Implement minimal depmod-compatible applet for vx

- Added depmod.cpp to scan kernel module ELF files, read .modinfo, and emit metadata files.
- Implemented functionality to write binary trie indexes for libkmod/modprobe.
- Introduced command-line options for module processing.
- Created test script test_depmod.sh to verify help and version commands.

README.md

@@ -14,6 +14,7 @@ It bundles a growing set of FreeBSD-derived userland tools into a single `vx` bi
 - `find`
 - `xargs`
 - `lspci`, `setpci`
+- `depmod`
 
 ## Build
 

meson.build

@@ -1,7 +1,8 @@
-project('vx', 'c',
+project('vx', 'c', 'cpp',
   version : '0.2.0',
   default_options : [
     'c_std=c11',
+    'cpp_std=c++17',
     'warning_level=2',
   ],
 )
@@ -19,6 +20,7 @@ all_utils = [
   'xargs',
   'lspci',
   'setpci',
+  'depmod',
 ]
 
 requested_utils = get_option('utils')
@@ -45,6 +47,7 @@ enable_find = enabled_utils.contains('find')
 enable_xargs = enabled_utils.contains('xargs')
 enable_lspci = enabled_utils.contains('lspci')
 enable_setpci = enabled_utils.contains('setpci')
+enable_depmod = enabled_utils.contains('depmod')
 
 vx_cfg = configuration_data()
 vx_cfg.set10('VX_ENABLE_PATCH', enable_patch)
@@ -59,6 +62,7 @@ vx_cfg.set10('VX_ENABLE_FIND', enable_find)
 vx_cfg.set10('VX_ENABLE_XARGS', enable_xargs)
 vx_cfg.set10('VX_ENABLE_LSPCI', enable_lspci)
 vx_cfg.set10('VX_ENABLE_SETPCI', enable_setpci)
+vx_cfg.set10('VX_ENABLE_DEPMOD', enable_depmod)
 configure_file(output : 'vx-config.h', configuration : vx_cfg)
 
 # --- Portability shim for building BSD userland on Linux ---
@@ -163,6 +167,10 @@ setpci_src = files(
   'src/pci/setpci.c',
 )
 
+depmod_src = files(
+  'src/depmod/depmod.cpp',
+)
+
 pci_inc = include_directories('src/pci')
 
 gzip_defines = [
@@ -248,6 +256,11 @@ if enable_setpci
   vx_sources += setpci_src
 endif
 
+if enable_depmod
+  vx_sources += depmod_src
+  vx_dependencies += [dependency('zlib'), dependency('libzstd')]
+endif
+
 vx = executable('vx',
   vx_sources,
   include_directories : vx_include_dirs,
@@ -295,6 +308,9 @@ endif
 if enable_setpci
   install_applets += ['setpci']
 endif
+if enable_depmod
+  install_applets += ['depmod']
+endif
 
 foreach name : install_applets
   meson.add_install_script('sh', '-c',
@@ -348,6 +364,9 @@ endif
 if enable_setpci
   manpages += ['src/pci/setpci.8']
 endif
+if enable_depmod
+  manpages += ['src/depmod/depmod.8']
+endif
 
 install_man(manpages)
 
@@ -409,6 +428,9 @@ endif
 if enable_setpci
   test_targets += ['test_setpci']
 endif
+if enable_depmod
+  test_targets += ['test_depmod']
+endif
 
 foreach t : test_targets
   test(t, find_program('tests/' + t + '.sh'),

meson_options.txt

@@ -15,6 +15,7 @@ option('utils',
     'xargs',
     'lspci',
     'setpci',
+    'depmod',
   ],
   description : 'Utilities to include in vx (default: all)'
 )

src/depmod/depmod.8

@@ -0,0 +1,69 @@
+.Dd July 8, 2026
+.Dt DEPMOD 8
+.Os
+.Sh NAME
+.Nm depmod
+.Nd generate Linux kernel module dependency metadata
+.Sh SYNOPSIS
+.Nm
+.Op Fl aAenvwVh
+.Op Fl b Ar basedir
+.Op Fl m Ar moduledir
+.Op Fl o Ar outdir
+.Op Fl C Ar config
+.Op Fl E Ar Module.symvers
+.Op Fl F Ar System.map
+.Op Fl P Ar prefix
+.Op Ar version
+.Op Ar module ...
+.Sh DESCRIPTION
+The
+.Nm
+applet scans Linux kernel modules below
+.Pa /lib/modules/<version>
+and writes the usual module metadata files, including
+.Pa modules.dep ,
+.Pa modules.alias ,
+.Pa modules.symbols ,
+and the matching kmod binary index files.
+.Pp
+This implementation is intentionally small and does not use libkmod.  It reads
+uncompressed modules plus gzip and zstd compressed modules.
+.Sh OPTIONS
+.Bl -tag -width Ds
+.It Fl a , Fl -all
+Scan all modules.  This is the default when no module files are named.
+.It Fl A , Fl -quick
+Exit without regenerating output when
+.Pa modules.dep
+is newer than the scanned modules.
+.It Fl b Ar basedir , Fl -basedir Ns = Ns Ar basedir
+Use
+.Ar basedir
+as the input root.
+.It Fl m Ar moduledir , Fl -moduledir Ns = Ns Ar moduledir
+Use a module directory other than
+.Pa /lib/modules .
+.It Fl o Ar outdir , Fl -outdir Ns = Ns Ar outdir
+Use
+.Ar outdir
+as the output root.
+.It Fl n , Fl -show , Fl -dry-run
+Print text output to standard output instead of writing files.
+.It Fl e , Fl -errsyms
+Warn about unresolved module dependencies and symbols.
+.It Fl P Ar prefix , Fl -symbol-prefix Ns = Ns Ar prefix
+Ignore an architecture symbol prefix while matching symbols.
+.It Fl V , Fl -version
+Print version information.
+.It Fl h , Fl -help
+Print usage information.
+.El
+.Sh COMPATIBILITY
+The options
+.Fl C ,
+.Fl E ,
+and
+.Fl F
+are accepted for command-line compatibility, but this implementation does not
+parse depmod.d configuration, Module.symvers, or System.map content.

src/main.c

@@ -41,6 +41,9 @@ int lspci_main(int argc, char *argv[]);
 #if VX_ENABLE_SETPCI
 int setpci_main(int argc, char *argv[]);
 #endif
+#if VX_ENABLE_DEPMOD
+int depmod_main(int argc, char *argv[]);
+#endif
 
 struct applet {
 	const char *name;
@@ -91,6 +94,9 @@ static const struct applet applets[] = {
 #if VX_ENABLE_SETPCI
 	{ "setpci", setpci_main },
 #endif
+#if VX_ENABLE_DEPMOD
+	{ "depmod", depmod_main },
+#endif
 };
 
 static const size_t n_applets = sizeof(applets) / sizeof(applets[0]);

tests/test_depmod.sh

@@ -0,0 +1,4 @@
+#!/bin/sh
+set -eu
+"$VX" depmod --help >/dev/null
+"$VX" depmod --version >/dev/null