arm: Fix floating point arguments in arm

The designated initializer in C makes implicit memset internally in arm
architecture.  Due to the memset, VFP registers are clobbered
unexpectedly, so this patch fixes the problem by replacing the
designated initializer to explicit 'mcount_memset4'.

In addition, the offset of VFP registers were incorrect because the
following commit pushs d1 register on top of the original d0.

  ffb69ce arm: Handle struct return type by keeping more regs on stack

So the offset is adjusted from -2 to -4 to cope with the change.

Source:
  #include <stdio.h>

  float float_add(float a, float b)
  {
          fprintf(stderr, "a = %f, b = %f\n", a, b);
          return a + b;
  }

  int main(int argc, char *argv[])
  {
          double c;

          c = float_add(-0.1, 0.2);
          fprintf(stderr, "c = %f\n", c);
          return c > 0;
  }

Before:
  $ uftrace -a -F main a.out
  a = 0.000000, b = 0.000000
  c = 0.000000
  # DURATION     TID     FUNCTION
              [ 25362] | main(1, 0x7ea25344) {
              [ 25362] |   float_add(0.000000, 0.000000) {
   503.228 us [ 25362] |     fprintf(&_IO_2_1_stderr_, "a = %f, b = %f\n") = 27;
   511.197 us [ 25362] |   } = 0.000000; /* float_add */
     9.687 us [ 25362] |   fprintf(&_IO_2_1_stderr_, "c = %f\n") = 13;
   531.977 us [ 25362] | } = 0; /* main */

After:
  $ uftrace -a -F main a.out
  a = -0.100000, b = 0.200000
  c = 0.100000
  # DURATION     TID     FUNCTION
              [ 25146] | main(1, 0x7edbb344) {
              [ 25146] |   float_add(-0.100000, 0.200000) {
   501.769 us [ 25146] |     fprintf(&_IO_2_1_stderr_, "a = %f, b = %f\n") = 28;
   509.321 us [ 25146] |   } = 0.100000; /* float_add */
    12.500 us [ 25146] |   fprintf(&_IO_2_1_stderr_, "c = %f\n") = 13;
   533.539 us [ 25146] | } = 1; /* main */

Fixed: #1088

Signed-off-by: Honggyu Kim <[email protected]>

arch/arm/mcount-support.c

@@ -488,8 +488,10 @@ void mcount_arch_get_retval(struct mcount_arg_context *ctx,
 	/* type of return value cannot be FLOAT, so check format instead */
 #ifdef HAVE_ARM_HARDFP
 	if (spec->fmt == ARG_FMT_FLOAT && use_hard_float) {
-		/* d0 register (64 bit) was saved below the r0 */
-		memcpy(ctx->val.v, ctx->retval - 2, spec->size);
+		/* d0, d1 registers (64 bit) were saved below the r0 */
+		long *float_retval = ctx->retval - 4;
+
+		mcount_memcpy4(ctx->val.v, float_retval, spec->size);
 	}
 	else
 #endif /* HAVE_ARM_HARDFP */

libmcount/plthook.c

@@ -732,16 +732,16 @@ static unsigned long __plthook_entry(unsigned long *ret_addr,
 	struct sym *sym;
 	struct mcount_thread_data *mtdp = NULL;
 	struct mcount_ret_stack *rstack;
-	struct uftrace_trigger tr = {
-		.flags = 0,
-	};
 	bool skip = false;
 	bool recursion = true;
 	enum filter_result filtered;
 	struct plthook_data *pd;
 	struct plthook_special_func *func;
 	unsigned long special_flag = 0;
 	unsigned long real_addr = 0;
+	struct uftrace_trigger tr;
+
+	mcount_memset4(&tr, 0, sizeof(tr));
 
 	// if necessary, implement it by architecture.
 	child_idx = mcount_arch_child_idx(child_idx);

libmcount/record.c

@@ -503,12 +503,13 @@ void save_argument(struct mcount_thread_data *mtdp,
 {
 	void *argbuf = get_argbuf(mtdp, rstack);
 	unsigned size;
-	struct mcount_arg_context ctx = {
-		.regs = regs,
-		.stack_base = rstack->parent_loc,
-		.regions = &mtdp->mem_regions,
-		.arch = &mtdp->arch,
-	};
+	struct mcount_arg_context ctx;
+
+	mcount_memset4(&ctx, 0, sizeof(ctx));
+	ctx.regs = regs;
+	ctx.stack_base = rstack->parent_loc;
+	ctx.regions = &mtdp->mem_regions;
+	ctx.arch = &mtdp->arch;
 
 	size = save_to_argbuf(argbuf, args_spec, &ctx);
 	if (size == -1U) {
@@ -526,11 +527,12 @@ void save_retval(struct mcount_thread_data *mtdp,
 	struct list_head *args_spec = rstack->pargs;
 	void *argbuf = get_argbuf(mtdp, rstack);
 	unsigned size;
-	struct mcount_arg_context ctx = {
-		.retval = retval,
-		.regions = &mtdp->mem_regions,
-		.arch = &mtdp->arch,
-	};
+	struct mcount_arg_context ctx;
+
+	mcount_memset4(&ctx, 0, sizeof(ctx));
+	ctx.retval = retval;
+	ctx.regions = &mtdp->mem_regions;
+	ctx.arch = &mtdp->arch;
 
 	size = save_to_argbuf(argbuf, args_spec, &ctx);
 	if (size == -1U) {

tests/t083_arg_float.py

@@ -31,7 +31,5 @@ def runcmd(self):
             # argument count follows the size of type
             argopt = argopt.replace('float_mul@fparg1/64,fparg2/32',
                                     'float_mul@fparg1/64,fparg3/32')
-            argopt = argopt.replace('float_div@fparg1,fparg2',
-                                    'float_div@fparg1,fparg3')
 
         return '%s %s %s' % (TestBase.uftrace_cmd, argopt, 't-' + self.name)