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Exploring ideas for static configuration

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As an embedded library, littlefs's configuration straddles two worlds.
In most cases the configuration is usually constant at build time, but
when integrated into OSs, the configuration needs to be dynamically
configurable.

To help with this, littlefs has a separate lfs_config struct that can be
placed into ROM when possible.

But you know what's better than ROM configuration? Truely inlinable
static configuration known at compile-time. In addition to avoiding the
RAM cost, compile-time configuration allows for additional compiler
optimizations, such as constexpr-elimination and removal of unused
code-paths.

So how to enable static configuration?

1. define LFS_STATICCFG
2. implement callbacks as global functions:
   - lfs_read
   - lfs_prog
   - lfs_erase
   - lfs_sync
2. define the now-required constants that configure littlefs:
   - LFS_READ_SIZE
   - LFS_PROG_SIZE
   - LFS_BLOCK_SIZE
   - LFS_BLOCK_COUNT
   - LFS_BLOCK_CYCLES
   - LFS_CACHE_SIZE
   - LFS_LOOKAHEAD_SIZE
   - LFS_READ_BUFFER (optional)
   - LFS_PROG_BUFFER (optional)
   - LFS_LOOKAHEAD_BUFFER (optional)
   - LFS_NAME_MAX (optional)
   - LFS_FILE_MAX (optional)
   - LFS_ATTR_MAX (optional)

Note, there is a separate configuration for the file configuration, this
can be enabled/disabled independently of LFS_STATICCFG. You will likely
want to define this as well if you are looking for the smallest code
size.

In order to avoid a mess of #ifdefs, the internals of littlefs use a
simple macro that redirects to either the dynamic or static config at
compile time:

    #ifdef LFS_STATICCFG
    #define LFS_CFG_READ_SIZE(lfs) ((void)lfs, LFS_READ_SIZE)
    #else
    #define LFS_CFG_READ_SIZE(lfs) lfs->cfg->read_size
    #endif

Unfortunately it does look like there still may be a lot of issues
related to warnings of comparisons against constants... If only C had
a way to ignore warnings on individual statements...

Original idea by apmorton
This commit is contained in:
Christopher Haster
2020-11-23 00:53:07 -06:00
parent ef9ba2d912
commit c44427f9ec
18 changed files with 873 additions and 627 deletions
Download Patch File Download Diff File Expand all files Collapse all files
tests/test_evil.toml
+37 -29
View File
@@ -9,10 +9,11 @@ define.INVALSET = [0x3, 0x1, 0x2]
in = "lfs.c"
code = '''
// create littlefs
lfs_format(&lfs, &cfg) => 0;
lfs_formatcfg(&lfs, &cfg) => 0;
// change tail-pointer to invalid pointers
lfs_init(&lfs, &cfg) => 0;
lfs.cfg = &cfg;
lfs_initcommon(&lfs) => 0;
lfs_mdir_t mdir;
lfs_dir_fetch(&lfs, &mdir, (lfs_block_t[2]){0, 1}) => 0;
lfs_dir_commit(&lfs, &mdir, LFS_MKATTRS(
@@ -23,7 +24,7 @@ code = '''
lfs_deinit(&lfs) => 0;
// test that mount fails gracefully
lfs_mount(&lfs, &cfg) => LFS_ERR_CORRUPT;
lfs_mountcfg(&lfs, &cfg) => LFS_ERR_CORRUPT;
'''
[[case]] # invalid dir pointer test
@@ -31,14 +32,15 @@ define.INVALSET = [0x3, 0x1, 0x2]
in = "lfs.c"
code = '''
// create littlefs
lfs_format(&lfs, &cfg) => 0;
lfs_formatcfg(&lfs, &cfg) => 0;
// make a dir
lfs_mount(&lfs, &cfg) => 0;
lfs_mountcfg(&lfs, &cfg) => 0;
lfs_mkdir(&lfs, "dir_here") => 0;
lfs_unmount(&lfs) => 0;
// change the dir pointer to be invalid
lfs_init(&lfs, &cfg) => 0;
lfs.cfg = &cfg;
lfs_initcommon(&lfs) => 0;
lfs_mdir_t mdir;
lfs_dir_fetch(&lfs, &mdir, (lfs_block_t[2]){0, 1}) => 0;
// make sure id 1 == our directory
@@ -57,7 +59,7 @@ code = '''
// test that accessing our bad dir fails, note there's a number
// of ways to access the dir, some can fail, but some don't
lfs_mount(&lfs, &cfg) => 0;
lfs_mountcfg(&lfs, &cfg) => 0;
lfs_stat(&lfs, "dir_here", &info) => 0;
assert(strcmp(info.name, "dir_here") == 0);
assert(info.type == LFS_TYPE_DIR);
@@ -77,16 +79,17 @@ in = "lfs.c"
define.SIZE = [10, 1000, 100000] # faked file size
code = '''
// create littlefs
lfs_format(&lfs, &cfg) => 0;
lfs_formatcfg(&lfs, &cfg) => 0;
// make a file
lfs_mount(&lfs, &cfg) => 0;
lfs_mountcfg(&lfs, &cfg) => 0;
lfs_file_open(&lfs, &file, "file_here",
LFS_O_WRONLY | LFS_O_CREAT) => 0;
lfs_file_close(&lfs, &file) => 0;
lfs_unmount(&lfs) => 0;
// change the file pointer to be invalid
lfs_init(&lfs, &cfg) => 0;
lfs.cfg = &cfg;
lfs_initcommon(&lfs) => 0;
lfs_mdir_t mdir;
lfs_dir_fetch(&lfs, &mdir, (lfs_block_t[2]){0, 1}) => 0;
// make sure id 1 == our file
@@ -103,7 +106,7 @@ code = '''
// test that accessing our bad file fails, note there's a number
// of ways to access the dir, some can fail, but some don't
lfs_mount(&lfs, &cfg) => 0;
lfs_mountcfg(&lfs, &cfg) => 0;
lfs_stat(&lfs, "file_here", &info) => 0;
assert(strcmp(info.name, "file_here") == 0);
assert(info.type == LFS_TYPE_REG);
@@ -125,9 +128,9 @@ define.SIZE = ['2*LFS_BLOCK_SIZE', '3*LFS_BLOCK_SIZE', '4*LFS_BLOCK_SIZE']
in = "lfs.c"
code = '''
// create littlefs
lfs_format(&lfs, &cfg) => 0;
lfs_formatcfg(&lfs, &cfg) => 0;
// make a file
lfs_mount(&lfs, &cfg) => 0;
lfs_mountcfg(&lfs, &cfg) => 0;
lfs_file_open(&lfs, &file, "file_here",
LFS_O_WRONLY | LFS_O_CREAT) => 0;
for (int i = 0; i < SIZE; i++) {
@@ -137,7 +140,8 @@ code = '''
lfs_file_close(&lfs, &file) => 0;
lfs_unmount(&lfs) => 0;
// change pointer in CTZ skip-list to be invalid
lfs_init(&lfs, &cfg) => 0;
lfs.cfg = &cfg;
lfs_initcommon(&lfs) => 0;
lfs_mdir_t mdir;
lfs_dir_fetch(&lfs, &mdir, (lfs_block_t[2]){0, 1}) => 0;
// make sure id 1 == our file and get our CTZ structure
@@ -164,7 +168,7 @@ code = '''
// test that accessing our bad file fails, note there's a number
// of ways to access the dir, some can fail, but some don't
lfs_mount(&lfs, &cfg) => 0;
lfs_mountcfg(&lfs, &cfg) => 0;
lfs_stat(&lfs, "file_here", &info) => 0;
assert(strcmp(info.name, "file_here") == 0);
assert(info.type == LFS_TYPE_REG);
@@ -187,10 +191,11 @@ define.INVALSET = [0x3, 0x1, 0x2]
in = "lfs.c"
code = '''
// create littlefs
lfs_format(&lfs, &cfg) => 0;
lfs_formatcfg(&lfs, &cfg) => 0;
// create an invalid gstate
lfs_init(&lfs, &cfg) => 0;
lfs.cfg = &cfg;
lfs_initcommon(&lfs) => 0;
lfs_mdir_t mdir;
lfs_dir_fetch(&lfs, &mdir, (lfs_block_t[2]){0, 1}) => 0;
lfs_fs_prepmove(&lfs, 1, (lfs_block_t [2]){
@@ -202,7 +207,7 @@ code = '''
// test that mount fails gracefully
// mount may not fail, but our first alloc should fail when
// we try to fix the gstate
lfs_mount(&lfs, &cfg) => 0;
lfs_mountcfg(&lfs, &cfg) => 0;
lfs_mkdir(&lfs, "should_fail") => LFS_ERR_CORRUPT;
lfs_unmount(&lfs) => 0;
'''
@@ -213,10 +218,11 @@ code = '''
in = "lfs.c"
code = '''
// create littlefs
lfs_format(&lfs, &cfg) => 0;
lfs_formatcfg(&lfs, &cfg) => 0;
// change tail-pointer to point to ourself
lfs_init(&lfs, &cfg) => 0;
lfs.cfg = &cfg;
lfs_initcommon(&lfs) => 0;
lfs_mdir_t mdir;
lfs_dir_fetch(&lfs, &mdir, (lfs_block_t[2]){0, 1}) => 0;
lfs_dir_commit(&lfs, &mdir, LFS_MKATTRS(
@@ -225,20 +231,21 @@ code = '''
lfs_deinit(&lfs) => 0;
// test that mount fails gracefully
lfs_mount(&lfs, &cfg) => LFS_ERR_CORRUPT;
lfs_mountcfg(&lfs, &cfg) => LFS_ERR_CORRUPT;
'''
[[case]] # metadata-pair threaded-list 2-length loop test
in = "lfs.c"
code = '''
// create littlefs with child dir
lfs_format(&lfs, &cfg) => 0;
lfs_mount(&lfs, &cfg) => 0;
lfs_formatcfg(&lfs, &cfg) => 0;
lfs_mountcfg(&lfs, &cfg) => 0;
lfs_mkdir(&lfs, "child") => 0;
lfs_unmount(&lfs) => 0;
// find child
lfs_init(&lfs, &cfg) => 0;
lfs.cfg = &cfg;
lfs_initcommon(&lfs) => 0;
lfs_mdir_t mdir;
lfs_block_t pair[2];
lfs_dir_fetch(&lfs, &mdir, (lfs_block_t[2]){0, 1}) => 0;
@@ -255,20 +262,21 @@ code = '''
lfs_deinit(&lfs) => 0;
// test that mount fails gracefully
lfs_mount(&lfs, &cfg) => LFS_ERR_CORRUPT;
lfs_mountcfg(&lfs, &cfg) => LFS_ERR_CORRUPT;
'''
[[case]] # metadata-pair threaded-list 1-length child loop test
in = "lfs.c"
code = '''
// create littlefs with child dir
lfs_format(&lfs, &cfg) => 0;
lfs_mount(&lfs, &cfg) => 0;
lfs_formatcfg(&lfs, &cfg) => 0;
lfs_mountcfg(&lfs, &cfg) => 0;
lfs_mkdir(&lfs, "child") => 0;
lfs_unmount(&lfs) => 0;
// find child
lfs_init(&lfs, &cfg) => 0;
lfs.cfg = &cfg;
lfs_initcommon(&lfs) => 0;
lfs_mdir_t mdir;
lfs_block_t pair[2];
lfs_dir_fetch(&lfs, &mdir, (lfs_block_t[2]){0, 1}) => 0;
@@ -284,5 +292,5 @@ code = '''
lfs_deinit(&lfs) => 0;
// test that mount fails gracefully
lfs_mount(&lfs, &cfg) => LFS_ERR_CORRUPT;
lfs_mountcfg(&lfs, &cfg) => LFS_ERR_CORRUPT;
'''