Dave Hansen [off-list ref] writes:

On 02/21/2018 05:55 PM, Ram Pai wrote:

quoted

-static inline unsigned int _rdpkey_reg(int line)
+static inline pkey_reg_t _rdpkey_reg(int line)
 {
-	unsigned int pkey_reg = __rdpkey_reg();
+	pkey_reg_t pkey_reg = __rdpkey_reg();

-	dprintf4("rdpkey_reg(line=%d) pkey_reg: %x shadow: %x\n",
+	dprintf4("rdpkey_reg(line=%d) pkey_reg: %016lx shadow: %016lx\n",
 			line, pkey_reg, shadow_pkey_reg);
 	assert(pkey_reg == shadow_pkey_reg);

Hmm.  So we're using %lx for an int?  Doesn't the compiler complain
about this?

It doesn't because dprintf4() doesn't have the annotation that tells the
compiler that it takes printf-like arguments. Once I add it:

--- a/tools/testing/selftests/vm/pkey-helpers.h
+++ b/tools/testing/selftests/vm/pkey-helpers.h

@@ -54,6 +54,10 @@
 #define DPRINT_IN_SIGNAL_BUF_SIZE 4096
 extern int dprint_in_signal;
 extern char dprint_in_signal_buffer[DPRINT_IN_SIGNAL_BUF_SIZE];
+
+#ifdef __GNUC__
+__attribute__((format(printf, 1, 2)))
+#endif
 static inline void sigsafe_printf(const char *format, ...)
 {
 	va_list ap;

Then it does complain about it. I'm working on a fix where each arch
will define a format string to use for its pkey_reg_t and use it like
this:

--- a/tools/testing/selftests/vm/pkey-helpers.h
+++ b/tools/testing/selftests/vm/pkey-helpers.h

@@ -19,6 +19,7 @@
 #define u32 uint32_t
 #define u64 uint64_t
 #define pkey_reg_t u32
+#define PKEY_REG_FMT "%016x"

 #ifdef __i386__
 #ifndef SYS_mprotect_key

@@ -112,7 +113,8 @@ static inline pkey_reg_t _read_pkey_reg(int line)
 {
 	pkey_reg_t pkey_reg = __read_pkey_reg();

-	dprintf4("read_pkey_reg(line=%d) pkey_reg: %016lx shadow: %016lx\n",
+	dprintf4("read_pkey_reg(line=%d) pkey_reg: "PKEY_REG_FMT
+			" shadow: "PKEY_REG_FMT"\n",
 			line, pkey_reg, shadow_pkey_reg);
 	assert(pkey_reg == shadow_pkey_reg);

--

Thiago Jung Bauermann
IBM Linux Technology Center