From 8964aa089c709fbf370be623d75a204480b26b3c Mon Sep 17 00:00:00 2001
From: "Jay Freeman (saurik)" <saurik@saurik.com>
Date: Fri, 3 Jan 2014 21:37:04 -0800
Subject: [PATCH] Copy libdyld error messages back from injection.

---
 Baton.hpp        |  1 +
 Mach/Inject.cpp  |  6 ++++++
 Mach/Memory.hpp  | 12 ++++++++++++
 Trampoline.t.cpp | 16 ++++++++++++++--
 4 files changed, 33 insertions(+), 2 deletions(-)

diff --git a/Baton.hpp b/Baton.hpp
index 3d29893..696a94d 100644
--- a/Baton.hpp
+++ b/Baton.hpp
@@ -28,5 +28,6 @@
 struct Baton {
     uint64_t dyld;
     pid_t pid;
+    char error[1024];
     char library[];
 } _packed;
diff --git a/Mach/Inject.cpp b/Mach/Inject.cpp
index 50ad0f8..982ffe4 100644
--- a/Mach/Inject.cpp
+++ b/Mach/Inject.cpp
@@ -288,6 +288,12 @@ void InjectLibrary(pid_t pid) {
 
     _krncall(mach_port_deallocate(self, thread));
 
+    mach_vm_size_t error(sizeof(baton->error));
+    _krncall(mach_vm_read_overwrite(task, data + offsetof(Baton, error), sizeof(baton->error), reinterpret_cast<mach_vm_address_t>(&baton->error), &error));
+    _assert(error == sizeof(baton->error));
+    if (baton->error[0] != '\0')
+        CYThrow("%s", baton->error);
+
     _krncall(mach_vm_deallocate(task, code, trampoline->size_));
     _krncall(mach_vm_deallocate(task, stack, size));
 
diff --git a/Mach/Memory.hpp b/Mach/Memory.hpp
index ed31a8d..47e376d 100644
--- a/Mach/Memory.hpp
+++ b/Mach/Memory.hpp
@@ -31,6 +31,18 @@ static kern_return_t cy_vm_protect(bool broken, vm_map_t target_task, mach_vm_ad
 #define mach_vm_protect(a, b, c, d, e) \
     cy_vm_protect(broken, a, b, c, d, e)
 
+static kern_return_t cy_vm_read_overwrite(bool broken, vm_map_t target_task, mach_vm_address_t address, mach_vm_size_t size, mach_vm_address_t data, mach_vm_size_t *outsize) {
+    if (!broken)
+        return mach_vm_read_overwrite(target_task, address, size, data, outsize);
+    vm_size_t outsize32(*outsize);
+    kern_return_t value(vm_read_overwrite(target_task, address, data, size, &outsize32));
+    *outsize = outsize32;
+    return value;
+}
+
+#define mach_vm_read_overwrite(a, b, c, d, e) \
+    cy_vm_read_overwrite(broken, a, b, c, d, e)
+
 static kern_return_t cy_vm_write(bool broken, vm_map_t target_task, mach_vm_address_t address, vm_offset_t data, mach_msg_type_number_t dataCnt) {
     if (!broken)
         return mach_vm_write(target_task, address, data, dataCnt);
diff --git a/Trampoline.t.cpp b/Trampoline.t.cpp
index 1bcbb18..0ae088d 100644
--- a/Trampoline.t.cpp
+++ b/Trampoline.t.cpp
@@ -52,6 +52,18 @@ static int $strcmp(const char *lhs, const char *rhs) {
     } return *lhs < *rhs ? -1 : 1;
 }
 
+static void $strlcpy(char *dst, const char *src, size_t size) {
+    if (size == 0)
+        return;
+    size_t i(0);
+    while (i != size - 1) {
+        char value(src[i]);
+        if (value == '\0')
+            break;
+        dst[i++] = value;
+    } dst[i] = '\0';
+}
+
 #ifdef __LP64__
 typedef struct mach_header_64 mach_header_xx;
 typedef struct nlist_64 nlist_xx;
@@ -177,7 +189,7 @@ void *Routine(void *arg) {
 
     void *handle($dlopen(baton->library, RTLD_LAZY | RTLD_LOCAL));
     if (handle == NULL) {
-        $dlerror();
+        $strlcpy(baton->error, $dlerror(), sizeof(baton->error));
         return NULL;
     }
 
@@ -187,7 +199,7 @@ void *Routine(void *arg) {
     void (*CYHandleServer)(pid_t);
     CYHandleServer = reinterpret_cast<void (*)(pid_t)>($dlsym(handle, "CYHandleServer"));
     if (CYHandleServer == NULL) {
-        $dlerror();
+        $strlcpy(baton->error, $dlerror(), sizeof(baton->error));
         return NULL;
     }
 
-- 
2.47.2