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@@ -2,7 +2,7 @@
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* Code for replacing ftrace calls with jumps.
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*
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* Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com>
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- * Copyright (C) 2009 DSLab, Lanzhou University, China
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+ * Copyright (C) 2009, 2010 DSLab, Lanzhou University, China
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* Author: Wu Zhangjin <wuzhangjin@gmail.com>
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*
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* Thanks goes to Steven Rostedt for writing the original x86 version.
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@@ -12,18 +12,62 @@
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#include <linux/init.h>
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#include <linux/ftrace.h>
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-#include <asm/cacheflush.h>
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#include <asm/asm.h>
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#include <asm/asm-offsets.h>
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+#include <asm/cacheflush.h>
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+#include <asm/uasm.h>
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+
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+/*
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+ * If the Instruction Pointer is in module space (0xc0000000), return true;
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+ * otherwise, it is in kernel space (0x80000000), return false.
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+ *
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+ * FIXME: This will not work when the kernel space and module space are the
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+ * same. If they are the same, we need to modify scripts/recordmcount.pl,
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+ * ftrace_make_nop/call() and the other related parts to ensure the
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+ * enabling/disabling of the calling site to _mcount is right for both kernel
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+ * and module.
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+ */
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+
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+static inline int in_module(unsigned long ip)
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+{
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+ return ip & 0x40000000;
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+}
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#ifdef CONFIG_DYNAMIC_FTRACE
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#define JAL 0x0c000000 /* jump & link: ip --> ra, jump to target */
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#define ADDR_MASK 0x03ffffff /* op_code|addr : 31...26|25 ....0 */
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-#define jump_insn_encode(op_code, addr) \
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- ((unsigned int)((op_code) | (((addr) >> 2) & ADDR_MASK)))
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-static unsigned int ftrace_nop = 0x00000000;
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+#define INSN_B_1F_4 0x10000004 /* b 1f; offset = 4 */
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+#define INSN_B_1F_5 0x10000005 /* b 1f; offset = 5 */
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+#define INSN_NOP 0x00000000 /* nop */
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+#define INSN_JAL(addr) \
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+ ((unsigned int)(JAL | (((addr) >> 2) & ADDR_MASK)))
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+
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+static unsigned int insn_jal_ftrace_caller __read_mostly;
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+static unsigned int insn_lui_v1_hi16_mcount __read_mostly;
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+static unsigned int insn_j_ftrace_graph_caller __maybe_unused __read_mostly;
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+
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+static inline void ftrace_dyn_arch_init_insns(void)
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+{
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+ u32 *buf;
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+ unsigned int v1;
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+
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+ /* lui v1, hi16_mcount */
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+ v1 = 3;
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+ buf = (u32 *)&insn_lui_v1_hi16_mcount;
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+ UASM_i_LA_mostly(&buf, v1, MCOUNT_ADDR);
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+
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+ /* jal (ftrace_caller + 8), jump over the first two instruction */
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+ buf = (u32 *)&insn_jal_ftrace_caller;
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+ uasm_i_jal(&buf, (FTRACE_ADDR + 8));
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+
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+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
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+ /* j ftrace_graph_caller */
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+ buf = (u32 *)&insn_j_ftrace_graph_caller;
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+ uasm_i_j(&buf, (unsigned long)ftrace_graph_caller);
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+#endif
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+}
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static int ftrace_modify_code(unsigned long ip, unsigned int new_code)
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{
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@@ -40,67 +84,56 @@ static int ftrace_modify_code(unsigned long ip, unsigned int new_code)
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return 0;
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}
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-static int lui_v1;
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-static int jal_mcount;
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-
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int ftrace_make_nop(struct module *mod,
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struct dyn_ftrace *rec, unsigned long addr)
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{
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unsigned int new;
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- int faulted;
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unsigned long ip = rec->ip;
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- /* We have compiled module with -mlong-calls, but compiled the kernel
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- * without it, we need to cope with them respectively. */
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- if (ip & 0x40000000) {
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- /* record it for ftrace_make_call */
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- if (lui_v1 == 0) {
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- /* lui_v1 = *(unsigned int *)ip; */
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- safe_load_code(lui_v1, ip, faulted);
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-
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- if (unlikely(faulted))
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- return -EFAULT;
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- }
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-
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- /* lui v1, hi_16bit_of_mcount --> b 1f (0x10000004)
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+ /*
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+ * We have compiled module with -mlong-calls, but compiled the kernel
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+ * without it, we need to cope with them respectively.
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+ */
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+ if (in_module(ip)) {
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+#if defined(KBUILD_MCOUNT_RA_ADDRESS) && defined(CONFIG_32BIT)
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+ /*
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+ * lui v1, hi_16bit_of_mcount --> b 1f (0x10000005)
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+ * addiu v1, v1, low_16bit_of_mcount
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+ * move at, ra
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+ * move $12, ra_address
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+ * jalr v1
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+ * sub sp, sp, 8
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+ * 1: offset = 5 instructions
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+ */
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+ new = INSN_B_1F_5;
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+#else
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+ /*
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+ * lui v1, hi_16bit_of_mcount --> b 1f (0x10000004)
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* addiu v1, v1, low_16bit_of_mcount
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* move at, ra
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* jalr v1
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- * nop
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- * 1f: (ip + 12)
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+ * nop | move $12, ra_address | sub sp, sp, 8
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+ * 1: offset = 4 instructions
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*/
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- new = 0x10000004;
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+ new = INSN_B_1F_4;
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+#endif
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} else {
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- /* record/calculate it for ftrace_make_call */
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- if (jal_mcount == 0) {
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- /* We can record it directly like this:
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- * jal_mcount = *(unsigned int *)ip;
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- * Herein, jump over the first two nop instructions */
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- jal_mcount = jump_insn_encode(JAL, (MCOUNT_ADDR + 8));
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- }
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-
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- /* move at, ra
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- * jalr v1 --> nop
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+ /*
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+ * move at, ra
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+ * jal _mcount --> nop
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*/
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- new = ftrace_nop;
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+ new = INSN_NOP;
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}
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return ftrace_modify_code(ip, new);
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}
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-static int modified; /* initialized as 0 by default */
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-
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int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
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{
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unsigned int new;
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unsigned long ip = rec->ip;
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- /* We just need to remove the "b ftrace_stub" at the fist time! */
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- if (modified == 0) {
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- modified = 1;
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- ftrace_modify_code(addr, ftrace_nop);
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- }
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/* ip, module: 0xc0000000, kernel: 0x80000000 */
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- new = (ip & 0x40000000) ? lui_v1 : jal_mcount;
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+ new = in_module(ip) ? insn_lui_v1_hi16_mcount : insn_jal_ftrace_caller;
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return ftrace_modify_code(ip, new);
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}
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@@ -111,44 +144,48 @@ int ftrace_update_ftrace_func(ftrace_func_t func)
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{
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unsigned int new;
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- new = jump_insn_encode(JAL, (unsigned long)func);
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+ new = INSN_JAL((unsigned long)func);
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return ftrace_modify_code(FTRACE_CALL_IP, new);
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}
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int __init ftrace_dyn_arch_init(void *data)
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{
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+ /* Encode the instructions when booting */
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+ ftrace_dyn_arch_init_insns();
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+
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+ /* Remove "b ftrace_stub" to ensure ftrace_caller() is executed */
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+ ftrace_modify_code(MCOUNT_ADDR, INSN_NOP);
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+
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/* The return code is retured via data */
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*(unsigned long *)data = 0;
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return 0;
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}
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-#endif /* CONFIG_DYNAMIC_FTRACE */
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+#endif /* CONFIG_DYNAMIC_FTRACE */
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#ifdef CONFIG_FUNCTION_GRAPH_TRACER
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#ifdef CONFIG_DYNAMIC_FTRACE
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extern void ftrace_graph_call(void);
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-#define JMP 0x08000000 /* jump to target directly */
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-#define CALL_FTRACE_GRAPH_CALLER \
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- jump_insn_encode(JMP, (unsigned long)(&ftrace_graph_caller))
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#define FTRACE_GRAPH_CALL_IP ((unsigned long)(&ftrace_graph_call))
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int ftrace_enable_ftrace_graph_caller(void)
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{
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return ftrace_modify_code(FTRACE_GRAPH_CALL_IP,
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- CALL_FTRACE_GRAPH_CALLER);
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+ insn_j_ftrace_graph_caller);
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}
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int ftrace_disable_ftrace_graph_caller(void)
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{
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- return ftrace_modify_code(FTRACE_GRAPH_CALL_IP, ftrace_nop);
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+ return ftrace_modify_code(FTRACE_GRAPH_CALL_IP, INSN_NOP);
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}
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-#endif /* !CONFIG_DYNAMIC_FTRACE */
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+#endif /* CONFIG_DYNAMIC_FTRACE */
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#ifndef KBUILD_MCOUNT_RA_ADDRESS
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+
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#define S_RA_SP (0xafbf << 16) /* s{d,w} ra, offset(sp) */
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#define S_R_SP (0xafb0 << 16) /* s{d,w} R, offset(sp) */
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#define OFFSET_MASK 0xffff /* stack offset range: 0 ~ PT_SIZE */
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@@ -162,17 +199,17 @@ unsigned long ftrace_get_parent_addr(unsigned long self_addr,
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unsigned int code;
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int faulted;
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- /* in module or kernel? */
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- if (self_addr & 0x40000000) {
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- /* module: move to the instruction "lui v1, HI_16BIT_OF_MCOUNT" */
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- ip = self_addr - 20;
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- } else {
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- /* kernel: move to the instruction "move ra, at" */
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- ip = self_addr - 12;
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- }
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+ /*
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+ * For module, move the ip from calling site of mcount to the
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+ * instruction "lui v1, hi_16bit_of_mcount"(offset is 20), but for
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+ * kernel, move to the instruction "move ra, at"(offset is 12)
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+ */
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+ ip = self_addr - (in_module(self_addr) ? 20 : 12);
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- /* search the text until finding the non-store instruction or "s{d,w}
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- * ra, offset(sp)" instruction */
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+ /*
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+ * search the text until finding the non-store instruction or "s{d,w}
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+ * ra, offset(sp)" instruction
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+ */
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do {
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ip -= 4;
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@@ -181,10 +218,11 @@ unsigned long ftrace_get_parent_addr(unsigned long self_addr,
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if (unlikely(faulted))
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return 0;
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-
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- /* If we hit the non-store instruction before finding where the
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+ /*
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+ * If we hit the non-store instruction before finding where the
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* ra is stored, then this is a leaf function and it does not
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- * store the ra on the stack. */
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+ * store the ra on the stack
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+ */
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if ((code & S_R_SP) != S_R_SP)
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return parent_addr;
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@@ -202,7 +240,7 @@ unsigned long ftrace_get_parent_addr(unsigned long self_addr,
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return 0;
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}
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-#endif
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+#endif /* !KBUILD_MCOUNT_RA_ADDRESS */
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/*
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* Hook the return address and push it in the stack of return addrs
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@@ -220,7 +258,8 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
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if (unlikely(atomic_read(¤t->tracing_graph_pause)))
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return;
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- /* "parent" is the stack address saved the return address of the caller
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+ /*
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+ * "parent" is the stack address saved the return address of the caller
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* of _mcount.
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*
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* if the gcc < 4.5, a leaf function does not save the return address
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@@ -242,10 +281,11 @@ void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
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goto out;
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#ifndef KBUILD_MCOUNT_RA_ADDRESS
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parent = (unsigned long *)ftrace_get_parent_addr(self_addr, old,
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- (unsigned long)parent,
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- fp);
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- /* If fails when getting the stack address of the non-leaf function's
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- * ra, stop function graph tracer and return */
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+ (unsigned long)parent, fp);
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+ /*
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+ * If fails when getting the stack address of the non-leaf function's
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+ * ra, stop function graph tracer and return
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+ */
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if (parent == 0)
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goto out;
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#endif
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@@ -272,4 +312,4 @@ out:
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ftrace_graph_stop();
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WARN_ON(1);
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}
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-#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
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+#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
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