORE_ALL
#endif

	/* We don't want to stumble over broken sign extensions from
	   userland. O32 does never use the upper half. */
	sll	a0, a0, 0
	sll	a1, a1, 0
	sll	a2, a2, 0
	sll	a3, a3, 0

	sd	a3, PT_R26(sp)		# save a3 for syscall restarting

	/*
	 * More than four arguments.  Try to deal with it by copying the
	 * stack arguments from the user stack to the kernel stack.
	 * This Sucks (TM).
	 *
	 * We intentionally keep the kernel stack a little below the top of
	 * userspace so we don't have to do a slower byte accurate check here.
	 */
	ld	t0, PT_R29(sp)		# get old user stack pointer
	daddu	t1, t0, 32
	bltz	t1, bad_stack

load_a4: lw	a4, 16(t0)		# argument #5 from usp
load_a5: lw	a5, 20(t0)		# argument #6 from usp
load_a6: lw	a6, 24(t0)		# argument #7 from usp
load_a7: lw	a7, 28(t0)		# argument #8 from usp
loads_done:

	.section __ex_table,"a"
	PTR_WD	load_a4, bad_stack_a4
	PTR_WD	load_a5, bad_stack_a5
	PTR_WD	load_a6, bad_stack_a6
	PTR_WD	load_a7, bad_stack_a7
	.previous

	/*
	 * absolute syscall number is in v0 unless we called syscall(__NR_###)
	 * where the real syscall number is in a0
	 * note: NR_syscall is the first O32 syscall but the macro is

Annotation

Implementation Notes