text: /*
   * Code for replacing ftrace calls with jumps.
   *
   * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
   *
   * Thanks goes out to P.A. Semi, Inc for supplying me with a PPC64 box.
   *
   * Added function graph tracer code, taken from x86 that was written
   * by Frederic Weisbecker, and ported to PPC by Steven Rostedt.
   *
   */
  
  #define pr_fmt(fmt) "ftrace-powerpc: " fmt
  
  #include <linux/spinlock.h>
  #include <linux/hardirq.h>
  #include <linux/uaccess.h>
  #include <linux/module.h>
  #include <linux/ftrace.h>
  #include <linux/percpu.h>
  #include <linux/init.h>
  #include <linux/list.h>
  
  #include <asm/cacheflush.h>
  #include <asm/code-patching.h>
  #include <asm/ftrace.h>
  #include <asm/syscall.h>
  
  
  #ifdef CONFIG_DYNAMIC_FTRACE
  static unsigned int
  ftrace_call_replace(unsigned long ip, unsigned long addr, int link)
  {
  	unsigned int op;
  
  	addr = ppc_function_entry((void *)addr);
  
  	/* if (link) set op to 'bl' else 'b' */
  	op = create_branch((unsigned int *)ip, addr, link ? 1 : 0);
  
  	return op;
  }
  
  static int
  ftrace_modify_code(unsigned long ip, unsigned int old, unsigned int new)
  {
  	unsigned int replaced;
  
  	/*
  	 * Note: Due to modules and __init, code can
  	 *  disappear and change, we need to protect against faulting
  	 *  as well as code changing. We do this by using the
  	 *  probe_kernel_* functions.
  	 *
  	 * No real locking needed, this code is run through
  	 * kstop_machine, or before SMP starts.
  	 */
  
  	/* read the text we want to modify */
  	if (probe_kernel_read(&replaced, (void *)ip, MCOUNT_INSN_SIZE))
  		return -EFAULT;
  
  	/* Make sure it is what we expect it to be */
  	if (replaced != old)
  		return -EINVAL;
  
  	/* replace the text with the new text */
  	if (patch_instruction((unsigned int *)ip, new))
  		return -EPERM;
  
  	return 0;
  }
  
  /*
   * Helper functions that are the same for both PPC64 and PPC32.
   */
  static int test_24bit_addr(unsigned long ip, unsigned long addr)
  {
  	addr = ppc_function_entry((void *)addr);
  
  	/* use the create_branch to verify that this offset can be branched */
  	return create_branch((unsigned int *)ip, addr, 0);
  }
  
  #ifdef CONFIG_MODULES
  
  static int is_bl_op(unsigned int op)
  {
  	return (op & 0xfc000003) == 0x48000001;
  }
  
  static unsigned long find_bl_target(unsigned long ip, unsigned int op)
  {
  	static int offset;
  
  	offset = (op & 0x03fffffc);
  	/* make it signed */
  	if (offset & 0x02000000)
  		offset |= 0xfe000000;
  
  	return ip + (long)offset;
  }
  
  #ifdef CONFIG_PPC64
  static int
  __ftrace_make_nop(struct module *mod,
  		  struct dyn_ftrace *rec, unsigned long addr)
  {
  	unsigned int op;
  	unsigned long entry, ptr;
  	unsigned long ip = rec->ip;
  	void *tramp;
  
  	/* read where this goes */
  	if (probe_kernel_read(&op, (void *)ip, sizeof(int)))
  		return -EFAULT;
  
  	/* Make sure that that this is still a 24bit jump */
  	if (!is_bl_op(op)) {
  		pr_err("Not expected bl: opcode is %x\n", op);
  		return -EINVAL;
  	}
  
  	/* lets find where the pointer goes */
  	tramp = (void *)find_bl_target(ip, op);
  
  	pr_devel("ip:%lx jumps to %p", ip, tramp);
  
  	if (!is_module_trampoline(tramp)) {
  		pr_err("Not a trampoline\n");
  		return -EINVAL;
  	}
  
  	if (module_trampoline_target(mod, tramp, &ptr)) {
  		pr_err("Failed to get trampoline target\n");
  		return -EFAULT;
  	}
  
  	pr_devel("trampoline target %lx", ptr);
  
  	entry = ppc_global_function_entry((void *)addr);
  	/* This should match what was called */
  	if (ptr != entry) {
  		pr_err("addr %lx does not match expected %lx\n", ptr, entry);
  		return -EINVAL;
  	}
  
  	/*
  	 * Our original call site looks like:
  	 *
  	 * bl <tramp>
  	 * ld r2,XX(r1)
  	 *
  	 * Milton Miller pointed out that we can not simply nop the branch.
  	 * If a task was preempted when calling a trace function, the nops
  	 * will remove the way to restore the TOC in r2 and the r2 TOC will
  	 * get corrupted.
  	 *
  	 * Use a b +8 to jump over the load.
  	 */
  	op = 0x48000008;	/* b +8 */
  
  	if (patch_instruction((unsigned int *)ip, op))
  		return -EPERM;
  
  	return 0;
  }
  
  #else /* !PPC64 */
  static int
  __ftrace_make_nop(struct module *mod,
  		  struct dyn_ftrace *rec, unsigned long addr)
  {
  	unsigned int op;
  	unsigned int jmp[4];
  	unsigned long ip = rec->ip;
  	unsigned long tramp;
  
  	if (probe_kernel_read(&op, (void *)ip, MCOUNT_INSN_SIZE))
  		return -EFAULT;
  
  	/* Make sure that that this is still a 24bit jump */
  	if (!is_bl_op(op)) {
  		pr_err("Not expected bl: opcode is %x\n", op);
  		return -EINVAL;
  	}
  
  	/* lets find where the pointer goes */
  	tramp = find_bl_target(ip, op);
  
  	/*
  	 * On PPC32 the trampoline looks like:
  	 *  0x3d, 0x80, 0x00, 0x00  lis r12,sym@ha
  	 *  0x39, 0x8c, 0x00, 0x00  addi r12,r12,sym@l
  	 *  0x7d, 0x89, 0x03, 0xa6  mtctr r12
  	 *  0x4e, 0x80, 0x04, 0x20  bctr
  	 */
  
  	pr_devel("ip:%lx jumps to %lx", ip, tramp);
  
  	/* Find where the trampoline jumps to */
  	if (probe_kernel_read(jmp, (void *)tramp, sizeof(jmp))) {
  		pr_err("Failed to read %lx\n", tramp);
  		return -EFAULT;
  	}
  
  	pr_devel(" %08x %08x ", jmp[0], jmp[1]);
  
  	/* verify that this is what we expect it to be */
  	if (((jmp[0] & 0xffff0000) != 0x3d800000) ||
  	    ((jmp[1] & 0xffff0000) != 0x398c0000) ||
  	    (jmp[2] != 0x7d8903a6) ||
  	    (jmp[3] != 0x4e800420)) {
  		pr_err("Not a trampoline\n");
  		return -EINVAL;
  	}
  
  	tramp = (jmp[1] & 0xffff) |
  		((jmp[0] & 0xffff) << 16);
  	if (tramp & 0x8000)
  		tramp -= 0x10000;
  
  	pr_devel(" %lx ", tramp);
  
  	if (tramp != addr) {
  		pr_err("Trampoline location %08lx does not match addr\n",
  		       tramp);
  		return -EINVAL;
  	}
  
  	op = PPC_INST_NOP;
  
  	if (patch_instruction((unsigned int *)ip, op))
  		return -EPERM;
  
  	return 0;
  }
  #endif /* PPC64 */
  #endif /* CONFIG_MODULES */
  
  int ftrace_make_nop(struct module *mod,
  		    struct dyn_ftrace *rec, unsigned long addr)
  {
  	unsigned long ip = rec->ip;
  	unsigned int old, new;
  
  	/*
  	 * If the calling address is more that 24 bits away,
  	 * then we had to use a trampoline to make the call.
  	 * Otherwise just update the call site.
  	 */
  	if (test_24bit_addr(ip, addr)) {
  		/* within range */
  		old = ftrace_call_replace(ip, addr, 1);
  		new = PPC_INST_NOP;
  		return ftrace_modify_code(ip, old, new);
  	}
  
  #ifdef CONFIG_MODULES
  	/*
  	 * Out of range jumps are called from modules.
  	 * We should either already have a pointer to the module
  	 * or it has been passed in.
  	 */
  	if (!rec->arch.mod) {
  		if (!mod) {
  			pr_err("No module loaded addr=%lx\n", addr);
  			return -EFAULT;
  		}
  		rec->arch.mod = mod;
  	} else if (mod) {
  		if (mod != rec->arch.mod) {
  			pr_err("Record mod %p not equal to passed in mod %p\n",
  			       rec->arch.mod, mod);
  			return -EINVAL;
  		}
  		/* nothing to do if mod == rec->arch.mod */
  	} else
  		mod = rec->arch.mod;
  
  	return __ftrace_make_nop(mod, rec, addr);
  #else
  	/* We should not get here without modules */
  	return -EINVAL;
  #endif /* CONFIG_MODULES */
  }
  
  #ifdef CONFIG_MODULES
  #ifdef CONFIG_PPC64
  static int
  __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
  {
  	unsigned int op[2];
  	void *ip = (void *)rec->ip;
  
  	/* read where this goes */
  	if (probe_kernel_read(op, ip, sizeof(op)))
  		return -EFAULT;
  
  	/*
  	 * We expect to see:
  	 *
  	 * b +8
  	 * ld r2,XX(r1)
  	 *
  	 * The load offset is different depending on the ABI. For simplicity
  	 * just mask it out when doing the compare.
  	 */
  	if ((op[0] != 0x48000008) || ((op[1] & 0xffff0000) != 0xe8410000)) {
  		pr_err("Unexpected call sequence: %x %x\n", op[0], op[1]);
  		return -EINVAL;
  	}
  
  	/* If we never set up a trampoline to ftrace_caller, then bail */
  	if (!rec->arch.mod->arch.tramp) {
  		pr_err("No ftrace trampoline\n");
  		return -EINVAL;
  	}
  
  	/* Ensure branch is within 24 bits */
  	if (!create_branch(ip, rec->arch.mod->arch.tramp, BRANCH_SET_LINK)) {
  		pr_err("Branch out of range\n");
  		return -EINVAL;
  	}
  
  	if (patch_branch(ip, rec->arch.mod->arch.tramp, BRANCH_SET_LINK)) {
  		pr_err("REL24 out of range!\n");
  		return -EINVAL;
  	}
  
  	return 0;
  }
  #else
  static int
  __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
  {
  	unsigned int op;
  	unsigned long ip = rec->ip;
  
  	/* read where this goes */
  	if (probe_kernel_read(&op, (void *)ip, MCOUNT_INSN_SIZE))
  		return -EFAULT;
  
  	/* It should be pointing to a nop */
  	if (op != PPC_INST_NOP) {
  		pr_err("Expected NOP but have %x\n", op);
  		return -EINVAL;
  	}
  
  	/* If we never set up a trampoline to ftrace_caller, then bail */
  	if (!rec->arch.mod->arch.tramp) {
  		pr_err("No ftrace trampoline\n");
  		return -EINVAL;
  	}
  
  	/* create the branch to the trampoline */
  	op = create_branch((unsigned int *)ip,
  			   rec->arch.mod->arch.tramp, BRANCH_SET_LINK);
  	if (!op) {
  		pr_err("REL24 out of range!\n");
  		return -EINVAL;
  	}
  
  	pr_devel("write to %lx\n", rec->ip);
  
  	if (patch_instruction((unsigned int *)ip, op))
  		return -EPERM;
  
  	return 0;
  }
  #endif /* CONFIG_PPC64 */
  #endif /* CONFIG_MODULES */
  
  int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
  {
  	unsigned long ip = rec->ip;
  	unsigned int old, new;
  
  	/*
  	 * If the calling address is more that 24 bits away,
  	 * then we had to use a trampoline to make the call.
  	 * Otherwise just update the call site.
  	 */
  	if (test_24bit_addr(ip, addr)) {
  		/* within range */
  		old = PPC_INST_NOP;
  		new = ftrace_call_replace(ip, addr, 1);
  		return ftrace_modify_code(ip, old, new);
  	}
  
  #ifdef CONFIG_MODULES
  	/*
  	 * Out of range jumps are called from modules.
  	 * Being that we are converting from nop, it had better
  	 * already have a module defined.
  	 */
  	if (!rec->arch.mod) {
  		pr_err("No module loaded\n");
  		return -EINVAL;
  	}
  
  	return __ftrace_make_call(rec, addr);
  #else
  	/* We should not get here without modules */
  	return -EINVAL;
  #endif /* CONFIG_MODULES */
  }
  
  int ftrace_update_ftrace_func(ftrace_func_t func)
  {
  	unsigned long ip = (unsigned long)(&ftrace_call);
  	unsigned int old, new;
  	int ret;
  
  	old = *(unsigned int *)&ftrace_call;
  	new = ftrace_call_replace(ip, (unsigned long)func, 1);
  	ret = ftrace_modify_code(ip, old, new);
  
  	return ret;
  }
  
  static int __ftrace_replace_code(struct dyn_ftrace *rec, int enable)
  {
  	unsigned long ftrace_addr = (unsigned long)FTRACE_ADDR;
  	int ret;
  
  	ret = ftrace_update_record(rec, enable);
  
  	switch (ret) {
  	case FTRACE_UPDATE_IGNORE:
  		return 0;
  	case FTRACE_UPDATE_MAKE_CALL:
  		return ftrace_make_call(rec, ftrace_addr);
  	case FTRACE_UPDATE_MAKE_NOP:
  		return ftrace_make_nop(NULL, rec, ftrace_addr);
  	}
  
  	return 0;
  }
  
  void ftrace_replace_code(int enable)
  {
  	struct ftrace_rec_iter *iter;
  	struct dyn_ftrace *rec;
  	int ret;
  
  	for (iter = ftrace_rec_iter_start(); iter;
  	     iter = ftrace_rec_iter_next(iter)) {
  		rec = ftrace_rec_iter_record(iter);
  		ret = __ftrace_replace_code(rec, enable);
  		if (ret) {
  			ftrace_bug(ret, rec->ip);
  			return;
  		}
  	}
  }
  
  void arch_ftrace_update_code(int command)
  {
  	if (command & FTRACE_UPDATE_CALLS)
  		ftrace_replace_code(1);
  	else if (command & FTRACE_DISABLE_CALLS)
  		ftrace_replace_code(0);
  
  	if (command & FTRACE_UPDATE_TRACE_FUNC)
  		ftrace_update_ftrace_func(ftrace_trace_function);
  
  	if (command & FTRACE_START_FUNC_RET)
  		ftrace_enable_ftrace_graph_caller();
  	else if (command & FTRACE_STOP_FUNC_RET)
  		ftrace_disable_ftrace_graph_caller();
  }
  
  int __init ftrace_dyn_arch_init(void)
  {
  	return 0;
  }
  #endif /* CONFIG_DYNAMIC_FTRACE */
  
  #ifdef CONFIG_FUNCTION_GRAPH_TRACER
  
  #ifdef CONFIG_DYNAMIC_FTRACE
  extern void ftrace_graph_call(void);
  extern void ftrace_graph_stub(void);
  
  int ftrace_enable_ftrace_graph_caller(void)
  {
  	unsigned long ip = (unsigned long)(&ftrace_graph_call);
  	unsigned long addr = (unsigned long)(&ftrace_graph_caller);
  	unsigned long stub = (unsigned long)(&ftrace_graph_stub);
  	unsigned int old, new;
  
  	old = ftrace_call_replace(ip, stub, 0);
  	new = ftrace_call_replace(ip, addr, 0);
  
  	return ftrace_modify_code(ip, old, new);
  }
  
  int ftrace_disable_ftrace_graph_caller(void)
  {
  	unsigned long ip = (unsigned long)(&ftrace_graph_call);
  	unsigned long addr = (unsigned long)(&ftrace_graph_caller);
  	unsigned long stub = (unsigned long)(&ftrace_graph_stub);
  	unsigned int old, new;
  
  	old = ftrace_call_replace(ip, addr, 0);
  	new = ftrace_call_replace(ip, stub, 0);
  
  	return ftrace_modify_code(ip, old, new);
  }
  #endif /* CONFIG_DYNAMIC_FTRACE */
  
  #ifdef CONFIG_PPC64
  extern void mod_return_to_handler(void);
  #endif
  
  /*
   * Hook the return address and push it in the stack of return addrs
   * in current thread info.
   */
  void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr)
  {
  	unsigned long old;
  	int faulted;
  	struct ftrace_graph_ent trace;
  	unsigned long return_hooker = (unsigned long)&return_to_handler;
  
  	if (unlikely(atomic_read(&current->tracing_graph_pause)))
  		return;
  
  #ifdef CONFIG_PPC64
  	/* non core kernel code needs to save and restore the TOC */
  	if (REGION_ID(self_addr) != KERNEL_REGION_ID)
  		return_hooker = (unsigned long)&mod_return_to_handler;
  #endif
  
  	return_hooker = ppc_function_entry((void *)return_hooker);
  
  	/*
  	 * Protect against fault, even if it shouldn't
  	 * happen. This tool is too much intrusive to
  	 * ignore such a protection.
  	 */
  	asm volatile(
  		"1: " PPC_LL "%[old], 0(%[parent])\n"
  		"2: " PPC_STL "%[return_hooker], 0(%[parent])\n"
  		"   li %[faulted], 0\n"
  		"3:\n"
  
  		".section .fixup, \"ax\"\n"
  		"4: li %[faulted], 1\n"
  		"   b 3b\n"
  		".previous\n"
  
  		".section __ex_table,\"a\"\n"
  			PPC_LONG_ALIGN "\n"
  			PPC_LONG "1b,4b\n"
  			PPC_LONG "2b,4b\n"
  		".previous"
  
  		: [old] "=&r" (old), [faulted] "=r" (faulted)
  		: [parent] "r" (parent), [return_hooker] "r" (return_hooker)
  		: "memory"
  	);
  
  	if (unlikely(faulted)) {
  		ftrace_graph_stop();
  		WARN_ON(1);
  		return;
  	}
  
  	trace.func = self_addr;
  	trace.depth = current->curr_ret_stack + 1;
  
  	/* Only trace if the calling function expects to */
  	if (!ftrace_graph_entry(&trace)) {
  		*parent = old;
  		return;
  	}
  
  	if (ftrace_push_return_trace(old, self_addr, &trace.depth, 0) == -EBUSY)
  		*parent = old;
  }
  #endif /* CONFIG_FUNCTION_GRAPH_TRACER */
  
  #if defined(CONFIG_FTRACE_SYSCALLS) && defined(CONFIG_PPC64)
  unsigned long __init arch_syscall_addr(int nr)
  {
  	return sys_call_table[nr*2];
  }
  #endif /* CONFIG_FTRACE_SYSCALLS && CONFIG_PPC64 */
  