cregit-Linux how code gets into the kernel

Release 4.14 arch/metag/oprofile/backtrace.c

/*
 * Copyright (C) 2010-2013 Imagination Technologies Ltd.
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 */

#include <linux/oprofile.h>
#include <linux/uaccess.h>
#include <asm/processor.h>
#include <asm/stacktrace.h>

#include "backtrace.h"


static void user_backtrace_fp(unsigned long __user *fp, unsigned int depth) { while (depth-- && access_ok(VERIFY_READ, fp, 8)) { unsigned long addr; unsigned long __user *fpnew; if (__copy_from_user_inatomic(&addr, fp + 1, sizeof(addr))) break; addr -= 4; oprofile_add_trace(addr); /* stack grows up, so frame pointers must decrease */ if (__copy_from_user_inatomic(&fpnew, fp + 0, sizeof(fpnew))) break; if (fpnew >= fp) break; fp = fpnew; } }

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static int kernel_backtrace_frame(struct stackframe *frame, void *data) { unsigned int *depth = data; oprofile_add_trace(frame->pc); /* decrement depth and stop if we reach 0 */ if ((*depth)-- == 0) return 1; /* otherwise onto the next frame */ return 0; }

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void metag_backtrace(struct pt_regs * const regs, unsigned int depth) { if (user_mode(regs)) { unsigned long *fp = (unsigned long *)regs->ctx.AX[1].U0; user_backtrace_fp((unsigned long __user __force *)fp, depth); } else { struct stackframe frame; frame.fp = regs->ctx.AX[1].U0; /* A0FrP */ frame.sp = user_stack_pointer(regs); /* A0StP */ frame.lr = 0; /* from stack */ frame.pc = regs->ctx.CurrPC; /* PC */ walk_stackframe(&frame, &kernel_backtrace_frame, &depth); } }

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