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

[Jordan Niethe <jniethe5@gmail.com>]

On Sun, May 17, 2020 at 4:39 AM Christophe Leroy
<christophe.leroy@csgroup.eu> 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.

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 <alistair@popple.id.au>
> > Signed-off-by: Jordan Niethe <jniethe5@gmail.com>
> > ---
> > 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);
> >       }
> >