KVM: arm64: selftests: Replace str_with_index with strdup_printf

The original author of aarch64/get-reg-list.c (me) was wearing
tunnel vision goggles when implementing str_with_index(). There's
no reason to have such a special case string function. Instead,
take inspiration from glib and implement strdup_printf. The
implementation builds on vasprintf() which requires _GNU_SOURCE,
but we require _GNU_SOURCE in most files already.

Signed-off-by: Andrew Jones <[e-mail]>
Signed-off-by: Haibo Xu <[e-mail]>
Signed-off-by: Anup Patel <[e-mail]>

tools/testing/selftests/kvm/aarch64/get-reg-list.c

···
 	return true;
 }
 
-static const char *str_with_index(const char *template, __u64 index)
-{
-	char *str, *p;
-	int n;
-
-	str = strdup(template);
-	p = strstr(str, "##");
-	n = sprintf(p, "%lld", index);
-	strcat(p + n, strstr(template, "##") + 2);
-
-	return (const char *)str;
-}
-
 #define REG_MASK (KVM_REG_ARCH_MASK | KVM_REG_SIZE_MASK | KVM_REG_ARM_COPROC_MASK)
 
 #define CORE_REGS_XX_NR_WORDS	2
···
 	     KVM_REG_ARM_CORE_REG(regs.regs[30]):
 		idx = (core_off - KVM_REG_ARM_CORE_REG(regs.regs[0])) / CORE_REGS_XX_NR_WORDS;
 		TEST_ASSERT(idx < 31, "%s: Unexpected regs.regs index: %lld", config_name(c), idx);
-		return str_with_index("KVM_REG_ARM_CORE_REG(regs.regs[##])", idx);
+		return strdup_printf("KVM_REG_ARM_CORE_REG(regs.regs[%lld])", idx);
 	case KVM_REG_ARM_CORE_REG(regs.sp):
 		return "KVM_REG_ARM_CORE_REG(regs.sp)";
 	case KVM_REG_ARM_CORE_REG(regs.pc):
···
 	     KVM_REG_ARM_CORE_REG(spsr[KVM_NR_SPSR - 1]):
 		idx = (core_off - KVM_REG_ARM_CORE_REG(spsr[0])) / CORE_SPSR_XX_NR_WORDS;
 		TEST_ASSERT(idx < KVM_NR_SPSR, "%s: Unexpected spsr index: %lld", config_name(c), idx);
-		return str_with_index("KVM_REG_ARM_CORE_REG(spsr[##])", idx);
+		return strdup_printf("KVM_REG_ARM_CORE_REG(spsr[%lld])", idx);
 	case KVM_REG_ARM_CORE_REG(fp_regs.vregs[0]) ...
 	     KVM_REG_ARM_CORE_REG(fp_regs.vregs[31]):
 		idx = (core_off - KVM_REG_ARM_CORE_REG(fp_regs.vregs[0])) / CORE_FPREGS_XX_NR_WORDS;
 		TEST_ASSERT(idx < 32, "%s: Unexpected fp_regs.vregs index: %lld", config_name(c), idx);
-		return str_with_index("KVM_REG_ARM_CORE_REG(fp_regs.vregs[##])", idx);
+		return strdup_printf("KVM_REG_ARM_CORE_REG(fp_regs.vregs[%lld])", idx);
 	case KVM_REG_ARM_CORE_REG(fp_regs.fpsr):
 		return "KVM_REG_ARM_CORE_REG(fp_regs.fpsr)";
 	case KVM_REG_ARM_CORE_REG(fp_regs.fpcr):
···
 		n = (id >> 5) & (KVM_ARM64_SVE_NUM_ZREGS - 1);
 		TEST_ASSERT(id == KVM_REG_ARM64_SVE_ZREG(n, 0),
 			    "%s: Unexpected bits set in SVE ZREG id: 0x%llx", config_name(c), id);
-		return str_with_index("KVM_REG_ARM64_SVE_ZREG(##, 0)", n);
+		return strdup_printf("KVM_REG_ARM64_SVE_ZREG(%lld, 0)", n);
 	case KVM_REG_ARM64_SVE_PREG_BASE ...
 	     KVM_REG_ARM64_SVE_PREG_BASE + (1ULL << 5) * KVM_ARM64_SVE_NUM_PREGS - 1:
 		n = (id >> 5) & (KVM_ARM64_SVE_NUM_PREGS - 1);
 		TEST_ASSERT(id == KVM_REG_ARM64_SVE_PREG(n, 0),
 			    "%s: Unexpected bits set in SVE PREG id: 0x%llx", config_name(c), id);
-		return str_with_index("KVM_REG_ARM64_SVE_PREG(##, 0)", n);
+		return strdup_printf("KVM_REG_ARM64_SVE_PREG(%lld, 0)", n);
 	case KVM_REG_ARM64_SVE_FFR_BASE:
 		TEST_ASSERT(id == KVM_REG_ARM64_SVE_FFR(0),
 			    "%s: Unexpected bits set in SVE FFR id: 0x%llx", config_name(c), id);

tools/testing/selftests/kvm/include/test_util.h

···
 	return num;
 }
 
+char *strdup_printf(const char *fmt, ...) __attribute__((format(printf, 1, 2), nonnull(1)));
+
 #endif /* SELFTEST_KVM_TEST_UTIL_H */

tools/testing/selftests/kvm/lib/test_util.c

···
  * Copyright (C) 2020, Google LLC.
  */
 
+#define _GNU_SOURCE
+#include <stdio.h>
+#include <stdarg.h>
 #include <assert.h>
 #include <ctype.h>
 #include <limits.h>
···
 		    "%ld not in range of [%d, %d]", num, INT_MIN, INT_MAX);
 
 	return num;
+}
+
+char *strdup_printf(const char *fmt, ...)
+{
+	va_list ap;
+	char *str;
+
+	va_start(ap, fmt);
+	vasprintf(&str, fmt, ap);
+	va_end(ap);
+
+	return str;
 }