Add TLS support

Initial support for `_Thread_local` (and `_Thread_local static`)
variables.

Limitations:
* Supports a single TLS region, but amenable to
future extensions if we want to implement multi-threaded compartments;
* Handles only symbols of type `TLSDESC`.

Other changes:
* Remove some old `struct Compartment` member variables that are now
  unneeded;
* Add `print_comp` back;
* Fix a bug regarding calculating scratch memory size for compartments;
* Fixed a bug with setting relocation target addresses.

include/comp_utils.h

@@ -4,6 +4,7 @@
 #include <err.h>
 #include <stddef.h>
 #include <string.h>
+#include <sys/mman.h>
 
 #include "cheriintrin.h"
 

include/compartment.h

@@ -34,11 +34,9 @@
 // currently there's quite a bit of redundancy to make things easier to think
 // about
 
-void
-compartment_transition_out();
 int64_t
-comp_exec_in(
-    void *, void *__capability, void *, void *, size_t, void *__capability);
+comp_exec_in(void *, void *__capability, void *, void *, size_t,
+    void *__capability, void *);
 void
 comp_exec_out();
 
@@ -48,8 +46,6 @@ extern void
 __clear_cache(void *, void *);
 
 // Number of instructions required by the transition function
-#define COMP_TRANS_FN_INSTR_CNT 4
-
 extern void *__capability sealed_redirect_cap;
 extern void *__capability comp_return_caps[2];
 
@@ -145,6 +141,26 @@ struct LibDependency
     // Symbols within this library that need eager relocation
     size_t rela_maps_count;
     struct LibRelaMapping *rela_maps;
+
+    // TLS-related variables
+    // TODO can there be more TLS sections?
+    void *tls_sec_addr;
+    size_t tls_sec_size;
+    size_t tls_data_size;
+};
+
+/**
+ * Struct representing TLS information for a compartment. Since we currently
+ * enforce only single-threaded code, we basically only have pointers for
+ * regions allocated for TLS for each dynamic shared object
+ */
+struct TLSDesc
+{
+    unsigned short region_count;
+    size_t region_size;
+    void *region_start;
+    unsigned short libs_count;
+    unsigned short *lib_idxs;
 };
 
 /**
@@ -166,29 +182,18 @@ struct Compartment
     // Scratch memory
     void *scratch_mem_base;
     size_t scratch_mem_size;
-    size_t scratch_mem_alloc;
 
     size_t scratch_mem_heap_size;
     void *scratch_mem_stack_top;
     size_t scratch_mem_stack_size;
-    void *stack_pointer;
-    struct MemAlloc *alloc_head;
-
-    // TODO double check / rework this process
-    void *manager_caps;
-    size_t max_manager_caps_count;
-    size_t active_manager_caps_count;
-
-    // Transition function (duplicated across compartments, but must be within
-    // to be within DDC bounds)
-    void *mng_trans_fn;
-    size_t mng_trans_fn_sz;
 
     // Internal libraries and relocations
     size_t libs_count;
     struct LibDependency **libs;
     size_t entry_point_count;
     struct CompEntryPoint *entry_points;
+    void *tls_lookup_func;
+    struct TLSDesc *libs_tls_sects;
 
     // Hardware info - maybe move
     size_t page_size;

include/manager.h

@@ -24,12 +24,6 @@ extern void *__capability manager_ddc;
 extern struct CompWithEntries **comps;
 extern struct Compartment *loaded_comp;
 
-/*******************************************************************************
- * Utility Functions
- ******************************************************************************/
-
-void print_full_cap(uintcap_t);
-
 /*******************************************************************************
  * Compartment
  ******************************************************************************/

src/comp_utils.c

@@ -3,15 +3,33 @@
 static void *malloc_ptr;
 static size_t heap_mem_left;
 
+#define NON_COMP_DEFAULT_SIZE (10 * 1024) // 10 MB
+
 void *
 malloc(size_t to_alloc)
 {
     if (!malloc_ptr)
     {
         void *__capability ddc = cheri_ddc_get();
-        malloc_ptr = (char *) cheri_address_get(ddc);
-        heap_mem_left = cheri_length_get(ddc) - cheri_offset_get(ddc);
+        if (cheri_base_get(ddc) == 0)
+        {
+            malloc_ptr = mmap(0, NON_COMP_DEFAULT_SIZE, PROT_WRITE | PROT_READ,
+                MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+            heap_mem_left = NON_COMP_DEFAULT_SIZE;
+            if (malloc_ptr == MAP_FAILED)
+            {
+                err(1, "Failed `mmap`");
+            }
+        }
+        else
+        {
+            malloc_ptr = (char *) cheri_address_get(ddc);
+            // TODO move heap to the end of the compartment; currently, it's at
+            // the beginning of the memory scratch area
+            heap_mem_left = cheri_length_get(ddc) - cheri_offset_get(ddc);
+        }
     }
+
     if (to_alloc > heap_mem_left)
     {
         errx(1, "Insufficient heap space left.");
@@ -44,3 +62,12 @@ realloc(void *to_realloc, size_t new_size)
 
     return malloc(new_size);
 }
+
+void
+tls_lookup_stub()
+{
+    // Get TLS index
+    // TODO works only for one TLS region
+    asm("ldr x0, [x0, #8]" : :);
+    return;
+}