From 5ac955065a4db27368d82e8e2c91be71accb1e74 Mon Sep 17 00:00:00 2001
From: "Michael S. Tsirkin" <mst@redhat.com>
Date: Mon, 16 Nov 2015 14:32:10 +0100
Subject: [PATCH 13/44] util: add memfd helpers
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Message-id: <1447684235-15638-7-git-send-email-mst@redhat.com>
Patchwork-id: 68357
O-Subject: [PATCH RHEV 7.3/7.2.z v2 06/36] util: add memfd helpers
Bugzilla: 1279388
RH-Acked-by: Xiao Wang <jasowang@redhat.com>
RH-Acked-by: Victor Kaplansky <vkaplans@redhat.com>
RH-Acked-by: Marcel Apfelbaum <marcel@redhat.com>
RH-Acked-by: Marc-André Lureau <mlureau@redhat.com>

From: Marc-André Lureau <marcandre.lureau@redhat.com>

Add qemu_memfd_alloc/free() helpers.

The function helps to allocate and seal shared memory.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Tested-by: Thibaut Collet <thibaut.collet@6wind.com>
(cherry picked from commit d3592199ba3db504c6585115b9531b4cf7c50a0d)
Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
---
 include/qemu/memfd.h |  4 +++
 util/memfd.c         | 73 +++++++++++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 76 insertions(+), 1 deletion(-)

diff --git a/include/qemu/memfd.h b/include/qemu/memfd.h
index 8b1fe6a..950fb88 100644
--- a/include/qemu/memfd.h
+++ b/include/qemu/memfd.h
@@ -17,4 +17,8 @@
 #define F_SEAL_WRITE    0x0008  /* prevent writes */
 #endif
 
+void *qemu_memfd_alloc(const char *name, size_t size, unsigned int seals,
+                       int *fd);
+void qemu_memfd_free(void *ptr, size_t size, int fd);
+
 #endif /* QEMU_MEMFD_H */
diff --git a/util/memfd.c b/util/memfd.c
index e43a3f8..f3ae34e 100644
--- a/util/memfd.c
+++ b/util/memfd.c
@@ -27,6 +27,12 @@
 
 #include "qemu/osdep.h"
 
+#include <glib.h>
+#include <glib/gprintf.h>
+
+#include <sys/mman.h>
+#include <fcntl.h>
+
 #include "qemu/memfd.h"
 
 #ifdef CONFIG_MEMFD
@@ -36,7 +42,7 @@
 #include <sys/syscall.h>
 #include <asm/unistd.h>
 
-inline static int memfd_create(const char *name, unsigned int flags)
+static int memfd_create(const char *name, unsigned int flags)
 {
 #ifdef __NR_memfd_create
     return syscall(__NR_memfd_create, name, flags);
@@ -53,3 +59,68 @@ inline static int memfd_create(const char *name, unsigned int flags)
 #ifndef MFD_ALLOW_SEALING
 #define MFD_ALLOW_SEALING 0x0002U
 #endif
+
+/*
+ * This is a best-effort helper for shared memory allocation, with
+ * optional sealing. The helper will do his best to allocate using
+ * memfd with sealing, but may fallback on other methods without
+ * sealing.
+ */
+void *qemu_memfd_alloc(const char *name, size_t size, unsigned int seals,
+                       int *fd)
+{
+    void *ptr;
+    int mfd = -1;
+
+    *fd = -1;
+
+#ifdef CONFIG_LINUX
+    if (seals) {
+        mfd = memfd_create(name, MFD_ALLOW_SEALING | MFD_CLOEXEC);
+    }
+
+    if (mfd == -1) {
+        /* some systems have memfd without sealing */
+        mfd = memfd_create(name, MFD_CLOEXEC);
+        seals = 0;
+    }
+#endif
+
+    if (mfd != -1) {
+        if (ftruncate(mfd, size) == -1) {
+            perror("ftruncate");
+            close(mfd);
+            return NULL;
+        }
+
+        if (seals && fcntl(mfd, F_ADD_SEALS, seals) == -1) {
+            perror("fcntl");
+            close(mfd);
+            return NULL;
+        }
+    } else {
+        perror("memfd");
+        return NULL;
+    }
+
+    ptr = mmap(0, size, PROT_READ | PROT_WRITE, MAP_SHARED, mfd, 0);
+    if (ptr == MAP_FAILED) {
+        perror("mmap");
+        close(mfd);
+        return NULL;
+    }
+
+    *fd = mfd;
+    return ptr;
+}
+
+void qemu_memfd_free(void *ptr, size_t size, int fd)
+{
+    if (ptr) {
+        munmap(ptr, size);
+    }
+
+    if (fd != -1) {
+        close(fd);
+    }
+}
-- 
1.8.3.1