e9b349f089
There is no need to worry about module and __init text disappearing case, because that ftrace has a module notifier that is called when a module is being unloaded and before the text goes away and this code grabs the ftrace_lock mutex and removes the module functions from the ftrace list, such that it will no longer do any modifications to that module's text, the update to make functions be traced or not is done under the ftrace_lock mutex as well. And by now, __init section codes should not been modified by ftrace, because it is black listed in recordmcount.c and ignored by ftrace. Link: http://lkml.kernel.org/r/1449367378-29430-3-git-send-email-huawei.libin@huawei.com Cc: linux-metag@vger.kernel.org Acked-by: James Hogan <james.hogan@imgtec.com> Suggested-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Li Bin <huawei.libin@huawei.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
123 lines
3.1 KiB
C
123 lines
3.1 KiB
C
/*
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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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/* run from kstop_machine */
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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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