1 files changed, 328 insertions, 0 deletions
diff --git a/arch/mips/kernel/ftrace.c b/arch/mips/kernel/ftrace.c
new file mode 100644
index 00000000..6a2d758d
--- /dev/null
+++ b/arch/mips/kernel/ftrace.c
@@ -0,0 +1,328 @@
+/*
+ * Code for replacing ftrace calls with jumps.
+ *
+ * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
+ * Copyright (C) 2009, 2010 DSLab, Lanzhou University, China
+ * Author: Wu Zhangjin <wuzhangjin@gmail.com>
+ *
+ * Thanks goes to Steven Rostedt for writing the original x86 version.
+ */
+
+#include <linux/uaccess.h>
+#include <linux/init.h>
+#include <linux/ftrace.h>
+
+#include <asm/asm.h>
+#include <asm/asm-offsets.h>
+#include <asm/cacheflush.h>
+#include <asm/uasm.h>
+
+#include <asm-generic/sections.h>
+
+#if defined(KBUILD_MCOUNT_RA_ADDRESS) && defined(CONFIG_32BIT)
+#define MCOUNT_OFFSET_INSNS 5
+#else
+#define MCOUNT_OFFSET_INSNS 4
+#endif
+
+/*
+ * Check if the address is in kernel space
+ *
+ * Clone core_kernel_text() from kernel/extable.c, but doesn't call
+ * init_kernel_text() for Ftrace doesn't trace functions in init sections.
+ */
+static inline int in_kernel_space(unsigned long ip)
+{
+	if (ip >= (unsigned long)_stext &&
+	    ip <= (unsigned long)_etext)
+		return 1;
+	return 0;
+}
+
+#ifdef CONFIG_DYNAMIC_FTRACE
+
+#define JAL 0x0c000000		/* jump & link: ip --> ra, jump to target */
+#define ADDR_MASK 0x03ffffff	/*  op_code|addr : 31...26|25 ....0 */
+#define JUMP_RANGE_MASK ((1UL << 28) - 1)
+
+#define INSN_NOP 0x00000000	/* nop */
+#define INSN_JAL(addr)	\
+	((unsigned int)(JAL | (((addr) >> 2) & ADDR_MASK)))
+
+static unsigned int insn_jal_ftrace_caller __read_mostly;
+static unsigned int insn_lui_v1_hi16_mcount __read_mostly;
+static unsigned int insn_j_ftrace_graph_caller __maybe_unused __read_mostly;
+
+static inline void ftrace_dyn_arch_init_insns(void)
+{
+	u32 *buf;
+	unsigned int v1;
+
+	/* lui v1, hi16_mcount */
+	v1 = 3;
+	buf = (u32 *)&insn_lui_v1_hi16_mcount;
+	UASM_i_LA_mostly(&buf, v1, MCOUNT_ADDR);
+
+	/* jal (ftrace_caller + 8), jump over the first two instruction */
+	buf = (u32 *)&insn_jal_ftrace_caller;
+	uasm_i_jal(&buf, (FTRACE_ADDR + 8) & JUMP_RANGE_MASK);
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+	/* j ftrace_graph_caller */
+	buf = (u32 *)&insn_j_ftrace_graph_caller;
+	uasm_i_j(&buf, (unsigned long)ftrace_graph_caller & JUMP_RANGE_MASK);
+#endif
+}
+
+static int ftrace_modify_code(unsigned long ip, unsigned int new_code)
+{
+	int faulted;
+
+	/* *(unsigned int *)ip = new_code; */
+	safe_store_code(new_code, ip, faulted);
+
+	if (unlikely(faulted))
+		return -EFAULT;
+
+	flush_icache_range(ip, ip + 8);
+
+	return 0;
+}
+
+/*
+ * The details about the calling site of mcount on MIPS
+ *
+ * 1. For kernel:
+ *
+ * move at, ra
+ * jal _mcount		--> nop
+ *
+ * 2. For modules:
+ *
+ * 2.1 For KBUILD_MCOUNT_RA_ADDRESS and CONFIG_32BIT
+ *
+ * lui v1, hi_16bit_of_mcount        --> b 1f (0x10000005)
+ * addiu v1, v1, low_16bit_of_mcount
+ * move at, ra
+ * move $12, ra_address
+ * jalr v1
+ *  sub sp, sp, 8
+ *                                  1: offset = 5 instructions
+ * 2.2 For the Other situations
+ *
+ * lui v1, hi_16bit_of_mcount        --> b 1f (0x10000004)
+ * addiu v1, v1, low_16bit_of_mcount
+ * move at, ra
+ * jalr v1
+ *  nop | move $12, ra_address | sub sp, sp, 8
+ *                                  1: offset = 4 instructions
+ */
+
+#define INSN_B_1F (0x10000000 | MCOUNT_OFFSET_INSNS)
+
+int ftrace_make_nop(struct module *mod,
+		    struct dyn_ftrace *rec, unsigned long addr)
+{
+	unsigned int new;
+	unsigned long ip = rec->ip;
+
+	/*
+	 * If ip is in kernel space, no long call, otherwise, long call is
+	 * needed.
+	 */
+	new = in_kernel_space(ip) ? INSN_NOP : INSN_B_1F;
+
+	return ftrace_modify_code(ip, new);
+}
+
+int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
+{
+	unsigned int new;
+	unsigned long ip = rec->ip;
+
+	new = in_kernel_space(ip) ? insn_jal_ftrace_caller :
+		insn_lui_v1_hi16_mcount;
+
+	return ftrace_modify_code(ip, new);
+}
+
+#define FTRACE_CALL_IP ((unsigned long)(&ftrace_call))
+
+int ftrace_update_ftrace_func(ftrace_func_t func)
+{
+	unsigned int new;
+
+	new = INSN_JAL((unsigned long)func);
+
+	return ftrace_modify_code(FTRACE_CALL_IP, new);
+}
+
+int __init ftrace_dyn_arch_init(void *data)
+{
+	/* Encode the instructions when booting */
+	ftrace_dyn_arch_init_insns();
+
+	/* Remove "b ftrace_stub" to ensure ftrace_caller() is executed */
+	ftrace_modify_code(MCOUNT_ADDR, INSN_NOP);
+
+	/* The return code is retured via data */
+	*(unsigned long *)data = 0;
+
+	return 0;
+}
+#endif	/* CONFIG_DYNAMIC_FTRACE */
+
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+
+#ifdef CONFIG_DYNAMIC_FTRACE
+
+extern void ftrace_graph_call(void);
+#define FTRACE_GRAPH_CALL_IP	((unsigned long)(&ftrace_graph_call))
+
+int ftrace_enable_ftrace_graph_caller(void)
+{
+	return ftrace_modify_code(FTRACE_GRAPH_CALL_IP,
+			insn_j_ftrace_graph_caller);
+}
+
+int ftrace_disable_ftrace_graph_caller(void)
+{
+	return ftrace_modify_code(FTRACE_GRAPH_CALL_IP, INSN_NOP);
+}
+
+#endif	/* CONFIG_DYNAMIC_FTRACE */
+
+#ifndef KBUILD_MCOUNT_RA_ADDRESS
+
+#define S_RA_SP	(0xafbf << 16)	/* s{d,w} ra, offset(sp) */
+#define S_R_SP	(0xafb0 << 16)  /* s{d,w} R, offset(sp) */
+#define OFFSET_MASK	0xffff	/* stack offset range: 0 ~ PT_SIZE */
+
+unsigned long ftrace_get_parent_ra_addr(unsigned long self_ra, unsigned long
+		old_parent_ra, unsigned long parent_ra_addr, unsigned long fp)
+{
+	unsigned long sp, ip, tmp;
+	unsigned int code;
+	int faulted;
+
+	/*
+	 * For module, move the ip from the return address after the
+	 * instruction "lui v1, hi_16bit_of_mcount"(offset is 24), but for
+	 * kernel, move after the instruction "move ra, at"(offset is 16)
+	 */
+	ip = self_ra - (in_kernel_space(self_ra) ? 16 : 24);
+
+	/*
+	 * search the text until finding the non-store instruction or "s{d,w}
+	 * ra, offset(sp)" instruction
+	 */
+	do {
+		/* get the code at "ip": code = *(unsigned int *)ip; */
+		safe_load_code(code, ip, faulted);
+
+		if (unlikely(faulted))
+			return 0;
+		/*
+		 * If we hit the non-store instruction before finding where the
+		 * ra is stored, then this is a leaf function and it does not
+		 * store the ra on the stack
+		 */
+		if ((code & S_R_SP) != S_R_SP)
+			return parent_ra_addr;
+
+		/* Move to the next instruction */
+		ip -= 4;
+	} while ((code & S_RA_SP) != S_RA_SP);
+
+	sp = fp + (code & OFFSET_MASK);
+
+	/* tmp = *(unsigned long *)sp; */
+	safe_load_stack(tmp, sp, faulted);
+	if (unlikely(faulted))
+		return 0;
+
+	if (tmp == old_parent_ra)
+		return sp;
+	return 0;
+}
+
+#endif	/* !KBUILD_MCOUNT_RA_ADDRESS */
+
+/*
+ * Hook the return address and push it in the stack of return addrs
+ * in current thread info.
+ */
+void prepare_ftrace_return(unsigned long *parent_ra_addr, unsigned long self_ra,
+			   unsigned long fp)
+{
+	unsigned long old_parent_ra;
+	struct ftrace_graph_ent trace;
+	unsigned long return_hooker = (unsigned long)
+	    &return_to_handler;
+	int faulted, insns;
+
+	if (unlikely(atomic_read(&current->tracing_graph_pause)))
+		return;
+
+	/*
+	 * "parent_ra_addr" is the stack address saved the return address of
+	 * the caller of _mcount.
+	 *
+	 * if the gcc < 4.5, a leaf function does not save the return address
+	 * in the stack address, so, we "emulate" one in _mcount's stack space,
+	 * and hijack it directly, but for a non-leaf function, it save the
+	 * return address to the its own stack space, we can not hijack it
+	 * directly, but need to find the real stack address,
+	 * ftrace_get_parent_addr() does it!
+	 *
+	 * if gcc>= 4.5, with the new -mmcount-ra-address option, for a
+	 * non-leaf function, the location of the return address will be saved
+	 * to $12 for us, and for a leaf function, only put a zero into $12. we
+	 * do it in ftrace_graph_caller of mcount.S.
+	 */
+
+	/* old_parent_ra = *parent_ra_addr; */
+	safe_load_stack(old_parent_ra, parent_ra_addr, faulted);
+	if (unlikely(faulted))
+		goto out;
+#ifndef KBUILD_MCOUNT_RA_ADDRESS
+	parent_ra_addr = (unsigned long *)ftrace_get_parent_ra_addr(self_ra,
+			old_parent_ra, (unsigned long)parent_ra_addr, fp);
+	/*
+	 * If fails when getting the stack address of the non-leaf function's
+	 * ra, stop function graph tracer and return
+	 */
+	if (parent_ra_addr == 0)
+		goto out;
+#endif
+	/* *parent_ra_addr = return_hooker; */
+	safe_store_stack(return_hooker, parent_ra_addr, faulted);
+	if (unlikely(faulted))
+		goto out;
+
+	if (ftrace_push_return_trace(old_parent_ra, self_ra, &trace.depth, fp)
+	    == -EBUSY) {
+		*parent_ra_addr = old_parent_ra;
+		return;
+	}
+
+	/*
+	 * Get the recorded ip of the current mcount calling site in the
+	 * __mcount_loc section, which will be used to filter the function
+	 * entries configured through the tracing/set_graph_function interface.
+	 */
+
+	insns = in_kernel_space(self_ra) ? 2 : MCOUNT_OFFSET_INSNS + 1;
+	trace.func = self_ra - (MCOUNT_INSN_SIZE * insns);
+
+	/* Only trace if the calling function expects to */
+	if (!ftrace_graph_entry(&trace)) {
+		current->curr_ret_stack--;
+		*parent_ra_addr = old_parent_ra;
+	}
+	return;
+out:
+	ftrace_graph_stop();
+	WARN_ON(1);
+}
+#endif	/* CONFIG_FUNCTION_GRAPH_TRACER */