Merge tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-tracegrafted

Pull tracing fixes from Steven Rostedt:

 - Fix error output of boot instance creation failure

   Currently if a boot instance creation fails, instead of printing out
   the name of the instance that failed, it prints "(null)". That is
   because it prints "cur_str" that had already been processed by
   strsep(). Print the saved name instead.

   While at it, print the error code of the failure.

 - Fix use-after-free for same named historgrams

   Histograms can be named so that they can be used in multiple events.
   But if the named histogram has a variable attached, the second event
   that uses the named histogram which duplicates it and needs to free
   the original after duplication leaves the old variable in place and
   still visible. If another histogram uses than variable, it will use
   the stale one which will try to reference the freed duplicate
   histogram and crash the kernel.

   Free the duplicate variables along with the duplicated histogram
   data.

 - Check return value of kthread_run() in event self test

   The events self tests uses a kthread for testing but does not check
   if it succeeded in creating a kthread. If the kthread creation were
   to fail, the code will still try to call kthread_stop() on the error
   returned.

 - Fix race between reading trace_pipe and updating subbuffer size

   If a user is reading the trace_pipe file at the same time they update
   the ring buffer sub-buffer size, can cause the trace_pipe read to
   read stale data. Add trace_access_lock() around updating the ring
   buffer sub-buffer size.

 - Fix eventfs_inode on failure path in creation of the events directory

   In the creation of the "events" directory, if after allocating the
   eventfs_inode a failure is detected, it calls cleanup_ei() which
   calls free_ei(). The free_ei() will test if eventfs_inode being freed
   has no children. It is a bug if it does. But on the failure case of
   the creation of the "events" directory, the children lists have not
   yet been initialized and the free will trigger a warning because
   list_empty() on an uninitialized list returns false.

   Move the initialization into init_ei() where it makes more sense and
   makes sure that a created eventfs_inode has its lists initialized
   upon creation.

 - Check return value of kthread_run() in ftrace direct sample code

   The sample code that shows how to use the ftrace direct calls does
   not test the return of kthread_run() to see if it succeeds. Return a
   failure if the kthread_run() doesn't succeed.

 - Clear user events state on fork in case of alloc failure

   On fork, the child gets a pointer to the parent's user events state.
   It makes a copy of it then updates the child's pointer to it. But if
   the allocation fails, the duplication function leaves the child with
   a pointer to its parent's descriptor. When the child cleans up its
   data, it will free the parent's descriptor while the parent is still
   using it.

   In the duplication function, set the child's user_event_mm to NULL
   before testing if the allocation succeeded, and when it exits it will
   not free the parent's descriptor.

 - Fix retry exhaustion in simple ring buffer reader swap

   simple_ring_buffer_swap_reader_page() starts with retry set to 8 and
   post-decrements it only after a failed link replacement. On the final
   attempt, a successful replacement leaves retry at zero, while a
   failed replacement leaves it at -1.

   But the check for success expects the retry value to be non-zero and
   exits with an error on zero. This is the opposite result. Fix it.

 - Fail nicely when the remote swap_reader_page() returns an error

   Currently, if the swap_reader_page() of a remote buffer fails, it
   triggers a WARN_ON_ONCE() and continues normally. Instead, have it
   exit with an error and a pr_warn() print instead of a full WARNING.

* tag 'trace-v7.3-2' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  ring-buffer: Stop remote reader update when page swap fails
  tracing: Fix retry exhaustion in simple ring buffer reader swap
  tracing/user_events: Clear copied tracing state before fork duplication
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-multi-modify
  samples/ftrace: Fix kthread_stop() on ERR_PTR in ftrace-direct-modify
  eventfs: Initialize ei->children and ei->list in init_ei()
  tracing: Fix use-after-free in trace_pipe read on sub-buffer order change
  tracing: Fix crash passing ERR_PTR to kthread_stop()
  tracing: Fix use-after-free with same-name named triggers
  tracing: Fix logged instance name on creation failure

1 files changed, 649 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..44ff9f684
--- /dev/null
+++ b/arch/powerpc/lib/code-patching.c
@@ -0,0 +1,649 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  Copyright 2008 Michael Ellerman, IBM Corporation.
+ */
+
+#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/text-patching.h>
+#include <asm/inst.h>
+
+static int __patch_mem(void *exec_addr, unsigned long val, void *patch_addr, bool is_dword)
+{
+	if (!IS_ENABLED(CONFIG_PPC64) || likely(!is_dword)) {
+		/* For big endian correctness: plain address would use the wrong half */
+		u32 val32 = val;
+
+		__put_kernel_nofault(patch_addr, &val32, u32, failed);
+	} else {
+		__put_kernel_nofault(patch_addr, &val, u64, failed);
+	}
+
+	asm ("dcbst 0, %0; sync; icbi 0,%1; sync; isync" :: "r" (patch_addr),
+							    "r" (exec_addr));
+
+	return 0;
+
+failed:
+	mb();  /* sync */
+	return -EPERM;
+}
+
+int raw_patch_instruction(u32 *addr, ppc_inst_t instr)
+{
+	if (ppc_inst_prefixed(instr))
+		return __patch_mem(addr, ppc_inst_as_ulong(instr), addr, true);
+	else
+		return __patch_mem(addr, ppc_inst_val(instr), addr, false);
+}
+
+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 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;
+	unsigned long addr;
+	int err;
+
+	area = get_vm_area(PAGE_SIZE, 0);
+	if (!area) {
+		WARN_ONCE(1, "Failed to create text area for cpu %d\n",
+			cpu);
+		return -1;
+	}
+
+	// Map/unmap the area to ensure all page tables are pre-allocated
+	addr = (unsigned long)area->addr;
+	err = map_kernel_page(addr, __pa_symbol(empty_zero_page), PAGE_KERNEL_RO);
+	if (err)
+		return err;
+
+	unmap_kernel_page(addr);
+
+	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(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);
+
+void __init poking_init(void)
+{
+	int ret;
+
+	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);
+}
+
+static unsigned long get_patch_pfn(void *addr)
+{
+	if (IS_ENABLED(CONFIG_EXECMEM) && is_vmalloc_or_module_addr(addr))
+		return vmalloc_to_pfn(addr);
+	else
+		return __pa_symbol(addr) >> PAGE_SHIFT;
+}
+
+static int __do_patch_mem_mm(void *addr, unsigned long val, bool is_dword)
+{
+	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_mem(addr, val, patch_addr, is_dword);
+
+	/* 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_mem(void *addr, unsigned long val, bool is_dword)
+{
+	int err;
+	u32 *patch_addr;
+	unsigned long text_poke_addr;
+	pte_t *pte;
+	unsigned long pfn = get_patch_pfn(addr);
+
+	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 = __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())
+		asm volatile("ptesync": : :"memory");
+
+	err = __patch_mem(addr, val, patch_addr, is_dword);
+
+	pte_clear(&init_mm, text_poke_addr, pte);
+	flush_tlb_kernel_range(text_poke_addr, text_poke_addr + PAGE_SIZE);
+
+	return err;
+}
+
+static int patch_mem(void *addr, unsigned long val, bool is_dword)
+{
+	int err;
+	unsigned long flags;
+
+	/*
+	 * 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 (!IS_ENABLED(CONFIG_STRICT_KERNEL_RWX) ||
+	    !static_branch_likely(&poking_init_done))
+		return __patch_mem(addr, val, addr, is_dword);
+
+	local_irq_save(flags);
+	if (mm_patch_enabled())
+		err = __do_patch_mem_mm(addr, val, is_dword);
+	else
+		err = __do_patch_mem(addr, val, is_dword);
+	local_irq_restore(flags);
+
+	return err;
+}
+
+#ifdef CONFIG_PPC64
+
+int patch_instruction(u32 *addr, ppc_inst_t instr)
+{
+	if (ppc_inst_prefixed(instr))
+		return patch_mem(addr, ppc_inst_as_ulong(instr), true);
+	else
+		return patch_mem(addr, ppc_inst_val(instr), false);
+}
+NOKPROBE_SYMBOL(patch_instruction);
+
+int patch_uint(void *addr, unsigned int val)
+{
+	if (!IS_ALIGNED((unsigned long)addr, sizeof(unsigned int)))
+		return -EINVAL;
+
+	return patch_mem(addr, val, false);
+}
+NOKPROBE_SYMBOL(patch_uint);
+
+int patch_ulong(void *addr, unsigned long val)
+{
+	if (!IS_ALIGNED((unsigned long)addr, sizeof(unsigned long)))
+		return -EINVAL;
+
+	return patch_mem(addr, val, true);
+}
+NOKPROBE_SYMBOL(patch_ulong);
+
+#else
+
+int patch_instruction(u32 *addr, ppc_inst_t instr)
+{
+	return patch_mem(addr, ppc_inst_val(instr), false);
+}
+NOKPROBE_SYMBOL(patch_instruction)
+
+#endif
+
+static int patch_memset64(u64 *addr, u64 val, size_t count)
+{
+	for (u64 *end = addr + count; addr < end; addr++)
+		__put_kernel_nofault(addr, &val, u64, failed);
+
+	return 0;
+
+failed:
+	return -EPERM;
+}
+
+static int patch_memset32(u32 *addr, u32 val, size_t count)
+{
+	for (u32 *end = addr + count; addr < end; addr++)
+		__put_kernel_nofault(addr, &val, u32, failed);
+
+	return 0;
+
+failed:
+	return -EPERM;
+}
+
+static int __patch_instructions(u32 *patch_addr, u32 *code, size_t len, bool repeat_instr)
+{
+	unsigned long start = (unsigned long)patch_addr;
+	int err;
+
+	/* Repeat instruction */
+	if (repeat_instr) {
+		ppc_inst_t instr = ppc_inst_read(code);
+
+		if (ppc_inst_prefixed(instr)) {
+			u64 val = ppc_inst_as_ulong(instr);
+
+			err = patch_memset64((u64 *)patch_addr, val, len / 8);
+		} else {
+			u32 val = ppc_inst_val(instr);
+
+			err = patch_memset32(patch_addr, val, len / 4);
+		}
+	} else {
+		err = copy_to_kernel_nofault(patch_addr, code, len);
+	}
+
+	smp_wmb();	/* smp write barrier */
+	flush_icache_range(start, start + len);
+	return err;
+}
+
+/*
+ * A page is mapped and instructions that fit the page are patched.
+ * Assumes 'len' to be (PAGE_SIZE - offset_in_page(addr)) or below.
+ */
+static int __do_patch_instructions_mm(u32 *addr, u32 *code, size_t len, bool repeat_instr)
+{
+	struct mm_struct *patching_mm, *orig_mm;
+	unsigned long pfn = get_patch_pfn(addr);
+	unsigned long text_poke_addr;
+	spinlock_t *ptl;
+	u32 *patch_addr;
+	pte_t *pte;
+	int err;
+
+	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);
+
+	kasan_disable_current();
+	err = __patch_instructions(patch_addr, code, len, repeat_instr);
+	kasan_enable_current();
+
+	/* context synchronisation performed by __patch_instructions */
+	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;
+}
+
+/*
+ * A page is mapped and instructions that fit the page are patched.
+ * Assumes 'len' to be (PAGE_SIZE - offset_in_page(addr)) or below.
+ */
+static int __do_patch_instructions(u32 *addr, u32 *code, size_t len, bool repeat_instr)
+{
+	unsigned long pfn = get_patch_pfn(addr);
+	unsigned long text_poke_addr;
+	u32 *patch_addr;
+	pte_t *pte;
+	int err;
+
+	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 = __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())
+		asm volatile("ptesync" ::: "memory");
+
+	err = __patch_instructions(patch_addr, code, len, repeat_instr);
+
+	pte_clear(&init_mm, text_poke_addr, pte);
+	flush_tlb_kernel_range(text_poke_addr, text_poke_addr + PAGE_SIZE);
+
+	return err;
+}
+
+/*
+ * Patch 'addr' with 'len' bytes of instructions from 'code'.
+ *
+ * If repeat_instr is true, the same instruction is filled for
+ * 'len' bytes.
+ */
+int patch_instructions(u32 *addr, u32 *code, size_t len, bool repeat_instr)
+{
+	while (len > 0) {
+		unsigned long flags;
+		size_t plen;
+		int err;
+
+		plen = min_t(size_t, PAGE_SIZE - offset_in_page(addr), len);
+
+		local_irq_save(flags);
+		if (mm_patch_enabled())
+			err = __do_patch_instructions_mm(addr, code, plen, repeat_instr);
+		else
+			err = __do_patch_instructions(addr, code, plen, repeat_instr);
+		local_irq_restore(flags);
+		if (err)
+			return err;
+
+		len -= plen;
+		addr = (u32 *)((unsigned long)addr + plen);
+		if (!repeat_instr)
+			code = (u32 *)((unsigned long)code + plen);
+	}
+
+	return 0;
+}
+NOKPROBE_SYMBOL(patch_instructions);
+
+int patch_branch(u32 *addr, unsigned long target, int flags)
+{
+	ppc_inst_t instr;
+
+	if (create_branch(&instr, addr, target, flags))
+		return -ERANGE;
+
+	return patch_instruction(addr, instr);
+}
+
+/*
+ * Helper to check if a given instruction is a conditional branch
+ * Derived from the conditional checks in analyse_instr()
+ */
+bool is_conditional_branch(ppc_inst_t instr)
+{
+	unsigned int opcode = ppc_inst_primary_opcode(instr);
+
+	if (opcode == 16)       /* bc, bca, bcl, bcla */
+		return true;
+	if (opcode == 19) {
+		switch ((ppc_inst_val(instr) >> 1) & 0x3ff) {
+		case 16:        /* bclr, bclrl */
+		case 528:       /* bcctr, bcctrl */
+		case 560:       /* bctar, bctarl */
+			return true;
+		}
+	}
+	return false;
+}
+NOKPROBE_SYMBOL(is_conditional_branch);
+
+int create_cond_branch(ppc_inst_t *instr, const u32 *addr,
+		       unsigned long target, int flags)
+{
+	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 1;
+
+	/* Mask out the flags and target, so they don't step on each other. */
+	*instr = ppc_inst(0x40000000 | (flags & 0x3FF0003) | (offset & 0xFFFC));
+
+	return 0;
+}
+
+int instr_is_relative_branch(ppc_inst_t instr)
+{
+	if (ppc_inst_val(instr) & BRANCH_ABSOLUTE)
+		return 0;
+
+	return instr_is_branch_iform(instr) || instr_is_branch_bform(instr);
+}
+
+int instr_is_relative_link_branch(ppc_inst_t instr)
+{
+	return instr_is_relative_branch(instr) && (ppc_inst_val(instr) & BRANCH_SET_LINK);
+}
+
+static unsigned long branch_iform_target(const u32 *instr)
+{
+	signed long imm;
+
+	imm = ppc_inst_val(ppc_inst_read(instr)) & 0x3FFFFFC;
+
+	/* If the top bit of the immediate value is set this is negative */
+	if (imm & 0x2000000)
+		imm -= 0x4000000;
+
+	if ((ppc_inst_val(ppc_inst_read(instr)) & BRANCH_ABSOLUTE) == 0)
+		imm += (unsigned long)instr;
+
+	return (unsigned long)imm;
+}
+
+static unsigned long branch_bform_target(const u32 *instr)
+{
+	signed long imm;
+
+	imm = ppc_inst_val(ppc_inst_read(instr)) & 0xFFFC;
+
+	/* If the top bit of the immediate value is set this is negative */
+	if (imm & 0x8000)
+		imm -= 0x10000;
+
+	if ((ppc_inst_val(ppc_inst_read(instr)) & BRANCH_ABSOLUTE) == 0)
+		imm += (unsigned long)instr;
+
+	return (unsigned long)imm;
+}
+
+unsigned long branch_target(const u32 *instr)
+{
+	if (instr_is_branch_iform(ppc_inst_read(instr)))
+		return branch_iform_target(instr);
+	else if (instr_is_branch_bform(ppc_inst_read(instr)))
+		return branch_bform_target(instr);
+
+	return 0;
+}
+
+int translate_branch(ppc_inst_t *instr, const u32 *dest, const u32 *src)
+{
+	unsigned long target;
+	target = branch_target(src);
+
+	if (instr_is_branch_iform(ppc_inst_read(src)))
+		return create_branch(instr, dest, target,
+				     ppc_inst_val(ppc_inst_read(src)));
+	else if (instr_is_branch_bform(ppc_inst_read(src)))
+		return create_cond_branch(instr, dest, target,
+					  ppc_inst_val(ppc_inst_read(src)));
+
+	return 1;
+}