1 files changed, 455 insertions, 0 deletions
diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
new file mode 100644
index 00000000..c9a281f2
--- /dev/null
+++ b/arch/x86/kernel/ftrace.c
@@ -0,0 +1,455 @@
+/*
+ * Code for replacing ftrace calls with jumps.
+ *
+ * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
+ *
+ * Thanks goes to Ingo Molnar, for suggesting the idea.
+ * Mathieu Desnoyers, for suggesting postponing the modifications.
+ * Arjan van de Ven, for keeping me straight, and explaining to me
+ * the dangers of modifying code on the run.
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/spinlock.h>
+#include <linux/hardirq.h>
+#include <linux/uaccess.h>
+#include <linux/ftrace.h>
+#include <linux/percpu.h>
+#include <linux/sched.h>
+#include <linux/init.h>
+#include <linux/list.h>
+#include <linux/module.h>
+
+#include <trace/syscall.h>
+
+#include <asm/cacheflush.h>
+#include <asm/ftrace.h>
+#include <asm/nops.h>
+#include <asm/nmi.h>
+
+
+#ifdef CONFIG_DYNAMIC_FTRACE
+
+/*
+ * modifying_code is set to notify NMIs that they need to use
+ * memory barriers when entering or exiting. But we don't want
+ * to burden NMIs with unnecessary memory barriers when code
+ * modification is not being done (which is most of the time).
+ *
+ * A mutex is already held when ftrace_arch_code_modify_prepare
+ * and post_process are called. No locks need to be taken here.
+ *
+ * Stop machine will make sure currently running NMIs are done
+ * and new NMIs will see the updated variable before we need
+ * to worry about NMIs doing memory barriers.
+ */
+static int modifying_code __read_mostly;
+static DEFINE_PER_CPU(int, save_modifying_code);
+
+int ftrace_arch_code_modify_prepare(void)
+{
+	set_kernel_text_rw();
+	set_all_modules_text_rw();
+	modifying_code = 1;
+	return 0;
+}
+
+int ftrace_arch_code_modify_post_process(void)
+{
+	modifying_code = 0;
+	set_all_modules_text_ro();
+	set_kernel_text_ro();
+	return 0;
+}
+
+union ftrace_code_union {
+	char code[MCOUNT_INSN_SIZE];
+	struct {
+		char e8;
+		int offset;
+	} __attribute__((packed));
+};
+
+static int ftrace_calc_offset(long ip, long addr)
+{
+	return (int)(addr - ip);
+}
+
+static unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr)
+{
+	static union ftrace_code_union calc;
+
+	calc.e8		= 0xe8;
+	calc.offset	= ftrace_calc_offset(ip + MCOUNT_INSN_SIZE, addr);
+
+	/*
+	 * No locking needed, this must be called via kstop_machine
+	 * which in essence is like running on a uniprocessor machine.
+	 */
+	return calc.code;
+}
+
+/*
+ * Modifying code must take extra care. On an SMP machine, if
+ * the code being modified is also being executed on another CPU
+ * that CPU will have undefined results and possibly take a GPF.
+ * We use kstop_machine to stop other CPUS from exectuing code.
+ * But this does not stop NMIs from happening. We still need
+ * to protect against that. We separate out the modification of
+ * the code to take care of this.
+ *
+ * Two buffers are added: An IP buffer and a "code" buffer.
+ *
+ * 1) Put the instruction pointer into the IP buffer
+ *    and the new code into the "code" buffer.
+ * 2) Wait for any running NMIs to finish and set a flag that says
+ *    we are modifying code, it is done in an atomic operation.
+ * 3) Write the code
+ * 4) clear the flag.
+ * 5) Wait for any running NMIs to finish.
+ *
+ * If an NMI is executed, the first thing it does is to call
+ * "ftrace_nmi_enter". This will check if the flag is set to write
+ * and if it is, it will write what is in the IP and "code" buffers.
+ *
+ * The trick is, it does not matter if everyone is writing the same
+ * content to the code location. Also, if a CPU is executing code
+ * it is OK to write to that code location if the contents being written
+ * are the same as what exists.
+ */
+
+#define MOD_CODE_WRITE_FLAG (1 << 31)	/* set when NMI should do the write */
+static atomic_t nmi_running = ATOMIC_INIT(0);
+static int mod_code_status;		/* holds return value of text write */
+static void *mod_code_ip;		/* holds the IP to write to */
+static const void *mod_code_newcode;	/* holds the text to write to the IP */
+
+static unsigned nmi_wait_count;
+static atomic_t nmi_update_count = ATOMIC_INIT(0);
+
+int ftrace_arch_read_dyn_info(char *buf, int size)
+{
+	int r;
+
+	r = snprintf(buf, size, "%u %u",
+		     nmi_wait_count,
+		     atomic_read(&nmi_update_count));
+	return r;
+}
+
+static void clear_mod_flag(void)
+{
+	int old = atomic_read(&nmi_running);
+
+	for (;;) {
+		int new = old & ~MOD_CODE_WRITE_FLAG;
+
+		if (old == new)
+			break;
+
+		old = atomic_cmpxchg(&nmi_running, old, new);
+	}
+}
+
+static void ftrace_mod_code(void)
+{
+	/*
+	 * Yes, more than one CPU process can be writing to mod_code_status.
+	 *    (and the code itself)
+	 * But if one were to fail, then they all should, and if one were
+	 * to succeed, then they all should.
+	 */
+	mod_code_status = probe_kernel_write(mod_code_ip, mod_code_newcode,
+					     MCOUNT_INSN_SIZE);
+
+	/* if we fail, then kill any new writers */
+	if (mod_code_status)
+		clear_mod_flag();
+}
+
+void ftrace_nmi_enter(void)
+{
+	__this_cpu_write(save_modifying_code, modifying_code);
+
+	if (!__this_cpu_read(save_modifying_code))
+		return;
+
+	if (atomic_inc_return(&nmi_running) & MOD_CODE_WRITE_FLAG) {
+		smp_rmb();
+		ftrace_mod_code();
+		atomic_inc(&nmi_update_count);
+	}
+	/* Must have previous changes seen before executions */
+	smp_mb();
+}
+
+void ftrace_nmi_exit(void)
+{
+	if (!__this_cpu_read(save_modifying_code))
+		return;
+
+	/* Finish all executions before clearing nmi_running */
+	smp_mb();
+	atomic_dec(&nmi_running);
+}
+
+static void wait_for_nmi_and_set_mod_flag(void)
+{
+	if (!atomic_cmpxchg(&nmi_running, 0, MOD_CODE_WRITE_FLAG))
+		return;
+
+	do {
+		cpu_relax();
+	} while (atomic_cmpxchg(&nmi_running, 0, MOD_CODE_WRITE_FLAG));
+
+	nmi_wait_count++;
+}
+
+static void wait_for_nmi(void)
+{
+	if (!atomic_read(&nmi_running))
+		return;
+
+	do {
+		cpu_relax();
+	} while (atomic_read(&nmi_running));
+
+	nmi_wait_count++;
+}
+
+static inline int
+within(unsigned long addr, unsigned long start, unsigned long end)
+{
+	return addr >= start && addr < end;
+}
+
+static int
+do_ftrace_mod_code(unsigned long ip, const void *new_code)
+{
+	/*
+	 * On x86_64, kernel text mappings are mapped read-only with
+	 * CONFIG_DEBUG_RODATA. So we use the kernel identity mapping instead
+	 * of the kernel text mapping to modify the kernel text.
+	 *
+	 * For 32bit kernels, these mappings are same and we can use
+	 * kernel identity mapping to modify code.
+	 */
+	if (within(ip, (unsigned long)_text, (unsigned long)_etext))
+		ip = (unsigned long)__va(__pa(ip));
+
+	mod_code_ip = (void *)ip;
+	mod_code_newcode = new_code;
+
+	/* The buffers need to be visible before we let NMIs write them */
+	smp_mb();
+
+	wait_for_nmi_and_set_mod_flag();
+
+	/* Make sure all running NMIs have finished before we write the code */
+	smp_mb();
+
+	ftrace_mod_code();
+
+	/* Make sure the write happens before clearing the bit */
+	smp_mb();
+
+	clear_mod_flag();
+	wait_for_nmi();
+
+	return mod_code_status;
+}
+
+static const unsigned char *ftrace_nop_replace(void)
+{
+	return ideal_nops[NOP_ATOMIC5];
+}
+
+static int
+ftrace_modify_code(unsigned long ip, unsigned const char *old_code,
+		   unsigned const char *new_code)
+{
+	unsigned char replaced[MCOUNT_INSN_SIZE];
+
+	/*
+	 * 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 (memcmp(replaced, old_code, MCOUNT_INSN_SIZE) != 0)
+		return -EINVAL;
+
+	/* replace the text with the new text */
+	if (do_ftrace_mod_code(ip, new_code))
+		return -EPERM;
+
+	sync_core();
+
+	return 0;
+}
+
+int ftrace_make_nop(struct module *mod,
+		    struct dyn_ftrace *rec, unsigned long addr)
+{
+	unsigned const char *new, *old;
+	unsigned long ip = rec->ip;
+
+	old = ftrace_call_replace(ip, addr);
+	new = ftrace_nop_replace();
+
+	return ftrace_modify_code(rec->ip, old, new);
+}
+
+int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
+{
+	unsigned const char *new, *old;
+	unsigned long ip = rec->ip;
+
+	old = ftrace_nop_replace();
+	new = ftrace_call_replace(ip, addr);
+
+	return ftrace_modify_code(rec->ip, old, new);
+}
+
+int ftrace_update_ftrace_func(ftrace_func_t func)
+{
+	unsigned long ip = (unsigned long)(&ftrace_call);
+	unsigned char old[MCOUNT_INSN_SIZE], *new;
+	int ret;
+
+	memcpy(old, &ftrace_call, MCOUNT_INSN_SIZE);
+	new = ftrace_call_replace(ip, (unsigned long)func);
+	ret = ftrace_modify_code(ip, old, new);
+
+	return ret;
+}
+
+int __init ftrace_dyn_arch_init(void *data)
+{
+	/* The return code is retured via data */
+	*(unsigned long *)data = 0;
+
+	return 0;
+}
+#endif
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+
+#ifdef CONFIG_DYNAMIC_FTRACE
+extern void ftrace_graph_call(void);
+
+static int ftrace_mod_jmp(unsigned long ip,
+			  int old_offset, int new_offset)
+{
+	unsigned char code[MCOUNT_INSN_SIZE];
+
+	if (probe_kernel_read(code, (void *)ip, MCOUNT_INSN_SIZE))
+		return -EFAULT;
+
+	if (code[0] != 0xe9 || old_offset != *(int *)(&code[1]))
+		return -EINVAL;
+
+	*(int *)(&code[1]) = new_offset;
+
+	if (do_ftrace_mod_code(ip, &code))
+		return -EPERM;
+
+	return 0;
+}
+
+int ftrace_enable_ftrace_graph_caller(void)
+{
+	unsigned long ip = (unsigned long)(&ftrace_graph_call);
+	int old_offset, new_offset;
+
+	old_offset = (unsigned long)(&ftrace_stub) - (ip + MCOUNT_INSN_SIZE);
+	new_offset = (unsigned long)(&ftrace_graph_caller) - (ip + MCOUNT_INSN_SIZE);
+
+	return ftrace_mod_jmp(ip, old_offset, new_offset);
+}
+
+int ftrace_disable_ftrace_graph_caller(void)
+{
+	unsigned long ip = (unsigned long)(&ftrace_graph_call);
+	int old_offset, new_offset;
+
+	old_offset = (unsigned long)(&ftrace_graph_caller) - (ip + MCOUNT_INSN_SIZE);
+	new_offset = (unsigned long)(&ftrace_stub) - (ip + MCOUNT_INSN_SIZE);
+
+	return ftrace_mod_jmp(ip, old_offset, new_offset);
+}
+
+#endif /* !CONFIG_DYNAMIC_FTRACE */
+
+/*
+ * 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 frame_pointer)
+{
+	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;
+
+	/*
+	 * Protect against fault, even if it shouldn't
+	 * happen. This tool is too much intrusive to
+	 * ignore such a protection.
+	 */
+	asm volatile(
+		"1: " _ASM_MOV " (%[parent]), %[old]\n"
+		"2: " _ASM_MOV " %[return_hooker], (%[parent])\n"
+		"   movl $0, %[faulted]\n"
+		"3:\n"
+
+		".section .fixup, \"ax\"\n"
+		"4: movl $1, %[faulted]\n"
+		"   jmp 3b\n"
+		".previous\n"
+
+		_ASM_EXTABLE(1b, 4b)
+		_ASM_EXTABLE(2b, 4b)
+
+		: [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,
+		    frame_pointer) == -EBUSY) {
+		*parent = old;
+		return;
+	}
+}
+#endif /* CONFIG_FUNCTION_GRAPH_TRACER */