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| # IVM Filesystem | ||
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| ## Introduction | ||
| This static filesystem generator allows to recreate a read/write | ||
| in-ram file system for testing the ivm64 ecosystem. | ||
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| By invoking the script ```ivm64-fsgen``` with the list of files to include in the filesystem, | ||
| it will print to stdout a C code with the file contents and some primitives | ||
| (open, read, lseek, ...) to access the files: | ||
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| ```ivm64-fsgen file1.c file2.c ... > ivmfs.c``` | ||
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| Note that files or directories are added individually to the filesystem and, therefore, to add a folder recursively you may wish to do: | ||
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| ```ivm64-fsgen $(find folder_name) ... > ivmfs.c``` | ||
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| ## Compiling | ||
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| Once the filesystem is generate, you can link a program with the generated C containing the filesystem, so that the primitives included in it will replace those of newlib, therefore enabling to access the | ||
| files in a stardard way: | ||
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| ```ivm64-gcc ivmfs.c main.c ``` ``` #compile ivmfs.c before libraries``` | ||
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| where main.c can be like this: | ||
| ``` | ||
| main(){ | ||
| FILE *f = fopen("file1.txt", "r"); | ||
| int n = fread(buff, 1, 5, f); | ||
| ... | ||
| } | ||
| ``` | ||
| ## Directories | ||
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| By default the current work directory of the generated ivm filesystem is ```/work```. In this way, when it is invoked ```ivm64-fsgen filename```, with ```filename``` a file in the current work directory, it will be mapped in the ivm filesystem with the path ```/work/filename```. | ||
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| The initial working directory is therefore ```/work``` (except when there are no files coming from the current directory in which case the working directory may be ```/```). | ||
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| On the other hand, if the file name is an absolute path, the path is considered part of the name, and the corresponding directories are (re)created. So when you use ```ivm64-fsgen /path/to/file```, the file can be opened as ```open("/path/to/file",...)```, or alternatively, you can do ```chdir("/path/to"); open("file", ...)```. | ||
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| Here is an example of the mapping: | ||
| ```sh | ||
| # The following code generates this ivmfs tree: | ||
| # / | ||
| # ├── etc | ||
| # │ └── services | ||
| # └── work | ||
| # ├── d | ||
| # │ └── file2 | ||
| # └── file1 | ||
| cd /tmp/ | ||
| touch file1 | ||
| mkdir d | ||
| touch d/file2 | ||
| # Let's include some files in the current directory and another absolute path: | ||
| # file1, d/file2 are relative to the working directory: mapped to /work | ||
| # /etc/services is absolute | ||
| ivm64-fsgen file1 d/file2 /etc/services > ivmfs.c | ||
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| ``` | ||
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| ## Standard input | ||
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| By default, the operations on the _standard input_ proceed with the current standard input of the console where the simulator is executed. The same happens with _standard_ and _error output_ streams. | ||
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| Nevertheless, the stdin can be simulated using the file defined by the macro STDIN_FILE ("stdin" by default). In this case, if a program requires the _standard input_, it will use the content of "stdin". Basically the file STDIN_FILE is redirected to the standard input (if included in the filesystem). To this end, this script should be invoked as: | ||
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| ```ivm64-fsgen stdin file1.c file2.c ... > ivmfs.c ``` | ||
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| ## Compilation options | ||
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| ```ivm64-gcc -DIVMFS_DEBUG ivmfs.c ... # print information for each file operation ``` | ||
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| ```ivm64-gcc -DIVMFS_DUMPFILES ivmfs.c ... # dump a list of files when the program exits ``` | ||
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| ```ivm64-gcc -DIVMFS_DUMPFILECONTENTS ivmfs.c ... # dump the contents of all files when the program exits ``` | ||
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| ## Coverage | ||
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| This is a list of low-level primitives that are supported: | ||
| ``` | ||
| open openat close read write lseek | ||
| stat fstat lstat fstatat access faccessat | ||
| getcwd get_current_dir_name isatty | ||
| truncate ftruncate | ||
| mkdir mkdirat chdir fchdir getdents | ||
| unlink unlinkat rmdir | ||
| rename renameat symlink symlinkat dup dup2 | ||
| readlink readlinkat realpath | ||
| ``` | ||
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| In addition to these, common higher filesystem functions from the C standard | ||
| library implemented by newlib can be used in your C codes, such as: | ||
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| ``` | ||
| fopen fclose fread fwrite fileno feof | ||
| printf scanf fscanf fprintf | ||
| opendir readdir scandir dirfd, ... | ||
| ``` | ||
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| Developers need keep in mind that this filesystem provides a **relaxed** implementation of the primitives, so all the potential described in POSIX manuals may not be available. | ||
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| Hard links and special file types are not yet supported. File permissions and ownership are not available either. | ||
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| Date: Nov 2023 |
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