Initial import

1 files changed, 244 insertions, 0 deletions

diff --git a/arch/s390/kernel/ftrace.c b/arch/s390/kernel/ftrace.c
new file mode 100644
index 000000000..e0eaf1113
--- /dev/null
+++ b/arch/s390/kernel/ftrace.c
@@ -0,0 +1,244 @@
+/*
+ * Dynamic function tracer architecture backend.
+ *
+ * Copyright IBM Corp. 2009,2014
+ *
+ *   Author(s): Heiko Carstens <heiko.carstens@de.ibm.com>,
+ *		Martin Schwidefsky <schwidefsky@de.ibm.com>
+ */
+
+#include <linux/moduleloader.h>
+#include <linux/hardirq.h>
+#include <linux/uaccess.h>
+#include <linux/ftrace.h>
+#include <linux/kernel.h>
+#include <linux/types.h>
+#include <linux/kprobes.h>
+#include <trace/syscall.h>
+#include <asm/asm-offsets.h>
+#include <asm/cacheflush.h>
+#include "entry.h"
+
+/*
+ * The mcount code looks like this:
+ *	stg	%r14,8(%r15)		# offset 0
+ *	larl	%r1,<&counter>		# offset 6
+ *	brasl	%r14,_mcount		# offset 12
+ *	lg	%r14,8(%r15)		# offset 18
+ * Total length is 24 bytes. Only the first instruction will be patched
+ * by ftrace_make_call / ftrace_make_nop.
+ * The enabled ftrace code block looks like this:
+ * >	brasl	%r0,ftrace_caller	# offset 0
+ *	larl	%r1,<&counter>		# offset 6
+ *	brasl	%r14,_mcount		# offset 12
+ *	lg	%r14,8(%r15)		# offset 18
+ * The ftrace function gets called with a non-standard C function call ABI
+ * where r0 contains the return address. It is also expected that the called
+ * function only clobbers r0 and r1, but restores r2-r15.
+ * For module code we can't directly jump to ftrace caller, but need a
+ * trampoline (ftrace_plt), which clobbers also r1.
+ * The return point of the ftrace function has offset 24, so execution
+ * continues behind the mcount block.
+ * The disabled ftrace code block looks like this:
+ * >	jg	.+24			# offset 0
+ *	larl	%r1,<&counter>		# offset 6
+ *	brasl	%r14,_mcount		# offset 12
+ *	lg	%r14,8(%r15)		# offset 18
+ * The jg instruction branches to offset 24 to skip as many instructions
+ * as possible.
+ * In case we use gcc's hotpatch feature the original and also the disabled
+ * function prologue contains only a single six byte instruction and looks
+ * like this:
+ * >	brcl	0,0			# offset 0
+ * To enable ftrace the code gets patched like above and afterwards looks
+ * like this:
+ * >	brasl	%r0,ftrace_caller	# offset 0
+ */
+
+unsigned long ftrace_plt;
+
+static inline void ftrace_generate_orig_insn(struct ftrace_insn *insn)
+{
+#ifdef CC_USING_HOTPATCH
+	/* brcl 0,0 */
+	insn->opc = 0xc004;
+	insn->disp = 0;
+#else
+	/* stg r14,8(r15) */
+	insn->opc = 0xe3e0;
+	insn->disp = 0xf0080024;
+#endif
+}
+
+static inline int is_kprobe_on_ftrace(struct ftrace_insn *insn)
+{
+#ifdef CONFIG_KPROBES
+	if (insn->opc == BREAKPOINT_INSTRUCTION)
+		return 1;
+#endif
+	return 0;
+}
+
+static inline void ftrace_generate_kprobe_nop_insn(struct ftrace_insn *insn)
+{
+#ifdef CONFIG_KPROBES
+	insn->opc = BREAKPOINT_INSTRUCTION;
+	insn->disp = KPROBE_ON_FTRACE_NOP;
+#endif
+}
+
+static inline void ftrace_generate_kprobe_call_insn(struct ftrace_insn *insn)
+{
+#ifdef CONFIG_KPROBES
+	insn->opc = BREAKPOINT_INSTRUCTION;
+	insn->disp = KPROBE_ON_FTRACE_CALL;
+#endif
+}
+
+int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
+		       unsigned long addr)
+{
+	return 0;
+}
+
+int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec,
+		    unsigned long addr)
+{
+	struct ftrace_insn orig, new, old;
+
+	if (probe_kernel_read(&old, (void *) rec->ip, sizeof(old)))
+		return -EFAULT;
+	if (addr == MCOUNT_ADDR) {
+		/* Initial code replacement */
+		ftrace_generate_orig_insn(&orig);
+		ftrace_generate_nop_insn(&new);
+	} else if (is_kprobe_on_ftrace(&old)) {
+		/*
+		 * If we find a breakpoint instruction, a kprobe has been
+		 * placed at the beginning of the function. We write the
+		 * constant KPROBE_ON_FTRACE_NOP into the remaining four
+		 * bytes of the original instruction so that the kprobes
+		 * handler can execute a nop, if it reaches this breakpoint.
+		 */
+		ftrace_generate_kprobe_call_insn(&orig);
+		ftrace_generate_kprobe_nop_insn(&new);
+	} else {
+		/* Replace ftrace call with a nop. */
+		ftrace_generate_call_insn(&orig, rec->ip);
+		ftrace_generate_nop_insn(&new);
+	}
+	/* Verify that the to be replaced code matches what we expect. */
+	if (memcmp(&orig, &old, sizeof(old)))
+		return -EINVAL;
+	s390_kernel_write((void *) rec->ip, &new, sizeof(new));
+	return 0;
+}
+
+int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
+{
+	struct ftrace_insn orig, new, old;
+
+	if (probe_kernel_read(&old, (void *) rec->ip, sizeof(old)))
+		return -EFAULT;
+	if (is_kprobe_on_ftrace(&old)) {
+		/*
+		 * If we find a breakpoint instruction, a kprobe has been
+		 * placed at the beginning of the function. We write the
+		 * constant KPROBE_ON_FTRACE_CALL into the remaining four
+		 * bytes of the original instruction so that the kprobes
+		 * handler can execute a brasl if it reaches this breakpoint.
+		 */
+		ftrace_generate_kprobe_nop_insn(&orig);
+		ftrace_generate_kprobe_call_insn(&new);
+	} else {
+		/* Replace nop with an ftrace call. */
+		ftrace_generate_nop_insn(&orig);
+		ftrace_generate_call_insn(&new, rec->ip);
+	}
+	/* Verify that the to be replaced code matches what we expect. */
+	if (memcmp(&orig, &old, sizeof(old)))
+		return -EINVAL;
+	s390_kernel_write((void *) rec->ip, &new, sizeof(new));
+	return 0;
+}
+
+int ftrace_update_ftrace_func(ftrace_func_t func)
+{
+	return 0;
+}
+
+int __init ftrace_dyn_arch_init(void)
+{
+	return 0;
+}
+
+static int __init ftrace_plt_init(void)
+{
+	unsigned int *ip;
+
+	ftrace_plt = (unsigned long) module_alloc(PAGE_SIZE);
+	if (!ftrace_plt)
+		panic("cannot allocate ftrace plt\n");
+	ip = (unsigned int *) ftrace_plt;
+	ip[0] = 0x0d10e310; /* basr 1,0; lg 1,10(1); br 1 */
+	ip[1] = 0x100a0004;
+	ip[2] = 0x07f10000;
+	ip[3] = FTRACE_ADDR >> 32;
+	ip[4] = FTRACE_ADDR & 0xffffffff;
+	set_memory_ro(ftrace_plt, 1);
+	return 0;
+}
+device_initcall(ftrace_plt_init);
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+/*
+ * Hook the return address and push it in the stack of return addresses
+ * in current thread info.
+ */
+unsigned long prepare_ftrace_return(unsigned long parent, unsigned long ip)
+{
+	struct ftrace_graph_ent trace;
+
+	if (unlikely(ftrace_graph_is_dead()))
+		goto out;
+	if (unlikely(atomic_read(&current->tracing_graph_pause)))
+		goto out;
+	ip = (ip & PSW_ADDR_INSN) - MCOUNT_INSN_SIZE;
+	trace.func = ip;
+	trace.depth = current->curr_ret_stack + 1;
+	/* Only trace if the calling function expects to. */
+	if (!ftrace_graph_entry(&trace))
+		goto out;
+	if (ftrace_push_return_trace(parent, ip, &trace.depth, 0) == -EBUSY)
+		goto out;
+	parent = (unsigned long) return_to_handler;
+out:
+	return parent;
+}
+NOKPROBE_SYMBOL(prepare_ftrace_return);
+
+/*
+ * Patch the kernel code at ftrace_graph_caller location. The instruction
+ * there is branch relative on condition. To enable the ftrace graph code
+ * block, we simply patch the mask field of the instruction to zero and
+ * turn the instruction into a nop.
+ * To disable the ftrace graph code the mask field will be patched to
+ * all ones, which turns the instruction into an unconditional branch.
+ */
+int ftrace_enable_ftrace_graph_caller(void)
+{
+	u8 op = 0x04; /* set mask field to zero */
+
+	s390_kernel_write(__va(ftrace_graph_caller)+1, &op, sizeof(op));
+	return 0;
+}
+
+int ftrace_disable_ftrace_graph_caller(void)
+{
+	u8 op = 0xf4; /* set mask field to all ones */
+
+	s390_kernel_write(__va(ftrace_graph_caller)+1, &op, sizeof(op));
+	return 0;
+}
+
+#endif /* CONFIG_FUNCTION_GRAPH_TRACER */