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From 30e78b5a6fc16e3669f83b27e02c8eb53e646b48 Mon Sep 17 00:00:00 2001
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From: Kevin Wolf <kwolf@redhat.com>
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Date: Tue, 25 Mar 2014 14:23:17 +0100
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Subject: [PATCH 10/49] bochs: Unify header structs and make them QEMU_PACKED
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RH-Author: Kevin Wolf <kwolf@redhat.com>
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Message-id: <1395753835-7591-11-git-send-email-kwolf@redhat.com>
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Patchwork-id: n/a
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O-Subject: [virt-devel] [EMBARGOED RHEL-7.0 qemu-kvm PATCH 10/48] bochs: Unify header structs and make them QEMU_PACKED
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Bugzilla: 1066691
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RH-Acked-by: Jeff Cody <jcody@redhat.com>
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
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Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1066691
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Upstream status: Series embargoed
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This is an on-disk structure, so offsets must be accurate.
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Before this patch, sizeof(bochs) != sizeof(header_v1), which makes the
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memcpy() between both invalid. We're lucky enough that the destination
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buffer happened to be the larger one, and the memcpy size to be taken
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from the smaller one, so we didn't get a buffer overflow in practice.
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This patch unifies the both structures, eliminating the need to do a
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memcpy in the first place. The common fields are extracted to the top
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level of the struct and the actually differing part gets a union of the
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two versions.
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
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---
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 block/bochs.c |   67 +++++++++++++++++++++-----------------------------------
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 1 files changed, 25 insertions(+), 42 deletions(-)
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diff --git a/block/bochs.c b/block/bochs.c
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index 51d9a90..708780d 100644
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--- a/block/bochs.c
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+++ b/block/bochs.c
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@@ -39,45 +39,30 @@
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 // not allocated: 0xffffffff
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 // always little-endian
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-struct bochs_header_v1 {
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-    char magic[32]; // "Bochs Virtual HD Image"
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-    char type[16]; // "Redolog"
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-    char subtype[16]; // "Undoable" / "Volatile" / "Growing"
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-    uint32_t version;
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-    uint32_t header; // size of header
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-
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-    union {
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-	struct {
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-	    uint32_t catalog; // num of entries
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-	    uint32_t bitmap; // bitmap size
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-	    uint32_t extent; // extent size
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-	    uint64_t disk; // disk size
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-	    char padding[HEADER_SIZE - 64 - 8 - 20];
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-	} redolog;
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-	char padding[HEADER_SIZE - 64 - 8];
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-    } extra;
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-};
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-
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-// always little-endian
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 struct bochs_header {
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-    char magic[32]; // "Bochs Virtual HD Image"
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-    char type[16]; // "Redolog"
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-    char subtype[16]; // "Undoable" / "Volatile" / "Growing"
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+    char magic[32];     /* "Bochs Virtual HD Image" */
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+    char type[16];      /* "Redolog" */
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+    char subtype[16];   /* "Undoable" / "Volatile" / "Growing" */
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     uint32_t version;
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-    uint32_t header; // size of header
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+    uint32_t header;    /* size of header */
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+
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+    uint32_t catalog;   /* num of entries */
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+    uint32_t bitmap;    /* bitmap size */
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+    uint32_t extent;    /* extent size */
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     union {
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-	struct {
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-	    uint32_t catalog; // num of entries
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-	    uint32_t bitmap; // bitmap size
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-	    uint32_t extent; // extent size
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-	    uint32_t reserved; // for ???
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-	    uint64_t disk; // disk size
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-	    char padding[HEADER_SIZE - 64 - 8 - 24];
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-	} redolog;
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-	char padding[HEADER_SIZE - 64 - 8];
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+        struct {
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+            uint32_t reserved;  /* for ??? */
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+            uint64_t disk;      /* disk size */
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+            char padding[HEADER_SIZE - 64 - 20 - 12];
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+        } QEMU_PACKED redolog;
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+        struct {
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+            uint64_t disk;      /* disk size */
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+            char padding[HEADER_SIZE - 64 - 20 - 8];
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+        } QEMU_PACKED redolog_v1;
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+        char padding[HEADER_SIZE - 64 - 20];
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     } extra;
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-};
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+} QEMU_PACKED;
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 typedef struct BDRVBochsState {
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     CoMutex lock;
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@@ -114,7 +99,6 @@ static int bochs_open(BlockDriverState *bs, QDict *options, int flags,
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     BDRVBochsState *s = bs->opaque;
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     int i;
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     struct bochs_header bochs;
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-    struct bochs_header_v1 header_v1;
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     int ret;
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     bs->read_only = 1; // no write support yet
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@@ -133,13 +117,12 @@ static int bochs_open(BlockDriverState *bs, QDict *options, int flags,
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     }
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     if (le32_to_cpu(bochs.version) == HEADER_V1) {
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-      memcpy(&header_v1, &bochs, sizeof(bochs));
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-      bs->total_sectors = le64_to_cpu(header_v1.extra.redolog.disk) / 512;
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+        bs->total_sectors = le64_to_cpu(bochs.extra.redolog_v1.disk) / 512;
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     } else {
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-      bs->total_sectors = le64_to_cpu(bochs.extra.redolog.disk) / 512;
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+        bs->total_sectors = le64_to_cpu(bochs.extra.redolog.disk) / 512;
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     }
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-    s->catalog_size = le32_to_cpu(bochs.extra.redolog.catalog);
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+    s->catalog_size = le32_to_cpu(bochs.catalog);
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     s->catalog_bitmap = g_malloc(s->catalog_size * 4);
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     ret = bdrv_pread(bs->file, le32_to_cpu(bochs.header), s->catalog_bitmap,
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@@ -153,10 +136,10 @@ static int bochs_open(BlockDriverState *bs, QDict *options, int flags,
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     s->data_offset = le32_to_cpu(bochs.header) + (s->catalog_size * 4);
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-    s->bitmap_blocks = 1 + (le32_to_cpu(bochs.extra.redolog.bitmap) - 1) / 512;
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-    s->extent_blocks = 1 + (le32_to_cpu(bochs.extra.redolog.extent) - 1) / 512;
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+    s->bitmap_blocks = 1 + (le32_to_cpu(bochs.bitmap) - 1) / 512;
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+    s->extent_blocks = 1 + (le32_to_cpu(bochs.extent) - 1) / 512;
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-    s->extent_size = le32_to_cpu(bochs.extra.redolog.extent);
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+    s->extent_size = le32_to_cpu(bochs.extent);
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     qemu_co_mutex_init(&s->lock);
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     return 0;
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-- 
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1.7.1
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