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-rw-r--r--arch/sh/kernel/ftrace.c401
1 files changed, 401 insertions, 0 deletions
diff --git a/arch/sh/kernel/ftrace.c b/arch/sh/kernel/ftrace.c
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+/*
+ * Copyright (C) 2008 Matt Fleming <matt@console-pimps.org>
+ * Copyright (C) 2008 Paul Mundt <lethal@linux-sh.org>
+ *
+ * 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.
+ */
+#include <linux/uaccess.h>
+#include <linux/ftrace.h>
+#include <linux/string.h>
+#include <linux/init.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <asm/ftrace.h>
+#include <asm/cacheflush.h>
+#include <asm/unistd.h>
+#include <trace/syscall.h>
+
+#ifdef CONFIG_DYNAMIC_FTRACE
+static unsigned char ftrace_replaced_code[MCOUNT_INSN_SIZE];
+
+static unsigned char ftrace_nop[4];
+/*
+ * If we're trying to nop out a call to a function, we instead
+ * place a call to the address after the memory table.
+ *
+ * 8c011060 <a>:
+ * 8c011060: 02 d1 mov.l 8c01106c <a+0xc>,r1
+ * 8c011062: 22 4f sts.l pr,@-r15
+ * 8c011064: 02 c7 mova 8c011070 <a+0x10>,r0
+ * 8c011066: 2b 41 jmp @r1
+ * 8c011068: 2a 40 lds r0,pr
+ * 8c01106a: 09 00 nop
+ * 8c01106c: 68 24 .word 0x2468 <--- ip
+ * 8c01106e: 1d 8c .word 0x8c1d
+ * 8c011070: 26 4f lds.l @r15+,pr <--- ip + MCOUNT_INSN_SIZE
+ *
+ * We write 0x8c011070 to 0x8c01106c so that on entry to a() we branch
+ * past the _mcount call and continue executing code like normal.
+ */
+static unsigned char *ftrace_nop_replace(unsigned long ip)
+{
+ __raw_writel(ip + MCOUNT_INSN_SIZE, ftrace_nop);
+ return ftrace_nop;
+}
+
+static unsigned char *ftrace_call_replace(unsigned long ip, unsigned long addr)
+{
+ /* Place the address in the memory table. */
+ __raw_writel(addr, ftrace_replaced_code);
+
+ /*
+ * No locking needed, this must be called via kstop_machine
+ * which in essence is like running on a uniprocessor machine.
+ */
+ return ftrace_replaced_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 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)
+{
+ 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)
+{
+ /* 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 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_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 int ftrace_modify_code(unsigned long ip, unsigned char *old_code,
+ unsigned 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;
+
+ flush_icache_range(ip, ip + MCOUNT_INSN_SIZE);
+
+ return 0;
+}
+
+int ftrace_update_ftrace_func(ftrace_func_t func)
+{
+ unsigned long ip = (unsigned long)(&ftrace_call) + MCOUNT_INSN_OFFSET;
+ unsigned char old[MCOUNT_INSN_SIZE], *new;
+
+ memcpy(old, (unsigned char *)ip, MCOUNT_INSN_SIZE);
+ new = ftrace_call_replace(ip, (unsigned long)func);
+
+ return ftrace_modify_code(ip, old, new);
+}
+
+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(ip);
+
+ 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(ip);
+ new = ftrace_call_replace(ip, addr);
+
+ return ftrace_modify_code(rec->ip, old, new);
+}
+
+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);
+
+static int ftrace_mod(unsigned long ip, unsigned long old_addr,
+ unsigned long new_addr)
+{
+ unsigned char code[MCOUNT_INSN_SIZE];
+
+ if (probe_kernel_read(code, (void *)ip, MCOUNT_INSN_SIZE))
+ return -EFAULT;
+
+ if (old_addr != __raw_readl((unsigned long *)code))
+ return -EINVAL;
+
+ __raw_writel(new_addr, ip);
+ return 0;
+}
+
+int ftrace_enable_ftrace_graph_caller(void)
+{
+ unsigned long ip, old_addr, new_addr;
+
+ ip = (unsigned long)(&ftrace_graph_call) + GRAPH_INSN_OFFSET;
+ old_addr = (unsigned long)(&skip_trace);
+ new_addr = (unsigned long)(&ftrace_graph_caller);
+
+ return ftrace_mod(ip, old_addr, new_addr);
+}
+
+int ftrace_disable_ftrace_graph_caller(void)
+{
+ unsigned long ip, old_addr, new_addr;
+
+ ip = (unsigned long)(&ftrace_graph_call) + GRAPH_INSN_OFFSET;
+ old_addr = (unsigned long)(&ftrace_graph_caller);
+ new_addr = (unsigned long)(&skip_trace);
+
+ return ftrace_mod(ip, old_addr, new_addr);
+}
+#endif /* CONFIG_DYNAMIC_FTRACE */
+
+/*
+ * Hook the return address and push it in the stack of return addrs
+ * in the current thread info.
+ *
+ * This is the main routine for the function graph tracer. The function
+ * graph tracer essentially works like this:
+ *
+ * parent is the stack address containing self_addr's return address.
+ * We pull the real return address out of parent and store it in
+ * current's ret_stack. Then, we replace the return address on the stack
+ * with the address of return_to_handler. self_addr is the function that
+ * called mcount.
+ *
+ * When self_addr returns, it will jump to return_to_handler which calls
+ * ftrace_return_to_handler. ftrace_return_to_handler will pull the real
+ * return address off of current's ret_stack and jump to it.
+ */
+void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr)
+{
+ unsigned long old;
+ int faulted, err;
+ struct ftrace_graph_ent trace;
+ unsigned long return_hooker = (unsigned long)&return_to_handler;
+
+ if (unlikely(ftrace_graph_is_dead()))
+ 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: \n\t"
+ "mov.l @%2, %0 \n\t"
+ "2: \n\t"
+ "mov.l %3, @%2 \n\t"
+ "mov #0, %1 \n\t"
+ "3: \n\t"
+ ".section .fixup, \"ax\" \n\t"
+ "4: \n\t"
+ "mov.l 5f, %0 \n\t"
+ "jmp @%0 \n\t"
+ " mov #1, %1 \n\t"
+ ".balign 4 \n\t"
+ "5: .long 3b \n\t"
+ ".previous \n\t"
+ ".section __ex_table,\"a\" \n\t"
+ ".long 1b, 4b \n\t"
+ ".long 2b, 4b \n\t"
+ ".previous \n\t"
+ : "=&r" (old), "=r" (faulted)
+ : "r" (parent), "r" (return_hooker)
+ );
+
+ if (unlikely(faulted)) {
+ ftrace_graph_stop();
+ WARN_ON(1);
+ return;
+ }
+
+ err = ftrace_push_return_trace(old, self_addr, &trace.depth, 0);
+ if (err == -EBUSY) {
+ __raw_writel(old, parent);
+ return;
+ }
+
+ trace.func = self_addr;
+
+ /* Only trace if the calling function expects to */
+ if (!ftrace_graph_entry(&trace)) {
+ current->curr_ret_stack--;
+ __raw_writel(old, parent);
+ }
+}
+#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
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