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- // SPDX-License-Identifier: GPL-2.0
- /*
- * functions to patch RO kernel text during runtime
- *
- * Copyright (c) 2019 Sven Schnelle <[email protected]>
- */
- #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;
- u32 *insn;
- unsigned int len;
- };
- static DEFINE_RAW_SPINLOCK(patch_lock);
- static void __kprobes *patch_map(void *addr, int fixmap, unsigned long *flags,
- int *need_unmap)
- {
- unsigned long uintaddr = (uintptr_t) addr;
- bool module = !core_kernel_text(uintaddr);
- struct page *page;
- *need_unmap = 0;
- 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;
- *need_unmap = 1;
- set_fixmap(fixmap, page_to_phys(page));
- raw_spin_lock_irqsave(&patch_lock, *flags);
- return (void *) (__fix_to_virt(fixmap) + (uintaddr & ~PAGE_MASK));
- }
- static void __kprobes patch_unmap(int fixmap, unsigned long *flags)
- {
- clear_fixmap(fixmap);
- raw_spin_unlock_irqrestore(&patch_lock, *flags);
- }
- void __kprobes __patch_text_multiple(void *addr, u32 *insn, unsigned int len)
- {
- unsigned long start = (unsigned long)addr;
- unsigned long end = (unsigned long)addr + len;
- unsigned long flags;
- u32 *p, *fixmap;
- int mapped;
- /* Make sure we don't have any aliases in cache */
- flush_kernel_dcache_range_asm(start, end);
- flush_kernel_icache_range_asm(start, end);
- flush_tlb_kernel_range(start, end);
- p = fixmap = patch_map(addr, FIX_TEXT_POKE0, &flags, &mapped);
- while (len >= 4) {
- *p++ = *insn++;
- addr += sizeof(u32);
- len -= sizeof(u32);
- if (len && offset_in_page(addr) == 0) {
- /*
- * We're crossing a page boundary, so
- * need to remap
- */
- flush_kernel_dcache_range_asm((unsigned long)fixmap,
- (unsigned long)p);
- flush_tlb_kernel_range((unsigned long)fixmap,
- (unsigned long)p);
- if (mapped)
- patch_unmap(FIX_TEXT_POKE0, &flags);
- p = fixmap = patch_map(addr, FIX_TEXT_POKE0, &flags,
- &mapped);
- }
- }
- flush_kernel_dcache_range_asm((unsigned long)fixmap, (unsigned long)p);
- flush_tlb_kernel_range((unsigned long)fixmap, (unsigned long)p);
- if (mapped)
- patch_unmap(FIX_TEXT_POKE0, &flags);
- }
- void __kprobes __patch_text(void *addr, u32 insn)
- {
- __patch_text_multiple(addr, &insn, sizeof(insn));
- }
- static int __kprobes patch_text_stop_machine(void *data)
- {
- struct patch *patch = data;
- __patch_text_multiple(patch->addr, patch->insn, patch->len);
- return 0;
- }
- void __kprobes patch_text(void *addr, unsigned int insn)
- {
- struct patch patch = {
- .addr = addr,
- .insn = &insn,
- .len = sizeof(insn),
- };
- stop_machine_cpuslocked(patch_text_stop_machine, &patch, NULL);
- }
- void __kprobes patch_text_multiple(void *addr, u32 *insn, unsigned int len)
- {
- struct patch patch = {
- .addr = addr,
- .insn = insn,
- .len = len
- };
- stop_machine_cpuslocked(patch_text_stop_machine, &patch, NULL);
- }
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