Using libunwind for mac, since backtrace do not expect thread context (i.e. working just with current thread)

Author: saf-e

src/unwinder/sentry_unwinder_libbacktrace.c

@@ -6,10 +6,97 @@
 #    define HAS_EXECINFO_H
 #endif
 
+#if defined(SENTRY_PLATFORM_MACOS) && defined(MAC_OS_X_VERSION_10_6)
+#    define HAS_LIBUNWIND
+#endif
+
 #ifdef HAS_EXECINFO_H
 #    include <execinfo.h>
 #endif
 
+#ifdef HAS_LIBUNWIND
+#    include <libunwind.h>
+
+#define ARRAY_SIZE(a) sizeof(a)/sizeof(a[0])
+
+static size_t sentry__unwind_stack_libbacktrace_libnuwind(const sentry_ucontext_t *uctx, void **ptrs, size_t max_frames)
+{
+    unw_context_t ctx;
+    if (unw_getcontext(&ctx))
+        return 0;
+
+    unw_cursor_t cursor;
+    if (unw_init_local(&cursor, &ctx))
+        return 0;
+
+#if defined(__x86_64__)
+    if (unw_set_reg(&cursor, UNW_X86_64_RAX, uctx->user_context->uc_mcontext->__ss.__rax) ||
+        unw_set_reg(&cursor, UNW_X86_64_RDX, uctx->user_context->uc_mcontext->__ss.__rdx) ||
+        unw_set_reg(&cursor, UNW_X86_64_RCX, uctx->user_context->uc_mcontext->__ss.__rcx) ||
+        unw_set_reg(&cursor, UNW_X86_64_RBX, uctx->user_context->uc_mcontext->__ss.__rbx) ||
+        unw_set_reg(&cursor, UNW_X86_64_RSI, uctx->user_context->uc_mcontext->__ss.__rsi) ||
+        unw_set_reg(&cursor, UNW_X86_64_RDI, uctx->user_context->uc_mcontext->__ss.__rdi) ||
+        unw_set_reg(&cursor, UNW_X86_64_RBP, uctx->user_context->uc_mcontext->__ss.__rbp) ||
+        unw_set_reg(&cursor, UNW_X86_64_RSP, uctx->user_context->uc_mcontext->__ss.__rsp) ||
+        unw_set_reg(&cursor, UNW_X86_64_R8, uctx->user_context->uc_mcontext->__ss.__r8)   ||
+        unw_set_reg(&cursor, UNW_X86_64_R9, uctx->user_context->uc_mcontext->__ss.__r9)   ||
+        unw_set_reg(&cursor, UNW_X86_64_R10, uctx->user_context->uc_mcontext->__ss.__r10) ||
+        unw_set_reg(&cursor, UNW_X86_64_R11, uctx->user_context->uc_mcontext->__ss.__r11) ||
+        unw_set_reg(&cursor, UNW_X86_64_R12, uctx->user_context->uc_mcontext->__ss.__r12) ||
+        unw_set_reg(&cursor, UNW_X86_64_R13, uctx->user_context->uc_mcontext->__ss.__r13) ||
+        unw_set_reg(&cursor, UNW_X86_64_R14, uctx->user_context->uc_mcontext->__ss.__r14) ||
+        unw_set_reg(&cursor, UNW_X86_64_R15, uctx->user_context->uc_mcontext->__ss.__r15) ||
+        unw_set_reg(&cursor, UNW_REG_IP, uctx->user_context->uc_mcontext->__ss.__rip)
+        )
+        return 0;
+
+#elif defined(__arm64__)
+    for(size_t i = 0; i < ARRAY_SIZE(uctx->user_context->uc_mcontext->__ss.__x); ++i)
+    {
+        if (unw_set_reg(&cursor, UNW_AARCH64_X0 + i, uctx->user_context->uc_mcontext->__ss.__x[i]))
+        {
+            return 0;
+        }
+    }
+
+    if (unw_set_reg(&cursor, UNW_AARCH64_FP, uctx->user_context->uc_mcontext->__ss.__fp) ||
+        unw_set_reg(&cursor, UNW_AARCH64_LR, uctx->user_context->uc_mcontext->__ss.__lr) ||
+        unw_set_reg(&cursor, UNW_AARCH64_SP, uctx->user_context->uc_mcontext->__ss.__sp) ||
+        unw_set_reg(&cursor, UNW_REG_IP, uctx->user_context->uc_mcontext->__ss.__pc)
+        )
+        return 0;
+
+#endif
+
+    size_t n = 0;
+    for(int err = 1; err >= 0 && n < max_frames; err = unw_step(&cursor))
+    {
+        unw_word_t ip;
+        if (unw_get_reg(&cursor, UNW_REG_IP, &ip))
+        {
+            break;
+        }
+
+#if defined(__arm64__)
+        // Strip pointer authentication, for some reason ptrauth_strip() not working
+        // https://developer.apple.com/documentation/security/preparing_your_app_to_work_with_pointer_authentication
+        ip &= 0x7fffffffffffull;
+#endif
+
+        ptrs[n++] = (void *)ip;
+
+        // last frame
+        if (err == 0)
+        {
+            break;
+        }
+    }
+
+    return n;
+}
+#endif
+
+
 size_t
 sentry__unwind_stack_libbacktrace(
     void *addr, const sentry_ucontext_t *uctx, void **ptrs, size_t max_frames)
@@ -23,7 +110,11 @@ sentry__unwind_stack_libbacktrace(
 #endif
         return 0;
     } else if (uctx) {
+#ifdef HAS_LIBUNWIND
+        return sentry__unwind_stack_libbacktrace_libnuwind(uctx, ptrs, max_frames);
+#else
         return 0;
+#endif
     }
 #ifdef HAS_EXECINFO_H
     return (size_t)backtrace(ptrs, (int)max_frames);