Add support for code tag context capture when registering a new code tag type. When context capture for a specific code tag is enabled, codetag_ref will point to a codetag_ctx object which can be attached to an application-specific object storing code invocation context. codetag_ctx has a pointer to its codetag_with_ctx object with embedded codetag object in it. All context objects of the same code tag are placed into codetag_with_ctx.ctx_head linked list. codetag.flag is used to indicate when a context capture for the associated code tag is initialized and enabled. Signed-off-by: Suren Baghdasaryan <surenb@xxxxxxxxxx> --- include/linux/codetag.h | 50 +++++++++++++- include/linux/codetag_ctx.h | 48 +++++++++++++ lib/codetag.c | 134 ++++++++++++++++++++++++++++++++++++ 3 files changed, 231 insertions(+), 1 deletion(-) create mode 100644 include/linux/codetag_ctx.h diff --git a/include/linux/codetag.h b/include/linux/codetag.h index 87207f199ac9..9ab2f017e845 100644 --- a/include/linux/codetag.h +++ b/include/linux/codetag.h @@ -5,8 +5,12 @@ #ifndef _LINUX_CODETAG_H #define _LINUX_CODETAG_H +#include <linux/container_of.h> +#include <linux/spinlock.h> #include <linux/types.h> +struct kref; +struct codetag_ctx; struct codetag_iterator; struct codetag_type; struct seq_buf; @@ -18,15 +22,38 @@ struct module; * an array of these. */ struct codetag { - unsigned int flags; /* used in later patches */ + unsigned int flags; /* has to be the first member shared with codetag_ctx */ unsigned int lineno; const char *modname; const char *function; const char *filename; } __aligned(8); +/* codetag_with_ctx flags */ +#define CTC_FLAG_CTX_PTR (1 << 0) +#define CTC_FLAG_CTX_READY (1 << 1) +#define CTC_FLAG_CTX_ENABLED (1 << 2) + +/* + * Code tag with context capture support. Contains a list to store context for + * each tag hit, a lock protecting the list and a flag to indicate whether + * context capture is enabled for the tag. + */ +struct codetag_with_ctx { + struct codetag ct; + struct list_head ctx_head; + spinlock_t ctx_lock; +} __aligned(8); + +/* + * Tag reference can point to codetag directly or indirectly via codetag_ctx. + * Direct codetag pointer is used when context capture is disabled or not + * supported. When context capture for the tag is used, the reference points + * to the codetag_ctx through which the codetag can be reached. + */ union codetag_ref { struct codetag *ct; + struct codetag_ctx *ctx; }; struct codetag_range { @@ -46,6 +73,7 @@ struct codetag_type_desc { struct codetag_module *cmod); bool (*module_unload)(struct codetag_type *cttype, struct codetag_module *cmod); + void (*free_ctx)(struct kref *ref); }; struct codetag_iterator { @@ -53,6 +81,7 @@ struct codetag_iterator { struct codetag_module *cmod; unsigned long mod_id; struct codetag *ct; + struct codetag_ctx *ctx; }; #define CODE_TAG_INIT { \ @@ -63,9 +92,28 @@ struct codetag_iterator { .flags = 0, \ } +static inline bool is_codetag_ctx_ref(union codetag_ref *ref) +{ + return !!(ref->ct->flags & CTC_FLAG_CTX_PTR); +} + +static inline +struct codetag_with_ctx *ct_to_ctc(struct codetag *ct) +{ + return container_of(ct, struct codetag_with_ctx, ct); +} + 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); +struct codetag_ctx *codetag_next_ctx(struct codetag_iterator *iter); + +bool codetag_enable_ctx(struct codetag_with_ctx *ctc, bool enable); +static inline bool codetag_ctx_enabled(struct codetag_with_ctx *ctc) +{ + return !!(ctc->ct.flags & CTC_FLAG_CTX_ENABLED); +} +bool codetag_has_ctx(struct codetag_with_ctx *ctc); void codetag_to_text(struct seq_buf *out, struct codetag *ct); diff --git a/include/linux/codetag_ctx.h b/include/linux/codetag_ctx.h new file mode 100644 index 000000000000..e741484f0e08 --- /dev/null +++ b/include/linux/codetag_ctx.h @@ -0,0 +1,48 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * code tag context + */ +#ifndef _LINUX_CODETAG_CTX_H +#define _LINUX_CODETAG_CTX_H + +#include <linux/codetag.h> +#include <linux/kref.h> + +/* Code tag hit context. */ +struct codetag_ctx { + unsigned int flags; /* has to be the first member shared with codetag */ + struct codetag_with_ctx *ctc; + struct list_head node; + struct kref refcount; +} __aligned(8); + +static inline struct codetag_ctx *kref_to_ctx(struct kref *refcount) +{ + return container_of(refcount, struct codetag_ctx, refcount); +} + +static inline void add_ctx(struct codetag_ctx *ctx, + struct codetag_with_ctx *ctc) +{ + kref_init(&ctx->refcount); + spin_lock(&ctc->ctx_lock); + ctx->flags = CTC_FLAG_CTX_PTR; + ctx->ctc = ctc; + list_add_tail(&ctx->node, &ctc->ctx_head); + spin_unlock(&ctc->ctx_lock); +} + +static inline void rem_ctx(struct codetag_ctx *ctx, + void (*free_ctx)(struct kref *refcount)) +{ + struct codetag_with_ctx *ctc = ctx->ctc; + + spin_lock(&ctc->ctx_lock); + /* ctx might have been removed while we were using it */ + if (!list_empty(&ctx->node)) + list_del_init(&ctx->node); + spin_unlock(&ctc->ctx_lock); + kref_put(&ctx->refcount, free_ctx); +} + +#endif /* _LINUX_CODETAG_CTX_H */ diff --git a/lib/codetag.c b/lib/codetag.c index 84f90f3b922c..d891bbe4481d 100644 --- a/lib/codetag.c +++ b/lib/codetag.c @@ -1,5 +1,6 @@ // SPDX-License-Identifier: GPL-2.0-only #include <linux/codetag.h> +#include <linux/codetag_ctx.h> #include <linux/idr.h> #include <linux/kallsyms.h> #include <linux/module.h> @@ -92,6 +93,139 @@ struct codetag *codetag_next_ct(struct codetag_iterator *iter) return ct; } +static struct codetag_ctx *next_ctx_from_ct(struct codetag_iterator *iter) +{ + struct codetag_with_ctx *ctc; + struct codetag_ctx *ctx = NULL; + struct codetag *ct = iter->ct; + + while (ct) { + if (!(ct->flags & CTC_FLAG_CTX_READY)) + goto next; + + ctc = ct_to_ctc(ct); + spin_lock(&ctc->ctx_lock); + if (!list_empty(&ctc->ctx_head)) { + ctx = list_first_entry(&ctc->ctx_head, + struct codetag_ctx, node); + kref_get(&ctx->refcount); + } + spin_unlock(&ctc->ctx_lock); + if (ctx) + break; +next: + ct = codetag_next_ct(iter); + } + + iter->ctx = ctx; + return ctx; +} + +struct codetag_ctx *codetag_next_ctx(struct codetag_iterator *iter) +{ + struct codetag_ctx *ctx = iter->ctx; + struct codetag_ctx *found = NULL; + + lockdep_assert_held(&iter->cttype->mod_lock); + + if (!ctx) + return next_ctx_from_ct(iter); + + spin_lock(&ctx->ctc->ctx_lock); + /* + * Do not advance if the object was isolated, restart at the same tag. + */ + if (!list_empty(&ctx->node)) { + if (list_is_last(&ctx->node, &ctx->ctc->ctx_head)) { + /* Finished with this tag, advance to the next */ + codetag_next_ct(iter); + } else { + found = list_next_entry(ctx, node); + kref_get(&found->refcount); + } + } + spin_unlock(&ctx->ctc->ctx_lock); + kref_put(&ctx->refcount, iter->cttype->desc.free_ctx); + + if (!found) + return next_ctx_from_ct(iter); + + iter->ctx = found; + return found; +} + +static struct codetag_type *find_cttype(struct codetag *ct) +{ + struct codetag_module *cmod; + struct codetag_type *cttype; + unsigned long mod_id; + unsigned long tmp; + + mutex_lock(&codetag_lock); + list_for_each_entry(cttype, &codetag_types, link) { + down_read(&cttype->mod_lock); + idr_for_each_entry_ul(&cttype->mod_idr, cmod, tmp, mod_id) { + if (ct >= cmod->range.start && ct < cmod->range.stop) { + up_read(&cttype->mod_lock); + goto found; + } + } + up_read(&cttype->mod_lock); + } + cttype = NULL; +found: + mutex_unlock(&codetag_lock); + + return cttype; +} + +bool codetag_enable_ctx(struct codetag_with_ctx *ctc, bool enable) +{ + struct codetag_type *cttype = find_cttype(&ctc->ct); + + if (!cttype || !cttype->desc.free_ctx) + return false; + + lockdep_assert_held(&cttype->mod_lock); + BUG_ON(!rwsem_is_locked(&cttype->mod_lock)); + + if (codetag_ctx_enabled(ctc) == enable) + return false; + + if (enable) { + /* Initialize context capture fields only once */ + if (!(ctc->ct.flags & CTC_FLAG_CTX_READY)) { + spin_lock_init(&ctc->ctx_lock); + INIT_LIST_HEAD(&ctc->ctx_head); + ctc->ct.flags |= CTC_FLAG_CTX_READY; + } + ctc->ct.flags |= CTC_FLAG_CTX_ENABLED; + } else { + /* + * The list of context objects is intentionally left untouched. + * It can be read back and if context capture is re-enablied it + * will append new objects. + */ + ctc->ct.flags &= ~CTC_FLAG_CTX_ENABLED; + } + + return true; +} + +bool codetag_has_ctx(struct codetag_with_ctx *ctc) +{ + bool no_ctx; + + if (!(ctc->ct.flags & CTC_FLAG_CTX_READY)) + return false; + + spin_lock(&ctc->ctx_lock); + no_ctx = list_empty(&ctc->ctx_head); + spin_unlock(&ctc->ctx_lock); + + return !no_ctx; +} + void codetag_to_text(struct seq_buf *out, struct codetag *ct) { seq_buf_printf(out, "%s:%u module:%s func:%s", -- 2.40.1.495.gc816e09b53d-goog