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From: Lucas De Marchi <lucas.demarchi@intel.com>
To: Alexey Gladkov <gladkov.alexey@gmail.com>
Cc: linux-modules@vger.kernel.org,
	Lucas De Marchi <lucas.de.marchi@gmail.com>
Subject: Re: [PATCH v1 1/4] libkmod: Add parser for modules.builtin.modinfo
Date: Thu, 7 Nov 2019 00:23:10 -0800
Message-ID: <20191107082310.as5zrubafgaaeb4e@ldmartin-desk1> (raw)
In-Reply-To: <20191011081956.4127892-2-gladkov.alexey@gmail.com>

On Fri, Oct 11, 2019 at 10:19:53AM +0200, Alexey Gladkov wrote:
>The kernel since version v5.2-rc1 exports information about built-in
>modules in the modules.builtin.modinfo. Information is stored in
>the same format as in the separate modules (null-terminated string
>array). The module name is a prefix for each line.
>
>$ tr '\0' '\n' < modules.builtin.modinfo
>ext4.softdep=pre: crc32c
>ext4.license=GPL
>ext4.description=Fourth Extended Filesystem
>ext4.author=Remy Card, Stephen Tweedie, Andrew Morton, Andreas Dilger, Theodore Ts'o and others
>ext4.alias=fs-ext4
>ext4.alias=ext3
>ext4.alias=fs-ext3
>ext4.alias=ext2
>ext4.alias=fs-ext2
>md_mod.alias=block-major-9-*
>md_mod.alias=md
>md_mod.description=MD RAID framework
>md_mod.license=GPL
>md_mod.parmtype=create_on_open:bool
>md_mod.parmtype=start_dirty_degraded:int


Apologies, I thought I had replied to this already. Having this
functionality is very welcome, thanks. I have some comments about the
implementation. See below.


>...
>
>Signed-off-by: Alexey Gladkov <gladkov.alexey@gmail.com>
>---
> Makefile.am                |   1 +
> libkmod/libkmod-builtin.c  | 231 +++++++++++++++++++++++++++++++++++++
> libkmod/libkmod-internal.h |   8 ++
> 3 files changed, 240 insertions(+)
> create mode 100644 libkmod/libkmod-builtin.c
>
>diff --git a/Makefile.am b/Makefile.am
>index c5c2f06..176dcfc 100644
>--- a/Makefile.am
>+++ b/Makefile.am
>@@ -68,6 +68,7 @@ libkmod_libkmod_la_SOURCES = \
> 	libkmod/libkmod.h \
> 	libkmod/libkmod-internal.h \
> 	libkmod/libkmod.c \
>+	libkmod/libkmod-builtin.c \
> 	libkmod/libkmod-list.c \
> 	libkmod/libkmod-config.c \
> 	libkmod/libkmod-index.c \
>diff --git a/libkmod/libkmod-builtin.c b/libkmod/libkmod-builtin.c
>new file mode 100644
>index 0000000..9da0010
>--- /dev/null
>+++ b/libkmod/libkmod-builtin.c
>@@ -0,0 +1,231 @@
>+/*
>+ * libkmod - interface to kernel built-in modules
>+ *
>+ * Copyright (C) 2019  Alexey Gladkov <gladkov.alexey@gmail.com>
>+ *
>+ * This library is free software; you can redistribute it and/or
>+ * modify it under the terms of the GNU Lesser General Public
>+ * License as published by the Free Software Foundation; either
>+ * version 2.1 of the License, or (at your option) any later version.
>+ *
>+ * This library is distributed in the hope that it will be useful,
>+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
>+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
>+ * Lesser General Public License for more details.
>+ *
>+ * You should have received a copy of the GNU Lesser General Public
>+ * License along with this library; if not, see <http://www.gnu.org/licenses/>.
>+ */

this remembers me we should convert these headers to spdx

>+
>+#include <stdio.h>
>+#include <stdlib.h>
>+#include <string.h>
>+#include <errno.h>
>+
>+#include "libkmod.h"
>+#include "libkmod-internal.h"
>+
>+#define MODULES_BUILTIN_MODINFO "modules.builtin.modinfo"
>+
>+struct kmod_builtin_iter {
>+	struct kmod_ctx *ctx;
>+	struct kmod_file *file;
>+	off_t pos;
>+	off_t next;
>+};
>+
>+struct kmod_builtin_iter *kmod_builtin_iter_new(struct kmod_ctx *ctx)
>+{
>+	char path[PATH_MAX];
>+	struct kmod_file *file;
>+	struct kmod_builtin_iter *iter;
>+	const char *dirname = kmod_get_dirname(ctx);
>+	size_t len = strlen(dirname);
>+
>+	if ((len + 1 + strlen(MODULES_BUILTIN_MODINFO) + 1) >= PATH_MAX) {
>+		errno = ENAMETOOLONG;
>+		return NULL;
>+	}
>+
>+	snprintf(path, PATH_MAX, "%s/%s", dirname, MODULES_BUILTIN_MODINFO);
>+
>+	file = kmod_file_open(ctx, path);
>+	if (!file)
>+		return NULL;
>+
>+	iter = malloc(sizeof(*iter));
>+	if (!iter) {
>+		kmod_file_unref(file);
>+		errno = ENOMEM;
>+		return NULL;
>+	}
>+
>+	iter->ctx = ctx;
>+	iter->file = file;
>+	iter->pos = 0;
>+	iter->next = 0;
>+
>+	return iter;
>+}
>+
>+bool kmod_builtin_iter_next(struct kmod_builtin_iter *iter)
>+{
>+	char *mm, *s, *dot;
>+	off_t offset, mmsize;
>+	size_t len, modlen;
>+	char *modname = NULL;
>+
>+	mm = kmod_file_get_contents(iter->file);
>+	mmsize = kmod_file_get_size(iter->file);

humn... kmod_file is more target for handling modules. This is only
< 100k  and we would access it sequentially. I think we are fine just
using stdio.

>+
>+	offset = iter->next;
>+
>+	while (offset < mmsize) {
>+		s = mm + offset;
>+
>+		dot = strchr(s, '.');
>+		if (!dot)
>+			return false;

wouldn't this fail if in the description of a module/param we have a dot?
I think a more correct approach is to search for \0 and then try to
match the prefix.

Actually, maybe even better to memmem() "\0<module-name>.", first being
an exception.


>+
>+		len = dot - s;
>+
>+		if (!modname) {
>+			modname = s;
>+			modlen = len;
>+		} else if (modlen != len || strncmp(modname, s, len)) {
>+			break;
>+		}
>+
>+		offset += strlen(s) + 1;
>+	}
>+
>+	if (!modname)
>+		return false;
>+
>+	iter->next = offset;
>+
>+	return true;
>+}
>+
>+void kmod_builtin_iter_free(struct kmod_builtin_iter *iter)
>+{
>+	kmod_file_unref(iter->file);
>+	free(iter);
>+}
>+
>+int kmod_builtin_iter_get_strings(struct kmod_builtin_iter *iter,
>+					const char **strings)
>+{
>+	char *mm = kmod_file_get_contents(iter->file);
>+	off_t pos = iter->pos;
>+
>+	char *start = NULL;
>+	size_t count = 0;
>+	size_t modlen = 0;
>+
>+	while (pos < iter->next) {
>+		char *dot = strchr(mm + pos, '.');
>+		size_t len;
>+
>+		if (!dot)
>+			return -1;
>+
>+		len = dot - (mm + pos);
>+
>+		if (!start) {
>+			start = mm + pos;
>+			modlen = len;
>+		} else if (modlen != len || strncmp(start, mm + pos, len)) {
>+			break;
>+		}
>+
>+		pos += strlen(mm + pos) + 1;
>+		count++;
>+	}
>+
>+	*strings = start;
>+	iter->pos = iter->next;
>+
>+	return count;
>+}
>+
>+/* array will be allocated with strings in a single malloc, just free *array */
>+int kmod_builtin_get_modinfo(struct kmod_ctx *ctx, const char *modname,
>+				char ***modinfo)
>+{
>+	char *mm, *s, *section, *dot;
>+	off_t n, size, offset, mmoffset, mmsize;
>+	size_t modlen, len;
>+	struct kmod_builtin_iter *iter;
>+	int count = 0;
>+
>+	iter = kmod_builtin_iter_new(ctx);
>+
>+	if (!iter)
>+		return -1;
>+
>+	modlen = strlen(modname);
>+
>+	mmsize = kmod_file_get_size(iter->file);
>+	mm = kmod_file_get_contents(iter->file);
>+
>+	section = NULL;
>+	size = 0;
>+
>+	for (mmoffset = 0; mmoffset < mmsize;) {
>+		s = mm + mmoffset;
>+		dot = strchr(s, '.');
>+
>+		if (!dot) {
>+			count = -ENODATA;
>+			goto fail;
>+		}
>+
>+		len = dot - s;
>+
>+		if (modlen != len || strncmp(modname, s, len)) {
>+			if (count)
>+				break;
>+			mmoffset += strlen(s) + 1;
>+			continue;
>+		} else if (!count) {
>+			section = s;
>+		}
>+
>+		len = strlen(dot + 1) + 1;
>+		mmoffset += modlen + 1 + len;
>+		size += len;
>+
>+		count++;
>+	}
>+
>+	if (!count) {
>+		count = -ENOSYS;
>+		goto fail;
>+	}
>+
>+	*modinfo = malloc(size + sizeof(char *) * (count + 1));
>+	if (!*modinfo) {
>+		count = -errno;
>+		goto fail;
>+	}
>+
>+	s = (char *)(*modinfo + count + 1);
>+
>+	n = 0;
>+	mmoffset = 0;
>+
>+	for (offset = 0; offset < size;) {
>+		len = strlen(section + mmoffset + modlen + 1) + 1;
>+
>+		strncpy(s + offset, section + mmoffset + modlen + 1, len);
>+		(*modinfo)[n++] = s + offset;
>+
>+		mmoffset += modlen + 1 + len;
>+		offset += len;
>+	}
>+
>+fail:
>+	kmod_builtin_iter_free(iter);
>+	return count;
>+}
>diff --git a/libkmod/libkmod-internal.h b/libkmod/libkmod-internal.h
>index a65ddd1..17ae541 100644
>--- a/libkmod/libkmod-internal.h
>+++ b/libkmod/libkmod-internal.h
>@@ -193,3 +193,11 @@ struct kmod_signature_info {
> };
> bool kmod_module_signature_info(const struct kmod_file *file, struct kmod_signature_info *sig_info) _must_check_ __attribute__((nonnull(1, 2)));
> void kmod_module_signature_info_free(struct kmod_signature_info *sig_info) __attribute__((nonnull));
>+
>+/* libkmod-builtin.c */
>+struct kmod_builtin_iter;
>+struct kmod_builtin_iter *kmod_builtin_iter_new(struct kmod_ctx *ctx) __attribute__((nonnull(1)));
>+void kmod_builtin_iter_free(struct kmod_builtin_iter *iter) __attribute__((nonnull(1)));
>+bool kmod_builtin_iter_next(struct kmod_builtin_iter *iter) __attribute__((nonnull(1)));
>+int kmod_builtin_iter_get_strings(struct kmod_builtin_iter *iter, const char **modinfo) __attribute__((nonnull(1, 2)));
>+int kmod_builtin_get_modinfo(struct kmod_ctx *ctx, const char *modname, char ***modinfo) __attribute__((nonnull(1, 2, 3)));
>-- 
>2.21.0
>

  reply index

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-11  8:19 [PATCH v1 0/4] Add modules.builtin.modinfo support Alexey Gladkov
2019-10-11  8:19 ` [PATCH v1 1/4] libkmod: Add parser for modules.builtin.modinfo Alexey Gladkov
2019-11-07  8:23   ` Lucas De Marchi [this message]
2019-11-08 17:31     ` Alexey Gladkov
2019-10-11  8:19 ` [PATCH v1 2/4] libkmod: Add function to get list of built-in modules Alexey Gladkov
2019-10-11  8:19 ` [PATCH v1 3/4] Lookup aliases in the modules.builtin.modinfo Alexey Gladkov
2019-10-11  8:19 ` [PATCH v1 4/4] modinfo: Show information about built-in modules Alexey Gladkov
2019-11-07 10:30 ` [PATCH v1 0/4] Add modules.builtin.modinfo support Alexey Gladkov

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