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References: <20200406080936.7180-1-jniethe5@gmail.com>
 <20200406080936.7180-4-jniethe5@gmail.com>
 <a0bfb808a0fe815ffbf7ad655d32ed837426943f.camel@linux.ibm.com>
In-Reply-To: <a0bfb808a0fe815ffbf7ad655d32ed837426943f.camel@linux.ibm.com>
From: Jordan Niethe <jniethe5@gmail.com>
Date: Tue, 7 Apr 2020 16:35:50 +1000
Message-ID: <CACzsE9qAUALdPkAA-0dx+L1Yhcj=3y7rw1yCTQNv0KF5MptwJw@mail.gmail.com>
Subject: Re: [PATCH v5 03/21] powerpc: Change calling convention for
 create_branch() et. al.
To: Balamuruhan S <bala24@linux.ibm.com>
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Cc: Alistair Popple <alistair@popple.id.au>,
 Nicholas Piggin <npiggin@gmail.com>, linuxppc-dev@lists.ozlabs.org,
 Daniel Axtens <dja@axtens.net>
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On Tue, Apr 7, 2020 at 4:10 PM Balamuruhan S <bala24@linux.ibm.com> wrote:
>
> On Mon, 2020-04-06 at 18:09 +1000, Jordan Niethe wrote:
> > create_branch(), create_cond_branch() and translate_branch() return the
> > instruction that they create, or return 0 to signal an error. Seperate
>
> s/seperate/separate
thanks.
>
> > these concerns in preparation for an instruction type that is not just
> > an unsigned int.  Fill the created instruction to a pointer passed as
> > the first parameter to the function and use a non-zero return value to
> > signify an error.
> >
> > Signed-off-by: Jordan Niethe <jniethe5@gmail.com>
> > ---
> > v5: New to series
> > ---
> >  arch/powerpc/include/asm/code-patching.h |  12 +-
> >  arch/powerpc/kernel/optprobes.c          |  24 ++--
> >  arch/powerpc/kernel/setup_32.c           |   2 +-
> >  arch/powerpc/kernel/trace/ftrace.c       |  24 ++--
> >  arch/powerpc/lib/code-patching.c         | 133 +++++++++++++----------
> >  arch/powerpc/lib/feature-fixups.c        |   5 +-
> >  6 files changed, 117 insertions(+), 83 deletions(-)
> >
> > diff --git a/arch/powerpc/include/asm/code-patching.h
> > b/arch/powerpc/include/asm/code-patching.h
> > index 898b54262881..351dda7215b6 100644
> > --- a/arch/powerpc/include/asm/code-patching.h
> > +++ b/arch/powerpc/include/asm/code-patching.h
> > @@ -22,10 +22,10 @@
> >  #define BRANCH_ABSOLUTE      0x2
> >
> >  bool is_offset_in_branch_range(long offset);
> > -unsigned int create_branch(const unsigned int *addr,
> > -                        unsigned long target, int flags);
> > -unsigned int create_cond_branch(const unsigned int *addr,
> > -                             unsigned long target, int flags);
> > +int create_branch(unsigned int *instr, const unsigned int *addr,
> > +               unsigned long target, int flags);
> > +int create_cond_branch(unsigned int *instr, const unsigned int *addr,
> > +                    unsigned long target, int flags);
> >  int patch_branch(unsigned int *addr, unsigned long target, int flags);
> >  int patch_instruction(unsigned int *addr, unsigned int instr);
> >  int raw_patch_instruction(unsigned int *addr, unsigned int instr);
> > @@ -60,8 +60,8 @@ int instr_is_relative_branch(unsigned int instr);
> >  int instr_is_relative_link_branch(unsigned int instr);
> >  int instr_is_branch_to_addr(const unsigned int *instr, unsigned long addr);
> >  unsigned long branch_target(const unsigned int *instr);
> > -unsigned int translate_branch(const unsigned int *dest,
> > -                           const unsigned int *src);
> > +int translate_branch(unsigned int *instr, const unsigned int *dest,
> > +                  const unsigned int *src);
> >  extern bool is_conditional_branch(unsigned int instr);
> >  #ifdef CONFIG_PPC_BOOK3E_64
> >  void __patch_exception(int exc, unsigned long addr);
> > diff --git a/arch/powerpc/kernel/optprobes.c
> > b/arch/powerpc/kernel/optprobes.c
> > index 024f7aad1952..445b3dad82dc 100644
> > --- a/arch/powerpc/kernel/optprobes.c
> > +++ b/arch/powerpc/kernel/optprobes.c
> > @@ -251,15 +251,17 @@ int arch_prepare_optimized_kprobe(struct
> > optimized_kprobe *op, struct kprobe *p)
> >               goto error;
> >       }
> >
> > -     branch_op_callback = create_branch((unsigned int *)buff +
> > TMPL_CALL_HDLR_IDX,
> > -                             (unsigned long)op_callback_addr,
> > -                             BRANCH_SET_LINK);
> > +     rc = create_branch(&branch_op_callback,
> > +                        (unsigned int *)buff + TMPL_CALL_HDLR_IDX,
> > +                        (unsigned long)op_callback_addr,
> > +                        BRANCH_SET_LINK);
> >
> > -     branch_emulate_step = create_branch((unsigned int *)buff +
> > TMPL_EMULATE_IDX,
> > -                             (unsigned long)emulate_step_addr,
> > -                             BRANCH_SET_LINK);
> > +     rc |= create_branch(&branch_emulate_step,
> > +                         (unsigned int *)buff + TMPL_EMULATE_IDX,
> > +                         (unsigned long)emulate_step_addr,
> > +                         BRANCH_SET_LINK);
> >
> > -     if (!branch_op_callback || !branch_emulate_step)
> > +     if (rc)
> >               goto error;
> >
> >       patch_instruction(buff + TMPL_CALL_HDLR_IDX, branch_op_callback);
> > @@ -305,6 +307,7 @@ int arch_check_optimized_kprobe(struct optimized_kprobe
> > *op)
> >
> >  void arch_optimize_kprobes(struct list_head *oplist)
> >  {
> > +     unsigned int instr;
> >       struct optimized_kprobe *op;
> >       struct optimized_kprobe *tmp;
> >
> > @@ -315,9 +318,10 @@ void arch_optimize_kprobes(struct list_head *oplist)
> >                */
> >               memcpy(op->optinsn.copied_insn, op->kp.addr,
> >                                              RELATIVEJUMP_SIZE);
> > -             patch_instruction(op->kp.addr,
> > -                     create_branch((unsigned int *)op->kp.addr,
> > -                                   (unsigned long)op->optinsn.insn, 0));
> > +             create_branch(&instr,
> > +                           (unsigned int *)op->kp.addr,
> > +                           (unsigned long)op->optinsn.insn, 0);
> > +             patch_instruction(op->kp.addr, instr);
> >               list_del_init(&op->list);
> >       }
> >  }
> > diff --git a/arch/powerpc/kernel/setup_32.c b/arch/powerpc/kernel/setup_32.c
> > index 5b49b26eb154..c1bdd462c5c0 100644
> > --- a/arch/powerpc/kernel/setup_32.c
> > +++ b/arch/powerpc/kernel/setup_32.c
> > @@ -88,7 +88,7 @@ notrace void __init machine_init(u64 dt_ptr)
> >
> >       patch_instruction_site(&patch__memcpy_nocache, PPC_INST_NOP);
> >
> > -     insn = create_cond_branch(addr, branch_target(addr), 0x820000);
> > +     create_cond_branch(&insn, addr, branch_target(addr), 0x820000);
> >       patch_instruction(addr, insn);  /* replace b by bne cr0 */
> >
> >       /* Do some early initialization based on the flat device tree */
> > diff --git a/arch/powerpc/kernel/trace/ftrace.c
> > b/arch/powerpc/kernel/trace/ftrace.c
> > index 7ea0ca044b65..4dcb379133f8 100644
> > --- a/arch/powerpc/kernel/trace/ftrace.c
> > +++ b/arch/powerpc/kernel/trace/ftrace.c
> > @@ -48,7 +48,7 @@ ftrace_call_replace(unsigned long ip, unsigned long addr,
> > int link)
> >       addr = ppc_function_entry((void *)addr);
> >
> >       /* if (link) set op to 'bl' else 'b' */
> > -     op = create_branch((unsigned int *)ip, addr, link ? 1 : 0);
> > +     create_branch(&op, (unsigned int *)ip, addr, link ? 1 : 0);
> >
> >       return op;
> >  }
> > @@ -89,10 +89,11 @@ ftrace_modify_code(unsigned long ip, unsigned int old,
> > unsigned int new)
> >   */
> >  static int test_24bit_addr(unsigned long ip, unsigned long addr)
> >  {
> > +     unsigned int op;
> >       addr = ppc_function_entry((void *)addr);
> >
> >       /* use the create_branch to verify that this offset can be branched */
> > -     return create_branch((unsigned int *)ip, addr, 0);
> > +     return create_branch(&op, (unsigned int *)ip, addr, 0) == 0;
> >  }
> >
> >  static int is_bl_op(unsigned int op)
> > @@ -287,6 +288,7 @@ __ftrace_make_nop(struct module *mod,
> >  static unsigned long find_ftrace_tramp(unsigned long ip)
> >  {
> >       int i;
> > +     unsigned int instr;
> >
> >       /*
> >        * We have the compiler generated long_branch tramps at the end
> > @@ -295,7 +297,8 @@ static unsigned long find_ftrace_tramp(unsigned long ip)
> >       for (i = NUM_FTRACE_TRAMPS - 1; i >= 0; i--)
> >               if (!ftrace_tramps[i])
> >                       continue;
> > -             else if (create_branch((void *)ip, ftrace_tramps[i], 0))
> > +             else if (create_branch(&instr, (void *)ip,
> > +                               ftrace_tramps[i], 0) == 0)
> >                       return ftrace_tramps[i];
> >
> >       return 0;
> > @@ -324,6 +327,7 @@ static int setup_mcount_compiler_tramp(unsigned long
> > tramp)
> >  {
> >       int i, op;
> >       unsigned long ptr;
> > +     unsigned int instr;
> >       static unsigned long ftrace_plt_tramps[NUM_FTRACE_TRAMPS];
> >
> >       /* Is this a known long jump tramp? */
> > @@ -366,7 +370,7 @@ static int setup_mcount_compiler_tramp(unsigned long
> > tramp)
> >  #else
> >       ptr = ppc_global_function_entry((void *)ftrace_caller);
> >  #endif
> > -     if (!create_branch((void *)tramp, ptr, 0)) {
> > +     if (create_branch(&instr, (void *)tramp, ptr, 0)) {
> >               pr_debug("%ps is not reachable from existing mcount tramp\n",
> >                               (void *)ptr);
> >               return -1;
> > @@ -511,6 +515,7 @@ static int
> >  __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
> >  {
> >       unsigned int op[2];
> > +     unsigned int instr;
> >       void *ip = (void *)rec->ip;
> >       unsigned long entry, ptr, tramp;
> >       struct module *mod = rec->arch.mod;
> > @@ -557,7 +562,7 @@ __ftrace_make_call(struct dyn_ftrace *rec, unsigned long
> > addr)
> >       }
> >
> >       /* Ensure branch is within 24 bits */
> > -     if (!create_branch(ip, tramp, BRANCH_SET_LINK)) {
> > +     if (create_branch(&instr, ip, tramp, BRANCH_SET_LINK)) {
> >               pr_err("Branch out of range\n");
> >               return -EINVAL;
> >       }
> > @@ -574,6 +579,7 @@ __ftrace_make_call(struct dyn_ftrace *rec, unsigned long
> > addr)
> >  static int
> >  __ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
> >  {
> > +     int err;
> >       unsigned int op;
> >       unsigned long ip = rec->ip;
> >
> > @@ -594,9 +600,9 @@ __ftrace_make_call(struct dyn_ftrace *rec, unsigned long
> > addr)
> >       }
> >
> >       /* create the branch to the trampoline */
> > -     op = create_branch((unsigned int *)ip,
> > -                        rec->arch.mod->arch.tramp, BRANCH_SET_LINK);
> > -     if (!op) {
> > +     err = create_branch(&op, (unsigned int *)ip,
> > +                         rec->arch.mod->arch.tramp, BRANCH_SET_LINK);
> > +     if (!err) {
>
>
> should this be `if (err)` as per your new changes ?
You are right.
>
>
> >               pr_err("REL24 out of range!\n");
> >               return -EINVAL;
> >       }
> > @@ -776,7 +782,7 @@ __ftrace_modify_call(struct dyn_ftrace *rec, unsigned
> > long old_addr,
> >       }
> >
> >       /* Ensure branch is within 24 bits */
> > -     if (!create_branch((unsigned int *)ip, tramp, BRANCH_SET_LINK)) {
> > +     if (create_branch(&op, (unsigned int *)ip, tramp, BRANCH_SET_LINK)) {
> >               pr_err("Branch out of range\n");
> >               return -EINVAL;
> >       }
> > diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-
> > patching.c
> > index 3345f039a876..4af564aeedf1 100644
> > --- a/arch/powerpc/lib/code-patching.c
> > +++ b/arch/powerpc/lib/code-patching.c
> > @@ -196,7 +196,10 @@ NOKPROBE_SYMBOL(patch_instruction);
> >
> >  int patch_branch(unsigned int *addr, unsigned long target, int flags)
> >  {
> > -     return patch_instruction(addr, create_branch(addr, target, flags));
> > +     unsigned int instr;
> > +
> > +     create_branch(&instr, addr, target, flags);
> > +     return patch_instruction(addr, instr);
> >  }
> >
> >  bool is_offset_in_branch_range(long offset)
> > @@ -243,30 +246,30 @@ bool is_conditional_branch(unsigned int instr)
> >  }
> >  NOKPROBE_SYMBOL(is_conditional_branch);
> >
> > -unsigned int create_branch(const unsigned int *addr,
> > -                        unsigned long target, int flags)
> > +int create_branch(unsigned int *instr,
> > +               const unsigned int *addr,
> > +               unsigned long target, int flags)
> >  {
> > -     unsigned int instruction;
> >       long offset;
> >
> > +     *instr = 0;
> >       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;
> > +             return 1;
> >
> >       /* Mask out the flags and target, so they don't step on each other. */
> > -     instruction = 0x48000000 | (flags & 0x3) | (offset & 0x03FFFFFC);
> > +     *instr = 0x48000000 | (flags & 0x3) | (offset & 0x03FFFFFC);
> >
> > -     return instruction;
> > +     return 0;
> >  }
> >
> > -unsigned int create_cond_branch(const unsigned int *addr,
> > -                             unsigned long target, int flags)
> > +int create_cond_branch(unsigned int *instr, const unsigned int *addr,
> > +                    unsigned long target, int flags)
> >  {
> > -     unsigned int instruction;
> >       long offset;
> >
> >       offset = target;
> > @@ -275,12 +278,12 @@ unsigned int create_cond_branch(const unsigned int
> > *addr,
> >
> >       /* Check we can represent the target in the instruction format */
> >       if (offset < -0x8000 || offset > 0x7FFF || offset & 0x3)
> > -             return 0;
> > +             return 1;
> >
> >       /* Mask out the flags and target, so they don't step on each other. */
> > -     instruction = 0x40000000 | (flags & 0x3FF0003) | (offset & 0xFFFC);
> > +     *instr = 0x40000000 | (flags & 0x3FF0003) | (offset & 0xFFFC);
> >
> > -     return instruction;
> > +     return 0;
> >  }
> >
> >  static unsigned int branch_opcode(unsigned int instr)
> > @@ -361,18 +364,18 @@ int instr_is_branch_to_addr(const unsigned int *instr,
> > unsigned long addr)
> >       return 0;
> >  }
> >
> > -unsigned int translate_branch(const unsigned int *dest, const unsigned int
> > *src)
> > +int translate_branch(unsigned int *instr, 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);
> > +             return create_branch(instr, dest, target, *src);
> >       else if (instr_is_branch_bform(*src))
> > -             return create_cond_branch(dest, target, *src);
> > +             return create_cond_branch(instr, dest, target, *src);
> >
> > -     return 0;
> > +     return 1;
> >  }
> >
> >  #ifdef CONFIG_PPC_BOOK3E_64
> > @@ -403,6 +406,7 @@ static void __init test_trampoline(void)
> >
> >  static void __init test_branch_iform(void)
> >  {
> > +     int err;
> >       unsigned int instr;
> >       unsigned long addr;
> >
> > @@ -443,35 +447,35 @@ static void __init test_branch_iform(void)
> >       check(instr_is_branch_to_addr(&instr, addr - 0x2000000));
> >
> >       /* Branch to self, with link */
> > -     instr = create_branch(&instr, addr, BRANCH_SET_LINK);
> > +     err = create_branch(&instr, &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);
> > +     err = create_branch(&instr, &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);
> > +     err = create_branch(&instr, &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);
> > +     err = create_branch(&instr, &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);
> > +     err = create_branch(&instr, &instr, addr - 0x2000004, BRANCH_SET_LINK);
> > +     check(err);
> >
> >       /* Out of range relative positive offset, + 32 MB */
> > -     instr = create_branch(&instr, addr + 0x2000000, BRANCH_SET_LINK);
> > -     check(instr == 0);
> > +     err = create_branch(&instr, &instr, addr + 0x2000000, BRANCH_SET_LINK);
> > +     check(err);
> >
> >       /* Unaligned target */
> > -     instr = create_branch(&instr, addr + 3, BRANCH_SET_LINK);
> > -     check(instr == 0);
> > +     err = create_branch(&instr, &instr, addr + 3, BRANCH_SET_LINK);
> > +     check(err);
> >
> >       /* Check flags are masked correctly */
> > -     instr = create_branch(&instr, addr, 0xFFFFFFFC);
> > +     err = create_branch(&instr, &instr, addr, 0xFFFFFFFC);
> >       check(instr_is_branch_to_addr(&instr, addr));
> >       check(instr == 0x48000000);
> >  }
> > @@ -480,16 +484,19 @@ static void __init test_create_function_call(void)
> >  {
> >       unsigned int *iptr;
> >       unsigned long dest;
> > +     unsigned int instr;
> >
> >       /* 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));
> > +     create_branch(&instr, iptr, dest, BRANCH_SET_LINK);
> > +     patch_instruction(iptr, instr);
>
>
> Are we sure that `create_branch()` would always succeed here to do
> patch_instruction() ?
>
>
> >       check(instr_is_branch_to_addr(iptr, dest));
> >  }
> >
> >  static void __init test_branch_bform(void)
> >  {
> > +     int err;
> >       unsigned long addr;
> >       unsigned int *iptr, instr, flags;
> >
> > @@ -525,35 +532,35 @@ static void __init test_branch_bform(void)
> >       flags = 0x3ff000 | BRANCH_SET_LINK;
> >
> >       /* Branch to self */
> > -     instr = create_cond_branch(iptr, addr, flags);
> > +     err = create_cond_branch(&instr, iptr, addr, flags);
> >       check(instr_is_branch_to_addr(&instr, addr));
> >
> >       /* Branch to self - 0x100 */
> > -     instr = create_cond_branch(iptr, addr - 0x100, flags);
> > +     err = create_cond_branch(&instr, 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);
> > +     err = create_cond_branch(&instr, 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);
> > +     err = create_cond_branch(&instr, 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);
> > +     err = create_cond_branch(&instr, iptr, addr - 0x8004, flags);
> > +     check(err);
> >
> >       /* Out of range relative positive offset, + 32 KB */
> > -     instr = create_cond_branch(iptr, addr + 0x8000, flags);
> > -     check(instr == 0);
> > +     err = create_cond_branch(&instr, iptr, addr + 0x8000, flags);
> > +     check(err);
> >
> >       /* Unaligned target */
> > -     instr = create_cond_branch(iptr, addr + 3, flags);
> > -     check(instr == 0);
> > +     err = create_cond_branch(&instr, iptr, addr + 3, flags);
> > +     check(err);
> >
> >       /* Check flags are masked correctly */
> > -     instr = create_cond_branch(iptr, addr, 0xFFFFFFFC);
> > +     err = create_cond_branch(&instr, iptr, addr, 0xFFFFFFFC);
> >       check(instr_is_branch_to_addr(&instr, addr));
> >       check(instr == 0x43FF0000);
> >  }
> > @@ -562,6 +569,7 @@ static void __init test_translate_branch(void)
> >  {
> >       unsigned long addr;
> >       unsigned int *p, *q;
> > +     unsigned int instr;
> >       void *buf;
> >
> >       buf = vmalloc(PAGE_ALIGN(0x2000000 + 1));
> > @@ -575,7 +583,8 @@ static void __init test_translate_branch(void)
> >       patch_branch(p, addr, 0);
> >       check(instr_is_branch_to_addr(p, addr));
> >       q = p + 1;
> > -     patch_instruction(q, translate_branch(q, p));
> > +     translate_branch(&instr, q, p);
> > +     patch_instruction(q, instr);
>
>
> same here and elsewhere in similar such places where we do patch_instruction()
I figured that if the existing code was not checking the return then
we probably did not need to add a check.
>
> -- Bala
>
> >       check(instr_is_branch_to_addr(q, addr));
> >
> >       /* Maximum negative case, move b . to addr + 32 MB */
> > @@ -583,7 +592,8 @@ static void __init test_translate_branch(void)
> >       addr = (unsigned long)p;
> >       patch_branch(p, addr, 0);
> >       q = buf + 0x2000000;
> > -     patch_instruction(q, translate_branch(q, p));
> > +     translate_branch(&instr, q, p);
> > +     patch_instruction(q, instr);
> >       check(instr_is_branch_to_addr(p, addr));
> >       check(instr_is_branch_to_addr(q, addr));
> >       check(*q == 0x4a000000);
> > @@ -593,7 +603,8 @@ static void __init test_translate_branch(void)
> >       addr = (unsigned long)p;
> >       patch_branch(p, addr, 0);
> >       q = buf + 4;
> > -     patch_instruction(q, translate_branch(q, p));
> > +     translate_branch(&instr, q, p);
> > +     patch_instruction(q, instr);
> >       check(instr_is_branch_to_addr(p, addr));
> >       check(instr_is_branch_to_addr(q, addr));
> >       check(*q == 0x49fffffc);
> > @@ -603,7 +614,8 @@ static void __init test_translate_branch(void)
> >       addr = 0x1000000 + (unsigned long)buf;
> >       patch_branch(p, addr, BRANCH_SET_LINK);
> >       q = buf + 0x1400000;
> > -     patch_instruction(q, translate_branch(q, p));
> > +     translate_branch(&instr, q, p);
> > +     patch_instruction(q, instr);
> >       check(instr_is_branch_to_addr(p, addr));
> >       check(instr_is_branch_to_addr(q, addr));
> >
> > @@ -612,7 +624,8 @@ static void __init test_translate_branch(void)
> >       addr = 0x2000000 + (unsigned long)buf;
> >       patch_branch(p, addr, 0);
> >       q = buf + 4;
> > -     patch_instruction(q, translate_branch(q, p));
> > +     translate_branch(&instr, q, p);
> > +     patch_instruction(q, instr);
> >       check(instr_is_branch_to_addr(p, addr));
> >       check(instr_is_branch_to_addr(q, addr));
> >
> > @@ -622,18 +635,22 @@ static void __init test_translate_branch(void)
> >       /* Simple case, branch to self moved a little */
> >       p = buf;
> >       addr = (unsigned long)p;
> > -     patch_instruction(p, create_cond_branch(p, addr, 0));
> > +     create_cond_branch(&instr, p, addr, 0);
> > +     patch_instruction(p, instr);
> >       check(instr_is_branch_to_addr(p, addr));
> >       q = p + 1;
> > -     patch_instruction(q, translate_branch(q, p));
> > +     translate_branch(&instr, q, p);
> > +     patch_instruction(q, instr);
> >       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));
> > +     create_cond_branch(&instr, p, addr, 0xFFFFFFFC);
> > +     patch_instruction(p, instr);
> >       q = buf + 0x8000;
> > -     patch_instruction(q, translate_branch(q, p));
> > +     translate_branch(&instr, q, p);
> > +     patch_instruction(q, instr);
> >       check(instr_is_branch_to_addr(p, addr));
> >       check(instr_is_branch_to_addr(q, addr));
> >       check(*q == 0x43ff8000);
> > @@ -641,9 +658,11 @@ static void __init test_translate_branch(void)
> >       /* 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));
> > +     create_cond_branch(&instr, p, addr, 0xFFFFFFFC);
> > +     patch_instruction(p, instr);
> >       q = buf + 4;
> > -     patch_instruction(q, translate_branch(q, p));
> > +     translate_branch(&instr, q, p);
> > +     patch_instruction(q, instr);
> >       check(instr_is_branch_to_addr(p, addr));
> >       check(instr_is_branch_to_addr(q, addr));
> >       check(*q == 0x43ff7ffc);
> > @@ -651,18 +670,22 @@ static void __init test_translate_branch(void)
> >       /* 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));
> > +     create_cond_branch(&instr, p, addr, BRANCH_SET_LINK);
> > +     patch_instruction(p, instr);
> >       q = buf + 0x5000;
> > -     patch_instruction(q, translate_branch(q, p));
> > +     translate_branch(&instr, q, p);
> > +     patch_instruction(q, instr);
> >       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));
> > +     create_cond_branch(&instr, p, addr, 0);
> > +     patch_instruction(p, instr);
> >       q = buf + 4;
> > -     patch_instruction(q, translate_branch(q, p));
> > +     translate_branch(&instr, q, p);
> > +     patch_instruction(q, instr);
> >       check(instr_is_branch_to_addr(p, addr));
> >       check(instr_is_branch_to_addr(q, addr));
> >
> > diff --git a/arch/powerpc/lib/feature-fixups.c b/arch/powerpc/lib/feature-
> > fixups.c
> > index 4ba634b89ce5..b129d7b4e7dd 100644
> > --- a/arch/powerpc/lib/feature-fixups.c
> > +++ b/arch/powerpc/lib/feature-fixups.c
> > @@ -44,6 +44,7 @@ static unsigned int *calc_addr(struct fixup_entry *fcur,
> > long offset)
> >  static int patch_alt_instruction(unsigned int *src, unsigned int *dest,
> >                                unsigned int *alt_start, unsigned int
> > *alt_end)
> >  {
> > +     int err;
> >       unsigned int instr;
> >
> >       instr = *src;
> > @@ -53,8 +54,8 @@ static int patch_alt_instruction(unsigned int *src,
> > unsigned int *dest,
> >
> >               /* Branch within the section doesn't need translating */
> >               if (target < alt_start || target > alt_end) {
> > -                     instr = translate_branch(dest, src);
> > -                     if (!instr)
> > +                     err = translate_branch(&instr, dest, src);
> > +                     if (err)
> >                               return 1;
> >               }
> >       }
>