1 // SPDX-License-Identifier: GPL-2.0-or-later
3 * Copyright 2008 Michael Ellerman, IBM Corporation.
6 #include <linux/kprobes.h>
7 #include <linux/mmu_context.h>
8 #include <linux/random.h>
9 #include <linux/vmalloc.h>
10 #include <linux/init.h>
11 #include <linux/cpuhotplug.h>
12 #include <linux/uaccess.h>
13 #include <linux/jump_label.h>
15 #include <asm/debug.h>
16 #include <asm/pgalloc.h>
18 #include <asm/tlbflush.h>
20 #include <asm/code-patching.h>
23 static int __patch_instruction(u32 *exec_addr, ppc_inst_t instr, u32 *patch_addr)
25 if (!ppc_inst_prefixed(instr)) {
26 u32 val = ppc_inst_val(instr);
28 __put_kernel_nofault(patch_addr, &val, u32, failed);
30 u64 val = ppc_inst_as_ulong(instr);
32 __put_kernel_nofault(patch_addr, &val, u64, failed);
35 asm ("dcbst 0, %0; sync; icbi 0,%1; sync; isync" :: "r" (patch_addr),
44 int raw_patch_instruction(u32 *addr, ppc_inst_t instr)
46 return __patch_instruction(addr, instr, addr);
49 struct patch_context {
51 struct vm_struct *area;
58 static DEFINE_PER_CPU(struct patch_context, cpu_patching_context);
60 static int map_patch_area(void *addr, unsigned long text_poke_addr);
61 static void unmap_patch_area(unsigned long addr);
63 static bool mm_patch_enabled(void)
65 return IS_ENABLED(CONFIG_SMP) && radix_enabled();
69 * The following applies for Radix MMU. Hash MMU has different requirements,
70 * and so is not supported.
72 * Changing mm requires context synchronising instructions on both sides of
73 * the context switch, as well as a hwsync between the last instruction for
74 * which the address of an associated storage access was translated using
75 * the current context.
77 * switch_mm_irqs_off() performs an isync after the context switch. It is
78 * the responsibility of the caller to perform the CSI and hwsync before
79 * starting/stopping the temp mm.
81 static struct mm_struct *start_using_temp_mm(struct mm_struct *temp_mm)
83 struct mm_struct *orig_mm = current->active_mm;
85 lockdep_assert_irqs_disabled();
86 switch_mm_irqs_off(orig_mm, temp_mm, current);
88 WARN_ON(!mm_is_thread_local(temp_mm));
90 suspend_breakpoints();
94 static void stop_using_temp_mm(struct mm_struct *temp_mm,
95 struct mm_struct *orig_mm)
97 lockdep_assert_irqs_disabled();
98 switch_mm_irqs_off(temp_mm, orig_mm, current);
99 restore_breakpoints();
102 static int text_area_cpu_up(unsigned int cpu)
104 struct vm_struct *area;
108 area = get_vm_area(PAGE_SIZE, VM_ALLOC);
110 WARN_ONCE(1, "Failed to create text area for cpu %d\n",
115 // Map/unmap the area to ensure all page tables are pre-allocated
116 addr = (unsigned long)area->addr;
117 err = map_patch_area(empty_zero_page, addr);
121 unmap_patch_area(addr);
123 this_cpu_write(cpu_patching_context.area, area);
124 this_cpu_write(cpu_patching_context.addr, addr);
125 this_cpu_write(cpu_patching_context.pte, virt_to_kpte(addr));
130 static int text_area_cpu_down(unsigned int cpu)
132 free_vm_area(this_cpu_read(cpu_patching_context.area));
133 this_cpu_write(cpu_patching_context.area, NULL);
134 this_cpu_write(cpu_patching_context.addr, 0);
135 this_cpu_write(cpu_patching_context.pte, NULL);
139 static void put_patching_mm(struct mm_struct *mm, unsigned long patching_addr)
141 struct mmu_gather tlb;
143 tlb_gather_mmu(&tlb, mm);
144 free_pgd_range(&tlb, patching_addr, patching_addr + PAGE_SIZE, 0, 0);
148 static int text_area_cpu_up_mm(unsigned int cpu)
150 struct mm_struct *mm;
160 * Choose a random page-aligned address from the interval
161 * [PAGE_SIZE .. DEFAULT_MAP_WINDOW - PAGE_SIZE].
162 * The lower address bound is PAGE_SIZE to avoid the zero-page.
164 addr = (1 + (get_random_long() % (DEFAULT_MAP_WINDOW / PAGE_SIZE - 2))) << PAGE_SHIFT;
167 * PTE allocation uses GFP_KERNEL which means we need to
168 * pre-allocate the PTE here because we cannot do the
169 * allocation during patching when IRQs are disabled.
171 * Using get_locked_pte() to avoid open coding, the lock
174 pte = get_locked_pte(mm, addr, &ptl);
177 pte_unmap_unlock(pte, ptl);
179 this_cpu_write(cpu_patching_context.mm, mm);
180 this_cpu_write(cpu_patching_context.addr, addr);
185 put_patching_mm(mm, addr);
190 static int text_area_cpu_down_mm(unsigned int cpu)
192 put_patching_mm(this_cpu_read(cpu_patching_context.mm),
193 this_cpu_read(cpu_patching_context.addr));
195 this_cpu_write(cpu_patching_context.mm, NULL);
196 this_cpu_write(cpu_patching_context.addr, 0);
201 static __ro_after_init DEFINE_STATIC_KEY_FALSE(poking_init_done);
203 void __init poking_init(void)
207 if (!IS_ENABLED(CONFIG_STRICT_KERNEL_RWX))
210 if (mm_patch_enabled())
211 ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN,
212 "powerpc/text_poke_mm:online",
214 text_area_cpu_down_mm);
216 ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN,
217 "powerpc/text_poke:online",
221 /* cpuhp_setup_state returns >= 0 on success */
222 if (WARN_ON(ret < 0))
225 static_branch_enable(&poking_init_done);
228 static unsigned long get_patch_pfn(void *addr)
230 if (IS_ENABLED(CONFIG_MODULES) && is_vmalloc_or_module_addr(addr))
231 return vmalloc_to_pfn(addr);
233 return __pa_symbol(addr) >> PAGE_SHIFT;
237 * This can be called for kernel text or a module.
239 static int map_patch_area(void *addr, unsigned long text_poke_addr)
241 unsigned long pfn = get_patch_pfn(addr);
243 return map_kernel_page(text_poke_addr, (pfn << PAGE_SHIFT), PAGE_KERNEL);
246 static void unmap_patch_area(unsigned long addr)
254 pgdp = pgd_offset_k(addr);
255 if (WARN_ON(pgd_none(*pgdp)))
258 p4dp = p4d_offset(pgdp, addr);
259 if (WARN_ON(p4d_none(*p4dp)))
262 pudp = pud_offset(p4dp, addr);
263 if (WARN_ON(pud_none(*pudp)))
266 pmdp = pmd_offset(pudp, addr);
267 if (WARN_ON(pmd_none(*pmdp)))
270 ptep = pte_offset_kernel(pmdp, addr);
271 if (WARN_ON(pte_none(*ptep)))
275 * In hash, pte_clear flushes the tlb, in radix, we have to
277 pte_clear(&init_mm, addr, ptep);
278 flush_tlb_kernel_range(addr, addr + PAGE_SIZE);
281 static int __do_patch_instruction_mm(u32 *addr, ppc_inst_t instr)
285 unsigned long text_poke_addr;
287 unsigned long pfn = get_patch_pfn(addr);
288 struct mm_struct *patching_mm;
289 struct mm_struct *orig_mm;
292 patching_mm = __this_cpu_read(cpu_patching_context.mm);
293 text_poke_addr = __this_cpu_read(cpu_patching_context.addr);
294 patch_addr = (u32 *)(text_poke_addr + offset_in_page(addr));
296 pte = get_locked_pte(patching_mm, text_poke_addr, &ptl);
300 __set_pte_at(patching_mm, text_poke_addr, pte, pfn_pte(pfn, PAGE_KERNEL), 0);
302 /* order PTE update before use, also serves as the hwsync */
303 asm volatile("ptesync": : :"memory");
305 /* order context switch after arbitrary prior code */
308 orig_mm = start_using_temp_mm(patching_mm);
310 err = __patch_instruction(addr, instr, patch_addr);
312 /* hwsync performed by __patch_instruction (sync) if successful */
316 /* context synchronisation performed by __patch_instruction (isync or exception) */
317 stop_using_temp_mm(patching_mm, orig_mm);
319 pte_clear(patching_mm, text_poke_addr, pte);
321 * ptesync to order PTE update before TLB invalidation done
322 * by radix__local_flush_tlb_page_psize (in _tlbiel_va)
324 local_flush_tlb_page_psize(patching_mm, text_poke_addr, mmu_virtual_psize);
326 pte_unmap_unlock(pte, ptl);
331 static int __do_patch_instruction(u32 *addr, ppc_inst_t instr)
335 unsigned long text_poke_addr;
337 unsigned long pfn = get_patch_pfn(addr);
339 text_poke_addr = (unsigned long)__this_cpu_read(cpu_patching_context.addr) & PAGE_MASK;
340 patch_addr = (u32 *)(text_poke_addr + offset_in_page(addr));
342 pte = __this_cpu_read(cpu_patching_context.pte);
343 __set_pte_at(&init_mm, text_poke_addr, pte, pfn_pte(pfn, PAGE_KERNEL), 0);
344 /* See ptesync comment in radix__set_pte_at() */
346 asm volatile("ptesync": : :"memory");
348 err = __patch_instruction(addr, instr, patch_addr);
350 pte_clear(&init_mm, text_poke_addr, pte);
351 flush_tlb_kernel_range(text_poke_addr, text_poke_addr + PAGE_SIZE);
356 int patch_instruction(u32 *addr, ppc_inst_t instr)
362 * During early early boot patch_instruction is called
363 * when text_poke_area is not ready, but we still need
364 * to allow patching. We just do the plain old patching
366 if (!IS_ENABLED(CONFIG_STRICT_KERNEL_RWX) ||
367 !static_branch_likely(&poking_init_done))
368 return raw_patch_instruction(addr, instr);
370 local_irq_save(flags);
371 if (mm_patch_enabled())
372 err = __do_patch_instruction_mm(addr, instr);
374 err = __do_patch_instruction(addr, instr);
375 local_irq_restore(flags);
379 NOKPROBE_SYMBOL(patch_instruction);
381 int patch_branch(u32 *addr, unsigned long target, int flags)
385 if (create_branch(&instr, addr, target, flags))
388 return patch_instruction(addr, instr);
392 * Helper to check if a given instruction is a conditional branch
393 * Derived from the conditional checks in analyse_instr()
395 bool is_conditional_branch(ppc_inst_t instr)
397 unsigned int opcode = ppc_inst_primary_opcode(instr);
399 if (opcode == 16) /* bc, bca, bcl, bcla */
402 switch ((ppc_inst_val(instr) >> 1) & 0x3ff) {
403 case 16: /* bclr, bclrl */
404 case 528: /* bcctr, bcctrl */
405 case 560: /* bctar, bctarl */
411 NOKPROBE_SYMBOL(is_conditional_branch);
413 int create_cond_branch(ppc_inst_t *instr, const u32 *addr,
414 unsigned long target, int flags)
419 if (! (flags & BRANCH_ABSOLUTE))
420 offset = offset - (unsigned long)addr;
422 /* Check we can represent the target in the instruction format */
423 if (!is_offset_in_cond_branch_range(offset))
426 /* Mask out the flags and target, so they don't step on each other. */
427 *instr = ppc_inst(0x40000000 | (flags & 0x3FF0003) | (offset & 0xFFFC));
432 int instr_is_relative_branch(ppc_inst_t instr)
434 if (ppc_inst_val(instr) & BRANCH_ABSOLUTE)
437 return instr_is_branch_iform(instr) || instr_is_branch_bform(instr);
440 int instr_is_relative_link_branch(ppc_inst_t instr)
442 return instr_is_relative_branch(instr) && (ppc_inst_val(instr) & BRANCH_SET_LINK);
445 static unsigned long branch_iform_target(const u32 *instr)
449 imm = ppc_inst_val(ppc_inst_read(instr)) & 0x3FFFFFC;
451 /* If the top bit of the immediate value is set this is negative */
455 if ((ppc_inst_val(ppc_inst_read(instr)) & BRANCH_ABSOLUTE) == 0)
456 imm += (unsigned long)instr;
458 return (unsigned long)imm;
461 static unsigned long branch_bform_target(const u32 *instr)
465 imm = ppc_inst_val(ppc_inst_read(instr)) & 0xFFFC;
467 /* If the top bit of the immediate value is set this is negative */
471 if ((ppc_inst_val(ppc_inst_read(instr)) & BRANCH_ABSOLUTE) == 0)
472 imm += (unsigned long)instr;
474 return (unsigned long)imm;
477 unsigned long branch_target(const u32 *instr)
479 if (instr_is_branch_iform(ppc_inst_read(instr)))
480 return branch_iform_target(instr);
481 else if (instr_is_branch_bform(ppc_inst_read(instr)))
482 return branch_bform_target(instr);
487 int translate_branch(ppc_inst_t *instr, const u32 *dest, const u32 *src)
489 unsigned long target;
490 target = branch_target(src);
492 if (instr_is_branch_iform(ppc_inst_read(src)))
493 return create_branch(instr, dest, target,
494 ppc_inst_val(ppc_inst_read(src)));
495 else if (instr_is_branch_bform(ppc_inst_read(src)))
496 return create_cond_branch(instr, dest, target,
497 ppc_inst_val(ppc_inst_read(src)));