Fix: integer overflow in main thread stack base detection

Using `getrlimit` led to invalid STACK SIZE limits in some cases
which in turn led to an integer overflow while detecting the stack
base of the main stack.

This patch replaces `getrlimit` with proper, but non portable, calls
to pthread functions that return the stack of a given thread.

fixes crystal-lang#7368
fixes crystal-lang#7369

src/fiber.cr

@@ -87,28 +87,12 @@ class Fiber
   end
 
   # :nodoc:
-  def initialize
+  def initialize(@stack : Void*)
     @proc = Proc(Void).new { }
     @stack_top = _fiber_get_stack_top
     @stack_bottom = GC.stack_bottom
     @name = "main"
 
-    # Determine location of the top of the stack.
-    # The technique here works only for the main stack on a POSIX platform.
-    # TODO: implement for Windows with GetCurrentThreadStackLimits
-    # TODO: implement for pthreads using
-    #    linux-glibc/musl: pthread_getattr_np
-    #              macosx: pthread_get_stackaddr_np, pthread_get_stacksize_np
-    #             freebsd: pthread_attr_get_np
-    #             openbsd: pthread_stackseg_np
-    @stack = Pointer(Void).null
-    {% unless flag?(:win32) %}
-      if LibC.getrlimit(LibC::RLIMIT_STACK, out rlim) == 0
-        stack_size = rlim.rlim_cur
-        @stack = Pointer(Void).new(@stack_bottom.address - stack_size)
-      end
-    {% end %}
-
     @@fibers.push(self)
   end
 

src/lib_c/aarch64-linux-gnu/c/pthread.cr

@@ -3,6 +3,8 @@ require "./sys/types"
 lib LibC
   PTHREAD_MUTEX_ERRORCHECK = 2
 
+  fun pthread_attr_destroy(attr : PthreadAttrT*) : Int
+  fun pthread_attr_getstack(addr : PthreadAttrT*, stackaddr : Void**, stacksize : SizeT*) : Int
   fun pthread_condattr_destroy(attr : PthreadCondattrT*) : Int
   fun pthread_condattr_init(attr : PthreadCondattrT*) : Int
   fun pthread_condattr_setclock(attr : PthreadCondattrT*, type : ClockidT) : Int
@@ -14,6 +16,7 @@ lib LibC
   fun pthread_cond_wait(cond : PthreadCondT*, mutex : PthreadMutexT*) : Int
   fun pthread_create(newthread : PthreadT*, attr : PthreadAttrT*, start_routine : Void* -> Void*, arg : Void*) : Int
   fun pthread_detach(th : PthreadT) : Int
+  fun pthread_getattr_np(thread : PthreadT, attr : PthreadAttrT*) : Int
   fun pthread_equal(thread1 : PthreadT, thread2 : PthreadT) : Int
   fun pthread_join(th : PthreadT, thread_return : Void**) : Int
   fun pthread_mutexattr_destroy(attr : PthreadMutexattrT*) : Int

src/lib_c/aarch64-linux-musl/c/pthread.cr

@@ -3,6 +3,8 @@ require "./sys/types"
 lib LibC
   PTHREAD_MUTEX_ERRORCHECK = 2
 
+  fun pthread_attr_destroy(x0 : PthreadAttrT*) : Int
+  fun pthread_attr_getstack(x0 : PthreadAttrT*, x1 : Void**, x2 : SizeT*) : Int
   fun pthread_condattr_destroy(x0 : PthreadCondattrT*) : Int
   fun pthread_condattr_init(x0 : PthreadCondattrT*) : Int
   fun pthread_condattr_setclock(x0 : PthreadCondattrT*, x1 : ClockidT) : Int
@@ -14,6 +16,7 @@ lib LibC
   fun pthread_cond_wait(x0 : PthreadCondT*, x1 : PthreadMutexT*) : Int
   fun pthread_create(x0 : PthreadT*, x1 : PthreadAttrT*, x2 : Void* -> Void*, x3 : Void*) : Int
   fun pthread_detach(x0 : PthreadT) : Int
+  fun pthread_getattr_np(x0 : PthreadT, x1 : PthreadAttrT*) : Int
   fun pthread_join(x0 : PthreadT, x1 : Void**) : Int
   fun pthread_mutexattr_destroy(x0 : PthreadMutexattrT*) : Int
   fun pthread_mutexattr_init(x0 : PthreadMutexattrT*) : Int

src/lib_c/arm-linux-gnueabihf/c/pthread.cr

@@ -3,6 +3,8 @@ require "./sys/types"
 lib LibC
   PTHREAD_MUTEX_ERRORCHECK = 2
 
+  fun pthread_attr_destroy(attr : PthreadAttrT*) : Int
+  fun pthread_attr_getstack(addr : PthreadAttrT*, stackaddr : Void**, stacksize : SizeT*) : Int
   fun pthread_condattr_destroy(attr : PthreadCondattrT*) : Int
   fun pthread_condattr_init(attr : PthreadCondattrT*) : Int
   fun pthread_condattr_setclock(attr : PthreadCondattrT*, type : ClockidT) : Int
@@ -14,6 +16,7 @@ lib LibC
   fun pthread_cond_wait(cond : PthreadCondT*, mutex : PthreadMutexT*) : Int
   fun pthread_create(newthread : PthreadT*, attr : PthreadAttrT*, start_routine : Void* -> Void*, arg : Void*) : Int
   fun pthread_detach(th : PthreadT) : Int
+  fun pthread_getattr_np(thread : PthreadT, attr : PthreadAttrT*) : Int
   fun pthread_equal(thread1 : PthreadT, thread2 : PthreadT) : Int
   fun pthread_join(th : PthreadT, thread_return : Void**) : Int
   fun pthread_mutexattr_destroy(attr : PthreadMutexattrT*) : Int

src/lib_c/i386-linux-gnu/c/pthread.cr

@@ -3,6 +3,8 @@ require "./sys/types"
 lib LibC
   PTHREAD_MUTEX_ERRORCHECK = 2
 
+  fun pthread_attr_destroy(attr : PthreadAttrT*) : Int
+  fun pthread_attr_getstack(addr : PthreadAttrT*, stackaddr : Void**, stacksize : SizeT*) : Int
   fun pthread_condattr_destroy(attr : PthreadCondattrT*) : Int
   fun pthread_condattr_init(attr : PthreadCondattrT*) : Int
   fun pthread_condattr_setclock(attr : PthreadCondattrT*, type : ClockidT) : Int
@@ -14,6 +16,7 @@ lib LibC
   fun pthread_cond_wait(cond : PthreadCondT*, mutex : PthreadMutexT*) : Int
   fun pthread_create(newthread : PthreadT*, attr : PthreadAttrT*, start_routine : Void* -> Void*, arg : Void*) : Int
   fun pthread_detach(th : PthreadT) : Int
+  fun pthread_getattr_np(thread : PthreadT, attr : PthreadAttrT*) : Int
   fun pthread_join(th : PthreadT, thread_return : Void**) : Int
   fun pthread_mutexattr_destroy(attr : PthreadMutexattrT*) : Int
   fun pthread_mutexattr_init(attr : PthreadMutexattrT*) : Int

src/lib_c/i386-linux-musl/c/pthread.cr

@@ -3,6 +3,8 @@ require "./sys/types"
 lib LibC
   PTHREAD_MUTEX_ERRORCHECK = 2
 
+  fun pthread_attr_destroy(x0 : PthreadAttrT*) : Int
+  fun pthread_attr_getstack(x0 : PthreadAttrT*, x1 : Void**, x2 : SizeT*) : Int
   fun pthread_condattr_destroy(x0 : PthreadCondattrT*) : Int
   fun pthread_condattr_init(x0 : PthreadCondattrT*) : Int
   fun pthread_condattr_setclock(x0 : PthreadCondattrT*, x1 : ClockidT) : Int
@@ -14,6 +16,7 @@ lib LibC
   fun pthread_cond_wait(x0 : PthreadCondT*, x1 : PthreadMutexT*) : Int
   fun pthread_create(x0 : PthreadT*, x1 : PthreadAttrT*, x2 : Void* -> Void*, x3 : Void*) : Int
   fun pthread_detach(x0 : PthreadT) : Int
+  fun pthread_getattr_np(x0 : PthreadT, x1 : PthreadAttrT*) : Int
   fun pthread_join(x0 : PthreadT, x1 : Void**) : Int
   fun pthread_mutexattr_destroy(x0 : PthreadMutexattrT*) : Int
   fun pthread_mutexattr_init(x0 : PthreadMutexattrT*) : Int

src/lib_c/x86_64-darwin/c/pthread.cr

@@ -13,6 +13,8 @@ lib LibC
   fun pthread_cond_wait(x0 : PthreadCondT*, x1 : PthreadMutexT*) : Int
   fun pthread_create(x0 : PthreadT*, x1 : PthreadAttrT*, x2 : Void* -> Void*, x3 : Void*) : Int
   fun pthread_detach(x0 : PthreadT) : Int
+  fun pthread_get_stackaddr_np(x0 : PthreadT) : Void*
+  fun pthread_get_stacksize_np(x0 : PthreadT) : SizeT
   fun pthread_join(x0 : PthreadT, x1 : Void**) : Int
   fun pthread_mutexattr_destroy(x0 : PthreadMutexattrT*) : Int
   fun pthread_mutexattr_init(x0 : PthreadMutexattrT*) : Int

src/lib_c/x86_64-freebsd/c/pthread.cr

@@ -4,6 +4,10 @@ require "./sys/types"
 lib LibC
   PTHREAD_MUTEX_ERRORCHECK = 1
 
+  fun pthread_attr_destroy(x0 : PthreadAttrT*) : Int
+  fun pthread_attr_get_np(x0 : PthreadT, x1 : PthreadAttrT*) : Int
+  fun pthread_attr_getstack(x0 : PthreadAttrT*, x1 : Void**, x2 : SizeT*) : Int
+  fun pthread_attr_init(x0 : PthreadAttrT*) : Int
   fun pthread_condattr_destroy(x0 : PthreadCondattrT*) : Int
   fun pthread_condattr_init(x0 : PthreadCondattrT*) : Int
   fun pthread_condattr_setclock(x0 : PthreadCondattrT*, x1 : ClockidT) : Int

src/lib_c/x86_64-linux-gnu/c/pthread.cr

@@ -3,6 +3,8 @@ require "./sys/types"
 lib LibC
   PTHREAD_MUTEX_ERRORCHECK = 2
 
+  fun pthread_attr_destroy(attr : PthreadAttrT*) : Int
+  fun pthread_attr_getstack(addr : PthreadAttrT*, stackaddr : Void**, stacksize : SizeT*) : Int
   fun pthread_condattr_destroy(attr : PthreadCondattrT*) : Int
   fun pthread_condattr_init(attr : PthreadCondattrT*) : Int
   fun pthread_condattr_setclock(attr : PthreadCondattrT*, type : ClockidT) : Int
@@ -14,6 +16,7 @@ lib LibC
   fun pthread_cond_wait(cond : PthreadCondT*, mutex : PthreadMutexT*) : Int
   fun pthread_create(newthread : PthreadT*, attr : PthreadAttrT*, start_routine : Void* -> Void*, arg : Void*) : Int
   fun pthread_detach(th : PthreadT) : Int
+  fun pthread_getattr_np(thread : PthreadT, attr : PthreadAttrT*) : Int
   fun pthread_join(th : PthreadT, thread_return : Void**) : Int
   fun pthread_mutexattr_destroy(attr : PthreadMutexattrT*) : Int
   fun pthread_mutexattr_init(attr : PthreadMutexattrT*) : Int

src/lib_c/x86_64-linux-musl/c/pthread.cr

@@ -3,6 +3,8 @@ require "./sys/types"
 lib LibC
   PTHREAD_MUTEX_ERRORCHECK = 2
 
+  fun pthread_attr_destroy(x0 : PthreadAttrT*) : Int
+  fun pthread_attr_getstack(x0 : PthreadAttrT*, x1 : Void**, x2 : SizeT*) : Int
   fun pthread_condattr_destroy(x0 : PthreadCondattrT*) : Int
   fun pthread_condattr_init(x0 : PthreadCondattrT*) : Int
   fun pthread_condattr_setclock(x0 : PthreadCondattrT*, x1 : ClockidT) : Int
@@ -14,6 +16,7 @@ lib LibC
   fun pthread_cond_wait(x0 : PthreadCondT*, x1 : PthreadMutexT*) : Int
   fun pthread_create(x0 : PthreadT*, x1 : PthreadAttrT*, x2 : Void* -> Void*, x3 : Void*) : Int
   fun pthread_detach(x0 : PthreadT) : Int
+  fun pthread_getattr_np(x0 : PthreadT, x1 : PthreadAttrT*) : Int
   fun pthread_join(x0 : PthreadT, x1 : Void**) : Int
   fun pthread_mutexattr_destroy(x0 : PthreadMutexattrT*) : Int
   fun pthread_mutexattr_init(x0 : PthreadMutexattrT*) : Int

src/lib_c/x86_64-openbsd/c/pthread.cr

@@ -20,6 +20,7 @@ lib LibC
   fun pthread_join(x0 : PthreadT, x1 : Void**) : Int
   alias PthreadKeyDestructor = (Void*) ->
   fun pthread_key_create(PthreadKeyT*, PthreadKeyDestructor) : Int
+  fun pthread_main_np : Int
   fun pthread_mutexattr_destroy(x0 : PthreadMutexattrT*) : Int
   fun pthread_mutexattr_init(x0 : PthreadMutexattrT*) : Int
   fun pthread_mutexattr_settype(x0 : PthreadMutexattrT*, x1 : Int) : Int
@@ -30,4 +31,5 @@ lib LibC
   fun pthread_mutex_unlock(x0 : PthreadMutexT*) : Int
   fun pthread_self : PthreadT
   fun pthread_setspecific(PthreadKeyT, Void*) : Int
+  fun pthread_stackseg_np(PthreadT, StackT*) : Int
 end

src/lib_c/x86_64-openbsd/c/signal.cr

@@ -42,6 +42,12 @@ lib LibC
   SIG_DFL = SighandlerT.new(Pointer(Void).new(0_u64), Pointer(Void).null)
   SIG_IGN = SighandlerT.new(Pointer(Void).new(1_u64), Pointer(Void).null)
 
+  struct StackT
+    ss_sp : Void*
+    ss_size : SizeT
+    ss_flags : Int
+  end
+
   fun kill(x0 : PidT, x1 : Int) : Int
   fun pthread_sigmask(Int, SigsetT*, SigsetT*) : Int
   fun signal(x0 : Int, x1 : Int -> Void) : Int -> Void

src/lib_c/x86_64-openbsd/c/unistd.cr

@@ -2,11 +2,12 @@ require "./sys/types"
 require "./stdint"
 
 lib LibC
-  F_OK       =    0
-  R_OK       = 0x04
-  W_OK       = 0x02
-  X_OK       = 0x01
-  SC_CLK_TCK =    3
+  F_OK        =    0
+  R_OK        = 0x04
+  W_OK        = 0x02
+  X_OK        = 0x01
+  SC_CLK_TCK  =    3
+  SC_PAGESIZE =   28
 
   fun chroot(dirname : Char*) : Int
   fun access(x0 : Char*, x1 : Int) : Int

src/thread.cr

@@ -42,7 +42,7 @@ class Thread
   def initialize
     @func = ->{}
     @th = LibC.pthread_self
-    @main_fiber = Fiber.new
+    @main_fiber = Fiber.new(stack_address)
 
     @@threads.push(self)
   end
@@ -124,7 +124,7 @@ class Thread
 
   protected def start
     Thread.current = self
-    @main_fiber = fiber = Fiber.new
+    @main_fiber = fiber = Fiber.new(stack_address)
 
     begin
       @func.call
@@ -135,4 +135,42 @@ class Thread
       Fiber.inactive(fiber)
     end
   end
+
+  private def stack_address : Void*
+    address = Pointer(Void).null
+
+    {% if flag?(:darwin) %}
+      address = LibC.pthread_get_stackaddr_np(@th) - pthread_get_stacksize_np(@th)
+
+    {% elsif flag?(:freebsd) %}
+      ret = LibC.pthread_attr_init(out attr)
+      raise Errno.new("pthread_attr_init", ret) unless ret == 0
+
+      if LibC.pthread_attr_get_np(@th, pointerof(attr)) == 0
+        LibC.pthread_attr_getstack(pointerof(attr), pointerof(address), out _)
+      end
+      ret = LibC.pthread_attr_destroy(pointerof(attr))
+      raise Errno.new("pthread_attr_destroy", ret) unless ret == 0
+
+    {% elsif flag?(:linux) %}
+      if LibC.pthread_getattr_np(@th, out attr) == 0
+        LibC.pthread_attr_getstack(pointerof(attr), pointerof(address), out _)
+      end
+      ret = LibC.pthread_attr_destroy(pointerof(attr))
+      raise Errno.new("pthread_attr_destroy", ret) unless ret == 0
+
+    {% elsif flag?(:openbsd) %}
+      ret = LibC.pthread_stackseg_np(@th, out stack)
+      raise Errno.new("pthread_stackseg_np", ret) unless ret == 0
+
+      address =
+        if LibC.pthread_main_np == 1
+          stack.ss_sp - stack.ss_size + sysconf(LibC::SC_PAGESIZE)
+        else
+          stack.ss_sp - stack.ss_size
+        end
+    {% end %}
+
+    address
+  end
 end