1 files changed, 167 insertions, 4 deletions

diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c
index 500b0f6..c9de03e 100644
--- a/arch/powerpc/lib/code-patching.c
+++ b/arch/powerpc/lib/code-patching.c
@@ -12,23 +12,186 @@
 #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));
+
+	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));