Ticket #10509: align-stack.diff

src/system/kernel/arch/x86/32/thread.cpp

@@ -114 +114 @@
 {
     STATIC_ASSERT(MAX_RANDOM_VALUE >= B_PAGE_SIZE - 1);
     value -= random_value() & (B_PAGE_SIZE - 1);
-    return value & ~addr_t(0xf);
+    return (value & ~addr_t(0xf)) - 4;
+        // This means, result % 16 == 12, which is what esp should adhere to
+        // when a function is entered for the stack to be considered aligned to
+        // 16 byte.
 }
 
 
 static uint8*
-get_signal_stack(Thread* thread, struct iframe* frame, struct sigaction* action)
+get_signal_stack(Thread* thread, struct iframe* frame, struct sigaction* action,
+    size_t spaceNeeded)
 {
     // use the alternate signal stack if we should and can
     if (thread->signal_stack_enabled
@@ -128 +132 @@
             || frame->user_sp >= thread->signal_stack_base
                 + thread->signal_stack_size)) {
         addr_t stackTop = thread->signal_stack_base + thread->signal_stack_size;
-        return (uint8*)arch_randomize_stack_pointer(stackTop);
+        return (uint8*)arch_randomize_stack_pointer(stackTop - spaceNeeded);
     }
 
-    return (uint8*)frame->user_sp;
+    return (uint8*)((frame->user_sp - spaceNeeded) & ~addr_t(0xf)) - 4;
+        // align stack pointer (cf. arch_randomize_stack_pointer())
 }
 
 
@@ -223 +228 @@
     TRACE(("arch_thread_enter_userspace: entry 0x%lx, args %p %p, "
         "ustack_top 0x%lx\n", entry, args1, args2, stackTop));
 
-    stackTop = arch_randomize_stack_pointer(stackTop);
+    stackTop = arch_randomize_stack_pointer(stackTop - sizeof(args));
 
     // Copy the address of the stub that calls exit_thread() when the thread
     // entry function returns to the top of the stack to act as the return
@@ -233 +238 @@
         + commPageAddress;
     args[1] = (uint32)args1;
     args[2] = (uint32)args2;
-    stackTop -= sizeof(args);
 
     if (user_memcpy((void *)stackTop, args, sizeof(args)) < B_OK)
         return B_BAD_ADDRESS;
@@ -325 +329 @@
 
     // get the stack to use -- that's either the current one or a special signal
     // stack
-    uint8* userStack = get_signal_stack(thread, frame, action);
+    uint32 stackFrame[2];
+    uint8* userStack = get_signal_stack(thread, frame, action,
+        sizeof(*signalFrameData) + sizeof(stackFrame));
 
     // copy the signal frame data onto the stack
-    userStack -= sizeof(*signalFrameData);
-    signal_frame_data* userSignalFrameData = (signal_frame_data*)userStack;
+    signal_frame_data* userSignalFrameData
+        = (signal_frame_data*)(userStack + sizeof(stackFrame));
     if (user_memcpy(userSignalFrameData, signalFrameData,
             sizeof(*signalFrameData)) != B_OK) {
         return B_BAD_ADDRESS;
@@ -337 +343 @@
 
     // prepare the user stack frame for a function call to the signal handler
     // wrapper function
-    uint32 stackFrame[2] = {
-        frame->ip,      // return address
-        (addr_t)userSignalFrameData, // parameter: pointer to signal frame data
-    };
+    stackFrame[0] = frame->ip;
+    stackFrame[1] = (addr_t)userSignalFrameData;
+        // parameter: pointer to signal frame data
 
-    userStack -= sizeof(stackFrame);
     if (user_memcpy(userStack, stackFrame, sizeof(stackFrame)) != B_OK)
         return B_BAD_ADDRESS;