1 files changed, 380 insertions, 10 deletions

diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
index 50ea0ac8c9bf..1b43086b097a 100644
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -14,14 +14,17 @@
 #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 <asm/ftrace.h>
+#include <linux/ftrace.h>
 #include <asm/nops.h>
+#include <asm/nmi.h>
 
 
-static unsigned char ftrace_nop[MCOUNT_INSN_SIZE];
+#ifdef CONFIG_DYNAMIC_FTRACE
 
 union ftrace_code_union {
         char code[MCOUNT_INSN_SIZE];
@@ -31,18 +34,12 @@ union ftrace_code_union {
         } __attribute__((packed));
 };
 
-
 static int ftrace_calc_offset(long ip, long addr)
 {
         return (int)(addr - ip);
 }
 
-unsigned char *ftrace_nop_replace(void)
-{
-        return ftrace_nop;
-}
-
-unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr)
+static unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr)
 {
         static union ftrace_code_union calc;
 
@@ -56,7 +53,142 @@ unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr)
         return calc.code;
 }
 
-int
+/*
+ * 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) Set a flag that says we are modifying code
+ * 3) Wait for any running NMIs to finish.
+ * 4) Write the code
+ * 5) clear the flag.
+ * 6) 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.
+ */
+
+static atomic_t in_nmi = ATOMIC_INIT(0);
+static int mod_code_status;             /* holds return value of text write */
+static int mod_code_write;              /* set when NMI should do the write */
+static void *mod_code_ip;               /* holds the IP to write to */
+static 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 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);
+}
+
+void ftrace_nmi_enter(void)
+{
+        atomic_inc(&in_nmi);
+        /* Must have in_nmi seen before reading write flag */
+        smp_mb();
+        if (mod_code_write) {
+                ftrace_mod_code();
+                atomic_inc(&nmi_update_count);
+        }
+}
+
+void ftrace_nmi_exit(void)
+{
+        /* Finish all executions before clearing in_nmi */
+        smp_wmb();
+        atomic_dec(&in_nmi);
+}
+
+static void wait_for_nmi(void)
+{
+        int waited = 0;
+
+        while (atomic_read(&in_nmi)) {
+                waited = 1;
+                cpu_relax();
+        }
+
+        if (waited)
+                nmi_wait_count++;
+}
+
+static int
+do_ftrace_mod_code(unsigned long ip, void *new_code)
+{
+        mod_code_ip = (void *)ip;
+        mod_code_newcode = new_code;
+
+        /* The buffers need to be visible before we let NMIs write them */
+        smp_wmb();
+
+        mod_code_write = 1;
+
+        /* Make sure write bit is visible before we wait on NMIs */
+        smp_mb();
+
+        wait_for_nmi();
+
+        /* 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_wmb();
+
+        mod_code_write = 0;
+
+        /* make sure NMIs see the cleared bit */
+        smp_mb();
+
+        wait_for_nmi();
+
+        return mod_code_status;
+}
+
+
+
+
+static unsigned char ftrace_nop[MCOUNT_INSN_SIZE];
+
+static unsigned char *ftrace_nop_replace(void)
+{
+        return ftrace_nop;
+}
+
+static int
 ftrace_modify_code(unsigned long ip, unsigned char *old_code,
                    unsigned char *new_code)
 {
@@ -81,7 +213,7 @@ ftrace_modify_code(unsigned long ip, unsigned char *old_code,
                 return -EINVAL;
 
         /* replace the text with the new text */
-        if (probe_kernel_write((void *)ip, new_code, MCOUNT_INSN_SIZE))
+        if (do_ftrace_mod_code(ip, new_code))
                 return -EPERM;
 
         sync_core();
@@ -89,6 +221,29 @@ ftrace_modify_code(unsigned long ip, unsigned char *old_code,
         return 0;
 }
 
+int ftrace_make_nop(struct module *mod,
+                    struct dyn_ftrace *rec, unsigned long addr)
+{
+        unsigned 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 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);
@@ -165,3 +320,218 @@ int __init ftrace_dyn_arch_init(void *data)
 
         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);
+}
+
+#else /* CONFIG_DYNAMIC_FTRACE */
+
+/*
+ * These functions are picked from those used on
+ * this page for dynamic ftrace. They have been
+ * simplified to ignore all traces in NMI context.
+ */
+static atomic_t in_nmi;
+
+void ftrace_nmi_enter(void)
+{
+        atomic_inc(&in_nmi);
+}
+
+void ftrace_nmi_exit(void)
+{
+        atomic_dec(&in_nmi);
+}
+
+#endif /* !CONFIG_DYNAMIC_FTRACE */
+
+/* Add a function return address to the trace stack on thread info.*/
+static int push_return_trace(unsigned long ret, unsigned long long time,
+                                unsigned long func, int *depth)
+{
+        int index;
+
+        if (!current->ret_stack)
+                return -EBUSY;
+
+        /* The return trace stack is full */
+        if (current->curr_ret_stack == FTRACE_RETFUNC_DEPTH - 1) {
+                atomic_inc(&current->trace_overrun);
+                return -EBUSY;
+        }
+
+        index = ++current->curr_ret_stack;
+        barrier();
+        current->ret_stack[index].ret = ret;
+        current->ret_stack[index].func = func;
+        current->ret_stack[index].calltime = time;
+        *depth = index;
+
+        return 0;
+}
+
+/* Retrieve a function return address to the trace stack on thread info.*/
+static void pop_return_trace(struct ftrace_graph_ret *trace, unsigned long *ret)
+{
+        int index;
+
+        index = current->curr_ret_stack;
+
+        if (unlikely(index < 0)) {
+                ftrace_graph_stop();
+                WARN_ON(1);
+                /* Might as well panic, otherwise we have no where to go */
+                *ret = (unsigned long)panic;
+                return;
+        }
+
+        *ret = current->ret_stack[index].ret;
+        trace->func = current->ret_stack[index].func;
+        trace->calltime = current->ret_stack[index].calltime;
+        trace->overrun = atomic_read(&current->trace_overrun);
+        trace->depth = index;
+        barrier();
+        current->curr_ret_stack--;
+
+}
+
+/*
+ * Send the trace to the ring-buffer.
+ * @return the original return address.
+ */
+unsigned long ftrace_return_to_handler(void)
+{
+        struct ftrace_graph_ret trace;
+        unsigned long ret;
+
+        pop_return_trace(&trace, &ret);
+        trace.rettime = cpu_clock(raw_smp_processor_id());
+        ftrace_graph_return(&trace);
+
+        if (unlikely(!ret)) {
+                ftrace_graph_stop();
+                WARN_ON(1);
+                /* Might as well panic. What else to do? */
+                ret = (unsigned long)panic;
+        }
+
+        return ret;
+}
+
+/*
+ * 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;
+        unsigned long long calltime;
+        int faulted;
+        struct ftrace_graph_ent trace;
+        unsigned long return_hooker = (unsigned long)
+                                &return_to_handler;
+
+        /* Nmi's are currently unsupported */
+        if (unlikely(atomic_read(&in_nmi)))
+                return;
+
+        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]), %[old]\n"
+                "2: " _ASM_MOV " %[return_hooker], (%[parent_replaced])\n"
+                "   movl $0, %[faulted]\n"
+
+                ".section .fixup, \"ax\"\n"
+                "3: movl $1, %[faulted]\n"
+                ".previous\n"
+
+                _ASM_EXTABLE(1b, 3b)
+                _ASM_EXTABLE(2b, 3b)
+
+                : [parent_replaced] "=r" (parent), [old] "=r" (old),
+                  [faulted] "=r" (faulted)
+                : [parent_old] "0" (parent), [return_hooker] "r" (return_hooker)
+                : "memory"
+        );
+
+        if (unlikely(faulted)) {
+                ftrace_graph_stop();
+                WARN_ON(1);
+                return;
+        }
+
+        if (unlikely(!__kernel_text_address(old))) {
+                ftrace_graph_stop();
+                *parent = old;
+                WARN_ON(1);
+                return;
+        }
+
+        calltime = cpu_clock(raw_smp_processor_id());
+
+        if (push_return_trace(old, calltime,
+                                self_addr, &trace.depth) == -EBUSY) {
+                *parent = old;
+                return;
+        }
+
+        trace.func = self_addr;
+
+        /* Only trace if the calling function expects to */
+        if (!ftrace_graph_entry(&trace)) {
+                current->curr_ret_stack--;
+                *parent = old;
+        }
+}
+#endif /* CONFIG_FUNCTION_GRAPH_TRACER */