// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *  Copyright 2008 Michael Ellerman, IBM Corporation.
 */

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

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

static int __patch_instruction(u32 *exec_addr, ppc_inst_t instr, u32 *patch_addr)
{
        if (!ppc_inst_prefixed(instr)) {
                u32 val = ppc_inst_val(instr);

                __put_kernel_nofault(patch_addr, &val, u32, failed);
        } else {
                u64 val = ppc_inst_as_ulong(instr);

                __put_kernel_nofault(patch_addr, &val, u64, failed);
        }

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

        return 0;

failed:
        return -EFAULT;
}

int raw_patch_instruction(u32 *addr, ppc_inst_t instr)
{
        return __patch_instruction(addr, instr, addr);
}

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

static int map_patch_area(void *addr, unsigned long text_poke_addr);
static void unmap_patch_area(unsigned long addr);

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

        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;
        }

        // Map/unmap the area to ensure all page tables are pre-allocated
        addr = (unsigned long)area->addr;
        err = map_patch_area(empty_zero_page, addr);
        if (err)
                return err;

        unmap_patch_area(addr);

        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;
}

/*
 * 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().
 */
void __init poking_init(void)
{
        BUG_ON(!cpuhp_setup_state(CPUHP_AP_ONLINE_DYN,
                "powerpc/text_poke:online", text_area_cpu_up,
                text_area_cpu_down));
}

/*
 * 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;

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

        return map_kernel_page(text_poke_addr, (pfn << PAGE_SHIFT), PAGE_KERNEL);
}

static void unmap_patch_area(unsigned long addr)
{
        pte_t *ptep;
        pmd_t *pmdp;
        pud_t *pudp;
        p4d_t *p4dp;
        pgd_t *pgdp;

        pgdp = pgd_offset_k(addr);
        if (WARN_ON(pgd_none(*pgdp)))
                return;

        p4dp = p4d_offset(pgdp, addr);
        if (WARN_ON(p4d_none(*p4dp)))
                return;

        pudp = pud_offset(p4dp, addr);
        if (WARN_ON(pud_none(*pudp)))
                return;

        pmdp = pmd_offset(pudp, addr);
        if (WARN_ON(pmd_none(*pmdp)))
                return;

        ptep = pte_offset_kernel(pmdp, addr);
        if (WARN_ON(pte_none(*ptep)))
                return;

        /*
         * 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);
}

static int __do_patch_instruction(u32 *addr, ppc_inst_t instr)
{
        int err;
        u32 *patch_addr;
        unsigned long text_poke_addr;

        text_poke_addr = (unsigned long)__this_cpu_read(text_poke_area)->addr;
        patch_addr = (u32 *)(text_poke_addr + offset_in_page(addr));

        err = map_patch_area(addr, text_poke_addr);
        if (err)
                return err;

        err = __patch_instruction(addr, instr, patch_addr);

        unmap_patch_area(text_poke_addr);

        return err;
}

static int do_patch_instruction(u32 *addr, ppc_inst_t instr)
{
        int err;
        unsigned long flags;

        /*
         * 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);
        err = __do_patch_instruction(addr, instr);
        local_irq_restore(flags);

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

static int do_patch_instruction(u32 *addr, ppc_inst_t instr)
{
        return raw_patch_instruction(addr, instr);
}

#endif /* CONFIG_STRICT_KERNEL_RWX */

int patch_instruction(u32 *addr, ppc_inst_t instr)
{
        /* Make sure we aren't patching a freed init section */
        if (system_state >= SYSTEM_FREEING_INITMEM && init_section_contains(addr, 4))
                return 0;

        return do_patch_instruction(addr, instr);
}
NOKPROBE_SYMBOL(patch_instruction);

int patch_branch(u32 *addr, unsigned long target, int flags)
{
        ppc_inst_t instr;

        if (create_branch(&instr, addr, target, flags))
                return -ERANGE;

        return patch_instruction(addr, instr);
}

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));
}

bool is_offset_in_cond_branch_range(long offset)
{
        return offset >= -0x8000 && offset <= 0x7fff && !(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(ppc_inst_t instr)
{
        unsigned int opcode = ppc_inst_primary_opcode(instr);

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

int create_branch(ppc_inst_t *instr, const u32 *addr,
                  unsigned long target, int flags)
{
        long offset;

        *instr = ppc_inst(0);
        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 1;

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

        return 0;
}

int create_cond_branch(ppc_inst_t *instr, const u32 *addr,
                       unsigned long target, int flags)
{
        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_cond_branch_range(offset))
                return 1;

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

        return 0;
}

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

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

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

static unsigned long branch_iform_target(const u32 *instr)
{
        signed long imm;

        imm = ppc_inst_val(ppc_inst_read(instr)) & 0x3FFFFFC;

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

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

        return (unsigned long)imm;
}

static unsigned long branch_bform_target(const u32 *instr)
{
        signed long imm;

        imm = ppc_inst_val(ppc_inst_read(instr)) & 0xFFFC;

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

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

        return (unsigned long)imm;
}

unsigned long branch_target(const u32 *instr)
{
        if (instr_is_branch_iform(ppc_inst_read(instr)))
                return branch_iform_target(instr);
        else if (instr_is_branch_bform(ppc_inst_read(instr)))
                return branch_bform_target(instr);

        return 0;
}

int translate_branch(ppc_inst_t *instr, const u32 *dest, const u32 *src)
{
        unsigned long target;
        target = branch_target(src);

        if (instr_is_branch_iform(ppc_inst_read(src)))
                return create_branch(instr, dest, target,
                                     ppc_inst_val(ppc_inst_read(src)));
        else if (instr_is_branch_bform(ppc_inst_read(src)))
                return create_cond_branch(instr, dest, target,
                                          ppc_inst_val(ppc_inst_read(src)));

        return 1;
}