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/*
* 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 *addr, unsigned int instr)
{
int err;
__put_user_size(instr, addr, 4, err);
if (err)
return err;
asm ("dcbst 0, %0; sync; icbi 0,%0; sync; isync" :: "r" (addr));
return 0;
}
#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;
}
int patch_instruction(unsigned int *addr, unsigned int instr)
{
int err;
unsigned int *dest = 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(*PTRRELOC(&text_poke_area)))
return __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;
}
dest = (unsigned int *)(text_poke_addr) +
((kaddr & ~PAGE_MASK) / sizeof(unsigned int));
/*
* We use __put_user_size so that we can handle faults while
* writing to dest and return err to handle faults gracefully
*/
__put_user_size(instr, dest, 4, err);
if (!err)
asm ("dcbst 0, %0; sync; icbi 0,%0; icbi 0,%1; sync; isync"
::"r" (dest), "r"(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 */
int patch_instruction(unsigned int *addr, unsigned int instr)
{
return __patch_instruction(addr, instr);
}
#endif /* CONFIG_STRICT_KERNEL_RWX */
NOKPROBE_SYMBOL(patch_instruction);
int patch_branch(unsigned int *addr, unsigned long target, int flags)
{
return patch_instruction(addr, create_branch(addr, target, flags));
}
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));
}
/*
* 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)
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