cregit-Linux how code gets into the kernel

Release 4.11 arch/metag/kernel/ftrace.c

/*
 * Copyright (C) 2008 Imagination Technologies Ltd.
 * Licensed under the GPL
 *
 * Dynamic ftrace support.
 */

#include <linux/ftrace.h>
#include <linux/io.h>
#include <linux/uaccess.h>

#include <asm/cacheflush.h>


#define D04_MOVT_TEMPLATE	0x02200005

#define D04_CALL_TEMPLATE	0xAC200005

#define D1RTP_MOVT_TEMPLATE	0x03200005

#define D1RTP_CALL_TEMPLATE	0xAC200006


static const unsigned long NOP[2] = {0xa0fffffe, 0xa0fffffe};

static unsigned long movt_and_call_insn[2];


static unsigned char *ftrace_nop_replace(void) { return (char *)&NOP[0]; }

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James Hogan21100.00%1100.00%
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static unsigned char *ftrace_call_replace(unsigned long pc, unsigned long addr) { unsigned long hi16, low16; hi16 = (addr & 0xffff0000) >> 13; low16 = (addr & 0x0000ffff) << 3; /* * The compiler makes the call to mcount_wrapper() * (Meta's wrapper around mcount()) through the register * D0.4. So whenever we're patching one of those compiler-generated * calls we also need to go through D0.4. Otherwise use D1RtP. */ if (pc == (unsigned long)&ftrace_call) { writel(D1RTP_MOVT_TEMPLATE | hi16, &movt_and_call_insn[0]); writel(D1RTP_CALL_TEMPLATE | low16, &movt_and_call_insn[1]); } else { writel(D04_MOVT_TEMPLATE | hi16, &movt_and_call_insn[0]); writel(D04_CALL_TEMPLATE | low16, &movt_and_call_insn[1]); } return (unsigned char *)&movt_and_call_insn[0]; }

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James Hogan123100.00%1100.00%
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static int ftrace_modify_code(unsigned long pc, unsigned char *old_code, unsigned char *new_code) { unsigned char replaced[MCOUNT_INSN_SIZE]; /* * Note: * We are paranoid about modifying text, as if a bug was to happen, it * could cause us to read or write to someplace that could cause harm. * Carefully read and modify the code with probe_kernel_*(), and make * sure what we read is what we expected it to be before modifying it. */ /* read the text we want to modify */ if (probe_kernel_read(replaced, (void *)pc, MCOUNT_INSN_SIZE)) return -EFAULT; /* Make sure it is what we expect it to be */ if (memcmp(replaced, old_code, MCOUNT_INSN_SIZE) != 0) return -EINVAL; /* replace the text with the new text */ if (probe_kernel_write((void *)pc, new_code, MCOUNT_INSN_SIZE)) return -EPERM; flush_icache_range(pc, pc + MCOUNT_INSN_SIZE); return 0; }

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James Hogan9798.98%150.00%
Li Bin11.02%150.00%
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int ftrace_update_ftrace_func(ftrace_func_t func) { int ret; unsigned long pc; unsigned char old[MCOUNT_INSN_SIZE], *new; pc = (unsigned long)&ftrace_call; memcpy(old, &ftrace_call, MCOUNT_INSN_SIZE); new = ftrace_call_replace(pc, (unsigned long)func); ret = ftrace_modify_code(pc, old, new); return ret; }

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int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long addr) { unsigned char *new, *old; unsigned long ip = rec->ip; old = ftrace_call_replace(ip, addr); new = ftrace_nop_replace(); return ftrace_modify_code(ip, old, new); }

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James Hogan59100.00%1100.00%
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int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) { unsigned char *new, *old; unsigned long ip = rec->ip; old = ftrace_nop_replace(); new = ftrace_call_replace(ip, addr); return ftrace_modify_code(ip, old, new); }

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James Hogan54100.00%1100.00%
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int __init ftrace_dyn_arch_init(void) { return 0; }

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James Hogan48899.80%150.00%
Li Bin10.20%150.00%
Total489100.00%2100.00%
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