/*
 * 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) {
                pr_err("%p: replaced (%#x) != old (%#x)",
                (void *)ip, 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 long entry, ptr, tramp;
        unsigned long ip = rec->ip;
        unsigned int op, pop;

        /* read where this goes */
        if (probe_kernel_read(&op, (void *)ip, sizeof(int))) {
                pr_err("Fetching opcode failed.\n");
                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);

        pr_devel("ip:%lx jumps to %lx", ip, tramp);

        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.
         */

        pop = PPC_INST_BRANCH | 8;      /* b +8 */

        /*
         * Check what is in the next instruction. We can see ld r2,40(r1), but
         * on first pass after boot we will see mflr r0.
         */
        if (probe_kernel_read(&op, (void *)(ip+4), MCOUNT_INSN_SIZE)) {
                pr_err("Fetching op failed.\n");
                return -EFAULT;
        }

        if (op != PPC_INST_LD_TOC) {
                unsigned int inst;

                if (probe_kernel_read(&inst, (void *)(ip - 4), 4)) {
                        pr_err("Fetching instruction at %lx failed.\n", ip - 4);
                        return -EFAULT;
                }

                /* We expect either a mlfr r0, or a std r0, LRSAVE(r1) */
                if (inst != PPC_INST_MFLR && inst != PPC_INST_STD_LR) {
                        pr_err("Unexpected instructions around bl _mcount\n"
                               "when enabling dynamic ftrace!\t"
                               "(%08x,bl,%08x)\n", inst, op);
                        return -EINVAL;
                }

                /* When using -mkernel_profile there is no load to jump over */
                pop = PPC_INST_NOP;
        }

        if (patch_instruction((unsigned int *)ip, pop)) {
                pr_err("Patching NOP failed.\n");
                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
/*
 * Examine the existing instructions for __ftrace_make_call.
 * They should effectively be a NOP, and follow formal constraints,
 * depending on the ABI. Return false if they don't.
 */
#ifndef CC_USING_MPROFILE_KERNEL
static int
expected_nop_sequence(void *ip, unsigned int op0, unsigned int op1)
{
        /*
         * 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 ((op0 != 0x48000008) || ((op1 & 0xffff0000) != 0xe8410000))
                return 0;
        return 1;
}
#else
static int
expected_nop_sequence(void *ip, unsigned int op0, unsigned int op1)
{
        /* look for patched "NOP" on ppc64 with -mprofile-kernel */
        if (op0 != PPC_INST_NOP)
                return 0;
        return 1;
}
#endif

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;

        if (!expected_nop_sequence(ip, op[0], op[1])) {
                pr_err("Unexpected call sequence at %p: %x %x\n",
                ip, 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;
}

#ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS
int ftrace_modify_call(struct dyn_ftrace *rec, unsigned long old_addr,
                        unsigned long addr)
{
        return ftrace_make_call(rec, addr);
}
#endif

#else  /* !CONFIG_PPC64: */
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;
                }
        }
}

/*
 * Use the default ftrace_modify_all_code, but without
 * stop_machine().
 */
void arch_ftrace_update_code(int command)
{
        ftrace_modify_all_code(command);
}

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(&current->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 */