diff options
Diffstat (limited to 'arch/powerpc/lib/code-patching.c')
| -rw-r--r-- | arch/powerpc/lib/code-patching.c | 713 |
1 files changed, 713 insertions, 0 deletions
diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c new file mode 100644 index 000000000..bb245dbf6 --- /dev/null +++ b/arch/powerpc/lib/code-patching.c @@ -0,0 +1,713 @@ +/* + * Copyright 2008 Michael Ellerman, IBM Corporation. + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation; either version + * 2 of the License, or (at your option) any later version. + */ + +#include <linux/kernel.h> +#include <linux/kprobes.h> +#include <linux/vmalloc.h> +#include <linux/init.h> +#include <linux/mm.h> +#include <linux/cpuhotplug.h> +#include <linux/slab.h> +#include <linux/uaccess.h> +#include <linux/kprobes.h> + +#include <asm/pgtable.h> +#include <asm/tlbflush.h> +#include <asm/page.h> +#include <asm/code-patching.h> +#include <asm/setup.h> + +static int __patch_instruction(unsigned int *exec_addr, unsigned int instr, + unsigned int *patch_addr) +{ + int err; + + __put_user_size(instr, patch_addr, 4, err); + if (err) + return err; + + asm ("dcbst 0, %0; sync; icbi 0,%1; sync; isync" :: "r" (patch_addr), + "r" (exec_addr)); + + return 0; +} + +int raw_patch_instruction(unsigned int *addr, unsigned int instr) +{ + return __patch_instruction(addr, instr, addr); +} + +#ifdef CONFIG_STRICT_KERNEL_RWX +static DEFINE_PER_CPU(struct vm_struct *, text_poke_area); + +static int text_area_cpu_up(unsigned int cpu) +{ + struct vm_struct *area; + + area = get_vm_area(PAGE_SIZE, VM_ALLOC); + if (!area) { + WARN_ONCE(1, "Failed to create text area for cpu %d\n", + cpu); + return -1; + } + this_cpu_write(text_poke_area, area); + + return 0; +} + +static int text_area_cpu_down(unsigned int cpu) +{ + free_vm_area(this_cpu_read(text_poke_area)); + return 0; +} + +/* + * Run as a late init call. This allows all the boot time patching to be done + * simply by patching the code, and then we're called here prior to + * mark_rodata_ro(), which happens after all init calls are run. 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(). + */ +static int __init setup_text_poke_area(void) +{ + BUG_ON(!cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, + "powerpc/text_poke:online", text_area_cpu_up, + text_area_cpu_down)); + + return 0; +} +late_initcall(setup_text_poke_area); + +/* + * This can be called for kernel text or a module. + */ +static int map_patch_area(void *addr, unsigned long text_poke_addr) +{ + unsigned long pfn; + int err; + + if (is_vmalloc_addr(addr)) + pfn = vmalloc_to_pfn(addr); + else + pfn = __pa_symbol(addr) >> PAGE_SHIFT; + + err = map_kernel_page(text_poke_addr, (pfn << PAGE_SHIFT), + pgprot_val(PAGE_KERNEL)); + + pr_devel("Mapped addr %lx with pfn %lx:%d\n", text_poke_addr, pfn, err); + if (err) + return -1; + + return 0; +} + +static inline int unmap_patch_area(unsigned long addr) +{ + pte_t *ptep; + pmd_t *pmdp; + pud_t *pudp; + pgd_t *pgdp; + + pgdp = pgd_offset_k(addr); + if (unlikely(!pgdp)) + return -EINVAL; + + pudp = pud_offset(pgdp, addr); + if (unlikely(!pudp)) + return -EINVAL; + + pmdp = pmd_offset(pudp, addr); + if (unlikely(!pmdp)) + return -EINVAL; + + ptep = pte_offset_kernel(pmdp, addr); + if (unlikely(!ptep)) + return -EINVAL; + + pr_devel("clearing mm %p, pte %p, addr %lx\n", &init_mm, ptep, addr); + + /* + * In hash, pte_clear flushes the tlb, in radix, we have to + */ + pte_clear(&init_mm, addr, ptep); + flush_tlb_kernel_range(addr, addr + PAGE_SIZE); + + return 0; +} + +static int do_patch_instruction(unsigned int *addr, unsigned int instr) +{ + int err; + unsigned int *patch_addr = NULL; + unsigned long flags; + unsigned long text_poke_addr; + unsigned long kaddr = (unsigned long)addr; + + /* + * During early early boot patch_instruction is called + * when text_poke_area is not ready, but we still need + * to allow patching. We just do the plain old patching + */ + if (!this_cpu_read(text_poke_area)) + return raw_patch_instruction(addr, instr); + + local_irq_save(flags); + + text_poke_addr = (unsigned long)__this_cpu_read(text_poke_area)->addr; + if (map_patch_area(addr, text_poke_addr)) { + err = -1; + goto out; + } + + patch_addr = (unsigned int *)(text_poke_addr) + + ((kaddr & ~PAGE_MASK) / sizeof(unsigned int)); + + __patch_instruction(addr, instr, patch_addr); + + err = unmap_patch_area(text_poke_addr); + if (err) + pr_warn("failed to unmap %lx\n", text_poke_addr); + +out: + local_irq_restore(flags); + + return err; +} +#else /* !CONFIG_STRICT_KERNEL_RWX */ + +static int do_patch_instruction(unsigned int *addr, unsigned int instr) +{ + return raw_patch_instruction(addr, instr); +} + +#endif /* CONFIG_STRICT_KERNEL_RWX */ + +int patch_instruction(unsigned int *addr, unsigned int instr) +{ + /* Make sure we aren't patching a freed init section */ + if (init_mem_is_free && init_section_contains(addr, 4)) { + pr_debug("Skipping init section patching addr: 0x%px\n", addr); + return 0; + } + return do_patch_instruction(addr, instr); +} +NOKPROBE_SYMBOL(patch_instruction); + +int patch_branch(unsigned int *addr, unsigned long target, int flags) +{ + return patch_instruction(addr, create_branch(addr, target, flags)); +} + +int patch_branch_site(s32 *site, unsigned long target, int flags) +{ + unsigned int *addr; + + addr = (unsigned int *)((unsigned long)site + *site); + return patch_instruction(addr, create_branch(addr, target, flags)); +} + +int patch_instruction_site(s32 *site, unsigned int instr) +{ + unsigned int *addr; + + addr = (unsigned int *)((unsigned long)site + *site); + return patch_instruction(addr, instr); +} + +bool is_offset_in_branch_range(long offset) +{ + /* + * Powerpc branch instruction is : + * + * 0 6 30 31 + * +---------+----------------+---+---+ + * | opcode | LI |AA |LK | + * +---------+----------------+---+---+ + * Where AA = 0 and LK = 0 + * + * LI is a signed 24 bits integer. The real branch offset is computed + * by: imm32 = SignExtend(LI:'0b00', 32); + * + * So the maximum forward branch should be: + * (0x007fffff << 2) = 0x01fffffc = 0x1fffffc + * The maximum backward branch should be: + * (0xff800000 << 2) = 0xfe000000 = -0x2000000 + */ + return (offset >= -0x2000000 && offset <= 0x1fffffc && !(offset & 0x3)); +} + +bool is_offset_in_cond_branch_range(long offset) +{ + return offset >= -0x8000 && offset <= 0x7fff && !(offset & 0x3); +} + +/* + * Helper to check if a given instruction is a conditional branch + * Derived from the conditional checks in analyse_instr() + */ +bool is_conditional_branch(unsigned int instr) +{ + unsigned int opcode = instr >> 26; + + if (opcode == 16) /* bc, bca, bcl, bcla */ + return true; + if (opcode == 19) { + switch ((instr >> 1) & 0x3ff) { + case 16: /* bclr, bclrl */ + case 528: /* bcctr, bcctrl */ + case 560: /* bctar, bctarl */ + return true; + } + } + return false; +} +NOKPROBE_SYMBOL(is_conditional_branch); + +unsigned int create_branch(const unsigned int *addr, + unsigned long target, int flags) +{ + unsigned int instruction; + long offset; + + offset = target; + if (! (flags & BRANCH_ABSOLUTE)) + offset = offset - (unsigned long)addr; + + /* Check we can represent the target in the instruction format */ + if (!is_offset_in_branch_range(offset)) + return 0; + + /* Mask out the flags and target, so they don't step on each other. */ + instruction = 0x48000000 | (flags & 0x3) | (offset & 0x03FFFFFC); + + return instruction; +} + +unsigned int create_cond_branch(const unsigned int *addr, + unsigned long target, int flags) +{ + unsigned int instruction; + long offset; + + offset = target; + if (! (flags & BRANCH_ABSOLUTE)) + offset = offset - (unsigned long)addr; + + /* Check we can represent the target in the instruction format */ + if (!is_offset_in_cond_branch_range(offset)) + return 0; + + /* Mask out the flags and target, so they don't step on each other. */ + instruction = 0x40000000 | (flags & 0x3FF0003) | (offset & 0xFFFC); + + return instruction; +} + +static unsigned int branch_opcode(unsigned int instr) +{ + return (instr >> 26) & 0x3F; +} + +static int instr_is_branch_iform(unsigned int instr) +{ + return branch_opcode(instr) == 18; +} + +static int instr_is_branch_bform(unsigned int instr) +{ + return branch_opcode(instr) == 16; +} + +int instr_is_relative_branch(unsigned int instr) +{ + if (instr & BRANCH_ABSOLUTE) + return 0; + + return instr_is_branch_iform(instr) || instr_is_branch_bform(instr); +} + +int instr_is_relative_link_branch(unsigned int instr) +{ + return instr_is_relative_branch(instr) && (instr & BRANCH_SET_LINK); +} + +static unsigned long branch_iform_target(const unsigned int *instr) +{ + signed long imm; + + imm = *instr & 0x3FFFFFC; + + /* If the top bit of the immediate value is set this is negative */ + if (imm & 0x2000000) + imm -= 0x4000000; + + if ((*instr & BRANCH_ABSOLUTE) == 0) + imm += (unsigned long)instr; + + return (unsigned long)imm; +} + +static unsigned long branch_bform_target(const unsigned int *instr) +{ + signed long imm; + + imm = *instr & 0xFFFC; + + /* If the top bit of the immediate value is set this is negative */ + if (imm & 0x8000) + imm -= 0x10000; + + if ((*instr & BRANCH_ABSOLUTE) == 0) + imm += (unsigned long)instr; + + return (unsigned long)imm; +} + +unsigned long branch_target(const unsigned int *instr) +{ + if (instr_is_branch_iform(*instr)) + return branch_iform_target(instr); + else if (instr_is_branch_bform(*instr)) + return branch_bform_target(instr); + + return 0; +} + +int instr_is_branch_to_addr(const unsigned int *instr, unsigned long addr) +{ + if (instr_is_branch_iform(*instr) || instr_is_branch_bform(*instr)) + return branch_target(instr) == addr; + + return 0; +} + +unsigned int translate_branch(const unsigned int *dest, const unsigned int *src) +{ + unsigned long target; + + target = branch_target(src); + + if (instr_is_branch_iform(*src)) + return create_branch(dest, target, *src); + else if (instr_is_branch_bform(*src)) + return create_cond_branch(dest, target, *src); + + return 0; +} + +#ifdef CONFIG_PPC_BOOK3E_64 +void __patch_exception(int exc, unsigned long addr) +{ + extern unsigned int interrupt_base_book3e; + unsigned int *ibase = &interrupt_base_book3e; + + /* Our exceptions vectors start with a NOP and -then- a branch + * to deal with single stepping from userspace which stops on + * the second instruction. Thus we need to patch the second + * instruction of the exception, not the first one + */ + + patch_branch(ibase + (exc / 4) + 1, addr, 0); +} +#endif + +#ifdef CONFIG_CODE_PATCHING_SELFTEST + +static void __init test_trampoline(void) +{ + asm ("nop;\n"); +} + +#define check(x) \ + if (!(x)) printk("code-patching: test failed at line %d\n", __LINE__); + +static void __init test_branch_iform(void) +{ + unsigned int instr; + unsigned long addr; + + addr = (unsigned long)&instr; + + /* The simplest case, branch to self, no flags */ + check(instr_is_branch_iform(0x48000000)); + /* All bits of target set, and flags */ + check(instr_is_branch_iform(0x4bffffff)); + /* High bit of opcode set, which is wrong */ + check(!instr_is_branch_iform(0xcbffffff)); + /* Middle bits of opcode set, which is wrong */ + check(!instr_is_branch_iform(0x7bffffff)); + + /* Simplest case, branch to self with link */ + check(instr_is_branch_iform(0x48000001)); + /* All bits of targets set */ + check(instr_is_branch_iform(0x4bfffffd)); + /* Some bits of targets set */ + check(instr_is_branch_iform(0x4bff00fd)); + /* Must be a valid branch to start with */ + check(!instr_is_branch_iform(0x7bfffffd)); + + /* Absolute branch to 0x100 */ + instr = 0x48000103; + check(instr_is_branch_to_addr(&instr, 0x100)); + /* Absolute branch to 0x420fc */ + instr = 0x480420ff; + check(instr_is_branch_to_addr(&instr, 0x420fc)); + /* Maximum positive relative branch, + 20MB - 4B */ + instr = 0x49fffffc; + check(instr_is_branch_to_addr(&instr, addr + 0x1FFFFFC)); + /* Smallest negative relative branch, - 4B */ + instr = 0x4bfffffc; + check(instr_is_branch_to_addr(&instr, addr - 4)); + /* Largest negative relative branch, - 32 MB */ + instr = 0x4a000000; + check(instr_is_branch_to_addr(&instr, addr - 0x2000000)); + + /* Branch to self, with link */ + instr = create_branch(&instr, addr, BRANCH_SET_LINK); + check(instr_is_branch_to_addr(&instr, addr)); + + /* Branch to self - 0x100, with link */ + instr = create_branch(&instr, addr - 0x100, BRANCH_SET_LINK); + check(instr_is_branch_to_addr(&instr, addr - 0x100)); + + /* Branch to self + 0x100, no link */ + instr = create_branch(&instr, addr + 0x100, 0); + check(instr_is_branch_to_addr(&instr, addr + 0x100)); + + /* Maximum relative negative offset, - 32 MB */ + instr = create_branch(&instr, addr - 0x2000000, BRANCH_SET_LINK); + check(instr_is_branch_to_addr(&instr, addr - 0x2000000)); + + /* Out of range relative negative offset, - 32 MB + 4*/ + instr = create_branch(&instr, addr - 0x2000004, BRANCH_SET_LINK); + check(instr == 0); + + /* Out of range relative positive offset, + 32 MB */ + instr = create_branch(&instr, addr + 0x2000000, BRANCH_SET_LINK); + check(instr == 0); + + /* Unaligned target */ + instr = create_branch(&instr, addr + 3, BRANCH_SET_LINK); + check(instr == 0); + + /* Check flags are masked correctly */ + instr = create_branch(&instr, addr, 0xFFFFFFFC); + check(instr_is_branch_to_addr(&instr, addr)); + check(instr == 0x48000000); +} + +static void __init test_create_function_call(void) +{ + unsigned int *iptr; + unsigned long dest; + + /* Check we can create a function call */ + iptr = (unsigned int *)ppc_function_entry(test_trampoline); + dest = ppc_function_entry(test_create_function_call); + patch_instruction(iptr, create_branch(iptr, dest, BRANCH_SET_LINK)); + check(instr_is_branch_to_addr(iptr, dest)); +} + +static void __init test_branch_bform(void) +{ + unsigned long addr; + unsigned int *iptr, instr, flags; + + iptr = &instr; + addr = (unsigned long)iptr; + + /* The simplest case, branch to self, no flags */ + check(instr_is_branch_bform(0x40000000)); + /* All bits of target set, and flags */ + check(instr_is_branch_bform(0x43ffffff)); + /* High bit of opcode set, which is wrong */ + check(!instr_is_branch_bform(0xc3ffffff)); + /* Middle bits of opcode set, which is wrong */ + check(!instr_is_branch_bform(0x7bffffff)); + + /* Absolute conditional branch to 0x100 */ + instr = 0x43ff0103; + check(instr_is_branch_to_addr(&instr, 0x100)); + /* Absolute conditional branch to 0x20fc */ + instr = 0x43ff20ff; + check(instr_is_branch_to_addr(&instr, 0x20fc)); + /* Maximum positive relative conditional branch, + 32 KB - 4B */ + instr = 0x43ff7ffc; + check(instr_is_branch_to_addr(&instr, addr + 0x7FFC)); + /* Smallest negative relative conditional branch, - 4B */ + instr = 0x43fffffc; + check(instr_is_branch_to_addr(&instr, addr - 4)); + /* Largest negative relative conditional branch, - 32 KB */ + instr = 0x43ff8000; + check(instr_is_branch_to_addr(&instr, addr - 0x8000)); + + /* All condition code bits set & link */ + flags = 0x3ff000 | BRANCH_SET_LINK; + + /* Branch to self */ + instr = create_cond_branch(iptr, addr, flags); + check(instr_is_branch_to_addr(&instr, addr)); + + /* Branch to self - 0x100 */ + instr = create_cond_branch(iptr, addr - 0x100, flags); + check(instr_is_branch_to_addr(&instr, addr - 0x100)); + + /* Branch to self + 0x100 */ + instr = create_cond_branch(iptr, addr + 0x100, flags); + check(instr_is_branch_to_addr(&instr, addr + 0x100)); + + /* Maximum relative negative offset, - 32 KB */ + instr = create_cond_branch(iptr, addr - 0x8000, flags); + check(instr_is_branch_to_addr(&instr, addr - 0x8000)); + + /* Out of range relative negative offset, - 32 KB + 4*/ + instr = create_cond_branch(iptr, addr - 0x8004, flags); + check(instr == 0); + + /* Out of range relative positive offset, + 32 KB */ + instr = create_cond_branch(iptr, addr + 0x8000, flags); + check(instr == 0); + + /* Unaligned target */ + instr = create_cond_branch(iptr, addr + 3, flags); + check(instr == 0); + + /* Check flags are masked correctly */ + instr = create_cond_branch(iptr, addr, 0xFFFFFFFC); + check(instr_is_branch_to_addr(&instr, addr)); + check(instr == 0x43FF0000); +} + +static void __init test_translate_branch(void) +{ + unsigned long addr; + unsigned int *p, *q; + void *buf; + + buf = vmalloc(PAGE_ALIGN(0x2000000 + 1)); + check(buf); + if (!buf) + return; + + /* Simple case, branch to self moved a little */ + p = buf; + addr = (unsigned long)p; + patch_branch(p, addr, 0); + check(instr_is_branch_to_addr(p, addr)); + q = p + 1; + patch_instruction(q, translate_branch(q, p)); + check(instr_is_branch_to_addr(q, addr)); + + /* Maximum negative case, move b . to addr + 32 MB */ + p = buf; + addr = (unsigned long)p; + patch_branch(p, addr, 0); + q = buf + 0x2000000; + patch_instruction(q, translate_branch(q, p)); + check(instr_is_branch_to_addr(p, addr)); + check(instr_is_branch_to_addr(q, addr)); + check(*q == 0x4a000000); + + /* Maximum positive case, move x to x - 32 MB + 4 */ + p = buf + 0x2000000; + addr = (unsigned long)p; + patch_branch(p, addr, 0); + q = buf + 4; + patch_instruction(q, translate_branch(q, p)); + check(instr_is_branch_to_addr(p, addr)); + check(instr_is_branch_to_addr(q, addr)); + check(*q == 0x49fffffc); + + /* Jump to x + 16 MB moved to x + 20 MB */ + p = buf; + addr = 0x1000000 + (unsigned long)buf; + patch_branch(p, addr, BRANCH_SET_LINK); + q = buf + 0x1400000; + patch_instruction(q, translate_branch(q, p)); + check(instr_is_branch_to_addr(p, addr)); + check(instr_is_branch_to_addr(q, addr)); + + /* Jump to x + 16 MB moved to x - 16 MB + 4 */ + p = buf + 0x1000000; + addr = 0x2000000 + (unsigned long)buf; + patch_branch(p, addr, 0); + q = buf + 4; + patch_instruction(q, translate_branch(q, p)); + check(instr_is_branch_to_addr(p, addr)); + check(instr_is_branch_to_addr(q, addr)); + + + /* Conditional branch tests */ + + /* Simple case, branch to self moved a little */ + p = buf; + addr = (unsigned long)p; + patch_instruction(p, create_cond_branch(p, addr, 0)); + check(instr_is_branch_to_addr(p, addr)); + q = p + 1; + patch_instruction(q, translate_branch(q, p)); + check(instr_is_branch_to_addr(q, addr)); + + /* Maximum negative case, move b . to addr + 32 KB */ + p = buf; + addr = (unsigned long)p; + patch_instruction(p, create_cond_branch(p, addr, 0xFFFFFFFC)); + q = buf + 0x8000; + patch_instruction(q, translate_branch(q, p)); + check(instr_is_branch_to_addr(p, addr)); + check(instr_is_branch_to_addr(q, addr)); + check(*q == 0x43ff8000); + + /* Maximum positive case, move x to x - 32 KB + 4 */ + p = buf + 0x8000; + addr = (unsigned long)p; + patch_instruction(p, create_cond_branch(p, addr, 0xFFFFFFFC)); + q = buf + 4; + patch_instruction(q, translate_branch(q, p)); + check(instr_is_branch_to_addr(p, addr)); + check(instr_is_branch_to_addr(q, addr)); + check(*q == 0x43ff7ffc); + + /* Jump to x + 12 KB moved to x + 20 KB */ + p = buf; + addr = 0x3000 + (unsigned long)buf; + patch_instruction(p, create_cond_branch(p, addr, BRANCH_SET_LINK)); + q = buf + 0x5000; + patch_instruction(q, translate_branch(q, p)); + check(instr_is_branch_to_addr(p, addr)); + check(instr_is_branch_to_addr(q, addr)); + + /* Jump to x + 8 KB moved to x - 8 KB + 4 */ + p = buf + 0x2000; + addr = 0x4000 + (unsigned long)buf; + patch_instruction(p, create_cond_branch(p, addr, 0)); + q = buf + 4; + patch_instruction(q, translate_branch(q, p)); + check(instr_is_branch_to_addr(p, addr)); + check(instr_is_branch_to_addr(q, addr)); + + /* Free the buffer we were using */ + vfree(buf); +} + +static int __init test_code_patching(void) +{ + printk(KERN_DEBUG "Running code patching self-tests ...\n"); + + test_branch_iform(); + test_branch_bform(); + test_create_function_call(); + test_translate_branch(); + + return 0; +} +late_initcall(test_code_patching); + +#endif /* CONFIG_CODE_PATCHING_SELFTEST */ |