This patch adds the /sys/module/<name>/notes/ magic directory, which has
a file for each allocated SHT_NOTE section that appears in <name>.ko.
This is the counterpart for each module of /sys/kernel/notes for vmlinux.
Reading this delivers the contents of the module's SHT_NOTE sections.
This lets userland easily glean any detailed information about that
module's build that was stored there at compile time (e.g. by ld --build-id).
Signed-off-by: Roland McGrath <[email protected]>
---
include/linux/module.h | 3 +
kernel/module.c | 106 ++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 109 insertions(+), 0 deletions(-)
diff --git a/include/linux/module.h b/include/linux/module.h
index b6a646c..65d0752 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -346,6 +346,9 @@ struct module
/* Section attributes */
struct module_sect_attrs *sect_attrs;
+
+ /* Notes attributes */
+ struct module_notes_attrs *notes_attrs;
#endif
/* Per-cpu data. */
diff --git a/kernel/module.c b/kernel/module.c
index 33c04ad..d7bbe1a 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -20,6 +20,7 @@
#include <linux/moduleloader.h>
#include <linux/init.h>
#include <linux/kallsyms.h>
+#include <linux/sysfs.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
@@ -1054,6 +1055,100 @@ static void remove_sect_attrs(struct module *mod)
}
}
+/*
+ * /sys/module/foo/notes/.section.name gives contents of SHT_NOTE sections.
+ */
+
+struct module_notes_attrs {
+ struct kobject *dir;
+ unsigned int notes;
+ struct bin_attribute attrs[0];
+};
+
+static ssize_t module_notes_read(struct kobject *kobj,
+ struct bin_attribute *bin_attr,
+ char *buf, loff_t pos, size_t count)
+{
+ /*
+ * The caller checked the pos and count against our size.
+ */
+ memcpy(buf, bin_attr->private + pos, count);
+ return count;
+}
+
+static void free_notes_attrs(struct module_notes_attrs *notes_attrs,
+ unsigned int i)
+{
+ if (notes_attrs->dir) {
+ while (i-- > 0)
+ sysfs_remove_bin_file(notes_attrs->dir,
+ ¬es_attrs->attrs[i]);
+ kobject_del(notes_attrs->dir);
+ }
+ kfree(notes_attrs);
+}
+
+static void add_notes_attrs(struct module *mod, unsigned int nsect,
+ char *secstrings, Elf_Shdr *sechdrs)
+{
+ unsigned int notes, loaded, i;
+ struct module_notes_attrs *notes_attrs;
+ struct bin_attribute *nattr;
+
+ /* Count notes sections and allocate structures. */
+ notes = 0;
+ for (i = 0; i < nsect; i++)
+ if ((sechdrs[i].sh_flags & SHF_ALLOC) &&
+ (sechdrs[i].sh_type == SHT_NOTE))
+ ++notes;
+
+ if (notes == 0)
+ return;
+
+ notes_attrs = kzalloc(sizeof(*notes_attrs)
+ + notes * sizeof(notes_attrs->attrs[0]),
+ GFP_KERNEL);
+ if (notes_attrs == NULL)
+ return;
+
+ notes_attrs->notes = notes;
+ nattr = ¬es_attrs->attrs[0];
+ for (loaded = i = 0; i < nsect; ++i) {
+ if (!(sechdrs[i].sh_flags & SHF_ALLOC))
+ continue;
+ if (sechdrs[i].sh_type == SHT_NOTE) {
+ nattr->attr.name = mod->sect_attrs->attrs[loaded].name;
+ nattr->attr.mode = S_IRUGO;
+ nattr->size = sechdrs[i].sh_size;
+ nattr->private = (void *) sechdrs[i].sh_addr;
+ nattr->read = module_notes_read;
+ ++nattr;
+ }
+ ++loaded;
+ }
+
+ notes_attrs->dir = kobject_add_dir(&mod->mkobj.kobj, "notes");
+ if (!notes_attrs->dir)
+ goto out;
+
+ for (i = 0; i < notes; ++i)
+ if (sysfs_create_bin_file(notes_attrs->dir,
+ ¬es_attrs->attrs[i]))
+ goto out;
+
+ mod->notes_attrs = notes_attrs;
+ return;
+
+ out:
+ free_notes_attrs(notes_attrs, i);
+}
+
+static void remove_notes_attrs(struct module *mod)
+{
+ if (mod->notes_attrs)
+ free_notes_attrs(mod->notes_attrs, mod->notes_attrs->notes);
+}
+
#else
static inline void add_sect_attrs(struct module *mod, unsigned int nsect,
@@ -1064,6 +1159,15 @@ static inline void add_sect_attrs(struct module *mod, unsigned int nsect,
static inline void remove_sect_attrs(struct module *mod)
{
}
+
+static inline void add_notes_attrs(struct module *mod, unsigned int nsect,
+ char *sectstrings, Elf_Shdr *sechdrs)
+{
+}
+
+static inline void remove_notes_attrs(struct module *mod)
+{
+}
#endif /* CONFIG_KALLSYMS */
#ifdef CONFIG_SYSFS
@@ -1198,6 +1302,7 @@ static void free_module(struct module *mod)
{
/* Delete from various lists */
stop_machine_run(__unlink_module, mod, NR_CPUS);
+ remove_notes_attrs(mod);
remove_sect_attrs(mod);
mod_kobject_remove(mod);
@@ -1925,6 +2030,7 @@ static struct module *load_module(void __user *umod,
if (err < 0)
goto arch_cleanup;
add_sect_attrs(mod, hdr->e_shnum, secstrings, sechdrs);
+ add_notes_attrs(mod, hdr->e_shnum, secstrings, sechdrs);
/* Size of section 0 is 0, so this works well if no unwind info. */
mod->unwind_info = unwind_add_table(mod,
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