[Qemu-devel] [PATCH -V3 18/32] virtio-9p: Fix sg usage in the code

["Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>]

sg list contain more than one element and we need to use the right
element when we are doing the marshaling and unmarshaling of data.
This patch also abstract out the pack/unpack interface and make sure
we use one function for doing both.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
---
 hw/virtio-9p-debug.c |   83 +++++++++++++++++++++++++++++++++----------------
 hw/virtio-9p.c       |   57 ++++++++++++++++++++--------------
 hw/virtio-9p.h       |    9 +++++
 3 files changed, 98 insertions(+), 51 deletions(-)

diff --git a/hw/virtio-9p-debug.c b/hw/virtio-9p-debug.c
index 9230659..ee222db 100644
--- a/hw/virtio-9p-debug.c
+++ b/hw/virtio-9p-debug.c
@@ -29,92 +29,121 @@ static struct iovec *get_sg(V9fsPDU *pdu, int rx)
     return pdu->elem.out_sg;
 }
 
+static int get_sg_count(V9fsPDU *pdu, int rx)
+{
+    if (rx)
+        return pdu->elem.in_num;
+    return pdu->elem.out_num;
+
+}
+
 static void pprint_int8(V9fsPDU *pdu, int rx, size_t *offsetp,
                         const char *name)
 {
-    struct iovec *sg = get_sg(pdu, rx);
+    size_t copied;
+    int count = get_sg_count(pdu, rx);
     size_t offset = *offsetp;
+    struct iovec *sg = get_sg(pdu, rx);
     int8_t value;
 
-    BUG_ON((offset + sizeof(value)) > sg[0].iov_len);
+    copied = do_pdu_unpack(&value, sg, count, offset, sizeof(value));
 
-    memcpy(&value, sg[0].iov_base + offset, sizeof(value));
+    BUG_ON(copied != sizeof(value));
     offset += sizeof(value);
-
     fprintf(llogfile, "%s=0x%x", name, value);
-
     *offsetp = offset;
 }
 
 static void pprint_int16(V9fsPDU *pdu, int rx, size_t *offsetp,
                         const char *name)
 {
+    size_t copied;
+    int count = get_sg_count(pdu, rx);
     struct iovec *sg = get_sg(pdu, rx);
     size_t offset = *offsetp;
     int16_t value;
 
-    BUG_ON((offset + sizeof(value)) > sg[0].iov_len);
 
-    memcpy(&value, sg[0].iov_base + offset, sizeof(value));
-    offset += sizeof(value);
+    copied = do_pdu_unpack(&value, sg, count, offset, sizeof(value));
 
+    BUG_ON(copied != sizeof(value));
+    offset += sizeof(value);
     fprintf(llogfile, "%s=0x%x", name, value);
-
     *offsetp = offset;
 }
 
 static void pprint_int32(V9fsPDU *pdu, int rx, size_t *offsetp,
                         const char *name)
 {
+    size_t copied;
+    int count = get_sg_count(pdu, rx);
     struct iovec *sg = get_sg(pdu, rx);
     size_t offset = *offsetp;
     int32_t value;
 
-    BUG_ON((offset + sizeof(value)) > sg[0].iov_len);
 
-    memcpy(&value, sg[0].iov_base + offset, sizeof(value));
-    offset += sizeof(value);
+    copied = do_pdu_unpack(&value, sg, count, offset, sizeof(value));
 
+    BUG_ON(copied != sizeof(value));
+    offset += sizeof(value);
     fprintf(llogfile, "%s=0x%x", name, value);
-
     *offsetp = offset;
 }
 
 static void pprint_int64(V9fsPDU *pdu, int rx, size_t *offsetp,
                         const char *name)
 {
+    size_t copied;
+    int count = get_sg_count(pdu, rx);
     struct iovec *sg = get_sg(pdu, rx);
     size_t offset = *offsetp;
     int64_t value;
 
-    BUG_ON((offset + sizeof(value)) > sg[0].iov_len);
 
-    memcpy(&value, sg[0].iov_base + offset, sizeof(value));
-    offset += sizeof(value);
+    copied = do_pdu_unpack(&value, sg, count, offset, sizeof(value));
 
+    BUG_ON(copied != sizeof(value));
+    offset += sizeof(value);
     fprintf(llogfile, "%s=0x%" PRIx64, name, value);
-
     *offsetp = offset;
 }
 
 static void pprint_str(V9fsPDU *pdu, int rx, size_t *offsetp, const char *name)
 {
+    int sg_count = get_sg_count(pdu, rx);
     struct iovec *sg = get_sg(pdu, rx);
     size_t offset = *offsetp;
-    int16_t size;
+    uint16_t tmp_size, size;
     size_t result;
+    size_t copied = 0;
+    int i = 0;
 
-    BUG_ON((offset + 2) > sg[0].iov_len);
-    memcpy(&size, sg[0].iov_base + offset, 2);
-    offset += 2;
+    /* get the size */
+    copied = do_pdu_unpack(&tmp_size, sg, sg_count, offset, sizeof(tmp_size));
+    BUG_ON(copied != sizeof(tmp_size));
+    size = le16_to_cpupu(&tmp_size);
+    offset += copied;
 
-    BUG_ON((offset + size) > sg[0].iov_len);
     fprintf(llogfile, "%s=", name);
-    result = fwrite(sg[0].iov_base + offset, 1, size, llogfile);
-    BUG_ON(result != size);
-    offset += size;
-
-    *offsetp = offset;
+    for (i = 0; size && i < sg_count; i++) {
+        size_t len;
+        if (offset >= sg[i].iov_len) {
+            /* skip this sg */
+            offset -= sg[i].iov_len;
+            continue;
+        } else {
+            len = MIN(sg[i].iov_len - offset, size);
+            result = fwrite(sg[i].iov_base + offset, 1, len, llogfile);
+            BUG_ON(result != len);
+            size -= len;
+            copied += len;
+            if (size) {
+                offset = 0;
+                continue;
+            }
+        }
+    }
+    *offsetp += copied;
 }
 
 static void pprint_qid(V9fsPDU *pdu, int rx, size_t *offsetp, const char *name)
diff --git a/hw/virtio-9p.c b/hw/virtio-9p.c
index 3a5b3f0..1237bac 100644
--- a/hw/virtio-9p.c
+++ b/hw/virtio-9p.c
@@ -351,42 +351,51 @@ static void free_pdu(V9fsState *s, V9fsPDU *pdu)
     }
 }
 
-static size_t pdu_unpack(void *dst, V9fsPDU *pdu, size_t offset, size_t size)
-{
-    struct iovec *sg = pdu->elem.out_sg;
-    BUG_ON((offset + size) > sg[0].iov_len);
-    memcpy(dst, sg[0].iov_base + offset, size);
-    return size;
-}
-
-/* FIXME i can do this with less variables */
-static size_t pdu_pack(V9fsPDU *pdu, size_t offset, const void *src,
-							size_t size)
+size_t pdu_packunpack(void *addr, struct iovec *sg, int sg_count,
+                        size_t offset, size_t size, int pack)
 {
-    struct iovec *sg = pdu->elem.in_sg;
-    size_t off = 0;
-    size_t copied = 0;
     int i = 0;
+    size_t copied = 0;
 
-    for (i = 0; size && i < pdu->elem.in_num; i++) {
+    for (i = 0; size && i < sg_count; i++) {
         size_t len;
+        if (offset >= sg[i].iov_len) {
+            /* skip this sg */
+            offset -= sg[i].iov_len;
+            continue;
+        } else {
 
-        if (offset >= off && offset < (off + sg[i].iov_len)) {
-            len = MIN(sg[i].iov_len - (offset - off), size);
-            memcpy(sg[i].iov_base + (offset - off), src, len);
+            len = MIN(sg[i].iov_len - offset, size);
+            if (pack) {
+                memcpy(sg[i].iov_base + offset, addr, len);
+            } else {
+                memcpy(addr, sg[i].iov_base + offset, len);
+            }
             size -= len;
-            offset += len;
-            off = offset;
             copied += len;
-            src += len;
-        } else {
-            off += sg[i].iov_len;
+            addr += len;
+            if (size) {
+                offset = 0;
+                continue;
+            }
         }
     }
-
     return copied;
 }
 
+static size_t pdu_unpack(void *dst, V9fsPDU *pdu, size_t offset, size_t size)
+{
+    return pdu_packunpack(dst, pdu->elem.out_sg, pdu->elem.out_num,
+                         offset, size, 0);
+}
+
+static size_t pdu_pack(V9fsPDU *pdu, size_t offset, const void *src,
+							size_t size)
+{
+    return pdu_packunpack((void *)src, pdu->elem.in_sg, pdu->elem.in_num,
+                             offset, size, 1);
+}
+
 static int pdu_copy_sg(V9fsPDU *pdu, size_t offset, int rx, struct iovec *sg)
 {
     size_t pos = 0;
diff --git a/hw/virtio-9p.h b/hw/virtio-9p.h
index da0aa64..81c2c59 100644
--- a/hw/virtio-9p.h
+++ b/hw/virtio-9p.h
@@ -187,5 +187,14 @@ typedef struct V9fsPosixFileOpertions
 } V9fsPosixFileOperations;
 
 V9fsPosixFileOperations *virtio_9p_init_local(const char *path);
+extern size_t pdu_packunpack(void *addr, struct iovec *sg, int sg_count,
+                            size_t offset, size_t size, int pack);
+
+static inline size_t do_pdu_unpack(void *dst, struct iovec *sg, int sg_count,
+                        size_t offset, size_t size)
+{
+    return pdu_packunpack(dst, sg, sg_count, offset, size, 0);
+}
+
 
 #endif
-- 
1.7.0.2.323.g0d092