RUM-16442: Fix profiler safe memory reads

DatadogProfiling/Mach/include/safe_read_testing.h

@@ -7,26 +7,73 @@
 #ifndef DD_PROFILER_SAFE_READ_TESTING_H_
 #define DD_PROFILER_SAFE_READ_TESTING_H_
 
-#include <stdbool.h>
 #include <stddef.h>
+#include <stdint.h>
 
 #ifdef __APPLE__
 #include <TargetConditionals.h>
 #if !TARGET_OS_WATCH
 
+#include "dd_profiler.h"  // stack_trace_t
+
 #ifdef __cplusplus
 extern "C" {
 #endif
 
 /**
- * Helper to manually re-install handlers if needed by tests.
+ * Reads a contiguous region of the calling task's virtual memory starting at sp
+ * into buf (which must be at least buf_size bytes).
+ *
+ * Mirrors the production read_stack_region used inside stack_trace_sample_thread.
+ * Returns the number of contiguous bytes actually read from sp; returns 0 if sp
+ * itself is unmapped or invalid.
+ */
+size_t read_stack_region_for_testing(void* sp, void* buf, size_t buf_size);
+
+/**
+ * Walks a frame pointer chain entirely from a pre-populated local buffer.
+ *
+ * This is the same walk used inside stack_trace_sample_thread, extracted so tests
+ * can exercise the bounds-check guards and cycle-termination behavior directly
+ * without needing to suspend a real thread or craft live stack memory.
+ *
+ * @param trace        Pre-allocated trace; trace->frames must point to at least
+ *                     max_depth entries. frame_count is reset to 0 on entry.
+ * @param initial_fp   First frame pointer to walk from (typically the suspended
+ *                     thread's FP register).
+ * @param initial_pc   First program counter to record (typically the suspended
+ *                     thread's PC register).
+ * @param stack_base   Base address that stack_buf was read from (typically SP).
+ * @param stack_buf    Buffer containing a snapshot of stack memory.
+ * @param bytes_read   Valid bytes in stack_buf.
+ * @param max_depth    Hard cap on frames to record.
  */
-void init_safe_read_handlers_for_testing(void);
+void walk_frames_in_buffer(
+    stack_trace_t* trace,
+    void* initial_fp,
+    void* initial_pc,
+    uintptr_t stack_base,
+    const uint8_t* stack_buf,
+    size_t bytes_read,
+    uint32_t max_depth
+);
 
 /**
- * Validates the Safe Read mechanism.
+ * Same as walk_frames_in_buffer, but enables the production safe-read fallback
+ * for valid frame pointers that are outside the copied stack buffer.
+ *
+ * This lets tests verify that large-but-mapped frame gaps do not silently
+ * truncate otherwise valid stacks.
  */
-bool safe_read_memory_for_testing(void* addr, void* buffer, size_t size);
+void walk_frames_with_safe_read_fallback_for_testing(
+    stack_trace_t* trace,
+    void* initial_fp,
+    void* initial_pc,
+    uintptr_t stack_base,
+    const uint8_t* stack_buf,
+    size_t bytes_read,
+    uint32_t max_depth
+);
 
 #ifdef __cplusplus
 }