395a59d0f8
Record the address of the mcount call-site. Currently all archs except sparc64 record the address of the instruction following the mcount call-site. Some general cleanups are entailed. Storing mcount addresses in rec->ip enables looking them up in the kprobe hash table later on to check if they're kprobe'd. Signed-off-by: Abhishek Sagar <sagar.abhishek@gmail.com> Cc: davem@davemloft.net Cc: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
141 lines
3.1 KiB
C
141 lines
3.1 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 to Ingo Molnar, for suggesting the idea.
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* Mathieu Desnoyers, for suggesting postponing the modifications.
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* Arjan van de Ven, for keeping me straight, and explaining to me
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* the dangers of modifying code on the run.
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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/alternative.h>
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#include <asm/ftrace.h>
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/* Long is fine, even if it is only 4 bytes ;-) */
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static long *ftrace_nop;
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union ftrace_code_union {
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char code[MCOUNT_INSN_SIZE];
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struct {
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char e8;
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int offset;
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} __attribute__((packed));
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};
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static 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 union ftrace_code_union calc;
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calc.e8 = 0xe8;
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calc.offset = ftrace_calc_offset(ip + MCOUNT_INSN_SIZE, addr);
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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 calc.code;
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}
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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; /* 4 bytes */
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unsigned new = *(unsigned *)new_code; /* 4 bytes */
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unsigned char newch = new_code[4];
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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: lock\n"
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" cmpxchg %3, (%2)\n"
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" jnz 2f\n"
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" movb %b4, 4(%2)\n"
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"2:\n"
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".section .fixup, \"ax\"\n"
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"3: movl $1, %0\n"
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" jmp 2b\n"
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".previous\n"
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_ASM_EXTABLE(1b, 3b)
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: "=r"(faulted), "=a"(replaced)
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: "r"(ip), "r"(new), "c"(newch),
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"0"(faulted), "a"(old)
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: "memory");
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sync_core();
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if (replaced != old && replaced != new)
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faulted = 2;
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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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const unsigned char *const *noptable = find_nop_table();
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/* This is running in kstop_machine */
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ftrace_mcount_set(data);
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ftrace_nop = (unsigned long *)noptable[MCOUNT_INSN_SIZE];
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return 0;
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}
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