libext2fs: add test facility UNIX_IO_FORCE_BOUNCE in unix_io.c

If the UNIX_IO_FORCE_BOUNCE environment is set, all I/O will be sent
through the bounce buffer code paths for debugging / testing purposes.

Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/lib/ext2fs/ext2_io.h b/lib/ext2fs/ext2_io.h
index 3a07b5d..6b7e977 100644 (file)
--- a/lib/ext2fs/ext2_io.h
+++ b/lib/ext2fs/ext2_io.h
@@ -101,6 +101,7 @@ struct struct_io_manager {
 #define IO_FLAG_RW             0x0001
 #define IO_FLAG_EXCLUSIVE      0x0002
 #define IO_FLAG_DIRECT_IO      0x0004
+#define IO_FLAG_FORCE_BOUNCE   0x0008
 
 /*
  * Convenience functions....

diff --git a/lib/ext2fs/unix_io.c b/lib/ext2fs/unix_io.c
index eee5566..ec92bf5 100644 (file)
--- a/lib/ext2fs/unix_io.c
+++ b/lib/ext2fs/unix_io.c
@@ -53,6 +53,11 @@
 #ifdef HAVE_SYS_MOUNT_H
 #include <sys/mount.h>
 #endif
+#ifdef HAVE_SYS_PRCTL_H
+#include <sys/prctl.h>
+#else
+#define PR_GET_DUMPABLE 3
+#endif
 #if HAVE_SYS_STAT_H
 #include <sys/stat.h>
 #endif
@@ -122,6 +127,29 @@ static errcode_t unix_get_stats(io_channel channel, io_stats *stats)
        return retval;
 }
 
+static char *safe_getenv(const char *arg)
+{
+       if ((getuid() != geteuid()) || (getgid() != getegid()))
+               return NULL;
+#ifdef HAVE_PRCTL
+       if (prctl(PR_GET_DUMPABLE, 0, 0, 0, 0) == 0)
+               return NULL;
+#else
+#if (defined(linux) && defined(SYS_prctl))
+       if (syscall(SYS_prctl, PR_GET_DUMPABLE, 0, 0, 0, 0) == 0)
+               return NULL;
+#endif
+#endif
+
+#if defined(HAVE_SECURE_GETENV)
+       return secure_getenv(arg);
+#elif defined(HAVE___SECURE_GETENV)
+       return __secure_getenv(arg);
+#else
+       return getenv(arg);
+#endif
+}
+
 /*
  * Here are the raw I/O functions
  */
@@ -140,6 +168,14 @@ static errcode_t raw_read_blk(io_channel channel,
        data->io_stats.bytes_read += size;
        location = ((ext2_loff_t) block * channel->block_size) + data->offset;
 
+       if (data->flags & IO_FLAG_FORCE_BOUNCE) {
+               if (ext2fs_llseek(data->dev, location, SEEK_SET) != location) {
+                       retval = errno ? errno : EXT2_ET_LLSEEK_FAILED;
+                       goto error_out;
+               }
+               goto bounce_read;
+       }
+
 #ifdef HAVE_PREAD64
        /* Try an aligned pread */
        if ((channel->align == 0) ||
@@ -188,6 +224,7 @@ static errcode_t raw_read_blk(io_channel channel,
         * The buffer or size which we're trying to read isn't aligned
         * to the O_DIRECT rules, so we need to do this the hard way...
         */
+bounce_read:
        while (size > 0) {
                actual = read(data->dev, data->bounce, channel->block_size);
                if (actual != channel->block_size)
@@ -232,6 +269,14 @@ static errcode_t raw_write_blk(io_channel channel,
 
        location = ((ext2_loff_t) block * channel->block_size) + data->offset;
 
+       if (data->flags & IO_FLAG_FORCE_BOUNCE) {
+               if (ext2fs_llseek(data->dev, location, SEEK_SET) != location) {
+                       retval = errno ? errno : EXT2_ET_LLSEEK_FAILED;
+                       goto error_out;
+               }
+               goto bounce_write;
+       }
+
 #ifdef HAVE_PWRITE64
        /* Try an aligned pwrite */
        if ((channel->align == 0) ||
@@ -278,6 +323,7 @@ static errcode_t raw_write_blk(io_channel channel,
         * The buffer or size which we're trying to write isn't aligned
         * to the O_DIRECT rules, so we need to do this the hard way...
         */
+bounce_write:
        while (size > 0) {
                if (size < channel->block_size) {
                        actual = read(data->dev, data->bounce,
@@ -336,7 +382,7 @@ static errcode_t alloc_cache(io_channel channel,
                if (retval)
                        return retval;
        }
-       if (channel->align) {
+       if (channel->align || data->flags & IO_FLAG_FORCE_BOUNCE) {
                if (data->bounce)
                        ext2fs_free_mem(&data->bounce);
                retval = io_channel_alloc_buf(channel, 0, &data->bounce);
@@ -496,6 +542,9 @@ static errcode_t unix_open_channel(const char *name, int fd,
        struct          utsname ut;
 #endif
 
+       if (safe_getenv("UNIX_IO_FORCE_BOUNCE"))
+               flags |= IO_FLAG_FORCE_BOUNCE;
+
        retval = ext2fs_get_mem(sizeof(struct struct_io_channel), &io);
        if (retval)
                goto cleanup;
@@ -1043,7 +1092,7 @@ static errcode_t unix_zeroout(io_channel channel, unsigned long long block,
        data = (struct unix_private_data *) channel->private_data;
        EXT2_CHECK_MAGIC(data, EXT2_ET_MAGIC_UNIX_IO_CHANNEL);
 
-       if (getenv("UNIX_IO_NOZEROOUT"))
+       if (safe_getenv("UNIX_IO_NOZEROOUT"))
                goto unimplemented;
 
        if (channel->flags & CHANNEL_FLAGS_BLOCK_DEVICE) {