X-Git-Url: http://git.lttng.org/?a=blobdiff_plain;f=libringbuffer%2Fshm.h;h=e8fc8d70384910139306e0d2d0fbcfc41cbcb615;hb=4318ae1be57eb7983ab4857a7a8eeb4a030a8216;hp=390a5b26bc2890f996577ebbda3d0dc0303cb726;hpb=a6352fd40a2090fd883a6c369144bf405c9e9ec4;p=lttng-ust.git

diff --git a/libringbuffer/shm.h b/libringbuffer/shm.h
index 390a5b26..e8fc8d70 100644
--- a/libringbuffer/shm.h
+++ b/libringbuffer/shm.h
@@ -10,62 +10,117 @@
  */
 
 #include <stdint.h>
-#include "ust/core.h"
-
-#define SHM_MAGIC	0x54335433
-#define SHM_MAJOR	0
-#define SHM_MINOR	1
+#include <lttng/usterr-signal-safe.h>
+#include "lttng/core.h"
+#include "shm_types.h"
 
 /*
- * Defining a max shm offset, for debugging purposes.
+ * Pointer dereferencing. We don't trust the shm_ref, so we validate
+ * both the index and offset with known boundaries.
+ *
+ * "shmp" and "shmp_index" guarantee that it's safe to use the pointer
+ * target type, even in the occurrence of shm_ref modification by an
+ * untrusted process having write access to the shm_ref. We return a
+ * NULL pointer if the ranges are invalid.
  */
-#if (CAA_BITS_PER_LONG == 32)
-/* Define the maximum shared memory size to 128MB on 32-bit machines */
-#define MAX_SHM_SIZE	134217728
-#else
-/* Define the maximum shared memory size to 8GB on 64-bit machines */
-#define MAX_SHM_SIZE	8589934592
-#endif
+static inline
+char *_shmp_offset(struct shm_object_table *table, struct shm_ref *ref,
+		   size_t idx, size_t elem_size)
+{
+	struct shm_object *obj;
+	size_t objindex, ref_offset;
 
-#define DECLARE_SHMP(type, name)	type *****name
+	objindex = (size_t) ref->index;
+	if (caa_unlikely(objindex >= table->allocated_len))
+		return NULL;
+	obj = &table->objects[objindex];
+	ref_offset = (size_t) ref->offset;
+	ref_offset += idx * elem_size;
+	/* Check if part of the element returned would exceed the limits. */
+	if (caa_unlikely(ref_offset + elem_size > obj->memory_map_size))
+		return NULL;
+	return &obj->memory_map[ref_offset];
+}
+
+#define shmp_index(handle, ref, index)					\
+	({								\
+		__typeof__((ref)._type) ____ptr_ret;			\
+		____ptr_ret = (__typeof__(____ptr_ret)) _shmp_offset((handle)->table, &(ref)._ref, index, sizeof(*____ptr_ret));	\
+		____ptr_ret;						\
+	})
+
+#define shmp(handle, ref)	shmp_index(handle, ref, 0)
 
-struct shm_header {
-	uint32_t magic;
-	uint8_t major;
-	uint8_t minor;
-	uint8_t bits_per_long;
-	size_t shm_size, shm_allocated;
+static inline
+void _set_shmp(struct shm_ref *ref, struct shm_ref src)
+{
+	*ref = src;
+}
 
-	DECLARE_SHMP(struct channel, chan);
-};
+#define set_shmp(ref, src)	_set_shmp(&(ref)._ref, src)
 
-#define shmp(shm_offset)		\
-	((__typeof__(****(shm_offset))) (((char *) &(shm_offset)) + (ptrdiff_t) (shm_offset)))
+struct shm_object_table *shm_object_table_create(size_t max_nb_obj);
+struct shm_object *shm_object_table_append_shadow(struct shm_object_table *table,
+			int shm_fd, int wait_fd, size_t memory_map_size);
+void shm_object_table_destroy(struct shm_object_table *table);
+struct shm_object *shm_object_table_append(struct shm_object_table *table,
+					   size_t memory_map_size);
 
-#define _shmp_abs(a)	((a < 0) ? -(a) : (a))
+/*
+ * zalloc_shm - allocate memory within a shm object.
+ *
+ * Shared memory is already zeroed by shmget.
+ * *NOT* multithread-safe (should be protected by mutex).
+ * Returns a -1, -1 tuple on error.
+ */
+struct shm_ref zalloc_shm(struct shm_object *obj, size_t len);
+void align_shm(struct shm_object *obj, size_t align);
 
 static inline
-void _set_shmp(ptrdiff_t *shm_offset, void *ptr)
+int shm_get_wakeup_fd(struct lttng_ust_shm_handle *handle, struct shm_ref *ref)
 {
-	*shm_offset = (((char *) ptr) - ((char *) shm_offset));
-	assert(_shmp_abs(*shm_offset) < MAX_SHM_SIZE);
+	struct shm_object_table *table = handle->table;
+	struct shm_object *obj;
+	size_t index;
+
+	index = (size_t) ref->index;
+	if (caa_unlikely(index >= table->allocated_len))
+		return -EPERM;
+	obj = &table->objects[index];
+	return obj->wait_fd[1];
+
 }
 
-#define set_shmp(shm_offset, ptr)	\
-	_set_shmp((ptrdiff_t *) ****(shm_offset), ptr)
+static inline
+int shm_get_wait_fd(struct lttng_ust_shm_handle *handle, struct shm_ref *ref)
+{
+	struct shm_object_table *table = handle->table;
+	struct shm_object *obj;
+	size_t index;
+
+	index = (size_t) ref->index;
+	if (caa_unlikely(index >= table->allocated_len))
+		return -EPERM;
+	obj = &table->objects[index];
+	return obj->wait_fd[0];
+}
 
-/* Shared memory is already zeroed by shmget */
-/* *NOT* multithread-safe (should be protected by mutex) */
 static inline
-void *zalloc_shm(struct shm_header *shm_header, size_t len)
+int shm_get_object_data(struct lttng_ust_shm_handle *handle, struct shm_ref *ref,
+		int *shm_fd, int *wait_fd, uint64_t *memory_map_size)
 {
-	void *ret;
+	struct shm_object_table *table = handle->table;
+	struct shm_object *obj;
+	size_t index;
 
-	if (shm_header->shm_size - shm_header->shm_allocated < len)
-		return NULL;
-	ret = (char *) shm_header + shm_header->shm_allocated;
-	shm_header->shm_allocated += len;
-	return ret;
+	index = (size_t) ref->index;
+	if (caa_unlikely(index >= table->allocated_len))
+		return -EPERM;
+	obj = &table->objects[index];
+	*shm_fd = obj->shm_fd;
+	*wait_fd = obj->wait_fd[0];
+	*memory_map_size = obj->allocated_len;
+	return 0;
 }
 
 #endif /* _LIBRINGBUFFER_SHM_H */