[dpdk-dev] [PATCH] linuxapp eal: set fd to -1 for MAP_ANONYMOUS cases

[Neil Horman]

https://dpdk.org/tracker/show_bug.cgi?id=18

Indicated that several mmap call sites in the linuxapp eal code used an
fd that was not -1 in their calls while using MAP_ANONYMOUS.  While
probably not a huge deal, the man page does say the fd should be -1 for
portability, as some implementations don't ignore fd as they should for
MAP_ANONYMOUS, and seting -1 here allows us to eliminate some code.

Signed-off-by: Neil Horman <nhorman at tuxdriver.com>
CC: Thomas Monjalon <thomas at monjalon.net>
CC: Ferruh Yigit <ferruh.yigit at intel.com>
---
 lib/librte_eal/linuxapp/eal/eal_memory.c | 32 +++++++-------------------------
 1 file changed, 7 insertions(+), 25 deletions(-)

diff --git a/lib/librte_eal/linuxapp/eal/eal_memory.c b/lib/librte_eal/linuxapp/eal/eal_memory.c
index 38853b753..acb553243 100644
--- a/lib/librte_eal/linuxapp/eal/eal_memory.c
+++ b/lib/librte_eal/linuxapp/eal/eal_memory.c
@@ -222,7 +222,7 @@ aslr_enabled(void)
 }
 
 /*
- * Try to mmap *size bytes in /dev/zero. If it is successful, return the
+ * Try to mmap *size bytes. If it is successful, return the
  * pointer to the mmap'd area and keep *size unmodified. Else, retry
  * with a smaller zone: decrease *size by hugepage_sz until it reaches
  * 0. In this case, return NULL. Note: this function returns an address
@@ -233,7 +233,6 @@ get_virtual_area(size_t *size, size_t hugepage_sz)
 {
 	void *addr;
 	void *addr_hint;
-	int fd;
 	long aligned_addr;
 
 	if (internal_config.base_virtaddr != 0) {
@@ -248,11 +247,6 @@ get_virtual_area(size_t *size, size_t hugepage_sz)
 	RTE_LOG(DEBUG, EAL, "Ask a virtual area of 0x%zx bytes\n", *size);
 
 
-	fd = open("/dev/zero", O_RDONLY);
-	if (fd < 0){
-		RTE_LOG(ERR, EAL, "Cannot open /dev/zero\n");
-		return NULL;
-	}
 	do {
 		addr = mmap(addr_hint, (*size) + hugepage_sz, PROT_READ,
 #ifdef RTE_ARCH_PPC_64
@@ -260,7 +254,7 @@ get_virtual_area(size_t *size, size_t hugepage_sz)
 #else
 				MAP_PRIVATE,
 #endif
-				fd, 0);
+				-1, 0);
 		if (addr == MAP_FAILED) {
 			*size -= hugepage_sz;
 		} else if (addr_hint != NULL && addr != addr_hint) {
@@ -273,14 +267,12 @@ get_virtual_area(size_t *size, size_t hugepage_sz)
 	} while (addr == MAP_FAILED && *size > 0);
 
 	if (addr == MAP_FAILED) {
-		close(fd);
 		RTE_LOG(ERR, EAL, "Cannot get a virtual area: %s\n",
 			strerror(errno));
 		return NULL;
 	}
 
 	munmap(addr, (*size) + hugepage_sz);
-	close(fd);
 
 	/* align addr to a huge page size boundary */
 	aligned_addr = (long)addr;
@@ -1011,7 +1003,7 @@ rte_eal_hugepage_init(void)
 	/* hugetlbfs can be disabled */
 	if (internal_config.no_hugetlbfs) {
 		addr = mmap(NULL, internal_config.memory, PROT_READ | PROT_WRITE,
-				MAP_PRIVATE | MAP_ANONYMOUS, 0, 0);
+				MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
 		if (addr == MAP_FAILED) {
 			RTE_LOG(ERR, EAL, "%s: mmap() failed: %s\n", __func__,
 					strerror(errno));
@@ -1339,7 +1331,7 @@ rte_eal_hugepage_attach(void)
 	unsigned i, s = 0; /* s used to track the segment number */
 	unsigned max_seg = RTE_MAX_MEMSEG;
 	off_t size = 0;
-	int fd, fd_zero = -1, fd_hugepage = -1;
+	int fd, fd_hugepage = -1;
 
 	if (aslr_enabled() > 0) {
 		RTE_LOG(WARNING, EAL, "WARNING: Address Space Layout Randomization "
@@ -1350,11 +1342,6 @@ rte_eal_hugepage_attach(void)
 
 	test_phys_addrs_available();
 
-	fd_zero = open("/dev/zero", O_RDONLY);
-	if (fd_zero < 0) {
-		RTE_LOG(ERR, EAL, "Could not open /dev/zero\n");
-		goto error;
-	}
 	fd_hugepage = open(eal_hugepage_info_path(), O_RDONLY);
 	if (fd_hugepage < 0) {
 		RTE_LOG(ERR, EAL, "Could not open %s\n", eal_hugepage_info_path());
@@ -1373,8 +1360,6 @@ rte_eal_hugepage_attach(void)
 			break;
 
 		/*
-		 * fdzero is mmapped to get a contiguous block of virtual
-		 * addresses of the appropriate memseg size.
 		 * use mmap to get identical addresses as the primary process.
 		 */
 		base_addr = mmap(mcfg->memseg[s].addr, mcfg->memseg[s].len,
@@ -1384,21 +1369,21 @@ rte_eal_hugepage_attach(void)
 #else
 				 MAP_PRIVATE,
 #endif
-				 fd_zero, 0);
+				 -1, 0);
 		if (base_addr == MAP_FAILED ||
 		    base_addr != mcfg->memseg[s].addr) {
 			max_seg = s;
 			if (base_addr != MAP_FAILED) {
 				/* errno is stale, don't use */
 				RTE_LOG(ERR, EAL, "Could not mmap %llu bytes "
-					"in /dev/zero at [%p], got [%p] - "
+					"at [%p], got [%p] - "
 					"please use '--base-virtaddr' option\n",
 					(unsigned long long)mcfg->memseg[s].len,
 					mcfg->memseg[s].addr, base_addr);
 				munmap(base_addr, mcfg->memseg[s].len);
 			} else {
 				RTE_LOG(ERR, EAL, "Could not mmap %llu bytes "
-					"in /dev/zero at [%p]: '%s'\n",
+					"at [%p]: '%s'\n",
 					(unsigned long long)mcfg->memseg[s].len,
 					mcfg->memseg[s].addr, strerror(errno));
 			}
@@ -1465,7 +1450,6 @@ rte_eal_hugepage_attach(void)
 	}
 	/* unmap the hugepage config file, since we are done using it */
 	munmap(hp, size);
-	close(fd_zero);
 	close(fd_hugepage);
 	return 0;
 
@@ -1474,8 +1458,6 @@ rte_eal_hugepage_attach(void)
 		munmap(mcfg->memseg[i].addr, mcfg->memseg[i].len);
 	if (hp != NULL && hp != MAP_FAILED)
 		munmap(hp, size);
-	if (fd_zero >= 0)
-		close(fd_zero);
 	if (fd_hugepage >= 0)
 		close(fd_hugepage);
 	return -1;
-- 
2.14.3