/*
 * 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.
 *
 */

#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>


#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 (probe_kernel_write((void *)ip, &new, MCOUNT_INSN_SIZE))
                return -EPERM;

        flush_icache_range(ip, ip + 8);

        return 0;
}

/*
 * Helper functions that are the same for both PPC64 and PPC32.
 */
static int test_24bit_addr(unsigned long ip, unsigned long 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 int jmp[5];
        unsigned long ptr;
        unsigned long ip = rec->ip;
        unsigned long tramp;
        int offset;

        /* 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)) {
                printk(KERN_ERR "Not expected bl: opcode is %x\n", op);
                return -EINVAL;
        }

        /* lets find where the pointer goes */
        tramp = find_bl_target(ip, op);

        /*
         * On PPC64 the trampoline looks like:
         * 0x3d, 0x82, 0x00, 0x00,    addis   r12,r2, <high>
         * 0x39, 0x8c, 0x00, 0x00,    addi    r12,r12, <low>
         *   Where the bytes 2,3,6 and 7 make up the 32bit offset
         *   to the TOC that holds the pointer.
         *   to jump to.
         * 0xf8, 0x41, 0x00, 0x28,    std     r2,40(r1)
         * 0xe9, 0x6c, 0x00, 0x20,    ld      r11,32(r12)
         *   The actually address is 32 bytes from the offset
         *   into the TOC.
         * 0xe8, 0x4c, 0x00, 0x28,    ld      r2,40(r12)
         */

        pr_devel("ip:%lx jumps to %lx r2: %lx", ip, tramp, mod->arch.toc);

        /* Find where the trampoline jumps to */
        if (probe_kernel_read(jmp, (void *)tramp, sizeof(jmp))) {
                printk(KERN_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) != 0x3d820000) ||
            ((jmp[1] & 0xffff0000) != 0x398c0000) ||
            (jmp[2] != 0xf8410028) ||
            (jmp[3] != 0xe96c0020) ||
            (jmp[4] != 0xe84c0028)) {
                printk(KERN_ERR "Not a trampoline\n");
                return -EINVAL;
        }

        /* The bottom half is signed extended */
        offset = ((unsigned)((unsigned short)jmp[0]) << 16) +
                (int)((short)jmp[1]);

        pr_devel(" %x ", offset);

        /* get the address this jumps too */
        tramp = mod->arch.toc + offset + 32;
        pr_devel("toc: %lx", tramp);

        if (probe_kernel_read(jmp, (void *)tramp, 8)) {
                printk(KERN_ERR "Failed to read %lx\n", tramp);
                return -EFAULT;
        }

        pr_devel(" %08x %08x\n", jmp[0], jmp[1]);

        ptr = ((unsigned long)jmp[0] << 32) + jmp[1];

        /* This should match what was called */
        if (ptr != ppc_function_entry((void *)addr)) {
                printk(KERN_ERR "addr does not match %lx\n", ptr);
                return -EINVAL;
        }

        /*
         * We want to nop the line, but the next line is
         *  0xe8, 0x41, 0x00, 0x28   ld r2,40(r1)
         * This needs to be turned to a nop too.
         */
        if (probe_kernel_read(&op, (void *)(ip+4), MCOUNT_INSN_SIZE))
                return -EFAULT;

        if (op != 0xe8410028) {
                printk(KERN_ERR "Next line is not ld! (%08x)\n", op);
                return -EINVAL;
        }

        /*
         * Milton Miller pointed out that we can not blindly do nops.
         * 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.
         */

        /*
         * Replace:
         *   bl <tramp>  <==== will be replaced with "b 1f"
         *   ld r2,40(r1)
         *  1:
         */
        op = 0x48000008;        /* b +8 */

        if (probe_kernel_write((void *)ip, &op, MCOUNT_INSN_SIZE))
                return -EPERM;


        flush_icache_range(ip, ip + 8);

        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)) {
                printk(KERN_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, 0x60, 0x00, 0x00  lis r11,sym@ha
         *  0x39, 0x6b, 0x00, 0x00  addi r11,r11,sym@l
         *  0x7d, 0x69, 0x03, 0xa6  mtctr r11
         *  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))) {
                printk(KERN_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) != 0x3d600000) ||
            ((jmp[1] & 0xffff0000) != 0x396b0000) ||
            (jmp[2] != 0x7d6903a6) ||
            (jmp[3] != 0x4e800420)) {
                printk(KERN_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) {
                printk(KERN_ERR
                       "Trampoline location %08lx does not match addr\n",
                       tramp);
                return -EINVAL;
        }

        op = PPC_INST_NOP;

        if (probe_kernel_write((void *)ip, &op, MCOUNT_INSN_SIZE))
                return -EPERM;

        flush_icache_range(ip, ip + 8);

        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) {
                        printk(KERN_ERR "No module loaded addr=%lx\n",
                               addr);
                        return -EFAULT;
                }
                rec->arch.mod = mod;
        } else if (mod) {
                if (mod != rec->arch.mod) {
                        printk(KERN_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];
        unsigned long ip = rec->ip;

        /* read where this goes */
        if (probe_kernel_read(op, (void *)ip, MCOUNT_INSN_SIZE * 2))
                return -EFAULT;

        /*
         * It should be pointing to two nops or
         *  b +8; ld r2,40(r1)
         */
        if (((op[0] != 0x48000008) || (op[1] != 0xe8410028)) &&
            ((op[0] != PPC_INST_NOP) || (op[1] != PPC_INST_NOP))) {
                printk(KERN_ERR "Expected NOPs but have %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) {
                printk(KERN_ERR "No ftrace trampoline\n");
                return -EINVAL;
        }

        /* create the branch to the trampoline */
        op[0] = create_branch((unsigned int *)ip,
                              rec->arch.mod->arch.tramp, BRANCH_SET_LINK);
        if (!op[0]) {
                printk(KERN_ERR "REL24 out of range!\n");
                return -EINVAL;
        }

        /* ld r2,40(r1) */
        op[1] = 0xe8410028;

        pr_devel("write to %lx\n", rec->ip);

        if (probe_kernel_write((void *)ip, op, MCOUNT_INSN_SIZE * 2))
                return -EPERM;

        flush_icache_range(ip, ip + 8);

        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) {
                printk(KERN_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) {
                printk(KERN_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) {
                printk(KERN_ERR "REL24 out of range!\n");
                return -EINVAL;
        }

        pr_devel("write to %lx\n", rec->ip);

        if (probe_kernel_write((void *)ip, &op, MCOUNT_INSN_SIZE))
                return -EPERM;

        flush_icache_range(ip, ip + 8);

        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) {
                printk(KERN_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;
}

int __init ftrace_dyn_arch_init(void *data)
{
        /* caller expects data to be zero */
        unsigned long *p = data;

        *p = 0;

        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 */

#ifdef CONFIG_PPC64
extern void mod_return_to_handler(void);
#endif

/*
 * 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 = (unsigned long)&return_to_handler;

        if (unlikely(atomic_read(&current->tracing_graph_pause)))
                return;

#ifdef CONFIG_PPC64
        /* non core kernel code needs to save and restore the TOC */
        if (REGION_ID(self_addr) != KERNEL_REGION_ID)
                return_hooker = (unsigned long)&mod_return_to_handler;
#endif

        return_hooker = ppc_function_entry((void *)return_hooker);

        /*
         * 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;
        }

        if (ftrace_push_return_trace(old, self_addr, &trace.depth, 0) == -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;
        }
}
#endif /* CONFIG_FUNCTION_GRAPH_TRACER */