/*
 *  Copyright 2008 Michael Ellerman, IBM Corporation.
 *
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU General Public License
 *  as published by the Free Software Foundation; either version
 *  2 of the License, or (at your option) any later version.
 */

#include <linux/kernel.h>
#include <linux/kprobes.h>
#include <linux/vmalloc.h>
#include <linux/init.h>
#include <linux/mm.h>
#include <linux/cpuhotplug.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/kprobes.h>

#include <asm/pgtable.h>
#include <asm/tlbflush.h>
#include <asm/page.h>
#include <asm/code-patching.h>
#include <asm/setup.h>

static int __patch_instruction(unsigned int *exec_addr, unsigned int instr,
                               unsigned int *patch_addr)
{
        int err;

        __put_user_size(instr, patch_addr, 4, err);
        if (err)
                return err;

        asm ("dcbst 0, %0; sync; icbi 0,%1; sync; isync" :: "r" (patch_addr),
                                                            "r" (exec_addr));

        return 0;
}

int raw_patch_instruction(unsigned int *addr, unsigned int instr)
{
        return __patch_instruction(addr, instr, addr);
}

#ifdef CONFIG_STRICT_KERNEL_RWX
static DEFINE_PER_CPU(struct vm_struct *, text_poke_area);

static int text_area_cpu_up(unsigned int cpu)
{
        struct vm_struct *area;

        area = get_vm_area(PAGE_SIZE, VM_ALLOC);
        if (!area) {
                WARN_ONCE(1, "Failed to create text area for cpu %d\n",
                        cpu);
                return -1;
        }
        this_cpu_write(text_poke_area, area);

        return 0;
}

static int text_area_cpu_down(unsigned int cpu)
{
        free_vm_area(this_cpu_read(text_poke_area));
        return 0;
}

/*
 * Run as a late init call. This allows all the boot time patching to be done
 * simply by patching the code, and then we're called here prior to
 * mark_rodata_ro(), which happens after all init calls are run. Although
 * BUG_ON() is rude, in this case it should only happen if ENOMEM, and we judge
 * it as being preferable to a kernel that will crash later when someone tries
 * to use patch_instruction().
 */
static int __init setup_text_poke_area(void)
{
        BUG_ON(!cpuhp_setup_state(CPUHP_AP_ONLINE_DYN,
                "powerpc/text_poke:online", text_area_cpu_up,
                text_area_cpu_down));

        return 0;
}
late_initcall(setup_text_poke_area);

/*
 * This can be called for kernel text or a module.
 */
static int map_patch_area(void *addr, unsigned long text_poke_addr)
{
        unsigned long pfn;
        int err;

        if (is_vmalloc_addr(addr))
                pfn = vmalloc_to_pfn(addr);
        else
                pfn = __pa_symbol(addr) >> PAGE_SHIFT;

        err = map_kernel_page(text_poke_addr, (pfn << PAGE_SHIFT),
                                pgprot_val(PAGE_KERNEL));

        pr_devel("Mapped addr %lx with pfn %lx:%d\n", text_poke_addr, pfn, err);
        if (err)
                return -1;

        return 0;
}

static inline int unmap_patch_area(unsigned long addr)
{
        pte_t *ptep;
        pmd_t *pmdp;
        pud_t *pudp;
        pgd_t *pgdp;

        pgdp = pgd_offset_k(addr);
        if (unlikely(!pgdp))
                return -EINVAL;

        pudp = pud_offset(pgdp, addr);
        if (unlikely(!pudp))
                return -EINVAL;

        pmdp = pmd_offset(pudp, addr);
        if (unlikely(!pmdp))
                return -EINVAL;

        ptep = pte_offset_kernel(pmdp, addr);
        if (unlikely(!ptep))
                return -EINVAL;

        pr_devel("clearing mm %p, pte %p, addr %lx\n", &init_mm, ptep, addr);

        /*
         * In hash, pte_clear flushes the tlb, in radix, we have to
         */
        pte_clear(&init_mm, addr, ptep);
        flush_tlb_kernel_range(addr, addr + PAGE_SIZE);

        return 0;
}

int patch_instruction(unsigned int *addr, unsigned int instr)
{
        int err;
        unsigned int *patch_addr = NULL;
        unsigned long flags;
        unsigned long text_poke_addr;
        unsigned long kaddr = (unsigned long)addr;

        /*
         * During early early boot patch_instruction is called
         * when text_poke_area is not ready, but we still need
         * to allow patching. We just do the plain old patching
         */
        if (!this_cpu_read(text_poke_area))
                return raw_patch_instruction(addr, instr);

        local_irq_save(flags);

        text_poke_addr = (unsigned long)__this_cpu_read(text_poke_area)->addr;
        if (map_patch_area(addr, text_poke_addr)) {
                err = -1;
                goto out;
        }

        patch_addr = (unsigned int *)(text_poke_addr) +
                        ((kaddr & ~PAGE_MASK) / sizeof(unsigned int));

        __patch_instruction(addr, instr, patch_addr);

        err = unmap_patch_area(text_poke_addr);
        if (err)
                pr_warn("failed to unmap %lx\n", text_poke_addr);

out:
        local_irq_restore(flags);

        return err;
}
#else /* !CONFIG_STRICT_KERNEL_RWX */

int patch_instruction(unsigned int *addr, unsigned int instr)
{
        return raw_patch_instruction(addr, instr);
}

#endif /* CONFIG_STRICT_KERNEL_RWX */
NOKPROBE_SYMBOL(patch_instruction);

int patch_branch(unsigned int *addr, unsigned long target, int flags)
{
        return patch_instruction(addr, create_branch(addr, target, flags));
}

bool is_offset_in_branch_range(long offset)
{
        /*
         * Powerpc branch instruction is :
         *
         *  0         6                 30   31
         *  +---------+----------------+---+---+
         *  | opcode  |     LI         |AA |LK |
         *  +---------+----------------+---+---+
         *  Where AA = 0 and LK = 0
         *
         * LI is a signed 24 bits integer. The real branch offset is computed
         * by: imm32 = SignExtend(LI:'0b00', 32);
         *
         * So the maximum forward branch should be:
         *   (0x007fffff << 2) = 0x01fffffc =  0x1fffffc
         * The maximum backward branch should be:
         *   (0xff800000 << 2) = 0xfe000000 = -0x2000000
         */
        return (offset >= -0x2000000 && offset <= 0x1fffffc && !(offset & 0x3));
}

/*
 * Helper to check if a given instruction is a conditional branch
 * Derived from the conditional checks in analyse_instr()
 */
bool is_conditional_branch(unsigned int instr)
{
        unsigned int opcode = instr >> 26;

        if (opcode == 16)       /* bc, bca, bcl, bcla */
                return true;
        if (opcode == 19) {
                switch ((instr >> 1) & 0x3ff) {
                case 16:        /* bclr, bclrl */
                case 528:       /* bcctr, bcctrl */
                case 560:       /* bctar, bctarl */
                        return true;
                }
        }
        return false;
}
NOKPROBE_SYMBOL(is_conditional_branch);

unsigned int create_branch(const unsigned int *addr,
                           unsigned long target, int flags)
{
        unsigned int instruction;
        long offset;

        offset = target;
        if (! (flags & BRANCH_ABSOLUTE))
                offset = offset - (unsigned long)addr;

        /* Check we can represent the target in the instruction format */
        if (!is_offset_in_branch_range(offset))
                return 0;

        /* Mask out the flags and target, so they don't step on each other. */
        instruction = 0x48000000 | (flags & 0x3) | (offset & 0x03FFFFFC);

        return instruction;
}

unsigned int create_cond_branch(const unsigned int *addr,
                                unsigned long target, int flags)
{
        unsigned int instruction;
        long offset;

        offset = target;
        if (! (flags & BRANCH_ABSOLUTE))
                offset = offset - (unsigned long)addr;

        /* Check we can represent the target in the instruction format */
        if (offset < -0x8000 || offset > 0x7FFF || offset & 0x3)
                return 0;

        /* Mask out the flags and target, so they don't step on each other. */
        instruction = 0x40000000 | (flags & 0x3FF0003) | (offset & 0xFFFC);

        return instruction;
}

static unsigned int branch_opcode(unsigned int instr)
{
        return (instr >> 26) & 0x3F;
}

static int instr_is_branch_iform(unsigned int instr)
{
        return branch_opcode(instr) == 18;
}

static int instr_is_branch_bform(unsigned int instr)
{
        return branch_opcode(instr) == 16;
}

int instr_is_relative_branch(unsigned int instr)
{
        if (instr & BRANCH_ABSOLUTE)
                return 0;

        return instr_is_branch_iform(instr) || instr_is_branch_bform(instr);
}

int instr_is_relative_link_branch(unsigned int instr)
{
        return instr_is_relative_branch(instr) && (instr & BRANCH_SET_LINK);
}

static unsigned long branch_iform_target(const unsigned int *instr)
{
        signed long imm;

        imm = *instr & 0x3FFFFFC;

        /* If the top bit of the immediate value is set this is negative */
        if (imm & 0x2000000)
                imm -= 0x4000000;

        if ((*instr & BRANCH_ABSOLUTE) == 0)
                imm += (unsigned long)instr;

        return (unsigned long)imm;
}

static unsigned long branch_bform_target(const unsigned int *instr)
{
        signed long imm;

        imm = *instr & 0xFFFC;

        /* If the top bit of the immediate value is set this is negative */
        if (imm & 0x8000)
                imm -= 0x10000;

        if ((*instr & BRANCH_ABSOLUTE) == 0)
                imm += (unsigned long)instr;

        return (unsigned long)imm;
}

unsigned long branch_target(const unsigned int *instr)
{
        if (instr_is_branch_iform(*instr))
                return branch_iform_target(instr);
        else if (instr_is_branch_bform(*instr))
                return branch_bform_target(instr);

        return 0;
}

int instr_is_branch_to_addr(const unsigned int *instr, unsigned long addr)
{
        if (instr_is_branch_iform(*instr) || instr_is_branch_bform(*instr))
                return branch_target(instr) == addr;

        return 0;
}

unsigned int translate_branch(const unsigned int *dest, const unsigned int *src)
{
        unsigned long target;

        target = branch_target(src);

        if (instr_is_branch_iform(*src))
                return create_branch(dest, target, *src);
        else if (instr_is_branch_bform(*src))
                return create_cond_branch(dest, target, *src);

        return 0;
}

#ifdef CONFIG_PPC_BOOK3E_64
void __patch_exception(int exc, unsigned long addr)
{
        extern unsigned int interrupt_base_book3e;
        unsigned int *ibase = &interrupt_base_book3e;

        /* Our exceptions vectors start with a NOP and -then- a branch
         * to deal with single stepping from userspace which stops on
         * the second instruction. Thus we need to patch the second
         * instruction of the exception, not the first one
         */

        patch_branch(ibase + (exc / 4) + 1, addr, 0);
}
#endif

#ifdef CONFIG_CODE_PATCHING_SELFTEST

static void __init test_trampoline(void)
{
        asm ("nop;\n");
}

#define check(x)        \
        if (!(x)) printk("code-patching: test failed at line %d\n", __LINE__);

static void __init test_branch_iform(void)
{
        unsigned int instr;
        unsigned long addr;

        addr = (unsigned long)&instr;

        /* The simplest case, branch to self, no flags */
        check(instr_is_branch_iform(0x48000000));
        /* All bits of target set, and flags */
        check(instr_is_branch_iform(0x4bffffff));
        /* High bit of opcode set, which is wrong */
        check(!instr_is_branch_iform(0xcbffffff));
        /* Middle bits of opcode set, which is wrong */
        check(!instr_is_branch_iform(0x7bffffff));

        /* Simplest case, branch to self with link */
        check(instr_is_branch_iform(0x48000001));
        /* All bits of targets set */
        check(instr_is_branch_iform(0x4bfffffd));
        /* Some bits of targets set */
        check(instr_is_branch_iform(0x4bff00fd));
        /* Must be a valid branch to start with */
        check(!instr_is_branch_iform(0x7bfffffd));

        /* Absolute branch to 0x100 */
        instr = 0x48000103;
        check(instr_is_branch_to_addr(&instr, 0x100));
        /* Absolute branch to 0x420fc */
        instr = 0x480420ff;
        check(instr_is_branch_to_addr(&instr, 0x420fc));
        /* Maximum positive relative branch, + 20MB - 4B */
        instr = 0x49fffffc;
        check(instr_is_branch_to_addr(&instr, addr + 0x1FFFFFC));
        /* Smallest negative relative branch, - 4B */
        instr = 0x4bfffffc;
        check(instr_is_branch_to_addr(&instr, addr - 4));
        /* Largest negative relative branch, - 32 MB */
        instr = 0x4a000000;
        check(instr_is_branch_to_addr(&instr, addr - 0x2000000));

        /* Branch to self, with link */
        instr = create_branch(&instr, addr, BRANCH_SET_LINK);
        check(instr_is_branch_to_addr(&instr, addr));

        /* Branch to self - 0x100, with link */
        instr = create_branch(&instr, addr - 0x100, BRANCH_SET_LINK);
        check(instr_is_branch_to_addr(&instr, addr - 0x100));

        /* Branch to self + 0x100, no link */
        instr = create_branch(&instr, addr + 0x100, 0);
        check(instr_is_branch_to_addr(&instr, addr + 0x100));

        /* Maximum relative negative offset, - 32 MB */
        instr = create_branch(&instr, addr - 0x2000000, BRANCH_SET_LINK);
        check(instr_is_branch_to_addr(&instr, addr - 0x2000000));

        /* Out of range relative negative offset, - 32 MB + 4*/
        instr = create_branch(&instr, addr - 0x2000004, BRANCH_SET_LINK);
        check(instr == 0);

        /* Out of range relative positive offset, + 32 MB */
        instr = create_branch(&instr, addr + 0x2000000, BRANCH_SET_LINK);
        check(instr == 0);

        /* Unaligned target */
        instr = create_branch(&instr, addr + 3, BRANCH_SET_LINK);
        check(instr == 0);

        /* Check flags are masked correctly */
        instr = create_branch(&instr, addr, 0xFFFFFFFC);
        check(instr_is_branch_to_addr(&instr, addr));
        check(instr == 0x48000000);
}

static void __init test_create_function_call(void)
{
        unsigned int *iptr;
        unsigned long dest;

        /* Check we can create a function call */
        iptr = (unsigned int *)ppc_function_entry(test_trampoline);
        dest = ppc_function_entry(test_create_function_call);
        patch_instruction(iptr, create_branch(iptr, dest, BRANCH_SET_LINK));
        check(instr_is_branch_to_addr(iptr, dest));
}

static void __init test_branch_bform(void)
{
        unsigned long addr;
        unsigned int *iptr, instr, flags;

        iptr = &instr;
        addr = (unsigned long)iptr;

        /* The simplest case, branch to self, no flags */
        check(instr_is_branch_bform(0x40000000));
        /* All bits of target set, and flags */
        check(instr_is_branch_bform(0x43ffffff));
        /* High bit of opcode set, which is wrong */
        check(!instr_is_branch_bform(0xc3ffffff));
        /* Middle bits of opcode set, which is wrong */
        check(!instr_is_branch_bform(0x7bffffff));

        /* Absolute conditional branch to 0x100 */
        instr = 0x43ff0103;
        check(instr_is_branch_to_addr(&instr, 0x100));
        /* Absolute conditional branch to 0x20fc */
        instr = 0x43ff20ff;
        check(instr_is_branch_to_addr(&instr, 0x20fc));
        /* Maximum positive relative conditional branch, + 32 KB - 4B */
        instr = 0x43ff7ffc;
        check(instr_is_branch_to_addr(&instr, addr + 0x7FFC));
        /* Smallest negative relative conditional branch, - 4B */
        instr = 0x43fffffc;
        check(instr_is_branch_to_addr(&instr, addr - 4));
        /* Largest negative relative conditional branch, - 32 KB */
        instr = 0x43ff8000;
        check(instr_is_branch_to_addr(&instr, addr - 0x8000));

        /* All condition code bits set & link */
        flags = 0x3ff000 | BRANCH_SET_LINK;

        /* Branch to self */
        instr = create_cond_branch(iptr, addr, flags);
        check(instr_is_branch_to_addr(&instr, addr));

        /* Branch to self - 0x100 */
        instr = create_cond_branch(iptr, addr - 0x100, flags);
        check(instr_is_branch_to_addr(&instr, addr - 0x100));

        /* Branch to self + 0x100 */
        instr = create_cond_branch(iptr, addr + 0x100, flags);
        check(instr_is_branch_to_addr(&instr, addr + 0x100));

        /* Maximum relative negative offset, - 32 KB */
        instr = create_cond_branch(iptr, addr - 0x8000, flags);
        check(instr_is_branch_to_addr(&instr, addr - 0x8000));

        /* Out of range relative negative offset, - 32 KB + 4*/
        instr = create_cond_branch(iptr, addr - 0x8004, flags);
        check(instr == 0);

        /* Out of range relative positive offset, + 32 KB */
        instr = create_cond_branch(iptr, addr + 0x8000, flags);
        check(instr == 0);

        /* Unaligned target */
        instr = create_cond_branch(iptr, addr + 3, flags);
        check(instr == 0);

        /* Check flags are masked correctly */
        instr = create_cond_branch(iptr, addr, 0xFFFFFFFC);
        check(instr_is_branch_to_addr(&instr, addr));
        check(instr == 0x43FF0000);
}

static void __init test_translate_branch(void)
{
        unsigned long addr;
        unsigned int *p, *q;
        void *buf;

        buf = vmalloc(PAGE_ALIGN(0x2000000 + 1));
        check(buf);
        if (!buf)
                return;

        /* Simple case, branch to self moved a little */
        p = buf;
        addr = (unsigned long)p;
        patch_branch(p, addr, 0);
        check(instr_is_branch_to_addr(p, addr));
        q = p + 1;
        patch_instruction(q, translate_branch(q, p));
        check(instr_is_branch_to_addr(q, addr));

        /* Maximum negative case, move b . to addr + 32 MB */
        p = buf;
        addr = (unsigned long)p;
        patch_branch(p, addr, 0);
        q = buf + 0x2000000;
        patch_instruction(q, translate_branch(q, p));
        check(instr_is_branch_to_addr(p, addr));
        check(instr_is_branch_to_addr(q, addr));
        check(*q == 0x4a000000);

        /* Maximum positive case, move x to x - 32 MB + 4 */
        p = buf + 0x2000000;
        addr = (unsigned long)p;
        patch_branch(p, addr, 0);
        q = buf + 4;
        patch_instruction(q, translate_branch(q, p));
        check(instr_is_branch_to_addr(p, addr));
        check(instr_is_branch_to_addr(q, addr));
        check(*q == 0x49fffffc);

        /* Jump to x + 16 MB moved to x + 20 MB */
        p = buf;
        addr = 0x1000000 + (unsigned long)buf;
        patch_branch(p, addr, BRANCH_SET_LINK);
        q = buf + 0x1400000;
        patch_instruction(q, translate_branch(q, p));
        check(instr_is_branch_to_addr(p, addr));
        check(instr_is_branch_to_addr(q, addr));

        /* Jump to x + 16 MB moved to x - 16 MB + 4 */
        p = buf + 0x1000000;
        addr = 0x2000000 + (unsigned long)buf;
        patch_branch(p, addr, 0);
        q = buf + 4;
        patch_instruction(q, translate_branch(q, p));
        check(instr_is_branch_to_addr(p, addr));
        check(instr_is_branch_to_addr(q, addr));


        /* Conditional branch tests */

        /* Simple case, branch to self moved a little */
        p = buf;
        addr = (unsigned long)p;
        patch_instruction(p, create_cond_branch(p, addr, 0));
        check(instr_is_branch_to_addr(p, addr));
        q = p + 1;
        patch_instruction(q, translate_branch(q, p));
        check(instr_is_branch_to_addr(q, addr));

        /* Maximum negative case, move b . to addr + 32 KB */
        p = buf;
        addr = (unsigned long)p;
        patch_instruction(p, create_cond_branch(p, addr, 0xFFFFFFFC));
        q = buf + 0x8000;
        patch_instruction(q, translate_branch(q, p));
        check(instr_is_branch_to_addr(p, addr));
        check(instr_is_branch_to_addr(q, addr));
        check(*q == 0x43ff8000);

        /* Maximum positive case, move x to x - 32 KB + 4 */
        p = buf + 0x8000;
        addr = (unsigned long)p;
        patch_instruction(p, create_cond_branch(p, addr, 0xFFFFFFFC));
        q = buf + 4;
        patch_instruction(q, translate_branch(q, p));
        check(instr_is_branch_to_addr(p, addr));
        check(instr_is_branch_to_addr(q, addr));
        check(*q == 0x43ff7ffc);

        /* Jump to x + 12 KB moved to x + 20 KB */
        p = buf;
        addr = 0x3000 + (unsigned long)buf;
        patch_instruction(p, create_cond_branch(p, addr, BRANCH_SET_LINK));
        q = buf + 0x5000;
        patch_instruction(q, translate_branch(q, p));
        check(instr_is_branch_to_addr(p, addr));
        check(instr_is_branch_to_addr(q, addr));

        /* Jump to x + 8 KB moved to x - 8 KB + 4 */
        p = buf + 0x2000;
        addr = 0x4000 + (unsigned long)buf;
        patch_instruction(p, create_cond_branch(p, addr, 0));
        q = buf + 4;
        patch_instruction(q, translate_branch(q, p));
        check(instr_is_branch_to_addr(p, addr));
        check(instr_is_branch_to_addr(q, addr));

        /* Free the buffer we were using */
        vfree(buf);
}

static int __init test_code_patching(void)
{
        printk(KERN_DEBUG "Running code patching self-tests ...\n");

        test_branch_iform();
        test_branch_bform();
        test_create_function_call();
        test_translate_branch();

        return 0;
}
late_initcall(test_code_patching);

#endif /* CONFIG_CODE_PATCHING_SELFTEST */