122 lines
3.0 KiB
C
Executable File
122 lines
3.0 KiB
C
Executable File
/*
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* Copyright (C) 2008 Imagination Technologies Ltd.
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* Licensed under the GPL
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*
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* Dynamic ftrace support.
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*/
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#include <linux/ftrace.h>
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#include <linux/io.h>
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#include <linux/uaccess.h>
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#include <asm/cacheflush.h>
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#define D04_MOVT_TEMPLATE 0x02200005
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#define D04_CALL_TEMPLATE 0xAC200005
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#define D1RTP_MOVT_TEMPLATE 0x03200005
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#define D1RTP_CALL_TEMPLATE 0xAC200006
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static const unsigned long NOP[2] = {0xa0fffffe, 0xa0fffffe};
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static unsigned long movt_and_call_insn[2];
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static unsigned char *ftrace_nop_replace(void)
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{
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return (char *)&NOP[0];
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}
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static unsigned char *ftrace_call_replace(unsigned long pc, unsigned long addr)
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{
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unsigned long hi16, low16;
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hi16 = (addr & 0xffff0000) >> 13;
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low16 = (addr & 0x0000ffff) << 3;
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/*
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* The compiler makes the call to mcount_wrapper()
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* (Meta's wrapper around mcount()) through the register
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* D0.4. So whenever we're patching one of those compiler-generated
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* calls we also need to go through D0.4. Otherwise use D1RtP.
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*/
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if (pc == (unsigned long)&ftrace_call) {
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writel(D1RTP_MOVT_TEMPLATE | hi16, &movt_and_call_insn[0]);
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writel(D1RTP_CALL_TEMPLATE | low16, &movt_and_call_insn[1]);
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} else {
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writel(D04_MOVT_TEMPLATE | hi16, &movt_and_call_insn[0]);
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writel(D04_CALL_TEMPLATE | low16, &movt_and_call_insn[1]);
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}
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return (unsigned char *)&movt_and_call_insn[0];
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}
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static int ftrace_modify_code(unsigned long pc, unsigned char *old_code,
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unsigned char *new_code)
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{
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unsigned char replaced[MCOUNT_INSN_SIZE];
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/*
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* Note:
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* We are paranoid about modifying text, as if a bug was to happen, it
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* could cause us to read or write to someplace that could cause harm.
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* Carefully read and modify the code with probe_kernel_*(), and make
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* sure what we read is what we expected it to be before modifying it.
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*/
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/* read the text we want to modify */
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if (probe_kernel_read(replaced, (void *)pc, MCOUNT_INSN_SIZE))
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return -EFAULT;
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/* Make sure it is what we expect it to be */
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if (memcmp(replaced, old_code, MCOUNT_INSN_SIZE) != 0)
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return -EINVAL;
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/* replace the text with the new text */
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if (probe_kernel_write((void *)pc, new_code, MCOUNT_INSN_SIZE))
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return -EPERM;
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flush_icache_range(pc, pc + MCOUNT_INSN_SIZE);
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return 0;
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}
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int ftrace_update_ftrace_func(ftrace_func_t func)
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{
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int ret;
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unsigned long pc;
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unsigned char old[MCOUNT_INSN_SIZE], *new;
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pc = (unsigned long)&ftrace_call;
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memcpy(old, &ftrace_call, MCOUNT_INSN_SIZE);
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new = ftrace_call_replace(pc, (unsigned long)func);
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ret = ftrace_modify_code(pc, old, new);
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return ret;
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}
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int ftrace_make_nop(struct module *mod,
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struct dyn_ftrace *rec, unsigned long addr)
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{
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unsigned char *new, *old;
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unsigned long ip = rec->ip;
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old = ftrace_call_replace(ip, addr);
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new = ftrace_nop_replace();
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return ftrace_modify_code(ip, old, new);
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}
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int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
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{
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unsigned char *new, *old;
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unsigned long ip = rec->ip;
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old = ftrace_nop_replace();
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new = ftrace_call_replace(ip, addr);
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return ftrace_modify_code(ip, old, new);
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}
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int __init ftrace_dyn_arch_init(void)
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{
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return 0;
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}
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