/* * Code for replacing ftrace calls with jumps. * * Copyright (C) 2007-2008 Steven Rostedt * Copyright (C) 2009, 2010 DSLab, Lanzhou University, China * Author: Wu Zhangjin * * Thanks goes to Steven Rostedt for writing the original x86 version. */ #include #include #include #include #include #include #include /* * If the Instruction Pointer is in module space (0xc0000000), return true; * otherwise, it is in kernel space (0x80000000), return false. * * FIXME: This will not work when the kernel space and module space are the * same. If they are the same, we need to modify scripts/recordmcount.pl, * ftrace_make_nop/call() and the other related parts to ensure the * enabling/disabling of the calling site to _mcount is right for both kernel * and module. */ static inline int in_module(unsigned long ip) { return ip & 0x40000000; } #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 INSN_B_1F_4 0x10000004 /* b 1f; offset = 4 */ #define INSN_B_1F_5 0x10000005 /* b 1f; offset = 5 */ #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)); #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); #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; } int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long addr) { unsigned int new; unsigned long ip = rec->ip; /* * We have compiled module with -mlong-calls, but compiled the kernel * without it, we need to cope with them respectively. */ if (in_module(ip)) { #if defined(KBUILD_MCOUNT_RA_ADDRESS) && defined(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 */ new = INSN_B_1F_5; #else /* * 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 */ new = INSN_B_1F_4; #endif } else { /* * move at, ra * jal _mcount --> nop */ new = INSN_NOP; } 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; /* ip, module: 0xc0000000, kernel: 0x80000000 */ new = in_module(ip) ? insn_lui_v1_hi16_mcount : insn_jal_ftrace_caller; 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_addr(unsigned long self_addr, unsigned long parent, unsigned long parent_addr, unsigned long fp) { unsigned long sp, ip, ra; unsigned int code; int faulted; /* * For module, move the ip from calling site of mcount to the * instruction "lui v1, hi_16bit_of_mcount"(offset is 20), but for * kernel, move to the instruction "move ra, at"(offset is 12) */ ip = self_addr - (in_module(self_addr) ? 20 : 12); /* * search the text until finding the non-store instruction or "s{d,w} * ra, offset(sp)" instruction */ do { ip -= 4; /* 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_addr; } while (((code & S_RA_SP) != S_RA_SP)); sp = fp + (code & OFFSET_MASK); /* ra = *(unsigned long *)sp; */ safe_load_stack(ra, sp, faulted); if (unlikely(faulted)) return 0; if (ra == parent) 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, unsigned long self_addr, unsigned long fp) { unsigned long old; struct ftrace_graph_ent trace; unsigned long return_hooker = (unsigned long) &return_to_handler; int faulted; if (unlikely(atomic_read(¤t->tracing_graph_pause))) return; /* * "parent" 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; */ safe_load_stack(old, parent, faulted); if (unlikely(faulted)) goto out; #ifndef KBUILD_MCOUNT_RA_ADDRESS parent = (unsigned long *)ftrace_get_parent_addr(self_addr, old, (unsigned long)parent, fp); /* * If fails when getting the stack address of the non-leaf function's * ra, stop function graph tracer and return */ if (parent == 0) goto out; #endif /* *parent = return_hooker; */ safe_store_stack(return_hooker, parent, faulted); if (unlikely(faulted)) goto out; if (ftrace_push_return_trace(old, self_addr, &trace.depth, fp) == -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; } return; out: ftrace_graph_stop(); WARN_ON(1); } #endif /* CONFIG_FUNCTION_GRAPH_TRACER */