diff options
Diffstat (limited to 'arch/powerpc/kernel/ftrace.c')
| -rw-r--r-- | arch/powerpc/kernel/ftrace.c | 551 |
1 files changed, 551 insertions, 0 deletions
diff --git a/arch/powerpc/kernel/ftrace.c b/arch/powerpc/kernel/ftrace.c new file mode 100644 index 000000000..44d4d8eb3 --- /dev/null +++ b/arch/powerpc/kernel/ftrace.c @@ -0,0 +1,551 @@ +/* + * Code for replacing ftrace calls with jumps. + * + * Copyright (C) 2007-2008 Steven Rostedt <srostedt@redhat.com> + * + * 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 <linux/spinlock.h> +#include <linux/hardirq.h> +#include <linux/uaccess.h> +#include <linux/module.h> +#include <linux/ftrace.h> +#include <linux/percpu.h> +#include <linux/init.h> +#include <linux/list.h> + +#include <asm/cacheflush.h> +#include <asm/code-patching.h> +#include <asm/ftrace.h> +#include <asm/syscall.h> + + +#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 <tramp> + * 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); + 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. Return the address we want to divert to. + */ +unsigned long prepare_ftrace_return(unsigned long parent, unsigned long ip) +{ + struct ftrace_graph_ent trace; + unsigned long return_hooker; + + if (unlikely(ftrace_graph_is_dead())) + goto out; + + if (unlikely(atomic_read(¤t->tracing_graph_pause))) + goto out; + + return_hooker = ppc_function_entry(return_to_handler); + + 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 = return_hooker; +out: + return parent; +} +#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 */ |