On Wed, 2020-04-08 at 12:18 +1000, Jordan Niethe wrote:

On Tue, Apr 7, 2020 at 9:31 PM Balamuruhan S [off-list ref] wrote:

quoted

On Mon, 2020-04-06 at 18:09 +1000, Jordan Niethe wrote:

quoted

Currently in xmon, mread() is used for reading instructions. In
preparation for prefixed instructions, create and use a new function,
mread_instr(), especially for reading instructions.

Signed-off-by: Jordan Niethe <redacted>
---
v5: New to series, seperated from "Add prefixed instructions to
instruction data type"
---
 arch/powerpc/xmon/xmon.c | 24 ++++++++++++++++++++----
 1 file changed, 20 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c
index 5e3949322a6c..6f4cf01a58c1 100644
--- a/arch/powerpc/xmon/xmon.c
+++ b/arch/powerpc/xmon/xmon.c

@@ -125,6 +125,7 @@ extern unsigned int bpt_table[NBPTS * BPT_WORDS];
 static int cmds(struct pt_regs *);
 static int mread(unsigned long, void *, int);
 static int mwrite(unsigned long, void *, int);
+static int mread_instr(unsigned long, struct ppc_inst *);
 static int handle_fault(struct pt_regs *);
 static void byterev(unsigned char *, int);
 static void memex(void);

@@ -899,7 +900,7 @@ static void insert_bpts(void)
      for (i = 0; i < NBPTS; ++i, ++bp) {
              if ((bp->enabled & (BP_TRAP|BP_CIABR)) == 0)
                      continue;
-             if (mread(bp->address, &instr, 4) != 4) {
+             if (!mread_instr(bp->address, &instr)) {

Are these checks made based on whether `ppc_inst_len()` returns bool from
mread_instr() ?

No, it was meant to be the length itself returned with a length of 0
indicating an error. I will need to fix that.

I doubt it would return 0, whether we read instruction or not ppc_inst_len()
would always return sizeof(struct ppc_inst).

can we do something like,

static int
mread_instr(unsigned long adrs, struct ppc_inst *instr)
{
	int size = 0;
	if (setjmp(bus_error_jmp) == 0) {
		catch_memory_errors = 1;
		sync();
		*instr = ppc_inst_read((struct ppc_inst *)adrs);
		sync();
		/* wait a little while to see if we get a machine check */
		__delay(200);
		size = ppc_inst_len(instr);
	}
	catch_memory_errors = 0;
	return size;
}

-- Bala

quoted

-- Bala

quoted

                      printf("Couldn't read instruction at %lx, "
                             "disabling breakpoint there\n", bp-

quoted

address);

                      bp->enabled = 0;

@@ -949,7 +950,7 @@ static void remove_bpts(void)
      for (i = 0; i < NBPTS; ++i, ++bp) {
              if ((bp->enabled & (BP_TRAP|BP_CIABR)) != BP_TRAP)
                      continue;
-             if (mread(bp->address, &instr, 4) == 4
+             if (mread_instr(bp->address, &instr)
                  && ppc_inst_equal(instr, ppc_inst(bpinstr))
                  && patch_instruction(
                      (struct ppc_inst *)bp->address, ppc_inst_read(bp-

quoted

instr)) != 0)

@@ -1165,7 +1166,7 @@ static int do_step(struct pt_regs *regs)
      force_enable_xmon();
      /* check we are in 64-bit kernel mode, translation enabled */
      if ((regs->msr & (MSR_64BIT|MSR_PR|MSR_IR)) == (MSR_64BIT|MSR_IR))

{
-             if (mread(regs->nip, &instr, 4) == 4) {
+             if (mread_instr(regs->nip, &instr)) {
                      stepped = emulate_step(regs, instr);
                      if (stepped < 0) {
                              printf("Couldn't single-step %s
instruction\n",

@@ -1332,7 +1333,7 @@ static long check_bp_loc(unsigned long addr)
              printf("Breakpoints may only be placed at kernel

addresses\n");
              return 0;
      }
-     if (!mread(addr, &instr, sizeof(instr))) {
+     if (!mread_instr(addr, &instr)) {
              printf("Can't read instruction at address %lx\n", addr);
              return 0;
      }

@@ -2125,6 +2126,21 @@ mwrite(unsigned long adrs, void *buf, int size)
      return n;
 }

+static int
+mread_instr(unsigned long adrs, struct ppc_inst *instr)
+{
+     if (setjmp(bus_error_jmp) == 0) {
+             catch_memory_errors = 1;
+             sync();
+             *instr = ppc_inst_read((struct ppc_inst *)adrs);
+             sync();
+             /* wait a little while to see if we get a machine check */
+             __delay(200);
+     }
+     catch_memory_errors = 0;
+     return ppc_inst_len(*instr);
+}
+
 static int fault_type;
 static int fault_except;
 static char *fault_chars[] = { "--", "**", "##" };