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With dynamic function tracer, by default, _mcount is defined as an "empty" function, it returns directly without any more action. When enabling it in user-space, it will jump to a real tracing function(ftrace_caller), and do the real job for us. Differ from the static function tracer, dynamic function tracer provides two functions ftrace_make_call()/ftrace_make_nop() to enable/disable the tracing of some indicated kernel functions(set_ftrace_filter). In the kernel version, there is only one "_mcount" string for every kernel function, so, we just need to match this one in mcount_regex of scripts/recordmcount.pl. For more information please look at code and Documentation/trace folder. Steven ACK that scripts/recordmcount.pl part. Acked-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Michal Simek <monstr@monstr.eu>
152 lines
4.2 KiB
C
152 lines
4.2 KiB
C
/*
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* Ftrace support for Microblaze.
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*
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* Copyright (C) 2009 Michal Simek <monstr@monstr.eu>
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* Copyright (C) 2009 PetaLogix
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*
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* Based on MIPS and PowerPC ftrace code
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*
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* This file is subject to the terms and conditions of the GNU General Public
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* License. See the file "COPYING" in the main directory of this archive
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* for more details.
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*/
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#include <asm/cacheflush.h>
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#include <linux/ftrace.h>
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#ifdef CONFIG_DYNAMIC_FTRACE
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/* save value to addr - it is save to do it in asm */
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static int ftrace_modify_code(unsigned long addr, unsigned int value)
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{
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int faulted = 0;
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__asm__ __volatile__(" 1: swi %2, %1, 0; \
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addik %0, r0, 0; \
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2: \
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.section .fixup, \"ax\"; \
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3: brid 2b; \
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addik %0, r0, 1; \
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.previous; \
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.section __ex_table,\"a\"; \
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.word 1b,3b; \
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.previous;" \
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: "=r" (faulted)
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: "r" (addr), "r" (value)
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);
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if (unlikely(faulted))
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return -EFAULT;
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return 0;
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}
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#define MICROBLAZE_NOP 0x80000000
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#define MICROBLAZE_BRI 0xb800000C
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static unsigned int recorded; /* if save was or not */
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static unsigned int imm; /* saving whole imm instruction */
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/* There are two approaches howto solve ftrace_make nop function - look below */
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#undef USE_FTRACE_NOP
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#ifdef USE_FTRACE_NOP
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static unsigned int bralid; /* saving whole bralid instruction */
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#endif
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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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/* we have this part of code which we are working with
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* b000c000 imm -16384
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* b9fc8e30 bralid r15, -29136 // c0008e30 <_mcount>
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* 80000000 or r0, r0, r0
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*
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* The first solution (!USE_FTRACE_NOP-could be called branch solution)
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* b000c000 bri 12 (0xC - jump to any other instruction)
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* b9fc8e30 bralid r15, -29136 // c0008e30 <_mcount>
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* 80000000 or r0, r0, r0
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* any other instruction
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*
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* The second solution (USE_FTRACE_NOP) - no jump just nops
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* 80000000 or r0, r0, r0
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* 80000000 or r0, r0, r0
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* 80000000 or r0, r0, r0
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*/
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int ret = 0;
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if (recorded == 0) {
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recorded = 1;
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imm = *(unsigned int *)rec->ip;
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pr_debug("%s: imm:0x%x\n", __func__, imm);
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#ifdef USE_FTRACE_NOP
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bralid = *(unsigned int *)(rec->ip + 4);
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pr_debug("%s: bralid 0x%x\n", __func__, bralid);
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#endif /* USE_FTRACE_NOP */
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}
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#ifdef USE_FTRACE_NOP
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ret = ftrace_modify_code(rec->ip, MICROBLAZE_NOP);
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ret += ftrace_modify_code(rec->ip + 4, MICROBLAZE_NOP);
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#else /* USE_FTRACE_NOP */
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ret = ftrace_modify_code(rec->ip, MICROBLAZE_BRI);
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#endif /* USE_FTRACE_NOP */
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return ret;
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}
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static int ret_addr; /* initialized as 0 by default */
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/* I believe that first is called ftrace_make_nop before this function */
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int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
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{
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int ret;
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ret_addr = addr; /* saving where the barrier jump is */
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pr_debug("%s: addr:0x%x, rec->ip: 0x%x, imm:0x%x\n",
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__func__, (unsigned int)addr, (unsigned int)rec->ip, imm);
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ret = ftrace_modify_code(rec->ip, imm);
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#ifdef USE_FTRACE_NOP
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pr_debug("%s: bralid:0x%x\n", __func__, bralid);
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ret += ftrace_modify_code(rec->ip + 4, bralid);
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#endif /* USE_FTRACE_NOP */
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return ret;
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}
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int __init ftrace_dyn_arch_init(void *data)
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{
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/* The return code is retured via data */
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*(unsigned long *)data = 0;
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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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unsigned long ip = (unsigned long)(&ftrace_call);
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unsigned int upper = (unsigned int)func;
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unsigned int lower = (unsigned int)func;
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int ret = 0;
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/* create proper saving to ftrace_call poll */
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upper = 0xb0000000 + (upper >> 16); /* imm func_upper */
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lower = 0x32800000 + (lower & 0xFFFF); /* addik r20, r0, func_lower */
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pr_debug("%s: func=0x%x, ip=0x%x, upper=0x%x, lower=0x%x\n",
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__func__, (unsigned int)func, (unsigned int)ip, upper, lower);
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/* save upper and lower code */
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ret = ftrace_modify_code(ip, upper);
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ret += ftrace_modify_code(ip + 4, lower);
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/* We just need to remove the rtsd r15, 8 by NOP */
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BUG_ON(!ret_addr);
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if (ret_addr)
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ret += ftrace_modify_code(ret_addr, MICROBLAZE_NOP);
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else
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ret = 1; /* fault */
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/* All changes are done - lets do caches consistent */
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flush_icache();
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return ret;
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}
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#endif /* CONFIG_DYNAMIC_FTRACE */
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