+// SPDX-License-Identifier: GPL-2.0-only
#define pr_fmt(fmt) "SMP alternatives: " fmt
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/kdebug.h>
#include <linux/kprobes.h>
+#include <linux/mmu_context.h>
+#include <linux/bsearch.h>
#include <asm/text-patching.h>
#include <asm/alternative.h>
#include <asm/sections.h>
extern struct alt_instr __alt_instructions[], __alt_instructions_end[];
extern s32 __smp_locks[], __smp_locks_end[];
-void *text_poke_early(void *addr, const void *opcode, size_t len);
+void text_poke_early(void *addr, const void *opcode, size_t len);
/*
* Are we looking at a near JMP with a 1 or 4-byte displacement.
__stop_parainstructions[];
#endif /* CONFIG_PARAVIRT */
+/*
+ * Self-test for the INT3 based CALL emulation code.
+ *
+ * This exercises int3_emulate_call() to make sure INT3 pt_regs are set up
+ * properly and that there is a stack gap between the INT3 frame and the
+ * previous context. Without this gap doing a virtual PUSH on the interrupted
+ * stack would corrupt the INT3 IRET frame.
+ *
+ * See entry_{32,64}.S for more details.
+ */
+static void __init int3_magic(unsigned int *ptr)
+{
+ *ptr = 1;
+}
+
+extern __initdata unsigned long int3_selftest_ip; /* defined in asm below */
+
+static int __init
+int3_exception_notify(struct notifier_block *self, unsigned long val, void *data)
+{
+ struct die_args *args = data;
+ struct pt_regs *regs = args->regs;
+
+ if (!regs || user_mode(regs))
+ return NOTIFY_DONE;
+
+ if (val != DIE_INT3)
+ return NOTIFY_DONE;
+
+ if (regs->ip - INT3_INSN_SIZE != int3_selftest_ip)
+ return NOTIFY_DONE;
+
+ int3_emulate_call(regs, (unsigned long)&int3_magic);
+ return NOTIFY_STOP;
+}
+
+static void __init int3_selftest(void)
+{
+ static __initdata struct notifier_block int3_exception_nb = {
+ .notifier_call = int3_exception_notify,
+ .priority = INT_MAX-1, /* last */
+ };
+ unsigned int val = 0;
+
+ BUG_ON(register_die_notifier(&int3_exception_nb));
+
+ /*
+ * Basically: int3_magic(&val); but really complicated :-)
+ *
+ * Stick the address of the INT3 instruction into int3_selftest_ip,
+ * then trigger the INT3, padded with NOPs to match a CALL instruction
+ * length.
+ */
+ asm volatile ("1: int3; nop; nop; nop; nop\n\t"
+ ".pushsection .init.data,\"aw\"\n\t"
+ ".align " __ASM_SEL(4, 8) "\n\t"
+ ".type int3_selftest_ip, @object\n\t"
+ ".size int3_selftest_ip, " __ASM_SEL(4, 8) "\n\t"
+ "int3_selftest_ip:\n\t"
+ __ASM_SEL(.long, .quad) " 1b\n\t"
+ ".popsection\n\t"
+ : : __ASM_SEL_RAW(a, D) (&val) : "memory");
+
+ BUG_ON(val != 1);
+
+ unregister_die_notifier(&int3_exception_nb);
+}
+
void __init alternative_instructions(void)
{
- /* The patching is not fully atomic, so try to avoid local interruptions
- that might execute the to be patched code.
- Other CPUs are not running. */
+ int3_selftest();
+
+ /*
+ * The patching is not fully atomic, so try to avoid local
+ * interruptions that might execute the to be patched code.
+ * Other CPUs are not running.
+ */
stop_nmi();
/*
_text, _etext);
}
- if (!uniproc_patched || num_possible_cpus() == 1)
+ if (!uniproc_patched || num_possible_cpus() == 1) {
free_init_pages("SMP alternatives",
(unsigned long)__smp_locks,
(unsigned long)__smp_locks_end);
+ }
#endif
apply_paravirt(__parainstructions, __parainstructions_end);
* instructions. And on the local CPU you need to be protected again NMI or MCE
* handlers seeing an inconsistent instruction while you patch.
*/
-void *__init_or_module text_poke_early(void *addr, const void *opcode,
- size_t len)
+void __init_or_module text_poke_early(void *addr, const void *opcode,
+ size_t len)
+{
+ unsigned long flags;
+
+ if (boot_cpu_has(X86_FEATURE_NX) &&
+ is_module_text_address((unsigned long)addr)) {
+ /*
+ * Modules text is marked initially as non-executable, so the
+ * code cannot be running and speculative code-fetches are
+ * prevented. Just change the code.
+ */
+ memcpy(addr, opcode, len);
+ } else {
+ local_irq_save(flags);
+ memcpy(addr, opcode, len);
+ local_irq_restore(flags);
+ sync_core();
+
+ /*
+ * Could also do a CLFLUSH here to speed up CPU recovery; but
+ * that causes hangs on some VIA CPUs.
+ */
+ }
+}
+
+__ro_after_init struct mm_struct *poking_mm;
+__ro_after_init unsigned long poking_addr;
+
+static void *__text_poke(void *addr, const void *opcode, size_t len)
{
+ bool cross_page_boundary = offset_in_page(addr) + len > PAGE_SIZE;
+ struct page *pages[2] = {NULL};
+ temp_mm_state_t prev;
unsigned long flags;
+ pte_t pte, *ptep;
+ spinlock_t *ptl;
+ pgprot_t pgprot;
+
+ /*
+ * While boot memory allocator is running we cannot use struct pages as
+ * they are not yet initialized. There is no way to recover.
+ */
+ BUG_ON(!after_bootmem);
+
+ if (!core_kernel_text((unsigned long)addr)) {
+ pages[0] = vmalloc_to_page(addr);
+ if (cross_page_boundary)
+ pages[1] = vmalloc_to_page(addr + PAGE_SIZE);
+ } else {
+ pages[0] = virt_to_page(addr);
+ WARN_ON(!PageReserved(pages[0]));
+ if (cross_page_boundary)
+ pages[1] = virt_to_page(addr + PAGE_SIZE);
+ }
+ /*
+ * If something went wrong, crash and burn since recovery paths are not
+ * implemented.
+ */
+ BUG_ON(!pages[0] || (cross_page_boundary && !pages[1]));
+
local_irq_save(flags);
- memcpy(addr, opcode, len);
+
+ /*
+ * Map the page without the global bit, as TLB flushing is done with
+ * flush_tlb_mm_range(), which is intended for non-global PTEs.
+ */
+ pgprot = __pgprot(pgprot_val(PAGE_KERNEL) & ~_PAGE_GLOBAL);
+
+ /*
+ * The lock is not really needed, but this allows to avoid open-coding.
+ */
+ ptep = get_locked_pte(poking_mm, poking_addr, &ptl);
+
+ /*
+ * This must not fail; preallocated in poking_init().
+ */
+ VM_BUG_ON(!ptep);
+
+ pte = mk_pte(pages[0], pgprot);
+ set_pte_at(poking_mm, poking_addr, ptep, pte);
+
+ if (cross_page_boundary) {
+ pte = mk_pte(pages[1], pgprot);
+ set_pte_at(poking_mm, poking_addr + PAGE_SIZE, ptep + 1, pte);
+ }
+
+ /*
+ * Loading the temporary mm behaves as a compiler barrier, which
+ * guarantees that the PTE will be set at the time memcpy() is done.
+ */
+ prev = use_temporary_mm(poking_mm);
+
+ kasan_disable_current();
+ memcpy((u8 *)poking_addr + offset_in_page(addr), opcode, len);
+ kasan_enable_current();
+
+ /*
+ * Ensure that the PTE is only cleared after the instructions of memcpy
+ * were issued by using a compiler barrier.
+ */
+ barrier();
+
+ pte_clear(poking_mm, poking_addr, ptep);
+ if (cross_page_boundary)
+ pte_clear(poking_mm, poking_addr + PAGE_SIZE, ptep + 1);
+
+ /*
+ * Loading the previous page-table hierarchy requires a serializing
+ * instruction that already allows the core to see the updated version.
+ * Xen-PV is assumed to serialize execution in a similar manner.
+ */
+ unuse_temporary_mm(prev);
+
+ /*
+ * Flushing the TLB might involve IPIs, which would require enabled
+ * IRQs, but not if the mm is not used, as it is in this point.
+ */
+ flush_tlb_mm_range(poking_mm, poking_addr, poking_addr +
+ (cross_page_boundary ? 2 : 1) * PAGE_SIZE,
+ PAGE_SHIFT, false);
+
+ /*
+ * If the text does not match what we just wrote then something is
+ * fundamentally screwy; there's nothing we can really do about that.
+ */
+ BUG_ON(memcmp(addr, opcode, len));
+
+ pte_unmap_unlock(ptep, ptl);
local_irq_restore(flags);
- sync_core();
- /* Could also do a CLFLUSH here to speed up CPU recovery; but
- that causes hangs on some VIA CPUs. */
return addr;
}
* It means the size must be writable atomically and the address must be aligned
* in a way that permits an atomic write. It also makes sure we fit on a single
* page.
+ *
+ * Note that the caller must ensure that if the modified code is part of a
+ * module, the module would not be removed during poking. This can be achieved
+ * by registering a module notifier, and ordering module removal and patching
+ * trough a mutex.
*/
void *text_poke(void *addr, const void *opcode, size_t len)
{
- unsigned long flags;
- char *vaddr;
- struct page *pages[2];
- int i;
-
- /*
- * While boot memory allocator is runnig we cannot use struct
- * pages as they are not yet initialized.
- */
- BUG_ON(!after_bootmem);
-
lockdep_assert_held(&text_mutex);
- if (!core_kernel_text((unsigned long)addr)) {
- pages[0] = vmalloc_to_page(addr);
- pages[1] = vmalloc_to_page(addr + PAGE_SIZE);
- } else {
- pages[0] = virt_to_page(addr);
- WARN_ON(!PageReserved(pages[0]));
- pages[1] = virt_to_page(addr + PAGE_SIZE);
- }
- BUG_ON(!pages[0]);
- local_irq_save(flags);
- set_fixmap(FIX_TEXT_POKE0, page_to_phys(pages[0]));
- if (pages[1])
- set_fixmap(FIX_TEXT_POKE1, page_to_phys(pages[1]));
- vaddr = (char *)fix_to_virt(FIX_TEXT_POKE0);
- memcpy(&vaddr[(unsigned long)addr & ~PAGE_MASK], opcode, len);
- clear_fixmap(FIX_TEXT_POKE0);
- if (pages[1])
- clear_fixmap(FIX_TEXT_POKE1);
- local_flush_tlb();
- sync_core();
- /* Could also do a CLFLUSH here to speed up CPU recovery; but
- that causes hangs on some VIA CPUs. */
- for (i = 0; i < len; i++)
- BUG_ON(((char *)addr)[i] != ((char *)opcode)[i]);
- local_irq_restore(flags);
- return addr;
+ return __text_poke(addr, opcode, len);
+}
+
+/**
+ * text_poke_kgdb - Update instructions on a live kernel by kgdb
+ * @addr: address to modify
+ * @opcode: source of the copy
+ * @len: length to copy
+ *
+ * Only atomic text poke/set should be allowed when not doing early patching.
+ * It means the size must be writable atomically and the address must be aligned
+ * in a way that permits an atomic write. It also makes sure we fit on a single
+ * page.
+ *
+ * Context: should only be used by kgdb, which ensures no other core is running,
+ * despite the fact it does not hold the text_mutex.
+ */
+void *text_poke_kgdb(void *addr, const void *opcode, size_t len)
+{
+ return __text_poke(addr, opcode, len);
}
static void do_sync_core(void *info)
sync_core();
}
-static bool bp_patching_in_progress;
-static void *bp_int3_handler, *bp_int3_addr;
+static struct bp_patching_desc {
+ struct text_poke_loc *vec;
+ int nr_entries;
+} bp_patching;
+
+static int patch_cmp(const void *key, const void *elt)
+{
+ struct text_poke_loc *tp = (struct text_poke_loc *) elt;
+
+ if (key < tp->addr)
+ return -1;
+ if (key > tp->addr)
+ return 1;
+ return 0;
+}
+NOKPROBE_SYMBOL(patch_cmp);
int poke_int3_handler(struct pt_regs *regs)
{
+ struct text_poke_loc *tp;
+ unsigned char int3 = 0xcc;
+ void *ip;
+
/*
* Having observed our INT3 instruction, we now must observe
- * bp_patching_in_progress.
+ * bp_patching.nr_entries.
*
- * in_progress = TRUE INT3
+ * nr_entries != 0 INT3
* WMB RMB
- * write INT3 if (in_progress)
+ * write INT3 if (nr_entries)
*
- * Idem for bp_int3_handler.
+ * Idem for other elements in bp_patching.
*/
smp_rmb();
- if (likely(!bp_patching_in_progress))
+ if (likely(!bp_patching.nr_entries))
return 0;
- if (user_mode(regs) || regs->ip != (unsigned long)bp_int3_addr)
+ if (user_mode(regs))
return 0;
- /* set up the specified breakpoint handler */
- regs->ip = (unsigned long) bp_int3_handler;
+ /*
+ * Discount the sizeof(int3). See text_poke_bp_batch().
+ */
+ ip = (void *) regs->ip - sizeof(int3);
+
+ /*
+ * Skip the binary search if there is a single member in the vector.
+ */
+ if (unlikely(bp_patching.nr_entries > 1)) {
+ tp = bsearch(ip, bp_patching.vec, bp_patching.nr_entries,
+ sizeof(struct text_poke_loc),
+ patch_cmp);
+ if (!tp)
+ return 0;
+ } else {
+ tp = bp_patching.vec;
+ if (tp->addr != ip)
+ return 0;
+ }
+
+ /* set up the specified breakpoint detour */
+ regs->ip = (unsigned long) tp->detour;
return 1;
}
NOKPROBE_SYMBOL(poke_int3_handler);
/**
- * text_poke_bp() -- update instructions on live kernel on SMP
- * @addr: address to patch
- * @opcode: opcode of new instruction
- * @len: length to copy
- * @handler: address to jump to when the temporary breakpoint is hit
+ * text_poke_bp_batch() -- update instructions on live kernel on SMP
+ * @tp: vector of instructions to patch
+ * @nr_entries: number of entries in the vector
*
* Modify multi-byte instruction by using int3 breakpoint on SMP.
* We completely avoid stop_machine() here, and achieve the
* synchronization using int3 breakpoint.
*
* The way it is done:
- * - add a int3 trap to the address that will be patched
+ * - For each entry in the vector:
+ * - add a int3 trap to the address that will be patched
* - sync cores
- * - update all but the first byte of the patched range
+ * - For each entry in the vector:
+ * - update all but the first byte of the patched range
* - sync cores
- * - replace the first byte (int3) by the first byte of
- * replacing opcode
+ * - For each entry in the vector:
+ * - replace the first byte (int3) by the first byte of
+ * replacing opcode
* - sync cores
*/
-void *text_poke_bp(void *addr, const void *opcode, size_t len, void *handler)
+void text_poke_bp_batch(struct text_poke_loc *tp, unsigned int nr_entries)
{
+ int patched_all_but_first = 0;
unsigned char int3 = 0xcc;
-
- bp_int3_handler = handler;
- bp_int3_addr = (u8 *)addr + sizeof(int3);
- bp_patching_in_progress = true;
+ unsigned int i;
lockdep_assert_held(&text_mutex);
+ bp_patching.vec = tp;
+ bp_patching.nr_entries = nr_entries;
+
/*
* Corresponding read barrier in int3 notifier for making sure the
- * in_progress and handler are correctly ordered wrt. patching.
+ * nr_entries and handler are correctly ordered wrt. patching.
*/
smp_wmb();
- text_poke(addr, &int3, sizeof(int3));
+ /*
+ * First step: add a int3 trap to the address that will be patched.
+ */
+ for (i = 0; i < nr_entries; i++)
+ text_poke(tp[i].addr, &int3, sizeof(int3));
on_each_cpu(do_sync_core, NULL, 1);
- if (len - sizeof(int3) > 0) {
- /* patch all but the first byte */
- text_poke((char *)addr + sizeof(int3),
- (const char *) opcode + sizeof(int3),
- len - sizeof(int3));
+ /*
+ * Second step: update all but the first byte of the patched range.
+ */
+ for (i = 0; i < nr_entries; i++) {
+ if (tp[i].len - sizeof(int3) > 0) {
+ text_poke((char *)tp[i].addr + sizeof(int3),
+ (const char *)tp[i].opcode + sizeof(int3),
+ tp[i].len - sizeof(int3));
+ patched_all_but_first++;
+ }
+ }
+
+ if (patched_all_but_first) {
/*
* According to Intel, this core syncing is very likely
* not necessary and we'd be safe even without it. But
on_each_cpu(do_sync_core, NULL, 1);
}
- /* patch the first byte */
- text_poke(addr, opcode, sizeof(int3));
+ /*
+ * Third step: replace the first byte (int3) by the first byte of
+ * replacing opcode.
+ */
+ for (i = 0; i < nr_entries; i++)
+ text_poke(tp[i].addr, tp[i].opcode, sizeof(int3));
on_each_cpu(do_sync_core, NULL, 1);
/*
* sync_core() implies an smp_mb() and orders this store against
* the writing of the new instruction.
*/
- bp_patching_in_progress = false;
-
- return addr;
+ bp_patching.vec = NULL;
+ bp_patching.nr_entries = 0;
}
+/**
+ * text_poke_bp() -- update instructions on live kernel on SMP
+ * @addr: address to patch
+ * @opcode: opcode of new instruction
+ * @len: length to copy
+ * @handler: address to jump to when the temporary breakpoint is hit
+ *
+ * Update a single instruction with the vector in the stack, avoiding
+ * dynamically allocated memory. This function should be used when it is
+ * not possible to allocate memory.
+ */
+void text_poke_bp(void *addr, const void *opcode, size_t len, void *handler)
+{
+ struct text_poke_loc tp = {
+ .detour = handler,
+ .addr = addr,
+ .len = len,
+ };
+
+ if (len > POKE_MAX_OPCODE_SIZE) {
+ WARN_ONCE(1, "len is larger than %d\n", POKE_MAX_OPCODE_SIZE);
+ return;
+ }
+
+ memcpy((void *)tp.opcode, opcode, len);
+
+ text_poke_bp_batch(&tp, 1);
+}
projects / linux-2.6-block.git / blobdiff