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Support Extended Modversions #270

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4e79a46
libkmod: Centralize modversions parsing
maurer Jan 3, 2025
ffe6c67
libkmod: Support EXTENDED_MODVERSIONS
maurer Dec 19, 2024
3eaf725
testsuite/test-modprobe: Test --show-modversions
maurer Dec 20, 2024
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195 changes: 126 additions & 69 deletions libkmod/libkmod-elf.c
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Original file line number Diff line number Diff line change
Expand Up @@ -33,6 +33,8 @@ enum kmod_elf_section {
KMOD_ELF_SECTION_STRTAB,
KMOD_ELF_SECTION_SYMTAB,
KMOD_ELF_SECTION_VERSIONS,
KMOD_ELF_SECTION_VERSION_EXT_NAMES,
KMOD_ELF_SECTION_VERSION_EXT_CRCS,
KMOD_ELF_SECTION_MAX,
};

Expand All @@ -42,6 +44,8 @@ static const char *const section_name_map[] = {
[KMOD_ELF_SECTION_STRTAB] = ".strtab",
[KMOD_ELF_SECTION_SYMTAB] = ".symtab",
[KMOD_ELF_SECTION_VERSIONS] = "__versions",
[KMOD_ELF_SECTION_VERSION_EXT_NAMES] = "__version_ext_names",
[KMOD_ELF_SECTION_VERSION_EXT_CRCS] = "__version_ext_crcs",
};

struct kmod_elf {
Expand Down Expand Up @@ -538,17 +542,15 @@ static inline void elf_get_modversion_lengths(const struct kmod_elf *elf, size_t
}
}

/* array will be allocated with strings in a single malloc, just free *array */
int kmod_elf_get_modversions(const struct kmod_elf *elf, struct kmod_modversion **array)
static int kmod_elf_get_basic_modversions(const struct kmod_elf *elf,
struct kmod_modversion **array)
{
size_t i, count, crclen, namlen, verlen;
uint64_t off, sec_off, size;
struct kmod_modversion *a;

elf_get_modversion_lengths(elf, &verlen, &crclen, &namlen);

*array = NULL;

sec_off = elf->sections[KMOD_ELF_SECTION_VERSIONS].offset;
size = elf->sections[KMOD_ELF_SECTION_VERSIONS].size;
if (sec_off == 0)
Expand Down Expand Up @@ -591,6 +593,86 @@ int kmod_elf_get_modversions(const struct kmod_elf *elf, struct kmod_modversion
return count;
}

static int kmod_elf_get_extended_modversions(const struct kmod_elf *elf,
struct kmod_modversion **array)
{
uint64_t name_off, name_size, crc_off, crc_size;
const char *name_cursor;
int count, i, ret;

name_off = elf->sections[KMOD_ELF_SECTION_VERSION_EXT_NAMES].offset;
name_size = elf->sections[KMOD_ELF_SECTION_VERSION_EXT_NAMES].size;
crc_off = elf->sections[KMOD_ELF_SECTION_VERSION_EXT_CRCS].offset;
crc_size = elf->sections[KMOD_ELF_SECTION_VERSION_EXT_CRCS].size;

if ((name_off == 0) || (crc_off == 0))
return -ENODATA;

if (crc_size == 0)
return 0;

if (crc_size % sizeof(uint32_t) != 0)
return -EINVAL;

count = crc_size / sizeof(uint32_t);
*array = malloc(sizeof(struct kmod_modversion) * count);
if (*array == NULL)
return -errno;

for (name_cursor = elf_get_mem(elf, name_off), i = 0; i < count; i++) {
size_t len;
uint32_t crc;

if (name_size == 0) {
ELFDBG(elf, "fewer symbol names than crcs\n");
ret = -EINVAL;
goto release_array;
}
len = strnlen(name_cursor, name_size);
if (len == name_size) {
ELFDBG(elf, "last symbol name not null-terminated\n");
ret = -EINVAL;
goto release_array;
}
crc = elf_get_uint(elf, crc_off, sizeof(uint32_t));

/* PPC sometimes prefixes names with `.` */
if (name_cursor[0] == '.') {
name_cursor++;
len--;
}

(*array)[i].crc = crc;
(*array)[i].bind = KMOD_SYMBOL_UNDEF;
(*array)[i].symbol = name_cursor;

/* len doesn't include the NUL, but our pointers and size do */
name_cursor += len + 1;
name_size -= len + 1;
crc_off += sizeof(uint32_t);
}

return count;

release_array:
free(*array);
return ret;
}

/* array will be allocated with strings in a single malloc, just free *array */
int kmod_elf_get_modversions(const struct kmod_elf *elf, struct kmod_modversion **array)
{
int ret;

*array = NULL;

ret = kmod_elf_get_extended_modversions(elf, array);
/* if no extended modversions, fall back, otherwise propagate error */
if (ret != -ENODATA)
return ret;
return kmod_elf_get_basic_modversions(elf, array);
}

static int elf_strip_versions_section(const struct kmod_elf *elf, uint8_t *changed)
{
uint64_t off, size;
Expand Down Expand Up @@ -945,25 +1027,18 @@ int kmod_elf_get_symbols(const struct kmod_elf *elf, struct kmod_modversion **ar
return kmod_elf_get_symbols_symtab(elf, array);
}

static int kmod_elf_crc_find(const struct kmod_elf *elf, uint64_t off,
uint64_t versionslen, const char *name, uint64_t *crc)
static int kmod_modversion_crc_find(const struct kmod_modversion *vers, size_t count,
const char *name, uint64_t *crc)
{
size_t namlen, verlen, crclen;
uint64_t i;

elf_get_modversion_lengths(elf, &verlen, &crclen, &namlen);
size_t i;

for (i = 0; i < versionslen; i += verlen) {
const char *symbol = elf_get_mem(elf, off + i + crclen);
if (strnlen(symbol, namlen) == namlen || !streq(name, symbol)) {
ELFDBG(elf, "symbol name at index %" PRIu64 " too long\n", i);
continue;
for (i = 0; i < count; i++) {
if (!strcmp(vers[i].symbol, name)) {
*crc = vers[i].crc;
return i;
}
*crc = elf_get_uint(elf, off + i, crclen);
return i / verlen;
}

ELFDBG(elf, "could not find crc for symbol '%s'\n", name);
*crc = 0;
return -1;
}
Expand All @@ -977,33 +1052,15 @@ static int kmod_elf_crc_find(const struct kmod_elf *elf, uint64_t off,
int kmod_elf_get_dependency_symbols(const struct kmod_elf *elf,
struct kmod_modversion **array)
{
uint64_t versionslen, strtablen, symtablen, str_off, sym_off, ver_off;
uint64_t strtablen, symtablen, str_off, sym_off;
uint64_t str_sec_off, sym_sec_off;
struct kmod_modversion *a;
size_t i, count, namlen, vercount, verlen, symcount, symlen, crclen;
struct kmod_modversion *a, *version_array;
size_t i, count, symcount, symlen, vercount;
int verres;
bool handle_register_symbols;
uint8_t *visited_versions;
uint64_t *symcrcs;

ver_off = elf->sections[KMOD_ELF_SECTION_VERSIONS].offset;
versionslen = elf->sections[KMOD_ELF_SECTION_VERSIONS].size;
if (ver_off == 0) {
versionslen = 0;
verlen = 0;
crclen = 0;
namlen = 0;
} else {
elf_get_modversion_lengths(elf, &verlen, &crclen, &namlen);
if (versionslen % verlen != 0) {
ELFDBG(elf,
"unexpected __versions of length %" PRIu64
", not multiple of %zu as expected.\n",
versionslen, verlen);
ver_off = 0;
versionslen = 0;
}
}

str_sec_off = elf->sections[KMOD_ELF_SECTION_STRTAB].offset;
strtablen = elf->sections[KMOD_ELF_SECTION_STRTAB].size;
if (str_sec_off == 0) {
Expand Down Expand Up @@ -1031,14 +1088,27 @@ int kmod_elf_get_dependency_symbols(const struct kmod_elf *elf,
return -EINVAL;
}

if (versionslen == 0) {
vercount = 0;
version_array = NULL;
verres = kmod_elf_get_modversions(elf, &version_array);
if (verres < 0) {
if (verres == -ENODATA)
/* we allow no MODVERSIONS */
vercount = 0;
else
/* but error out on bugged MODVERSIONS */
return verres;
} else {
vercount = verres;
}

if (vercount == 0) {
visited_versions = NULL;
} else {
vercount = versionslen / verlen;
visited_versions = calloc(vercount, sizeof(uint8_t));
if (visited_versions == NULL)
if (visited_versions == NULL) {
free(version_array);
return -ENOMEM;
}
}

handle_register_symbols =
Expand All @@ -1052,6 +1122,7 @@ int kmod_elf_get_dependency_symbols(const struct kmod_elf *elf,
symcrcs = calloc(symcount, sizeof(uint64_t));
if (symcrcs == NULL) {
free(visited_versions);
free(version_array);
return -ENOMEM;
}

Expand Down Expand Up @@ -1105,6 +1176,7 @@ int kmod_elf_get_dependency_symbols(const struct kmod_elf *elf,
".\n",
strtablen, i, name_off);
free(visited_versions);
free(version_array);
free(symcrcs);
return -EINVAL;
}
Expand All @@ -1117,32 +1189,20 @@ int kmod_elf_get_dependency_symbols(const struct kmod_elf *elf,

count++;

idx = kmod_elf_crc_find(elf, ver_off, versionslen, name, &crc);
idx = kmod_modversion_crc_find(version_array, vercount, name, &crc);
if (idx >= 0 && visited_versions != NULL)
visited_versions[idx] = 1;
else
ELFDBG(elf, "could not find crc for symbol '%s'\n", name);
symcrcs[i] = crc;
}

if (visited_versions != NULL) {
/* module_layout/struct_module are not visited, but needed */
for (i = 0; i < vercount; i++) {
if (visited_versions[i] == 0) {
const char *name;
size_t nlen;

name = elf_get_mem(elf, ver_off + i * verlen + crclen);
nlen = strnlen(name, namlen);

if (nlen == namlen) {
ELFDBG(elf, "symbol name at index %zu too long\n",
i);
free(visited_versions);
free(symcrcs);
return -EINVAL;
}

if (visited_versions[i] == 0)
/* no verification; version_array handled it */
count++;
}
}
}

Expand All @@ -1156,6 +1216,7 @@ int kmod_elf_get_dependency_symbols(const struct kmod_elf *elf,

if (count == 0) {
free(visited_versions);
free(version_array);
free(symcrcs);
*array = NULL;
return 0;
Expand All @@ -1164,6 +1225,7 @@ int kmod_elf_get_dependency_symbols(const struct kmod_elf *elf,
*array = a = malloc(sizeof(struct kmod_modversion) * count);
if (*array == NULL) {
free(visited_versions);
free(version_array);
free(symcrcs);
return -errno;
}
Expand Down Expand Up @@ -1244,21 +1306,16 @@ int kmod_elf_get_dependency_symbols(const struct kmod_elf *elf,

/* add unvisited (module_layout/struct_module) */
for (i = 0; i < vercount; i++) {
const char *name;
uint64_t crc;

if (visited_versions[i] != 0)
continue;

name = elf_get_mem(elf, ver_off + i * verlen + crclen);
crc = elf_get_uint(elf, ver_off + i * verlen, crclen);

a[count].crc = crc;
a[count].crc = version_array[i].crc;
a[count].bind = KMOD_SYMBOL_UNDEF;
a[count].symbol = name;
a[count].symbol = version_array[i].symbol;

count++;
}
free(visited_versions);
free(version_array);
return count;
}
1 change: 1 addition & 0 deletions scripts/setup-rootfs.sh
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Original file line number Diff line number Diff line change
Expand Up @@ -97,6 +97,7 @@ map=(
["test-modprobe/external/lib/modules/external/"]="mod-simple.ko"
["test-modprobe/module-from-abspath/home/foo/"]="mod-simple.ko"
["test-modprobe/module-from-relpath/home/foo/"]="mod-simple.ko"
["test-modprobe/show-modversions/mod-simple.ko"]="mod-simple.ko"
["test-depmod/modules-order-compressed$MODULE_DIRECTORY/4.4.4/kernel/drivers/block/cciss.ko"]="mod-fake-cciss.ko"
["test-depmod/modules-order-compressed$MODULE_DIRECTORY/4.4.4/kernel/drivers/scsi/hpsa.ko"]="mod-fake-hpsa.ko"
["test-depmod/modules-order-compressed$MODULE_DIRECTORY/4.4.4/kernel/drivers/scsi/scsi_mod.ko"]="mod-fake-scsi-mod.ko"
Expand Down
11 changes: 11 additions & 0 deletions testsuite/rootfs-pristine/test-modprobe/show-modversions/versions-mod-simple.txt
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Original file line number Diff line number Diff line change
@@ -0,0 +1,11 @@
0x........ single_open
0x........ seq_write
0x........ debugfs_remove
0x........ seq_lseek
0x........ seq_read
0x........ single_release
0x........ __fentry__
0x........ debugfs_create_dir
0x........ debugfs_create_file
0x........ __x86_return_thunk
0x........ module_layout
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@stoeckmann / @evelikov do you see a way to also test the extended format? Maybe we could:

  1. build the module with that config set
  2. extract the 2 sections and save it, base64-encoded

when building the kmods, we just add the sections to one of the modules with objcopy --add-section. Thoughts?

16 changes: 16 additions & 0 deletions testsuite/test-modprobe.c
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Expand Up @@ -361,4 +361,20 @@ DEFINE_TEST(modprobe_module_from_relpath,
.modules_loaded = "mod-simple",
);

static noreturn int modprobe_show_modversions(const struct test *t)
{
EXEC_MODPROBE("--show-modversions", "/mod-simple.ko");
exit(EXIT_FAILURE);
}
DEFINE_TEST(modprobe_show_modversions,
.description = "check if output for modprobe --show-modversions is correct",
.config = {
[TC_UNAME_R] = "4.4.4",
[TC_ROOTFS] = TESTSUITE_ROOTFS "test-modprobe/show-modversions",
},
.output = {
.out = TESTSUITE_ROOTFS "test-modprobe/show-modversions/versions-mod-simple.txt",
.regex = true,
});

TESTSUITE_MAIN();
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