/* * Code for replacing ftrace calls with jumps. * * Copyright (C) 2007-2008 Steven Rostedt * * Thanks goes out to P.A. Semi, Inc for supplying me with a PPC64 box. * * Added function graph tracer code, taken from x86 that was written * by Frederic Weisbecker, and ported to PPC by Steven Rostedt. * */ #define pr_fmt(fmt) "ftrace-powerpc: " fmt #include #include #include #include #include #include #include #include #include #include #include #include #ifdef CONFIG_DYNAMIC_FTRACE static unsigned int ftrace_call_replace(unsigned long ip, unsigned long addr, int link) { unsigned int op; addr = ppc_function_entry((void *)addr); /* if (link) set op to 'bl' else 'b' */ op = create_branch((unsigned int *)ip, addr, link ? 1 : 0); return op; } static int ftrace_modify_code(unsigned long ip, unsigned int old, unsigned int new) { unsigned int replaced; /* * 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 (replaced != old) return -EINVAL; /* replace the text with the new text */ if (patch_instruction((unsigned int *)ip, new)) return -EPERM; return 0; } /* * Helper functions that are the same for both PPC64 and PPC32. */ static int test_24bit_addr(unsigned long ip, unsigned long addr) { addr = ppc_function_entry((void *)addr); /* use the create_branch to verify that this offset can be branched */ return create_branch((unsigned int *)ip, addr, 0); } #ifdef CONFIG_MODULES static int is_bl_op(unsigned int op) { return (op & 0xfc000003) == 0x48000001; } static unsigned long find_bl_target(unsigned long ip, unsigned int op) { static int offset; offset = (op & 0x03fffffc); /* make it signed */ if (offset & 0x02000000) offset |= 0xfe000000; return ip + (long)offset; } #ifdef CONFIG_PPC64 static int __ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long addr) { unsigned int op; unsigned long entry, ptr; unsigned long ip = rec->ip; void *tramp; /* read where this goes */ if (probe_kernel_read(&op, (void *)ip, sizeof(int))) return -EFAULT; /* Make sure that that this is still a 24bit jump */ if (!is_bl_op(op)) { pr_err("Not expected bl: opcode is %x\n", op); return -EINVAL; } /* lets find where the pointer goes */ tramp = (void *)find_bl_target(ip, op); pr_devel("ip:%lx jumps to %p", ip, tramp); if (!is_module_trampoline(tramp)) { pr_err("Not a trampoline\n"); return -EINVAL; } if (module_trampoline_target(mod, tramp, &ptr)) { pr_err("Failed to get trampoline target\n"); return -EFAULT; } pr_devel("trampoline target %lx", ptr); entry = ppc_global_function_entry((void *)addr); /* This should match what was called */ if (ptr != entry) { pr_err("addr %lx does not match expected %lx\n", ptr, entry); return -EINVAL; } /* * Our original call site looks like: * * bl * ld r2,XX(r1) * * Milton Miller pointed out that we can not simply nop the branch. * If a task was preempted when calling a trace function, the nops * will remove the way to restore the TOC in r2 and the r2 TOC will * get corrupted. * * Use a b +8 to jump over the load. */ op = 0x48000008; /* b +8 */ if (patch_instruction((unsigned int *)ip, op)) return -EPERM; return 0; } #else /* !PPC64 */ static int __ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long addr) { unsigned int op; unsigned int jmp[4]; unsigned long ip = rec->ip; unsigned long tramp; if (probe_kernel_read(&op, (void *)ip, MCOUNT_INSN_SIZE)) return -EFAULT; /* Make sure that that this is still a 24bit jump */ if (!is_bl_op(op)) { pr_err("Not expected bl: opcode is %x\n", op); return -EINVAL; } /* lets find where the pointer goes */ tramp = find_bl_target(ip, op); /* * On PPC32 the trampoline looks like: * 0x3d, 0x80, 0x00, 0x00 lis r12,sym@ha * 0x39, 0x8c, 0x00, 0x00 addi r12,r12,sym@l * 0x7d, 0x89, 0x03, 0xa6 mtctr r12 * 0x4e, 0x80, 0x04, 0x20 bctr */ pr_devel("ip:%lx jumps to %lx", ip, tramp); /* Find where the trampoline jumps to */ if (probe_kernel_read(jmp, (void *)tramp, sizeof(jmp))) { pr_err("Failed to read %lx\n", tramp); return -EFAULT; } pr_devel(" %08x %08x ", jmp[0], jmp[1]); /* verify that this is what we expect it to be */ if (((jmp[0] & 0xffff0000) != 0x3d800000) || ((jmp[1] & 0xffff0000) != 0x398c0000) || (jmp[2] != 0x7d8903a6) || (jmp[3] != 0x4e800420)) { pr_err("Not a trampoline\n"); return -EINVAL; } tramp = (jmp[1] & 0xffff) | ((jmp[0] & 0xffff) << 16); if (tramp & 0x8000) tramp -= 0x10000; pr_devel(" %lx ", tramp); if (tramp != addr) { pr_err("Trampoline location %08lx does not match addr\n", tramp); return -EINVAL; } op = PPC_INST_NOP; if (patch_instruction((unsigned int *)ip, op)) return -EPERM; return 0; } #endif /* PPC64 */ #endif /* CONFIG_MODULES */ int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long addr) { unsigned long ip = rec->ip; unsigned int old, new; /* * If the calling address is more that 24 bits away, * then we had to use a trampoline to make the call. * Otherwise just update the call site. */ if (test_24bit_addr(ip, addr)) { /* within range */ old = ftrace_call_replace(ip, addr, 1); new = PPC_INST_NOP; return ftrace_modify_code(ip, old, new); } #ifdef CONFIG_MODULES /* * Out of range jumps are called from modules. * We should either already have a pointer to the module * or it has been passed in. */ if (!rec->arch.mod) { if (!mod) { pr_err("No module loaded addr=%lx\n", addr); return -EFAULT; } rec->arch.mod = mod; } else if (mod) { if (mod != rec->arch.mod) { pr_err("Record mod %p not equal to passed in mod %p\n", rec->arch.mod, mod); return -EINVAL; } /* nothing to do if mod == rec->arch.mod */ } else mod = rec->arch.mod; return __ftrace_make_nop(mod, rec, addr); #else /* We should not get here without modules */ return -EINVAL; #endif /* CONFIG_MODULES */ } #ifdef CONFIG_MODULES #ifdef CONFIG_PPC64 static int __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) { unsigned int op[2]; void *ip = (void *)rec->ip; /* read where this goes */ if (probe_kernel_read(op, ip, sizeof(op))) return -EFAULT; /* * We expect to see: * * b +8 * ld r2,XX(r1) * * The load offset is different depending on the ABI. For simplicity * just mask it out when doing the compare. */ if ((op[0] != 0x48000008) || ((op[1] & 0xffff0000) != 0xe8410000)) { pr_err("Unexpected call sequence: %x %x\n", op[0], op[1]); return -EINVAL; } /* If we never set up a trampoline to ftrace_caller, then bail */ if (!rec->arch.mod->arch.tramp) { pr_err("No ftrace trampoline\n"); return -EINVAL; } /* Ensure branch is within 24 bits */ if (!create_branch(ip, rec->arch.mod->arch.tramp, BRANCH_SET_LINK)) { pr_err("Branch out of range\n"); return -EINVAL; } if (patch_branch(ip, rec->arch.mod->arch.tramp, BRANCH_SET_LINK)) { pr_err("REL24 out of range!\n"); return -EINVAL; } return 0; } #else static int __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) { unsigned int op; unsigned long ip = rec->ip; /* read where this goes */ if (probe_kernel_read(&op, (void *)ip, MCOUNT_INSN_SIZE)) return -EFAULT; /* It should be pointing to a nop */ if (op != PPC_INST_NOP) { pr_err("Expected NOP but have %x\n", op); return -EINVAL; } /* If we never set up a trampoline to ftrace_caller, then bail */ if (!rec->arch.mod->arch.tramp) { pr_err("No ftrace trampoline\n"); return -EINVAL; } /* create the branch to the trampoline */ op = create_branch((unsigned int *)ip, rec->arch.mod->arch.tramp, BRANCH_SET_LINK); if (!op) { pr_err("REL24 out of range!\n"); return -EINVAL; } pr_devel("write to %lx\n", rec->ip); if (patch_instruction((unsigned int *)ip, op)) return -EPERM; return 0; } #endif /* CONFIG_PPC64 */ #endif /* CONFIG_MODULES */ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr) { unsigned long ip = rec->ip; unsigned int old, new; /* * If the calling address is more that 24 bits away, * then we had to use a trampoline to make the call. * Otherwise just update the call site. */ if (test_24bit_addr(ip, addr)) { /* within range */ old = PPC_INST_NOP; new = ftrace_call_replace(ip, addr, 1); return ftrace_modify_code(ip, old, new); } #ifdef CONFIG_MODULES /* * Out of range jumps are called from modules. * Being that we are converting from nop, it had better * already have a module defined. */ if (!rec->arch.mod) { pr_err("No module loaded\n"); return -EINVAL; } return __ftrace_make_call(rec, addr); #else /* We should not get here without modules */ return -EINVAL; #endif /* CONFIG_MODULES */ } int ftrace_update_ftrace_func(ftrace_func_t func) { unsigned long ip = (unsigned long)(&ftrace_call); unsigned int old, new; int ret; old = *(unsigned int *)&ftrace_call; new = ftrace_call_replace(ip, (unsigned long)func, 1); ret = ftrace_modify_code(ip, old, new); return ret; } static int __ftrace_replace_code(struct dyn_ftrace *rec, int enable) { unsigned long ftrace_addr = (unsigned long)FTRACE_ADDR; int ret; ret = ftrace_update_record(rec, enable); switch (ret) { case FTRACE_UPDATE_IGNORE: return 0; case FTRACE_UPDATE_MAKE_CALL: return ftrace_make_call(rec, ftrace_addr); case FTRACE_UPDATE_MAKE_NOP: return ftrace_make_nop(NULL, rec, ftrace_addr); } return 0; } void ftrace_replace_code(int enable) { struct ftrace_rec_iter *iter; struct dyn_ftrace *rec; int ret; for (iter = ftrace_rec_iter_start(); iter; iter = ftrace_rec_iter_next(iter)) { rec = ftrace_rec_iter_record(iter); ret = __ftrace_replace_code(rec, enable); if (ret) { ftrace_bug(ret, rec->ip); return; } } } void arch_ftrace_update_code(int command) { if (command & FTRACE_UPDATE_CALLS) ftrace_replace_code(1); else if (command & FTRACE_DISABLE_CALLS) ftrace_replace_code(0); if (command & FTRACE_UPDATE_TRACE_FUNC) ftrace_update_ftrace_func(ftrace_trace_function); if (command & FTRACE_START_FUNC_RET) ftrace_enable_ftrace_graph_caller(); else if (command & FTRACE_STOP_FUNC_RET) ftrace_disable_ftrace_graph_caller(); } 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); extern void ftrace_graph_stub(void); int ftrace_enable_ftrace_graph_caller(void) { unsigned long ip = (unsigned long)(&ftrace_graph_call); unsigned long addr = (unsigned long)(&ftrace_graph_caller); unsigned long stub = (unsigned long)(&ftrace_graph_stub); unsigned int old, new; old = ftrace_call_replace(ip, stub, 0); new = ftrace_call_replace(ip, addr, 0); return ftrace_modify_code(ip, old, new); } int ftrace_disable_ftrace_graph_caller(void) { unsigned long ip = (unsigned long)(&ftrace_graph_call); unsigned long addr = (unsigned long)(&ftrace_graph_caller); unsigned long stub = (unsigned long)(&ftrace_graph_stub); unsigned int old, new; old = ftrace_call_replace(ip, addr, 0); new = ftrace_call_replace(ip, stub, 0); return ftrace_modify_code(ip, old, new); } #endif /* CONFIG_DYNAMIC_FTRACE */ /* * 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 old; int faulted; struct ftrace_graph_ent trace; unsigned long return_hooker; if (unlikely(ftrace_graph_is_dead())) return; if (unlikely(atomic_read(¤t->tracing_graph_pause))) return; return_hooker = ppc_function_entry(return_to_handler); /* * Protect against fault, even if it shouldn't * happen. This tool is too much intrusive to * ignore such a protection. */ asm volatile( "1: " PPC_LL "%[old], 0(%[parent])\n" "2: " PPC_STL "%[return_hooker], 0(%[parent])\n" " li %[faulted], 0\n" "3:\n" ".section .fixup, \"ax\"\n" "4: li %[faulted], 1\n" " b 3b\n" ".previous\n" ".section __ex_table,\"a\"\n" PPC_LONG_ALIGN "\n" PPC_LONG "1b,4b\n" PPC_LONG "2b,4b\n" ".previous" : [old] "=&r" (old), [faulted] "=r" (faulted) : [parent] "r" (parent), [return_hooker] "r" (return_hooker) : "memory" ); if (unlikely(faulted)) { ftrace_graph_stop(); WARN_ON(1); return; } trace.func = self_addr; trace.depth = current->curr_ret_stack + 1; /* Only trace if the calling function expects to */ if (!ftrace_graph_entry(&trace)) { *parent = old; return; } if (ftrace_push_return_trace(old, self_addr, &trace.depth, 0) == -EBUSY) *parent = old; } #endif /* CONFIG_FUNCTION_GRAPH_TRACER */ #if defined(CONFIG_FTRACE_SYSCALLS) && defined(CONFIG_PPC64) unsigned long __init arch_syscall_addr(int nr) { return sys_call_table[nr*2]; } #endif /* CONFIG_FTRACE_SYSCALLS && CONFIG_PPC64 */