// SPDX-License-Identifier: GPL-2.0
#include <linux/kernel.h>
#include <linux/spinlock.h>
#include <linux/kprobes.h>
#include <linux/mm.h>
#include <linux/stop_machine.h>

#include <asm/cacheflush.h>
#include <asm/fixmap.h>
#include <asm/smp_plat.h>
#include <asm/opcodes.h>
#include <asm/text-patching.h>

struct patch {
        void *addr;
        unsigned int insn;
};

#ifdef CONFIG_MMU
static DEFINE_RAW_SPINLOCK(patch_lock);

static void __kprobes *patch_map(void *addr, int fixmap, unsigned long *flags)
{
        unsigned int uintaddr = (uintptr_t) addr;
        bool module = !core_kernel_text(uintaddr);
        struct page *page;

        if (module && IS_ENABLED(CONFIG_STRICT_MODULE_RWX))
                page = vmalloc_to_page(addr);
        else if (!module && IS_ENABLED(CONFIG_STRICT_KERNEL_RWX))
                page = virt_to_page(addr);
        else
                return addr;

        if (flags)
                raw_spin_lock_irqsave(&patch_lock, *flags);

        set_fixmap(fixmap, page_to_phys(page));

        return (void *) (__fix_to_virt(fixmap) + (uintaddr & ~PAGE_MASK));
}

static void __kprobes patch_unmap(int fixmap, unsigned long *flags)
{
        clear_fixmap(fixmap);

        if (flags)
                raw_spin_unlock_irqrestore(&patch_lock, *flags);
}
#else
static void __kprobes *patch_map(void *addr, int fixmap, unsigned long *flags)
{
        return addr;
}
static void __kprobes patch_unmap(int fixmap, unsigned long *flags) { }
#endif

void __kprobes __patch_text_real(void *addr, unsigned int insn, bool remap)
{
        bool thumb2 = IS_ENABLED(CONFIG_THUMB2_KERNEL);
        unsigned int uintaddr = (uintptr_t) addr;
        bool twopage = false;
        unsigned long flags;
        void *waddr = addr;
        int size;

        if (remap)
                waddr = patch_map(addr, FIX_TEXT_POKE0, &flags);

        if (thumb2 && __opcode_is_thumb16(insn)) {
                *(u16 *)waddr = __opcode_to_mem_thumb16(insn);
                size = sizeof(u16);
        } else if (thumb2 && (uintaddr & 2)) {
                u16 first = __opcode_thumb32_first(insn);
                u16 second = __opcode_thumb32_second(insn);
                u16 *addrh0 = waddr;
                u16 *addrh1 = waddr + 2;

                twopage = (uintaddr & ~PAGE_MASK) == PAGE_SIZE - 2;
                if (twopage && remap)
                        addrh1 = patch_map(addr + 2, FIX_TEXT_POKE1, NULL);

                *addrh0 = __opcode_to_mem_thumb16(first);
                *addrh1 = __opcode_to_mem_thumb16(second);

                if (twopage && addrh1 != addr + 2) {
                        flush_kernel_vmap_range(addrh1, 2);
                        patch_unmap(FIX_TEXT_POKE1, NULL);
                }

                size = sizeof(u32);
        } else {
                if (thumb2)
                        insn = __opcode_to_mem_thumb32(insn);
                else
                        insn = __opcode_to_mem_arm(insn);

                *(u32 *)waddr = insn;
                size = sizeof(u32);
        }

        if (waddr != addr) {
                flush_kernel_vmap_range(waddr, twopage ? size / 2 : size);
                patch_unmap(FIX_TEXT_POKE0, &flags);
        }

        flush_icache_range((uintptr_t)(addr),
                           (uintptr_t)(addr) + size);
}

static int __kprobes patch_text_stop_machine(void *data)
{
        struct patch *patch = data;

        __patch_text(patch->addr, patch->insn);

        return 0;
}

void __kprobes patch_text(void *addr, unsigned int insn)
{
        struct patch patch = {
                .addr = addr,
                .insn = insn,
        };

        stop_machine_cpuslocked(patch_text_stop_machine, &patch, NULL);
}