Subject: Re: [PATCH v8 12/30] powerpc: Use a function for reading instructions

From: Michael Ellerman <[email-masked]>
Date: Tue, 19 May 2020 14:05:25 +1000

Jordan Niethe <[email-masked]> writes:
> On Sun, May 17, 2020 at 4:39 AM Christophe Leroy
> <[email-masked]> wrote:
>>
>> Le 06/05/2020 à 05:40, Jordan Niethe a écrit :
>> > Prefixed instructions will mean there are instructions of different
>> > length. As a result dereferencing a pointer to an instruction will not
>> > necessarily give the desired result. Introduce a function for reading
>> > instructions from memory into the instruction data type.
>>
>>
>> Shouldn't this function be used in mmu_patch_addis() in mm/nohash/8xx.c ?
>>
>> Christophe

> Yes, that would be a good idea.

> mpe here is a fix, along with one I'll
> post for [PATCH v8 11/30] powerpc: Use a datatype for instructions.

I didn't fold this in because I'd prefer one of you send me a patch on
top of the series that converts that code to use the new type.

That way it can be tested separately from this big series.

cheers

> diff --git a/arch/powerpc/mm/nohash/8xx.c b/arch/powerpc/mm/nohash/8xx.c
> --- a/arch/powerpc/mm/nohash/8xx.c
> +++ b/arch/powerpc/mm/nohash/8xx.c
> @@ -98,7 +98,7 @@ static void mmu_patch_cmp_limit(s32 *site, unsigned
> long mapped)
>
>  static void mmu_patch_addis(s32 *site, long simm)
>  {
> -    struct ppc_inst instr = *(struct ppc_inst *)patch_site_addr(site);
> +    struct ppc_inst instr = ppc_inst_read((struct ppc_inst
> *)patch_site_addr(site));
>      unsigned int val = ppc_inst_val(instr);
>
>      val &= 0xffff0000;
> -- 
>>
>> >
>> > Reviewed-by: Alistair Popple <[email-masked]>
>> > Signed-off-by: Jordan Niethe <[email-masked]>
>> > ---
>> > v4: New to series
>> > v5: - Rename read_inst() -> probe_kernel_read_inst()
>> >      - No longer modify uprobe probe type in this patch
>> > v6: - feature-fixups.c: do_final_fixups(): Use here
>> >      - arch_prepare_kprobe(): patch_instruction(): no longer part of this
>> >        patch
>> >      - Move probe_kernel_read_inst() out of this patch
>> >      - Use in uprobes
>> > v8: style
>> > ---
>> >   arch/powerpc/include/asm/inst.h    |  5 +++++
>> >   arch/powerpc/kernel/kprobes.c      |  6 +++---
>> >   arch/powerpc/kernel/mce_power.c    |  2 +-
>> >   arch/powerpc/kernel/optprobes.c    |  4 ++--
>> >   arch/powerpc/kernel/trace/ftrace.c |  4 ++--
>> >   arch/powerpc/kernel/uprobes.c      |  2 +-
>> >   arch/powerpc/lib/code-patching.c   | 26 ++++++++++++++------------
>> >   arch/powerpc/lib/feature-fixups.c  |  4 ++--
>> >   arch/powerpc/xmon/xmon.c           |  6 +++---
>> >   9 files changed, 33 insertions(+), 26 deletions(-)
>> >
>> > diff --git a/arch/powerpc/include/asm/inst.h b/arch/powerpc/include/asm/inst.h
>> > index 19d8bb7a1c2b..552e953bf04f 100644
>> > --- a/arch/powerpc/include/asm/inst.h
>> > +++ b/arch/powerpc/include/asm/inst.h
>> > @@ -27,6 +27,11 @@ static inline struct ppc_inst ppc_inst_swab(struct ppc_inst x)
>> >       return ppc_inst(swab32(ppc_inst_val(x)));
>> >   }
>> >
>> > +static inline struct ppc_inst ppc_inst_read(const struct ppc_inst *ptr)
>> > +{
>> > +     return *ptr;
>> > +}
>> > +
>> >   static inline bool ppc_inst_equal(struct ppc_inst x, struct ppc_inst y)
>> >   {
>> >       return ppc_inst_val(x) == ppc_inst_val(y);
>> > diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
>> > index a08ae5803622..f64312dca84f 100644
>> > --- a/arch/powerpc/kernel/kprobes.c
>> > +++ b/arch/powerpc/kernel/kprobes.c
>> > @@ -106,7 +106,7 @@ kprobe_opcode_t *kprobe_lookup_name(const char *name, unsigned int offset)
>> >   int arch_prepare_kprobe(struct kprobe *p)
>> >   {
>> >       int ret = 0;
>> > -     struct ppc_inst insn = *(struct ppc_inst *)p->addr;
>> > +     struct ppc_inst insn = ppc_inst_read((struct ppc_inst *)p->addr);
>> >
>> >       if ((unsigned long)p->addr & 0x03) {
>> >               printk("Attempt to register kprobe at an unaligned address\n");
>> > @@ -127,7 +127,7 @@ int arch_prepare_kprobe(struct kprobe *p)
>> >       if (!ret) {
>> >               memcpy(p->ainsn.insn, p->addr,
>> >                               MAX_INSN_SIZE * sizeof(kprobe_opcode_t));
>> > -             p->opcode = *p->addr;
>> > +             p->opcode = ppc_inst_val(insn);
>> >               flush_icache_range((unsigned long)p->ainsn.insn,
>> >                       (unsigned long)p->ainsn.insn + sizeof(kprobe_opcode_t));
>> >       }
>> > @@ -217,7 +217,7 @@ NOKPROBE_SYMBOL(arch_prepare_kretprobe);
>> >   static int try_to_emulate(struct kprobe *p, struct pt_regs *regs)
>> >   {
>> >       int ret;
>> > -     struct ppc_inst insn = *(struct ppc_inst *)p->ainsn.insn;
>> > +     struct ppc_inst insn = ppc_inst_read((struct ppc_inst *)p->ainsn.insn);
>> >
>> >       /* regs->nip is also adjusted if emulate_step returns 1 */
>> >       ret = emulate_step(regs, insn);
>> > diff --git a/arch/powerpc/kernel/mce_power.c b/arch/powerpc/kernel/mce_power.c
>> > index cd23218c60bb..45c51ba0071b 100644
>> > --- a/arch/powerpc/kernel/mce_power.c
>> > +++ b/arch/powerpc/kernel/mce_power.c
>> > @@ -374,7 +374,7 @@ static int mce_find_instr_ea_and_phys(struct pt_regs *regs, uint64_t *addr,
>> >       pfn = addr_to_pfn(regs, regs->nip);
>> >       if (pfn != ULONG_MAX) {
>> >               instr_addr = (pfn << PAGE_SHIFT) + (regs->nip & ~PAGE_MASK);
>> > -             instr = *(struct ppc_inst *)(instr_addr);
>> > +             instr = ppc_inst_read((struct ppc_inst *)instr_addr);
>> >               if (!analyse_instr(&op, &tmp, instr)) {
>> >                       pfn = addr_to_pfn(regs, op.ea);
>> >                       *addr = op.ea;
>> > diff --git a/arch/powerpc/kernel/optprobes.c b/arch/powerpc/kernel/optprobes.c
>> > index 5a71fef71c22..52c1ab3f85aa 100644
>> > --- a/arch/powerpc/kernel/optprobes.c
>> > +++ b/arch/powerpc/kernel/optprobes.c
>> > @@ -100,9 +100,9 @@ static unsigned long can_optimize(struct kprobe *p)
>> >        * Ensure that the instruction is not a conditional branch,
>> >        * and that can be emulated.
>> >        */
>> > -     if (!is_conditional_branch(*(struct ppc_inst *)p->ainsn.insn) &&
>> > +     if (!is_conditional_branch(ppc_inst_read((struct ppc_inst *)p->ainsn.insn)) &&
>> >           analyse_instr(&op, &regs,
>> > -                       *(struct ppc_inst *)p->ainsn.insn) == 1) {
>> > +                       ppc_inst_read((struct ppc_inst *)p->ainsn.insn)) == 1) {
>> >               emulate_update_regs(&regs, &op);
>> >               nip = regs.nip;
>> >       }
>> > diff --git a/arch/powerpc/kernel/trace/ftrace.c b/arch/powerpc/kernel/trace/ftrace.c
>> > index 3117ed675735..acd5b889815f 100644
>> > --- a/arch/powerpc/kernel/trace/ftrace.c
>> > +++ b/arch/powerpc/kernel/trace/ftrace.c
>> > @@ -848,7 +848,7 @@ int ftrace_update_ftrace_func(ftrace_func_t func)
>> >       struct ppc_inst old, new;
>> >       int ret;
>> >
>> > -     old = *(struct ppc_inst *)&ftrace_call;
>> > +     old = ppc_inst_read((struct ppc_inst *)&ftrace_call);
>> >       new = ftrace_call_replace(ip, (unsigned long)func, 1);
>> >       ret = ftrace_modify_code(ip, old, new);
>> >
>> > @@ -856,7 +856,7 @@ int ftrace_update_ftrace_func(ftrace_func_t func)
>> >       /* Also update the regs callback function */
>> >       if (!ret) {
>> >               ip = (unsigned long)(&ftrace_regs_call);
>> > -             old = *(struct ppc_inst *)&ftrace_regs_call;
>> > +             old = ppc_inst_read((struct ppc_inst *)&ftrace_regs_call);
>> >               new = ftrace_call_replace(ip, (unsigned long)func, 1);
>> >               ret = ftrace_modify_code(ip, old, new);
>> >       }
>> > diff --git a/arch/powerpc/kernel/uprobes.c b/arch/powerpc/kernel/uprobes.c
>> > index 31c870287f2b..6893d40a48c5 100644
>> > --- a/arch/powerpc/kernel/uprobes.c
>> > +++ b/arch/powerpc/kernel/uprobes.c
>> > @@ -174,7 +174,7 @@ bool arch_uprobe_skip_sstep(struct arch_uprobe *auprobe, struct pt_regs *regs)
>> >        * emulate_step() returns 1 if the insn was successfully emulated.
>> >        * For all other cases, we need to single-step in hardware.
>> >        */
>> > -     ret = emulate_step(regs, auprobe->insn);
>> > +     ret = emulate_step(regs, ppc_inst_read(&auprobe->insn));
>> >       if (ret > 0)
>> >               return true;
>> >
>> > diff --git a/arch/powerpc/lib/code-patching.c b/arch/powerpc/lib/code-patching.c
>> > index 1dff9d9d6645..435fc8e9f45d 100644
>> > --- a/arch/powerpc/lib/code-patching.c
>> > +++ b/arch/powerpc/lib/code-patching.c
>> > @@ -348,9 +348,9 @@ static unsigned long branch_bform_target(const struct ppc_inst *instr)
>> >
>> >   unsigned long branch_target(const struct ppc_inst *instr)
>> >   {
>> > -     if (instr_is_branch_iform(*instr))
>> > +     if (instr_is_branch_iform(ppc_inst_read(instr)))
>> >               return branch_iform_target(instr);
>> > -     else if (instr_is_branch_bform(*instr))
>> > +     else if (instr_is_branch_bform(ppc_inst_read(instr)))
>> >               return branch_bform_target(instr);
>> >
>> >       return 0;
>> > @@ -358,7 +358,8 @@ unsigned long branch_target(const struct ppc_inst *instr)
>> >
>> >   int instr_is_branch_to_addr(const struct ppc_inst *instr, unsigned long addr)
>> >   {
>> > -     if (instr_is_branch_iform(*instr) || instr_is_branch_bform(*instr))
>> > +     if (instr_is_branch_iform(ppc_inst_read(instr)) ||
>> > +         instr_is_branch_bform(ppc_inst_read(instr)))
>> >               return branch_target(instr) == addr;
>> >
>> >       return 0;
>> > @@ -368,13 +369,14 @@ int translate_branch(struct ppc_inst *instr, const struct ppc_inst *dest,
>> >                    const struct ppc_inst *src)
>> >   {
>> >       unsigned long target;
>> > -
>> >       target = branch_target(src);
>> >
>> > -     if (instr_is_branch_iform(*src))
>> > -             return create_branch(instr, dest, target, ppc_inst_val(*src));
>> > -     else if (instr_is_branch_bform(*src))
>> > -             return create_cond_branch(instr, dest, target, ppc_inst_val(*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;
>> >   }
>> > @@ -598,7 +600,7 @@ static void __init test_translate_branch(void)
>> >       patch_instruction(q, instr);
>> >       check(instr_is_branch_to_addr(p, addr));
>> >       check(instr_is_branch_to_addr(q, addr));
>> > -     check(ppc_inst_equal(*q, ppc_inst(0x4a000000)));
>> > +     check(ppc_inst_equal(ppc_inst_read(q), ppc_inst(0x4a000000)));
>> >
>> >       /* Maximum positive case, move x to x - 32 MB + 4 */
>> >       p = buf + 0x2000000;
>> > @@ -609,7 +611,7 @@ static void __init test_translate_branch(void)
>> >       patch_instruction(q, instr);
>> >       check(instr_is_branch_to_addr(p, addr));
>> >       check(instr_is_branch_to_addr(q, addr));
>> > -     check(ppc_inst_equal(*q, ppc_inst(0x49fffffc)));
>> > +     check(ppc_inst_equal(ppc_inst_read(q), ppc_inst(0x49fffffc)));
>> >
>> >       /* Jump to x + 16 MB moved to x + 20 MB */
>> >       p = buf;
>> > @@ -655,7 +657,7 @@ static void __init test_translate_branch(void)
>> >       patch_instruction(q, instr);
>> >       check(instr_is_branch_to_addr(p, addr));
>> >       check(instr_is_branch_to_addr(q, addr));
>> > -     check(ppc_inst_equal(*q, ppc_inst(0x43ff8000)));
>> > +     check(ppc_inst_equal(ppc_inst_read(q), ppc_inst(0x43ff8000)));
>> >
>> >       /* Maximum positive case, move x to x - 32 KB + 4 */
>> >       p = buf + 0x8000;
>> > @@ -667,7 +669,7 @@ static void __init test_translate_branch(void)
>> >       patch_instruction(q, instr);
>> >       check(instr_is_branch_to_addr(p, addr));
>> >       check(instr_is_branch_to_addr(q, addr));
>> > -     check(ppc_inst_equal(*q, ppc_inst(0x43ff7ffc)));
>> > +     check(ppc_inst_equal(ppc_inst_read(q), ppc_inst(0x43ff7ffc)));
>> >
>> >       /* Jump to x + 12 KB moved to x + 20 KB */
>> >       p = buf;
>> > diff --git a/arch/powerpc/lib/feature-fixups.c b/arch/powerpc/lib/feature-fixups.c
>> > index fb6e8e8abf4e..c0d3ed4efb7e 100644
>> > --- a/arch/powerpc/lib/feature-fixups.c
>> > +++ b/arch/powerpc/lib/feature-fixups.c
>> > @@ -48,7 +48,7 @@ static int patch_alt_instruction(struct ppc_inst *src, struct ppc_inst *dest,
>> >       int err;
>> >       struct ppc_inst instr;
>> >
>> > -     instr = *src;
>> > +     instr = ppc_inst_read(src);
>> >
>> >       if (instr_is_relative_branch(*src)) {
>> >               struct ppc_inst *target = (struct ppc_inst *)branch_target(src);
>> > @@ -403,7 +403,7 @@ static void do_final_fixups(void)
>> >       length = (__end_interrupts - _stext) / sizeof(struct ppc_inst);
>> >
>> >       while (length--) {
>> > -             raw_patch_instruction(dest, *src);
>> > +             raw_patch_instruction(dest, ppc_inst_read(src));
>> >               src++;
>> >               dest++;
>> >       }
>> > diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c
>> > index e0132d6d24d0..68e0b05d9226 100644
>> > --- a/arch/powerpc/xmon/xmon.c
>> > +++ b/arch/powerpc/xmon/xmon.c
>> > @@ -702,13 +702,13 @@ static int xmon_core(struct pt_regs *regs, int fromipi)
>> >       if ((regs->msr & (MSR_IR|MSR_PR|MSR_64BIT)) == (MSR_IR|MSR_64BIT)) {
>> >               bp = at_breakpoint(regs->nip);
>> >               if (bp != NULL) {
>> > -                     int stepped = emulate_step(regs, bp->instr[0]);
>> > +                     int stepped = emulate_step(regs, ppc_inst_read(bp->instr));
>> >                       if (stepped == 0) {
>> >                               regs->nip = (unsigned long) &bp->instr[0];
>> >                               atomic_inc(&bp->ref_count);
>> >                       } else if (stepped < 0) {
>> >                               printf("Couldn't single-step %s instruction\n",
>> > -                                 (IS_RFID(bp->instr[0])? "rfid": "mtmsrd"));
>> > +                                 IS_RFID(ppc_inst_read(bp->instr))? "rfid": "mtmsrd");
>> >                       }
>> >               }
>> >       }
>> > @@ -949,7 +949,7 @@ static void remove_bpts(void)
>> >               if (mread(bp->address, &instr, 4) == 4
>> >                   && ppc_inst_equal(instr, ppc_inst(bpinstr))
>> >                   && patch_instruction(
>> > -                     (struct ppc_inst *)bp->address, bp->instr[0]) != 0)
>> > +                     (struct ppc_inst *)bp->address, ppc_inst_read(bp->instr)) != 0)
>> >                       printf("Couldn't remove breakpoint at %lx\n",
>> >                              bp->address);
>> >       }
>> >