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// SPDX-License-Identifier: GPL-2.0
/*
* functions to patch RO kernel text during runtime
*
* Copyright (c) 2019 Sven Schnelle <svens@stackframe.org>
*/
#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/patch.h>
struct patch {
void *addr;
unsigned int insn;
};
static void __kprobes *patch_map(void *addr, int fixmap)
{
unsigned long 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;
set_fixmap(fixmap, page_to_phys(page));
return (void *) (__fix_to_virt(fixmap) + (uintaddr & ~PAGE_MASK));
}
static void __kprobes patch_unmap(int fixmap)
{
clear_fixmap(fixmap);
}
void __kprobes __patch_text(void *addr, unsigned int insn)
{
void *waddr = addr;
int size;
waddr = patch_map(addr, FIX_TEXT_POKE0);
*(u32 *)waddr = insn;
size = sizeof(u32);
flush_kernel_vmap_range(waddr, size);
patch_unmap(FIX_TEXT_POKE0);
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);
}
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