linux-kernel - Re: [PATCH v12 04/22] selftests/vm: typecast the pkey register

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Message-Id: <87h8p239v8.fsf@morokweng.localdomain>
Date:   Mon, 26 Mar 2018 16:38:51 -0300
From:   Thiago Jung Bauermann <bauerman@...ux.vnet.ibm.com>
To:     Dave Hansen <dave.hansen@...el.com>
Cc:     Ram Pai <linuxram@...ibm.com>, shuahkh@....samsung.com,
        linux-kselftest@...r.kernel.org, mpe@...erman.id.au,
        linuxppc-dev@...ts.ozlabs.org, linux-mm@...ck.org, x86@...nel.org,
        linux-arch@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, mingo@...hat.com,
        akpm@...ux-foundation.org, benh@...nel.crashing.org,
        paulus@...ba.org, khandual@...ux.vnet.ibm.com,
        aneesh.kumar@...ux.vnet.ibm.com, bsingharora@...il.com,
        hbabu@...ibm.com, mhocko@...nel.org, ebiederm@...ssion.com,
        arnd@...db.de
Subject: Re: [PATCH v12 04/22] selftests/vm: typecast the pkey register


Dave Hansen <dave.hansen@...el.com> writes:

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