155 lines
3.3 KiB
C
155 lines
3.3 KiB
C
/*
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* Code for replacing ftrace calls with jumps.
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*
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* Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
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*
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* Thanks goes out to P.A. Semi, Inc for supplying me with a PPC64 box.
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*
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*/
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#include <linux/spinlock.h>
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#include <linux/hardirq.h>
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#include <linux/ftrace.h>
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#include <linux/percpu.h>
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#include <linux/init.h>
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#include <linux/list.h>
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#include <asm/cacheflush.h>
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#include <asm/ftrace.h>
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static unsigned int ftrace_nop = 0x60000000;
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#ifdef CONFIG_PPC32
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# define GET_ADDR(addr) addr
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#else
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/* PowerPC64's functions are data that points to the functions */
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# define GET_ADDR(addr) *(unsigned long *)addr
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#endif
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static unsigned int notrace ftrace_calc_offset(long ip, long addr)
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{
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return (int)(addr - ip);
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}
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notrace unsigned char *ftrace_nop_replace(void)
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{
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return (char *)&ftrace_nop;
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}
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notrace unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr)
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{
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static unsigned int op;
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/*
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* It would be nice to just use create_function_call, but that will
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* update the code itself. Here we need to just return the
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* instruction that is going to be modified, without modifying the
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* code.
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*/
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addr = GET_ADDR(addr);
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/* Set to "bl addr" */
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op = 0x48000001 | (ftrace_calc_offset(ip, addr) & 0x03fffffc);
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/*
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* No locking needed, this must be called via kstop_machine
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* which in essence is like running on a uniprocessor machine.
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*/
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return (unsigned char *)&op;
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}
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#ifdef CONFIG_PPC64
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# define _ASM_ALIGN " .align 3 "
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# define _ASM_PTR " .llong "
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#else
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# define _ASM_ALIGN " .align 2 "
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# define _ASM_PTR " .long "
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#endif
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notrace int
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ftrace_modify_code(unsigned long ip, unsigned char *old_code,
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unsigned char *new_code)
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{
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unsigned replaced;
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unsigned old = *(unsigned *)old_code;
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unsigned new = *(unsigned *)new_code;
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int faulted = 0;
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/*
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* Note: Due to modules and __init, code can
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* disappear and change, we need to protect against faulting
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* as well as code changing.
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*
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* No real locking needed, this code is run through
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* kstop_machine.
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*/
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asm volatile (
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"1: lwz %1, 0(%2)\n"
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" cmpw %1, %5\n"
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" bne 2f\n"
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" stwu %3, 0(%2)\n"
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"2:\n"
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".section .fixup, \"ax\"\n"
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"3: li %0, 1\n"
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" b 2b\n"
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".previous\n"
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".section __ex_table,\"a\"\n"
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_ASM_ALIGN "\n"
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_ASM_PTR "1b, 3b\n"
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".previous"
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: "=r"(faulted), "=r"(replaced)
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: "r"(ip), "r"(new),
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"0"(faulted), "r"(old)
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: "memory");
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if (replaced != old && replaced != new)
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faulted = 2;
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if (!faulted)
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flush_icache_range(ip, ip + 8);
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return faulted;
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}
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notrace int ftrace_update_ftrace_func(ftrace_func_t func)
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{
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unsigned long ip = (unsigned long)(&ftrace_call);
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unsigned char old[MCOUNT_INSN_SIZE], *new;
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int ret;
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memcpy(old, &ftrace_call, MCOUNT_INSN_SIZE);
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new = ftrace_call_replace(ip, (unsigned long)func);
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ret = ftrace_modify_code(ip, old, new);
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return ret;
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}
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notrace int ftrace_mcount_set(unsigned long *data)
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{
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unsigned long ip = (long)(&mcount_call);
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unsigned long *addr = data;
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unsigned char old[MCOUNT_INSN_SIZE], *new;
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/*
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* Replace the mcount stub with a pointer to the
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* ip recorder function.
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*/
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memcpy(old, &mcount_call, MCOUNT_INSN_SIZE);
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new = ftrace_call_replace(ip, *addr);
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*addr = ftrace_modify_code(ip, old, new);
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return 0;
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}
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int __init ftrace_dyn_arch_init(void *data)
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{
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/* This is running in kstop_machine */
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ftrace_mcount_set(data);
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return 0;
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}
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