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

On Sun, May 17, 2020 at 4:39 AM Christophe Leroy
[off-list ref] wrote:

Le 06/05/2020 à 05:40, Jordan Niethe a écrit :

quoted

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;
-- 

quoted

Reviewed-by: Alistair Popple <redacted>
Signed-off-by: Jordan Niethe <redacted>
---
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);
      }