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authorDavid Oberhollenzer <david.oberhollenzer@sigma-star.at>2019-10-07 11:20:55 +0200
committerDavid Oberhollenzer <david.oberhollenzer@sigma-star.at>2019-10-07 12:22:05 +0200
commita68eb730558fb90bc8d9524564d8f9e58f3ccac1 (patch)
treede7a678b28786ec2e47e4956d8cdb0f4466f3d5c
parentc7fdb2b305ed8b4deb67bfc6ef3257e7e6773397 (diff)
Improve ABI backward & forward compatibillity
- Padd the compressor config union - 128 bytes aught to be enough for everyone, i.e. future compressors. - Insist that the padding space is initialized to 0. If a field gets added to an existing compressor, it can test for 0 as a sentinel value. - Add a size field to the hook structure, aka "the Microsoft way". - The explanation is in the comment. - Don't make the Microsoft mistake of checking for >=, insist on *exact* size match. Future users will need a fallback if their hooks are rejected. But at least they will be rejected instead of silently not being used. - Add an unsupported flag check to the dir tree reader. - Add a basic abi unit test that, for now, checks the size of the compressor config struct fields. Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>
-rw-r--r--include/sqfs/compressor.h15
-rw-r--r--include/sqfs/data_writer.h19
-rw-r--r--include/sqfs/dir_reader.h2
-rw-r--r--lib/sqfs/comp/compressor.c30
-rw-r--r--lib/sqfs/data_writer/common.c8
-rw-r--r--lib/sqfs/read_tree.c3
-rw-r--r--lib/sqfshelper/statistics.c1
-rw-r--r--tests/Makemodule.am6
-rw-r--r--tests/abi.c25
9 files changed, 104 insertions, 5 deletions
diff --git a/include/sqfs/compressor.h b/include/sqfs/compressor.h
index 46bdf58..a53fbc1 100644
--- a/include/sqfs/compressor.h
+++ b/include/sqfs/compressor.h
@@ -100,6 +100,11 @@ struct sqfs_compressor_t {
* @struct sqfs_compressor_config_t
*
* @brief Configuration parameters for instantiating a compressor backend.
+ *
+ * The unused fields MUST be set to 0. The easiest way to do this is by always
+ * clearing the struct using memset before setting anything, or using
+ * @ref sqfs_compressor_config_init to set defaults and then modify the struct
+ * from there.
*/
struct sqfs_compressor_config_t {
/**
@@ -138,6 +143,8 @@ struct sqfs_compressor_config_t {
* Default is 15, i.e. 32k window.
*/
sqfs_u16 window_size;
+
+ sqfs_u32 padd0[3];
} gzip;
/**
@@ -150,6 +157,8 @@ struct sqfs_compressor_config_t {
* Default is 15.
*/
sqfs_u16 level;
+
+ sqfs_u16 padd0[7];
} zstd;
/**
@@ -174,6 +183,8 @@ struct sqfs_compressor_config_t {
* Defaults to 9, i.e. best compression.
*/
sqfs_u16 level;
+
+ sqfs_u32 padd0[3];
} lzo;
/**
@@ -190,7 +201,11 @@ struct sqfs_compressor_config_t {
* block size.
*/
sqfs_u32 dict_size;
+
+ sqfs_u32 padd0[3];
} xz;
+
+ sqfs_u64 padd0[2];
} opt;
};
diff --git a/include/sqfs/data_writer.h b/include/sqfs/data_writer.h
index 210a08d..4623493 100644
--- a/include/sqfs/data_writer.h
+++ b/include/sqfs/data_writer.h
@@ -59,6 +59,18 @@
*/
struct sqfs_block_hooks_t {
/**
+ * @brief Set this to the size of the struct.
+ *
+ * This is required for future expandabillity while maintaining ABI
+ * compatibillity. At the current time, the implementation of
+ * @ref sqfs_data_writer_set_hooks rejects any hook struct where this
+ * isn't the exact size. If new hooks are added in the future, the
+ * struct grows and the future implementation can tell by the size
+ * whether the application uses the new version or the old one.
+ */
+ size_t size;
+
+ /**
* @brief Gets called before writing a block to disk.
*
* If this is not NULL, it gets called before a block is written to
@@ -283,10 +295,13 @@ int sqfs_data_writer_write_fragment_table(sqfs_data_writer_t *proc,
* @param proc A pointer to a data writer object.
* @param user_ptr A user pointer to pass to the callbacks.
* @param hooks A structure containing the hooks.
+ *
+ * @return Zero on success, @ref SQFS_ERROR_UNSUPPORTED if the size field of
+ * the hooks doesn't match any size knwon to the library.
*/
SQFS_API
-void sqfs_data_writer_set_hooks(sqfs_data_writer_t *proc, void *user_ptr,
- const sqfs_block_hooks_t *hooks);
+int sqfs_data_writer_set_hooks(sqfs_data_writer_t *proc, void *user_ptr,
+ const sqfs_block_hooks_t *hooks);
#ifdef __cplusplus
}
diff --git a/include/sqfs/dir_reader.h b/include/sqfs/dir_reader.h
index 8377fdd..ec84d98 100644
--- a/include/sqfs/dir_reader.h
+++ b/include/sqfs/dir_reader.h
@@ -99,6 +99,8 @@ typedef enum {
* of parent nodes with the subtree stored at the end.
*/
SQFS_TREE_STORE_PARENTS = 0x40,
+
+ SQFS_TREE_ALL_FLAGS = 0x7F,
} E_SQFS_TREE_FILTER_FLAGS;
/**
diff --git a/lib/sqfs/comp/compressor.c b/lib/sqfs/comp/compressor.c
index bfc20b7..902ce92 100644
--- a/lib/sqfs/comp/compressor.c
+++ b/lib/sqfs/comp/compressor.c
@@ -87,12 +87,42 @@ bool sqfs_compressor_exists(E_SQFS_COMPRESSOR id)
sqfs_compressor_t *sqfs_compressor_create(const sqfs_compressor_config_t *cfg)
{
+ sqfs_u8 padd0[sizeof(cfg->opt)];
+ int ret;
+
if (cfg == NULL || cfg->id < SQFS_COMP_MIN || cfg->id > SQFS_COMP_MAX)
return NULL;
if (compressors[cfg->id] == NULL)
return NULL;
+ memset(padd0, 0, sizeof(padd0));
+
+ switch (cfg->id) {
+ case SQFS_COMP_XZ:
+ ret = memcmp(cfg->opt.xz.padd0, padd0,
+ sizeof(cfg->opt.xz.padd0));
+ break;
+ case SQFS_COMP_LZO:
+ ret = memcmp(cfg->opt.lzo.padd0, padd0,
+ sizeof(cfg->opt.lzo.padd0));
+ break;
+ case SQFS_COMP_ZSTD:
+ ret = memcmp(cfg->opt.zstd.padd0, padd0,
+ sizeof(cfg->opt.zstd.padd0));
+ break;
+ case SQFS_COMP_GZIP:
+ ret = memcmp(cfg->opt.gzip.padd0, padd0,
+ sizeof(cfg->opt.gzip.padd0));
+ break;
+ default:
+ ret = memcmp(cfg->opt.padd0, padd0, sizeof(cfg->opt.padd0));
+ break;
+ }
+
+ if (ret != 0)
+ return NULL;
+
return compressors[cfg->id](cfg);
}
diff --git a/lib/sqfs/data_writer/common.c b/lib/sqfs/data_writer/common.c
index 059ef41..a19eb6d 100644
--- a/lib/sqfs/data_writer/common.c
+++ b/lib/sqfs/data_writer/common.c
@@ -157,9 +157,13 @@ int sqfs_data_writer_write_fragment_table(sqfs_data_writer_t *proc,
return 0;
}
-void sqfs_data_writer_set_hooks(sqfs_data_writer_t *proc, void *user_ptr,
- const sqfs_block_hooks_t *hooks)
+int sqfs_data_writer_set_hooks(sqfs_data_writer_t *proc, void *user_ptr,
+ const sqfs_block_hooks_t *hooks)
{
+ if (hooks->size != sizeof(*hooks))
+ return SQFS_ERROR_UNSUPPORTED;
+
proc->hooks = hooks;
proc->user_ptr = user_ptr;
+ return 0;
}
diff --git a/lib/sqfs/read_tree.c b/lib/sqfs/read_tree.c
index 46c7ec0..3a43769 100644
--- a/lib/sqfs/read_tree.c
+++ b/lib/sqfs/read_tree.c
@@ -199,6 +199,9 @@ int sqfs_dir_reader_get_full_hierarchy(sqfs_dir_reader_t *rd,
const char *ptr;
int ret;
+ if (flags & ~SQFS_TREE_ALL_FLAGS)
+ return SQFS_ERROR_UNSUPPORTED;
+
ret = sqfs_dir_reader_get_root_inode(rd, &inode);
if (ret)
return ret;
diff --git a/lib/sqfshelper/statistics.c b/lib/sqfshelper/statistics.c
index 3f9f595..fb70615 100644
--- a/lib/sqfshelper/statistics.c
+++ b/lib/sqfshelper/statistics.c
@@ -55,6 +55,7 @@ static void notify_fragment_discard(void *user, const sqfs_block_t *block)
}
static const sqfs_block_hooks_t hooks = {
+ .size = sizeof(hooks),
.post_block_write = post_block_write,
.pre_fragment_store = pre_fragment_store,
.notify_blocks_erased = notify_blocks_erased,
diff --git a/tests/Makemodule.am b/tests/Makemodule.am
index d7f8013..8a2241f 100644
--- a/tests/Makemodule.am
+++ b/tests/Makemodule.am
@@ -70,6 +70,9 @@ test_str_table_SOURCES = tests/str_table.c
test_str_table_LDADD = libutil.la
test_str_table_CPPFLAGS = $(AM_CPPFLAGS) -DTESTPATH=$(top_srcdir)/tests
+test_abi_SOURCES = tests/abi.c
+test_abi_LDADD = libsquashfs.la
+
fstree_fuzz_SOURCES = tests/fstree_fuzz.c
fstree_fuzz_LDADD = libfstree.a libutil.la
@@ -83,6 +86,7 @@ check_PROGRAMS += test_fstree_from_file test_fstree_init
check_PROGRAMS += test_tar_ustar test_tar_pax test_tar_gnu test_tar_sparse_gnu
check_PROGRAMS += test_tar_sparse_gnu1 test_tar_sparse_gnu2
check_PROGRAMS += test_tar_xattr_bsd test_tar_xattr_schily test_str_table
+check_PROGRAMS += test_abi
noinst_PROGRAMS += fstree_fuzz tar_fuzz
@@ -92,6 +96,6 @@ TESTS += test_add_by_path test_get_path test_fstree_sort test_fstree_from_file
TESTS += test_fstree_init test_tar_ustar test_tar_pax
TESTS += test_tar_gnu test_tar_sparse_gnu test_tar_sparse_gnu1
TESTS += test_tar_sparse_gnu2 test_tar_xattr_bsd test_tar_xattr_schily
-TESTS += test_str_table
+TESTS += test_str_table test_abi
EXTRA_DIST += $(top_srcdir)/tests/tar $(top_srcdir)/tests/words.txt
diff --git a/tests/abi.c b/tests/abi.c
new file mode 100644
index 0000000..1601e0a
--- /dev/null
+++ b/tests/abi.c
@@ -0,0 +1,25 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+/*
+ * abi.c
+ *
+ * Copyright (C) 2019 David Oberhollenzer <goliath@infraroot.at>
+ */
+#include "config.h"
+
+#include "sqfs/compressor.h"
+
+#include <assert.h>
+#include <stdlib.h>
+
+int main(void)
+{
+ sqfs_compressor_config_t cfg;
+
+ assert(sizeof(cfg.opt.gzip) == sizeof(cfg.opt));
+ assert(sizeof(cfg.opt.zstd) == sizeof(cfg.opt));
+ assert(sizeof(cfg.opt.lzo) == sizeof(cfg.opt));
+ assert(sizeof(cfg.opt.xz) == sizeof(cfg.opt));
+ assert(sizeof(cfg.opt.padd0) == sizeof(cfg.opt));
+
+ return EXIT_SUCCESS;
+}