powerpc/lib/code-patching: Use alternate map for patch_instruction()

#include <linux/vmalloc.h>

#include <linux/init.h>

#include <linux/mm.h>

#include <asm/page.h>

#include <asm/code-patching.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>

int patch_instruction(unsigned int *addr, unsigned int instr)

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

	 * We use slab_is_available and per cpu read * via this_cpu_read

	 * of text_poke_area. Per-CPU areas might not be up early

	 * this can create problems with just using this_cpu_read()

	 */

	if (!slab_is_available() || !this_cpu_read(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));