From 2ed9bf330709e75c2f066f6ec13ece1ecdb4e9db Mon Sep 17 00:00:00 2001

From: Aaron Conole <aconole@redhat.com>

Date: Mon, 2 Apr 2018 14:24:34 -0400

Subject: [PATCH] eal: abstract away the auxiliary vector

Rather than attempting to load the contents of the auxv directly,

prefer to use an exposed API - and if that doesn't exist then attempt

to load the vector.  This is because on some systems, when a user

is downgraded, the /proc/self/auxv file retains the old ownership

and permissions.  The original method of /proc/self/auxv is retained.

This also removes a potential abort() in the code when compiled with

NDEBUG.  A quick parse of the code shows that many (if not all) of

the CPU flag parsing isn't used internally, so it should be okay.

Signed-off-by: Aaron Conole <aconole@redhat.com>

Signed-off-by: Timothy Redaelli <tredaelli@redhat.com>

---

 lib/librte_eal/common/arch/arm/rte_cpuflags.c | 20 +----

 .../common/arch/ppc_64/rte_cpuflags.c         | 15 +---

 lib/librte_eal/common/eal_common_cpuflags.c   | 79 +++++++++++++++++++

 .../common/include/generic/rte_cpuflags.h     | 21 +++++

 4 files changed, 106 insertions(+), 29 deletions(-)

diff --git a/lib/librte_eal/common/arch/arm/rte_cpuflags.c b/lib/librte_eal/common/arch/arm/rte_cpuflags.c

index 390a19a26..caf3dc83a 100644

--- a/lib/librte_eal/common/arch/arm/rte_cpuflags.c

+++ b/lib/librte_eal/common/arch/arm/rte_cpuflags.c

@@ -105,22 +105,10 @@ const struct feature_entry rte_cpu_feature_table[] = {

 static void

 rte_cpu_get_features(hwcap_registers_t out)

 {

-	int auxv_fd;

-	_Elfx_auxv_t auxv;

-

-	auxv_fd = open("/proc/self/auxv", O_RDONLY);

-	assert(auxv_fd != -1);

-	while (read(auxv_fd, &auxv, sizeof(auxv)) == sizeof(auxv)) {

-		if (auxv.a_type == AT_HWCAP) {

-			out[REG_HWCAP] = auxv.a_un.a_val;

-		} else if (auxv.a_type == AT_HWCAP2) {

-			out[REG_HWCAP2] = auxv.a_un.a_val;

-		} else if (auxv.a_type == AT_PLATFORM) {

-			if (!strcmp((const char *)auxv.a_un.a_val, PLATFORM_STR))

-				out[REG_PLATFORM] = 0x0001;

-		}

-	}

-	close(auxv_fd);

+	out[REG_HWCAP] = rte_cpu_getauxval(AT_HWCAP);

+	out[REG_HWCAP2] = rte_cpu_getauxval(AT_HWCAP2);

+	if (!rte_cpu_strcmp_auxval(AT_PLATFORM, PLATFORM_STR))

+		out[REG_PLATFORM] = 0x0001;

 }

 /*

diff --git a/lib/librte_eal/common/arch/ppc_64/rte_cpuflags.c b/lib/librte_eal/common/arch/ppc_64/rte_cpuflags.c

index 970a61c5e..e7a82452b 100644

--- a/lib/librte_eal/common/arch/ppc_64/rte_cpuflags.c

+++ b/lib/librte_eal/common/arch/ppc_64/rte_cpuflags.c

@@ -104,19 +104,8 @@ const struct feature_entry rte_cpu_feature_table[] = {

 static void

 rte_cpu_get_features(hwcap_registers_t out)

 {

-	int auxv_fd;

-	Elf64_auxv_t auxv;

-

-	auxv_fd = open("/proc/self/auxv", O_RDONLY);

-	assert(auxv_fd != -1);

-	while (read(auxv_fd, &auxv,

-		sizeof(Elf64_auxv_t)) == sizeof(Elf64_auxv_t)) {

-		if (auxv.a_type == AT_HWCAP)

-			out[REG_HWCAP] = auxv.a_un.a_val;

-		else if (auxv.a_type == AT_HWCAP2)

-			out[REG_HWCAP2] = auxv.a_un.a_val;

-	}

-	close(auxv_fd);

+	out[REG_HWCAP] = rte_cpu_getauxval(AT_HWCAP);

+	out[REG_HWCAP2] = rte_cpu_getauxval(AT_HWCAP2);

 }

 /*

diff --git a/lib/librte_eal/common/eal_common_cpuflags.c b/lib/librte_eal/common/eal_common_cpuflags.c

index 3a055f7c7..a09667563 100644

--- a/lib/librte_eal/common/eal_common_cpuflags.c

+++ b/lib/librte_eal/common/eal_common_cpuflags.c

@@ -2,11 +2,90 @@

  *   OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

  */

+#include <elf.h>

+#include <fcntl.h>

 #include <stdio.h>

+#include <string.h>

+#include <sys/stat.h>

+#include <sys/types.h>

+#include <unistd.h>

+

+#if defined(__GLIBC__) && defined(__GLIBC_PREREQ)

+#if __GLIBC_PREREQ(2, 16)

+#include <sys/auxv.h>

+#define HAS_AUXV 1

+#endif

+#endif

 #include <rte_common.h>

 #include <rte_cpuflags.h>

+#ifndef HAS_AUXV

+static unsigned long

+getauxval(unsigned long type)

+{

+	errno = ENOTSUP;

+	return 0;

+}

+#endif

+

+#ifdef RTE_ARCH_64

+typedef Elf64_auxv_t Internal_Elfx_auxv_t;

+#else

+typedef Elf32_auxv_t Internal_Elfx_auxv_t;

+#endif

+

+

+/**

+ * Provides a method for retrieving values from the auxiliary vector and

+ * possibly running a string comparison.

+ *

+ * @return Always returns a result.  When the result is 0, check errno

+ * to see if an error occurred during processing.

+ */

+static unsigned long

+_rte_cpu_getauxval(unsigned long type, const char *str)

+{

+	unsigned long val;

+

+	errno = 0;

+	val = getauxval(type);

+

+	if (!val && (errno == ENOTSUP || errno == ENOENT)) {

+		int auxv_fd = open("/proc/self/auxv", O_RDONLY);

+		Internal_Elfx_auxv_t auxv;

+

+		if (auxv_fd == -1)

+			return 0;

+

+		errno = ENOENT;

+		while (read(auxv_fd, &auxv, sizeof(auxv)) == sizeof(auxv)) {

+			if (auxv.a_type == type) {

+				errno = 0;

+				val = auxv.a_un.a_val;

+				if (str)

+					val = strcmp((const char *)val, str);

+				break;

+			}

+		}

+		close(auxv_fd);

+	}

+

+	return val;

+}

+

+unsigned long

+rte_cpu_getauxval(unsigned long type)

+{

+	return _rte_cpu_getauxval(type, NULL);

+}

+

+int

+rte_cpu_strcmp_auxval(unsigned long type, const char *str)

+{

+	return _rte_cpu_getauxval(type, str);

+}

+

 /**

  * Checks if the machine is adequate for running the binary. If it is not, the

  * program exits with status 1.

diff --git a/lib/librte_eal/common/include/generic/rte_cpuflags.h b/lib/librte_eal/common/include/generic/rte_cpuflags.h

index 8d31687d8..156ea0029 100644

--- a/lib/librte_eal/common/include/generic/rte_cpuflags.h

+++ b/lib/librte_eal/common/include/generic/rte_cpuflags.h

@@ -64,4 +64,25 @@ rte_cpu_check_supported(void);

 int

 rte_cpu_is_supported(void);

+/**

+ * This function attempts to retrieve a value from the auxiliary vector.

+ * If it is unsuccessful, the result will be 0, and errno will be set.

+ *

+ * @return A value from the auxiliary vector.  When the value is 0, check

+ * errno to determine if an error occurred.

+ */

+unsigned long

+rte_cpu_getauxval(unsigned long type);

+

+/**

+ * This function retrieves a value from the auxiliary vector, and compares it

+ * as a string against the value retrieved.

+ *

+ * @return The result of calling strcmp() against the value retrieved from

+ * the auxiliary vector.  When the value is 0 (meaning a match is found),

+ * check errno to determine if an error occurred.

+ */

+int

+rte_cpu_strcmp_auxval(unsigned long type, const char *str);

+

 #endif /* _RTE_CPUFLAGS_H_ */

-- 

2.17.0