Subject: Re: [PATCH bpf-next 1/3] libbpf: add asm/unistd.h to xsk to get __NR_mmap2

From: Ivan Khoronzhuk <[email-masked]>
Date: Wed, 14 Aug 2019 14:57:01 +0300

On Wed, Aug 14, 2019 at 12:24:05PM +0300, Ivan Khoronzhuk wrote:
>On Tue, Aug 13, 2019 at 04:38:13PM -0700, Andrii Nakryiko wrote:
>
>Hi, Andrii
>
>>On Tue, Aug 13, 2019 at 3:24 AM Ivan Khoronzhuk
>><[email-masked]> wrote:
>>>
>>>That's needed to get __NR_mmap2 when mmap2 syscall is used.
>>>
>>>Signed-off-by: Ivan Khoronzhuk <[email-masked]>
>>>---
>>> tools/lib/bpf/xsk.c | 1 +
>>> 1 file changed, 1 insertion(+)
>>>
>>>diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c
>>>index 5007b5d4fd2c..f2fc40f9804c 100644
>>>--- a/tools/lib/bpf/xsk.c
>>>+++ b/tools/lib/bpf/xsk.c
>>>@@ -12,6 +12,7 @@
>>> #include <stdlib.h>
>>> #include <string.h>
>>> #include <unistd.h>
>>>+#include <asm/unistd.h>
>>
>>asm/unistd.h is not present in Github libbpf projection. Is there any
>
>Look on includes from
>tools/lib/bpf/libpf.c
>tools/lib/bpf/bpf.c
>
>That's how it's done... Copping headers to arch/arm will not
>solve this, it includes both of them anyway, and anyway it needs
>asm/unistd.h inclusion here, only because xsk.c needs __NR_*
>
>

There is one more radical solution for this I can send, but I'm not sure how it
can impact on other syscals/arches...

Looks like:

diff --git a/tools/lib/bpf/Makefile b/tools/lib/bpf/Makefile
index 9312066a1ae3..8b2f8ff7ce44 100644
--- a/tools/lib/bpf/Makefile
+++ b/tools/lib/bpf/Makefile
@@ -113,6 +113,7 @@ override CFLAGS += -Werror -Wall
 override CFLAGS += -fPIC
 override CFLAGS += $(INCLUDES)
 override CFLAGS += -fvisibility=hidden
+override CFLAGS += -D_FILE_OFFSET_BITS=64
 
 ifeq ($(VERBOSE),1)
   Q =
diff --git a/tools/lib/bpf/xsk.c b/tools/lib/bpf/xsk.c
index f2fc40f9804c..ff2d03b8380d 100644
--- a/tools/lib/bpf/xsk.c
+++ b/tools/lib/bpf/xsk.c
@@ -75,23 +75,6 @@ struct xsk_nl_info {
 	int fd;
 };
 
-/* For 32-bit systems, we need to use mmap2 as the offsets are 64-bit.
- * Unfortunately, it is not part of glibc.
- */
-static inline void *xsk_mmap(void *addr, size_t length, int prot, int flags,
-			     int fd, __u64 offset)
-{
-#ifdef __NR_mmap2
-	unsigned int page_shift = __builtin_ffs(getpagesize()) - 1;
-	long ret = syscall(__NR_mmap2, addr, length, prot, flags, fd,
-			   (off_t)(offset >> page_shift));
-
-	return (void *)ret;
-#else
-	return mmap(addr, length, prot, flags, fd, offset);
-#endif
-}
-
 int xsk_umem__fd(const struct xsk_umem *umem)
 {
 	return umem ? umem->fd : -EINVAL;
@@ -211,10 +194,9 @@ int xsk_umem__create(struct xsk_umem **umem_ptr, void *umem_area, __u64 size,
 		goto out_socket;
 	}
 
-	map = xsk_mmap(NULL, off.fr.desc +
-		       umem->config.fill_size * sizeof(__u64),
-		       PROT_READ | PROT_WRITE, MAP_SHARED | MAP_POPULATE,
-		       umem->fd, XDP_UMEM_PGOFF_FILL_RING);
+	map = mmap(NULL, off.fr.desc + umem->config.fill_size * sizeof(__u64),
+		   PROT_READ | PROT_WRITE, MAP_SHARED | MAP_POPULATE, umem->fd,
+		   XDP_UMEM_PGOFF_FILL_RING);
 	if (map == MAP_FAILED) {
 		err = -errno;
 		goto out_socket;
@@ -228,10 +210,9 @@ int xsk_umem__create(struct xsk_umem **umem_ptr, void *umem_area, __u64 size,
 	fill->ring = map + off.fr.desc;
 	fill->cached_cons = umem->config.fill_size;
 
-	map = xsk_mmap(NULL,
-		       off.cr.desc + umem->config.comp_size * sizeof(__u64),
-		       PROT_READ | PROT_WRITE, MAP_SHARED | MAP_POPULATE,
-		       umem->fd, XDP_UMEM_PGOFF_COMPLETION_RING);
+	map = mmap(NULL, off.cr.desc + umem->config.comp_size * sizeof(__u64),
+		   PROT_READ | PROT_WRITE, MAP_SHARED | MAP_POPULATE, umem->fd,
+		   XDP_UMEM_PGOFF_COMPLETION_RING);
 	if (map == MAP_FAILED) {
 		err = -errno;
 		goto out_mmap;
@@ -552,11 +533,10 @@ int xsk_socket__create(struct xsk_socket **xsk_ptr, const char *ifname,
 	}
 
 	if (rx) {
-		rx_map = xsk_mmap(NULL, off.rx.desc +
-				  xsk->config.rx_size * sizeof(struct xdp_desc),
-				  PROT_READ | PROT_WRITE,
-				  MAP_SHARED | MAP_POPULATE,
-				  xsk->fd, XDP_PGOFF_RX_RING);
+		rx_map = mmap(NULL, off.rx.desc +
+			      xsk->config.rx_size * sizeof(struct xdp_desc),
+			      PROT_READ | PROT_WRITE, MAP_SHARED | MAP_POPULATE,
+			      xsk->fd, XDP_PGOFF_RX_RING);
 		if (rx_map == MAP_FAILED) {
 			err = -errno;
 			goto out_socket;
@@ -571,11 +551,10 @@ int xsk_socket__create(struct xsk_socket **xsk_ptr, const char *ifname,
 	xsk->rx = rx;
 
 	if (tx) {
-		tx_map = xsk_mmap(NULL, off.tx.desc +
-				  xsk->config.tx_size * sizeof(struct xdp_desc),
-				  PROT_READ | PROT_WRITE,
-				  MAP_SHARED | MAP_POPULATE,
-				  xsk->fd, XDP_PGOFF_TX_RING);
+		tx_map = mmap(NULL, off.tx.desc +
+			      xsk->config.tx_size * sizeof(struct xdp_desc),
+			      PROT_READ | PROT_WRITE, MAP_SHARED | MAP_POPULATE,
+			      xsk->fd, XDP_PGOFF_TX_RING);
 		if (tx_map == MAP_FAILED) {
 			err = -errno;
 			goto out_mmap_rx;

If maintainers are ready to accept this I can send.
What do you say?

-- 
Regards,
Ivan Khoronzhuk