Re: [PATCH v3 08/14] powerpc/xmon: Remove store_inst() for patch_instruction()

On Wed, Feb 26, 2020 at 6:04 PM Nicholas Piggin [off-list ref] wrote:

Jordan Niethe's on February 26, 2020 2:07 pm:

quoted

For modifying instructions in xmon, patch_instruction() can serve the
same role that store_inst() is performing with the advantage of not
being specific to xmon. In some places patch_instruction() is already
being using followed by store_inst(). In these cases just remove the
store_inst(). Otherwise replace store_inst() with patch_instruction().

Signed-off-by: Jordan Niethe <redacted>
---
 arch/powerpc/xmon/xmon.c | 13 ++-----------
 1 file changed, 2 insertions(+), 11 deletions(-)

diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c
index 897e512c6379..a673cf55641c 100644
--- a/arch/powerpc/xmon/xmon.c
+++ b/arch/powerpc/xmon/xmon.c

@@ -325,11 +325,6 @@ static inline void sync(void)
      asm volatile("sync; isync");
 }

-static inline void store_inst(void *p)
-{
-     asm volatile ("dcbst 0,%0; sync; icbi 0,%0; isync" : : "r" (p));
-}
-
 static inline void cflush(void *p)
 {
      asm volatile ("dcbf 0,%0; icbi 0,%0" : : "r" (p));

@@ -882,8 +877,7 @@ static struct bpt *new_breakpoint(unsigned long a)
      for (bp = bpts; bp < &bpts[NBPTS]; ++bp) {
              if (!bp->enabled && atomic_read(&bp->ref_count) == 0) {
                      bp->address = a;
-                     bp->instr[1] = bpinstr;
-                     store_inst(&bp->instr[1]);
+                     patch_instruction(&bp->instr[1], bpinstr);
                      return bp;
              }
      }

@@ -913,7 +907,7 @@ static void insert_bpts(void)
                      bp->enabled = 0;
                      continue;
              }
-             store_inst(&bp->instr[0]);
+             patch_instruction(&bp->instr[0], bp->instr[0]);

Hmm that's a bit weird. Can you read instructions into a local variable
first, do the checks on them, then patch them into their execution
location?

I agree it is weird, local variables would be better.

Otherwise, good cleanup.

Thanks,
Nick