diff options
Diffstat (limited to 'arch/powerpc/lib/code-patching.c')
| -rw-r--r-- | arch/powerpc/lib/code-patching.c | 238 |
1 files changed, 202 insertions, 36 deletions
diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c index ad0cf3108dd0..b00112d7ad46 100644 --- a/arch/powerpc/lib/code-patching.c +++ b/arch/powerpc/lib/code-patching.c @@ -4,12 +4,17 @@ */ #include <linux/kprobes.h> +#include <linux/mmu_context.h> +#include <linux/random.h> #include <linux/vmalloc.h> #include <linux/init.h> #include <linux/cpuhotplug.h> #include <linux/uaccess.h> #include <linux/jump_label.h> +#include <asm/debug.h> +#include <asm/pgalloc.h> +#include <asm/tlb.h> #include <asm/tlbflush.h> #include <asm/page.h> #include <asm/code-patching.h> @@ -41,12 +46,59 @@ int raw_patch_instruction(u32 *addr, ppc_inst_t instr) return __patch_instruction(addr, instr, addr); } -#ifdef CONFIG_STRICT_KERNEL_RWX -static DEFINE_PER_CPU(struct vm_struct *, text_poke_area); +struct patch_context { + union { + struct vm_struct *area; + struct mm_struct *mm; + }; + unsigned long addr; + pte_t *pte; +}; + +static DEFINE_PER_CPU(struct patch_context, cpu_patching_context); static int map_patch_area(void *addr, unsigned long text_poke_addr); static void unmap_patch_area(unsigned long addr); +static bool mm_patch_enabled(void) +{ + return IS_ENABLED(CONFIG_SMP) && radix_enabled(); +} + +/* + * The following applies for Radix MMU. Hash MMU has different requirements, + * and so is not supported. + * + * Changing mm requires context synchronising instructions on both sides of + * the context switch, as well as a hwsync between the last instruction for + * which the address of an associated storage access was translated using + * the current context. + * + * switch_mm_irqs_off() performs an isync after the context switch. It is + * the responsibility of the caller to perform the CSI and hwsync before + * starting/stopping the temp mm. + */ +static struct mm_struct *start_using_temp_mm(struct mm_struct *temp_mm) +{ + struct mm_struct *orig_mm = current->active_mm; + + lockdep_assert_irqs_disabled(); + switch_mm_irqs_off(orig_mm, temp_mm, current); + + WARN_ON(!mm_is_thread_local(temp_mm)); + + suspend_breakpoints(); + return orig_mm; +} + +static void stop_using_temp_mm(struct mm_struct *temp_mm, + struct mm_struct *orig_mm) +{ + lockdep_assert_irqs_disabled(); + switch_mm_irqs_off(temp_mm, orig_mm, current); + restore_breakpoints(); +} + static int text_area_cpu_up(unsigned int cpu) { struct vm_struct *area; @@ -68,29 +120,108 @@ static int text_area_cpu_up(unsigned int cpu) unmap_patch_area(addr); - this_cpu_write(text_poke_area, area); + this_cpu_write(cpu_patching_context.area, area); + this_cpu_write(cpu_patching_context.addr, addr); + this_cpu_write(cpu_patching_context.pte, virt_to_kpte(addr)); return 0; } static int text_area_cpu_down(unsigned int cpu) { - free_vm_area(this_cpu_read(text_poke_area)); + free_vm_area(this_cpu_read(cpu_patching_context.area)); + this_cpu_write(cpu_patching_context.area, NULL); + this_cpu_write(cpu_patching_context.addr, 0); + this_cpu_write(cpu_patching_context.pte, NULL); + return 0; +} + +static void put_patching_mm(struct mm_struct *mm, unsigned long patching_addr) +{ + struct mmu_gather tlb; + + tlb_gather_mmu(&tlb, mm); + free_pgd_range(&tlb, patching_addr, patching_addr + PAGE_SIZE, 0, 0); + mmput(mm); +} + +static int text_area_cpu_up_mm(unsigned int cpu) +{ + struct mm_struct *mm; + unsigned long addr; + pte_t *pte; + spinlock_t *ptl; + + mm = mm_alloc(); + if (WARN_ON(!mm)) + goto fail_no_mm; + + /* + * Choose a random page-aligned address from the interval + * [PAGE_SIZE .. DEFAULT_MAP_WINDOW - PAGE_SIZE]. + * The lower address bound is PAGE_SIZE to avoid the zero-page. + */ + addr = (1 + (get_random_long() % (DEFAULT_MAP_WINDOW / PAGE_SIZE - 2))) << PAGE_SHIFT; + + /* + * PTE allocation uses GFP_KERNEL which means we need to + * pre-allocate the PTE here because we cannot do the + * allocation during patching when IRQs are disabled. + * + * Using get_locked_pte() to avoid open coding, the lock + * is unnecessary. + */ + pte = get_locked_pte(mm, addr, &ptl); + if (!pte) + goto fail_no_pte; + pte_unmap_unlock(pte, ptl); + + this_cpu_write(cpu_patching_context.mm, mm); + this_cpu_write(cpu_patching_context.addr, addr); + + return 0; + +fail_no_pte: + put_patching_mm(mm, addr); +fail_no_mm: + return -ENOMEM; +} + +static int text_area_cpu_down_mm(unsigned int cpu) +{ + put_patching_mm(this_cpu_read(cpu_patching_context.mm), + this_cpu_read(cpu_patching_context.addr)); + + this_cpu_write(cpu_patching_context.mm, NULL); + this_cpu_write(cpu_patching_context.addr, 0); + return 0; } static __ro_after_init DEFINE_STATIC_KEY_FALSE(poking_init_done); -/* - * Although BUG_ON() is rude, in this case it should only happen if ENOMEM, and - * we judge it as being preferable to a kernel that will crash later when - * someone tries to use patch_instruction(). - */ void __init poking_init(void) { - BUG_ON(!cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, - "powerpc/text_poke:online", text_area_cpu_up, - text_area_cpu_down)); + int ret; + + if (!IS_ENABLED(CONFIG_STRICT_KERNEL_RWX)) + return; + + if (mm_patch_enabled()) + ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, + "powerpc/text_poke_mm:online", + text_area_cpu_up_mm, + text_area_cpu_down_mm); + else + ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, + "powerpc/text_poke:online", + text_area_cpu_up, + text_area_cpu_down); + + /* cpuhp_setup_state returns >= 0 on success */ + if (WARN_ON(ret < 0)) + return; + static_branch_enable(&poking_init_done); } @@ -147,6 +278,56 @@ static void unmap_patch_area(unsigned long addr) flush_tlb_kernel_range(addr, addr + PAGE_SIZE); } +static int __do_patch_instruction_mm(u32 *addr, ppc_inst_t instr) +{ + int err; + u32 *patch_addr; + unsigned long text_poke_addr; + pte_t *pte; + unsigned long pfn = get_patch_pfn(addr); + struct mm_struct *patching_mm; + struct mm_struct *orig_mm; + spinlock_t *ptl; + + patching_mm = __this_cpu_read(cpu_patching_context.mm); + text_poke_addr = __this_cpu_read(cpu_patching_context.addr); + patch_addr = (u32 *)(text_poke_addr + offset_in_page(addr)); + + pte = get_locked_pte(patching_mm, text_poke_addr, &ptl); + if (!pte) + return -ENOMEM; + + __set_pte_at(patching_mm, text_poke_addr, pte, pfn_pte(pfn, PAGE_KERNEL), 0); + + /* order PTE update before use, also serves as the hwsync */ + asm volatile("ptesync": : :"memory"); + + /* order context switch after arbitrary prior code */ + isync(); + + orig_mm = start_using_temp_mm(patching_mm); + + err = __patch_instruction(addr, instr, patch_addr); + + /* hwsync performed by __patch_instruction (sync) if successful */ + if (err) + mb(); /* sync */ + + /* context synchronisation performed by __patch_instruction (isync or exception) */ + stop_using_temp_mm(patching_mm, orig_mm); + + pte_clear(patching_mm, text_poke_addr, pte); + /* + * ptesync to order PTE update before TLB invalidation done + * by radix__local_flush_tlb_page_psize (in _tlbiel_va) + */ + local_flush_tlb_page_psize(patching_mm, text_poke_addr, mmu_virtual_psize); + + pte_unmap_unlock(pte, ptl); + + return err; +} + static int __do_patch_instruction(u32 *addr, ppc_inst_t instr) { int err; @@ -155,10 +336,10 @@ static int __do_patch_instruction(u32 *addr, ppc_inst_t instr) pte_t *pte; unsigned long pfn = get_patch_pfn(addr); - text_poke_addr = (unsigned long)__this_cpu_read(text_poke_area)->addr & PAGE_MASK; + text_poke_addr = (unsigned long)__this_cpu_read(cpu_patching_context.addr) & PAGE_MASK; patch_addr = (u32 *)(text_poke_addr + offset_in_page(addr)); - pte = virt_to_kpte(text_poke_addr); + pte = __this_cpu_read(cpu_patching_context.pte); __set_pte_at(&init_mm, text_poke_addr, pte, pfn_pte(pfn, PAGE_KERNEL), 0); /* See ptesync comment in radix__set_pte_at() */ if (radix_enabled()) @@ -172,7 +353,7 @@ static int __do_patch_instruction(u32 *addr, ppc_inst_t instr) return err; } -static int do_patch_instruction(u32 *addr, ppc_inst_t instr) +int patch_instruction(u32 *addr, ppc_inst_t instr) { int err; unsigned long flags; @@ -182,34 +363,19 @@ static int do_patch_instruction(u32 *addr, ppc_inst_t instr) * when text_poke_area is not ready, but we still need * to allow patching. We just do the plain old patching */ - if (!static_branch_likely(&poking_init_done)) + if (!IS_ENABLED(CONFIG_STRICT_KERNEL_RWX) || + !static_branch_likely(&poking_init_done)) return raw_patch_instruction(addr, instr); local_irq_save(flags); - err = __do_patch_instruction(addr, instr); + if (mm_patch_enabled()) + err = __do_patch_instruction_mm(addr, instr); + else + err = __do_patch_instruction(addr, instr); local_irq_restore(flags); return err; } -#else /* !CONFIG_STRICT_KERNEL_RWX */ - -static int do_patch_instruction(u32 *addr, ppc_inst_t instr) -{ - return raw_patch_instruction(addr, instr); -} - -#endif /* CONFIG_STRICT_KERNEL_RWX */ - -__ro_after_init DEFINE_STATIC_KEY_FALSE(init_mem_is_free); - -int patch_instruction(u32 *addr, ppc_inst_t instr) -{ - /* Make sure we aren't patching a freed init section */ - if (static_branch_likely(&init_mem_is_free) && init_section_contains(addr, 4)) - return 0; - - return do_patch_instruction(addr, instr); -} NOKPROBE_SYMBOL(patch_instruction); int patch_branch(u32 *addr, unsigned long target, int flags) |