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Mon, 12 Feb 2024 14:27:13 -0800 (PST) Date: Mon, 12 Feb 2024 14:27:13 -0800 From: Kees Cook To: Suren Baghdasaryan Cc: akpm@linux-foundation.org, kent.overstreet@linux.dev, mhocko@suse.com, vbabka@suse.cz, hannes@cmpxchg.org, roman.gushchin@linux.dev, mgorman@suse.de, dave@stgolabs.net, willy@infradead.org, liam.howlett@oracle.com, corbet@lwn.net, void@manifault.com, peterz@infradead.org, juri.lelli@redhat.com, catalin.marinas@arm.com, will@kernel.org, arnd@arndb.de, tglx@linutronix.de, mingo@redhat.com, dave.hansen@linux.intel.com, x86@kernel.org, peterx@redhat.com, david@redhat.com, axboe@kernel.dk, mcgrof@kernel.org, masahiroy@kernel.org, nathan@kernel.org, dennis@kernel.org, tj@kernel.org, muchun.song@linux.dev, rppt@kernel.org, paulmck@kernel.org, pasha.tatashin@soleen.com, yosryahmed@google.com, yuzhao@google.com, dhowells@redhat.com, hughd@google.com, andreyknvl@gmail.com, ndesaulniers@google.com, vvvvvv@google.com, gregkh@linuxfoundation.org, ebiggers@google.com, ytcoode@gmail.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, bristot@redhat.com, vschneid@redhat.com, cl@linux.com, penberg@kernel.org, iamjoonsoo.kim@lge.com, 42.hyeyoo@gmail.com, glider@google.com, elver@google.com, dvyukov@google.com, shakeelb@google.com, songmuchun@bytedance.com, jbaron@akamai.com, rientjes@google.com, minchan@google.com, kaleshsingh@google.com, kernel-team@android.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, iommu@lists.linux.dev, linux-arch@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-modules@vger.kernel.org, kasan-dev@googlegroups.com, cgroups@vger.kernel.org Subject: Re: [PATCH v3 10/35] lib: code tagging framework Message-ID: <202402121419.7C4AAF27ED@keescook> References: <20240212213922.783301-1-surenb@google.com> <20240212213922.783301-11-surenb@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240212213922.783301-11-surenb@google.com> X-Rspamd-Queue-Id: 59222180017 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: jj8oe87frrtpfq5emxgtophma9zh8na4 X-HE-Tag: 1707776835-552060 X-HE-Meta: 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 ynUR2ZRw IP30hrbEauV0bMLd/tBVys29Yo5kL093hyjyOEv9TJv5cA849tA3ZNb82d2zogBwEdfRl1oaNMX5sl19LhMlK7hOl7NBYmrtKWYCwCr/J4tftAdIXWQQ7VJWGV6JO26rewRZxxhF+KknPvQ4olt0Yy4tMeBH5XXqoxz+8EC/icBhHaOUDaxi4JCfvA+aHzRLgsZxyyQX0e0+/1I1UjXAEH0tjORdb3VQYwxL+gtWLK5q5JkggRF4V5wwanfwRXWjBh92OcvCaDQuVX42KMmE90j9tWGGgAQuOQz6FOtDzNFjfBmFgUCxbcuqvkTdP8YVa/IWEiqpqe/X18Zr2rKLQzBEiRO26hjeaQ8QWu7nbUvcV2Ux9SSnSEsQKJvgfHrl+sxNvd4RUw9zbUos9STOtrz4MClEkCtcLjT3/+5Zx8mK7nQPPSeM7Q/gEmjign+d/vRA7zRFmiZ1G6ldOKTDqF7tS3w2OpB2PRE5vmt0LvK5ZVRM= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Feb 12, 2024 at 01:38:56PM -0800, Suren Baghdasaryan wrote: > Add basic infrastructure to support code tagging which stores tag common > information consisting of the module name, function, file name and line > number. Provide functions to register a new code tag type and navigate > between code tags. > > Co-developed-by: Kent Overstreet > Signed-off-by: Kent Overstreet > Signed-off-by: Suren Baghdasaryan > --- > include/linux/codetag.h | 71 ++++++++++++++ > lib/Kconfig.debug | 4 + > lib/Makefile | 1 + > lib/codetag.c | 199 ++++++++++++++++++++++++++++++++++++++++ > 4 files changed, 275 insertions(+) > create mode 100644 include/linux/codetag.h > create mode 100644 lib/codetag.c > > diff --git a/include/linux/codetag.h b/include/linux/codetag.h > new file mode 100644 > index 000000000000..a9d7adecc2a5 > --- /dev/null > +++ b/include/linux/codetag.h > @@ -0,0 +1,71 @@ > +/* SPDX-License-Identifier: GPL-2.0 */ > +/* > + * code tagging framework > + */ > +#ifndef _LINUX_CODETAG_H > +#define _LINUX_CODETAG_H > + > +#include > + > +struct codetag_iterator; > +struct codetag_type; > +struct seq_buf; > +struct module; > + > +/* > + * An instance of this structure is created in a special ELF section at every > + * code location being tagged. At runtime, the special section is treated as > + * an array of these. > + */ > +struct codetag { > + unsigned int flags; /* used in later patches */ > + unsigned int lineno; > + const char *modname; > + const char *function; > + const char *filename; > +} __aligned(8); > + > +union codetag_ref { > + struct codetag *ct; > +}; > + > +struct codetag_range { > + struct codetag *start; > + struct codetag *stop; > +}; > + > +struct codetag_module { > + struct module *mod; > + struct codetag_range range; > +}; > + > +struct codetag_type_desc { > + const char *section; > + size_t tag_size; > +}; > + > +struct codetag_iterator { > + struct codetag_type *cttype; > + struct codetag_module *cmod; > + unsigned long mod_id; > + struct codetag *ct; > +}; > + > +#define CODE_TAG_INIT { \ > + .modname = KBUILD_MODNAME, \ > + .function = __func__, \ > + .filename = __FILE__, \ > + .lineno = __LINE__, \ > + .flags = 0, \ > +} > + > +void codetag_lock_module_list(struct codetag_type *cttype, bool lock); > +struct codetag_iterator codetag_get_ct_iter(struct codetag_type *cttype); > +struct codetag *codetag_next_ct(struct codetag_iterator *iter); > + > +void codetag_to_text(struct seq_buf *out, struct codetag *ct); > + > +struct codetag_type * > +codetag_register_type(const struct codetag_type_desc *desc); > + > +#endif /* _LINUX_CODETAG_H */ > diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug > index 975a07f9f1cc..0be2d00c3696 100644 > --- a/lib/Kconfig.debug > +++ b/lib/Kconfig.debug > @@ -968,6 +968,10 @@ config DEBUG_STACKOVERFLOW > > If in doubt, say "N". > > +config CODE_TAGGING > + bool > + select KALLSYMS > + > source "lib/Kconfig.kasan" > source "lib/Kconfig.kfence" > source "lib/Kconfig.kmsan" > diff --git a/lib/Makefile b/lib/Makefile > index 6b09731d8e61..6b48b22fdfac 100644 > --- a/lib/Makefile > +++ b/lib/Makefile > @@ -235,6 +235,7 @@ obj-$(CONFIG_OF_RECONFIG_NOTIFIER_ERROR_INJECT) += \ > of-reconfig-notifier-error-inject.o > obj-$(CONFIG_FUNCTION_ERROR_INJECTION) += error-inject.o > > +obj-$(CONFIG_CODE_TAGGING) += codetag.o > lib-$(CONFIG_GENERIC_BUG) += bug.o > > obj-$(CONFIG_HAVE_ARCH_TRACEHOOK) += syscall.o > diff --git a/lib/codetag.c b/lib/codetag.c > new file mode 100644 > index 000000000000..7708f8388e55 > --- /dev/null > +++ b/lib/codetag.c > @@ -0,0 +1,199 @@ > +// SPDX-License-Identifier: GPL-2.0-only > +#include > +#include > +#include > +#include > +#include > +#include > + > +struct codetag_type { > + struct list_head link; > + unsigned int count; > + struct idr mod_idr; > + struct rw_semaphore mod_lock; /* protects mod_idr */ > + struct codetag_type_desc desc; > +}; > + > +static DEFINE_MUTEX(codetag_lock); > +static LIST_HEAD(codetag_types); > + > +void codetag_lock_module_list(struct codetag_type *cttype, bool lock) > +{ > + if (lock) > + down_read(&cttype->mod_lock); > + else > + up_read(&cttype->mod_lock); > +} > + > +struct codetag_iterator codetag_get_ct_iter(struct codetag_type *cttype) > +{ > + struct codetag_iterator iter = { > + .cttype = cttype, > + .cmod = NULL, > + .mod_id = 0, > + .ct = NULL, > + }; > + > + return iter; > +} > + > +static inline struct codetag *get_first_module_ct(struct codetag_module *cmod) > +{ > + return cmod->range.start < cmod->range.stop ? cmod->range.start : NULL; > +} > + > +static inline > +struct codetag *get_next_module_ct(struct codetag_iterator *iter) > +{ > + struct codetag *res = (struct codetag *) > + ((char *)iter->ct + iter->cttype->desc.tag_size); > + > + return res < iter->cmod->range.stop ? res : NULL; > +} > + > +struct codetag *codetag_next_ct(struct codetag_iterator *iter) > +{ > + struct codetag_type *cttype = iter->cttype; > + struct codetag_module *cmod; > + struct codetag *ct; > + > + lockdep_assert_held(&cttype->mod_lock); > + > + if (unlikely(idr_is_empty(&cttype->mod_idr))) > + return NULL; > + > + ct = NULL; > + while (true) { > + cmod = idr_find(&cttype->mod_idr, iter->mod_id); > + > + /* If module was removed move to the next one */ > + if (!cmod) > + cmod = idr_get_next_ul(&cttype->mod_idr, > + &iter->mod_id); > + > + /* Exit if no more modules */ > + if (!cmod) > + break; > + > + if (cmod != iter->cmod) { > + iter->cmod = cmod; > + ct = get_first_module_ct(cmod); > + } else > + ct = get_next_module_ct(iter); > + > + if (ct) > + break; > + > + iter->mod_id++; > + } > + > + iter->ct = ct; > + return ct; > +} > + > +void codetag_to_text(struct seq_buf *out, struct codetag *ct) > +{ > + seq_buf_printf(out, "%s:%u module:%s func:%s", > + ct->filename, ct->lineno, > + ct->modname, ct->function); > +} Thank you for using seq_buf here! Also, will this need an EXPORT_SYMBOL_GPL()? > + > +static inline size_t range_size(const struct codetag_type *cttype, > + const struct codetag_range *range) > +{ > + return ((char *)range->stop - (char *)range->start) / > + cttype->desc.tag_size; > +} > + > +static void *get_symbol(struct module *mod, const char *prefix, const char *name) > +{ > + char buf[64]; Why is 64 enough? I was expecting KSYM_NAME_LEN here, but perhaps this is specialized enough to section names that it will not be a problem? If so, please document it clearly with a comment. > + int res; > + > + res = snprintf(buf, sizeof(buf), "%s%s", prefix, name); > + if (WARN_ON(res < 1 || res > sizeof(buf))) > + return NULL; Please use a seq_buf here instead of snprintf, which we're trying to get rid of. DECLARE_SEQ_BUF(sb, KSYM_NAME_LEN); char *buf; seq_buf_printf(sb, "%s%s", prefix, name); if (seq_buf_has_overflowed(sb)) return NULL; buf = seq_buf_str(sb); > + > + return mod ? > + (void *)find_kallsyms_symbol_value(mod, buf) : > + (void *)kallsyms_lookup_name(buf); > +} > + > +static struct codetag_range get_section_range(struct module *mod, > + const char *section) > +{ > + return (struct codetag_range) { > + get_symbol(mod, "__start_", section), > + get_symbol(mod, "__stop_", section), > + }; > +} > + > +static int codetag_module_init(struct codetag_type *cttype, struct module *mod) > +{ > + struct codetag_range range; > + struct codetag_module *cmod; > + int err; > + > + range = get_section_range(mod, cttype->desc.section); > + if (!range.start || !range.stop) { > + pr_warn("Failed to load code tags of type %s from the module %s\n", > + cttype->desc.section, > + mod ? mod->name : "(built-in)"); > + return -EINVAL; > + } > + > + /* Ignore empty ranges */ > + if (range.start == range.stop) > + return 0; > + > + BUG_ON(range.start > range.stop); > + > + cmod = kmalloc(sizeof(*cmod), GFP_KERNEL); > + if (unlikely(!cmod)) > + return -ENOMEM; > + > + cmod->mod = mod; > + cmod->range = range; > + > + down_write(&cttype->mod_lock); > + err = idr_alloc(&cttype->mod_idr, cmod, 0, 0, GFP_KERNEL); > + if (err >= 0) > + cttype->count += range_size(cttype, &range); > + up_write(&cttype->mod_lock); > + > + if (err < 0) { > + kfree(cmod); > + return err; > + } > + > + return 0; > +} > + > +struct codetag_type * > +codetag_register_type(const struct codetag_type_desc *desc) > +{ > + struct codetag_type *cttype; > + int err; > + > + BUG_ON(desc->tag_size <= 0); > + > + cttype = kzalloc(sizeof(*cttype), GFP_KERNEL); > + if (unlikely(!cttype)) > + return ERR_PTR(-ENOMEM); > + > + cttype->desc = *desc; > + idr_init(&cttype->mod_idr); > + init_rwsem(&cttype->mod_lock); > + > + err = codetag_module_init(cttype, NULL); > + if (unlikely(err)) { > + kfree(cttype); > + return ERR_PTR(err); > + } > + > + mutex_lock(&codetag_lock); > + list_add_tail(&cttype->link, &codetag_types); > + mutex_unlock(&codetag_lock); > + > + return cttype; > +} > -- > 2.43.0.687.g38aa6559b0-goog > -- Kees Cook