libdl: Support link ordered loading of ELF sections.

The ARM C++ exception ABI uses an address ordered index table to
locate the correct frame data and this requires the EXIDX sections are
loaded in the order the order the matching text is loaded.

The EXIDX sections set the SHF_LINK_ORDER flag and link field. This patch
adds support to load those flagged sections in the linked-to section
order.

Updates #2955.
Closes #2959

5 files changed, 166 insertions, 36 deletions

diff --git a/cpukit/libdl/include/sys/exec_elf.h b/cpukit/libdl/include/sys/exec_elf.h
index 08da7e809e..4242415f54 100644
--- a/cpukit/libdl/include/sys/exec_elf.h
+++ b/cpukit/libdl/include/sys/exec_elf.h
@@ -459,6 +459,10 @@ typedef struct {
 #define	SHF_WRITE	0x1		/* Section contains writable data */
 #define	SHF_ALLOC	0x2		/* Section occupies memory */
 #define	SHF_EXECINSTR	0x4		/* Section contains executable insns */
+#define	SHF_MERGE	0x10		/* Section contains data that can be merged */
+#define	SHF_STRINGS	0x20		/* Section contains null-terminated strings */
+#define	SHF_INFO_LINK	0x40		/* Section header's sh_info holds table index */
+#define	SHF_LINK_ORDER	0x80		/* Section has special ordering requirements */
 
 #define	SHF_MASKOS	0x0f000000	/* Operating system specific values */
 #define	SHF_MASKPROC	0xf0000000	/* Processor-specific values */
@@ -949,13 +953,13 @@ typedef struct {
 #define	SYMINFO_NUM		2
 
 /*
- * These constants are used for Elf32_Verdef struct's version number.  
+ * These constants are used for Elf32_Verdef struct's version number.
  */
 #define VER_DEF_NONE		0
 #define	VER_DEF_CURRENT		1
 
 /*
- * These constants are used for Elf32_Verdef struct's vd_flags.  
+ * These constants are used for Elf32_Verdef struct's vd_flags.
  */
 #define VER_FLG_BASE		0x1
 #define	VER_FLG_WEAK		0x2
@@ -967,7 +971,7 @@ typedef struct {
 #define	VER_NDX_GLOBAL		1
 
 /*
- * These constants are used for Elf32_Verneed struct's version number.  
+ * These constants are used for Elf32_Verneed struct's version number.
  */
 #define	VER_NEED_NONE		0
 #define	VER_NEED_CURRENT	1
diff --git a/cpukit/libdl/rtl-elf.c b/cpukit/libdl/rtl-elf.c
index 37775ff776..be2f06a7ba 100644
--- a/cpukit/libdl/rtl-elf.c
+++ b/cpukit/libdl/rtl-elf.c
@@ -656,6 +656,11 @@ rtems_rtl_elf_parse_sections (rtems_rtl_obj_t* obj, int fd, Elf_Ehdr* ehdr)
 
     flags = 0;
 
+    if (rtems_rtl_trace (RTEMS_RTL_TRACE_DETAIL))
+      printf ("rtl: section: %2d: type=%d flags=%08x link=%d info=%d\n",
+              section, (int) shdr.sh_type, (unsigned int) shdr.sh_flags,
+              (int) shdr.sh_link, (int) shdr.sh_info);
+
     switch (shdr.sh_type)
     {
       case SHT_NULL:
@@ -712,7 +717,7 @@ rtems_rtl_elf_parse_sections (rtems_rtl_obj_t* obj, int fd, Elf_Ehdr* ehdr)
 
       default:
         /*
-         * See there are architecture specific flags?
+         * See if there are architecture specific flags?
          */
         flags = rtems_rtl_elf_section_flags (obj, &shdr);
         if (flags == 0)
@@ -729,6 +734,13 @@ rtems_rtl_elf_parse_sections (rtems_rtl_obj_t* obj, int fd, Elf_Ehdr* ehdr)
       char*  name;
       size_t len;
 
+      /*
+       * If link ordering this section must appear in the same order in memory
+       * as the linked-to section relative to the sections it loads with.
+       */
+      if ((shdr.sh_flags & SHF_LINK_ORDER) != 0)
+        flags |= RTEMS_RTL_OBJ_SECT_LINK;
+
       len = RTEMS_RTL_ELF_STRING_MAX;
       if (!rtems_rtl_obj_cache_read (strings, fd,
                                      sectstroff + shdr.sh_name,
diff --git a/cpukit/libdl/rtl-mdreloc-sparc.c b/cpukit/libdl/rtl-mdreloc-sparc.c
index 38b385070e..8d1239421d 100644
--- a/cpukit/libdl/rtl-mdreloc-sparc.c
+++ b/cpukit/libdl/rtl-mdreloc-sparc.c
@@ -253,7 +253,8 @@ rtems_rtl_elf_relocate_rela (const rtems_rtl_obj_t*      obj,
 
   if (rtems_rtl_trace (RTEMS_RTL_TRACE_RELOC))
     printf ("rtl: %s %p @ %p in %s\n",
-            reloc_names[type], (void *)tmp, where, rtems_rtl_obj_oname (obj));
+            reloc_names[ELF_R_TYPE(rela->r_info)],
+            (void *)tmp, where, rtems_rtl_obj_oname (obj));
 
   return true;
 }
diff --git a/cpukit/libdl/rtl-obj.c b/cpukit/libdl/rtl-obj.c
index b27f28b9a9..bb0bc8d543 100644
--- a/cpukit/libdl/rtl-obj.c
+++ b/cpukit/libdl/rtl-obj.c
@@ -601,12 +601,12 @@ typedef struct
 static bool
 rtems_rtl_obj_sect_sync_handler (rtems_chain_node* node, void* data)
 {
-  rtems_rtl_obj_sect_t*   sect = (rtems_rtl_obj_sect_t*) node;
+  rtems_rtl_obj_sect_t*          sect = (rtems_rtl_obj_sect_t*) node;
   rtems_rtl_obj_sect_sync_ctx_t* sync_ctx = data;
-  uintptr_t old_end;
-  uintptr_t new_start;
+  uintptr_t                      old_end;
+  uintptr_t                      new_start;
 
-  if ( !(sect->flags & sync_ctx->mask) || !sect->size)
+  if ((sect->flags & sync_ctx->mask) == 0 || sect->size == 0)
     return true;
 
   if (sync_ctx->end_va == sync_ctx->start_va)
@@ -632,7 +632,7 @@ rtems_rtl_obj_sect_sync_handler (rtems_chain_node* node, void* data)
 }
 
 void
-rtems_rtl_obj_synchronize_cache (rtems_rtl_obj_t*    obj)
+rtems_rtl_obj_synchronize_cache (rtems_rtl_obj_t* obj)
 {
   rtems_rtl_obj_sect_sync_ctx_t sync_ctx;
 
@@ -643,7 +643,7 @@ rtems_rtl_obj_synchronize_cache (rtems_rtl_obj_t*    obj)
 
   sync_ctx.mask = RTEMS_RTL_OBJ_SECT_TEXT | RTEMS_RTL_OBJ_SECT_CONST |
                   RTEMS_RTL_OBJ_SECT_DATA | RTEMS_RTL_OBJ_SECT_BSS |
-                  RTEMS_RTL_OBJ_SECT_EXEC;
+                  RTEMS_RTL_OBJ_SECT_EH   | RTEMS_RTL_OBJ_SECT_EXEC;
 
   sync_ctx.start_va = 0;
   sync_ctx.end_va = sync_ctx.start_va;
@@ -667,6 +667,87 @@ rtems_rtl_obj_load_symbols (rtems_rtl_obj_t*             obj,
   return rtems_rtl_obj_section_handler (mask, obj, fd, handler, data);
 }
 
+static int
+rtems_rtl_obj_sections_linked_to_order (rtems_rtl_obj_t* obj,
+                                        int              section,
+                                        uint32_t         visited_mask)
+{
+  rtems_chain_control* sections = &obj->sections;
+  rtems_chain_node*    node = rtems_chain_first (sections);
+  /*
+   * Find the section being linked-to. If the linked-to link field is 0 we have
+   * the end and the section's order is the position we are after.
+   */
+  while (!rtems_chain_is_tail (sections, node))
+  {
+    rtems_rtl_obj_sect_t* sect = (rtems_rtl_obj_sect_t*) node;
+    if (sect->section == section)
+    {
+      const uint32_t mask = sect->flags & RTEMS_RTL_OBJ_SECT_TYPES;
+      int            order = 0;
+      if (sect->link != 0)
+      {
+        /*
+         * Have we already visited this type of section? Avoid nesting for
+         * ever.
+         */
+        if ((sect->flags & visited_mask) != 0)
+        {
+          rtems_rtl_set_error (errno, "section link loop");
+          return -1;
+        }
+        return rtems_rtl_obj_sections_linked_to_order (obj,
+                                                       sect->link,
+                                                       visited_mask | mask);
+      }
+      node = rtems_chain_first (sections);
+      while (!rtems_chain_is_tail (sections, node))
+      {
+        sect = (rtems_rtl_obj_sect_t*) node;
+        if ((sect->flags & mask) == mask)
+        {
+          if (sect->section == section)
+            return order;
+          ++order;
+        }
+        node = rtems_chain_next (node);
+      }
+    }
+    node = rtems_chain_next (node);
+  }
+  rtems_rtl_set_error (errno, "section link not found");
+  return -1;
+}
+
+static void
+rtems_rtl_obj_sections_link_order (uint32_t mask, rtems_rtl_obj_t* obj)
+{
+  rtems_chain_control* sections = &obj->sections;
+  rtems_chain_node*    node = rtems_chain_first (sections);
+  int                  order = 0;
+  while (!rtems_chain_is_tail (sections, node))
+  {
+    rtems_rtl_obj_sect_t* sect = (rtems_rtl_obj_sect_t*) node;
+    if ((sect->flags & mask) == mask)
+    {
+      /*
+       * If the section is linked in order find the linked-to section's order
+       * and move the section in the section list to
+       */
+      if (sect->link == 0)
+        sect->load_order = order++;
+      else
+      {
+        sect->load_order =
+          rtems_rtl_obj_sections_linked_to_order (obj,
+                                                  sect->link,
+                                                  mask);
+      }
+    }
+    node = rtems_chain_next (node);
+  }
+}
+
 static size_t
 rtems_rtl_obj_sections_loader (uint32_t                     mask,
                                rtems_rtl_obj_t*             obj,
@@ -679,42 +760,54 @@ rtems_rtl_obj_sections_loader (uint32_t                     mask,
   rtems_chain_node*    node = rtems_chain_first (sections);
   size_t               base_offset = 0;
   bool                 first = true;
+  int                  order = 0;
+
   while (!rtems_chain_is_tail (sections, node))
   {
     rtems_rtl_obj_sect_t* sect = (rtems_rtl_obj_sect_t*) node;
 
     if ((sect->size != 0) && ((sect->flags & mask) != 0))
     {
-      if (!first)
-        base_offset = rtems_rtl_sect_align (base_offset, sect->alignment);
+      if (sect->load_order == order)
+      {
+        if (!first)
+          base_offset = rtems_rtl_sect_align (base_offset, sect->alignment);
 
-      sect->base = base + base_offset;
+        first = false;
 
-      if (rtems_rtl_trace (RTEMS_RTL_TRACE_LOAD_SECT))
-        printf ("rtl: loading: %s -> %8p (l:%zi m:%04lx)\n",
-                sect->name, sect->base, sect->size, sect->flags);
+        sect->base = base + base_offset;
 
-      if ((sect->flags & RTEMS_RTL_OBJ_SECT_LOAD) == RTEMS_RTL_OBJ_SECT_LOAD)
-      {
-        if (!handler (obj, fd, sect, data))
+        if (rtems_rtl_trace (RTEMS_RTL_TRACE_LOAD_SECT))
+          printf ("rtl: loading:%2d: %s -> %8p (s:%zi f:%04lx a:%lu l:%02d)\n",
+                  order, sect->name, sect->base, sect->size,
+                  sect->flags, sect->alignment, sect->link);
+
+        if ((sect->flags & RTEMS_RTL_OBJ_SECT_LOAD) == RTEMS_RTL_OBJ_SECT_LOAD)
+        {
+          if (!handler (obj, fd, sect, data))
+          {
+            sect->base = 0;
+            return false;
+          }
+        }
+        else if ((sect->flags & RTEMS_RTL_OBJ_SECT_ZERO) == RTEMS_RTL_OBJ_SECT_ZERO)
+        {
+          memset (base + base_offset, 0, sect->size);
+        }
+        else
         {
           sect->base = 0;
+          rtems_rtl_set_error (errno, "section has no load/clear op");
           return false;
         }
-      }
-      else if ((sect->flags & RTEMS_RTL_OBJ_SECT_ZERO) == RTEMS_RTL_OBJ_SECT_ZERO)
-      {
-        memset (base + base_offset, 0, sect->size);
-      }
-      else
-      {
-        sect->base = 0;
-        rtems_rtl_set_error (errno, "section has no load op");
-        return false;
-      }
 
-      base_offset += sect->size;
-      first = false;
+        base_offset += sect->size;
+
+        ++order;
+
+        node = rtems_chain_first (sections);
+        continue;
+      }
     }
 
     node = rtems_chain_next (node);
@@ -763,7 +856,7 @@ rtems_rtl_obj_load_sections (rtems_rtl_obj_t*             obj,
     return false;
   }
 
-  obj->exec_size = text_size + const_size + data_size + bss_size;
+  obj->exec_size = text_size + const_size + eh_size + data_size + bss_size;
 
   if (rtems_rtl_trace (RTEMS_RTL_TRACE_LOAD_SECT))
   {
@@ -780,6 +873,14 @@ rtems_rtl_obj_load_sections (rtems_rtl_obj_t*             obj,
   }
 
   /*
+   * Determine the load order.
+   */
+  rtems_rtl_obj_sections_link_order (RTEMS_RTL_OBJ_SECT_TEXT,  obj);
+  rtems_rtl_obj_sections_link_order (RTEMS_RTL_OBJ_SECT_CONST, obj);
+  rtems_rtl_obj_sections_link_order (RTEMS_RTL_OBJ_SECT_EH,    obj);
+  rtems_rtl_obj_sections_link_order (RTEMS_RTL_OBJ_SECT_DATA,  obj);
+
+  /*
    * Load all text then data then bss sections in seperate operations so each
    * type of section is grouped together.
    */
diff --git a/cpukit/libdl/rtl-obj.h b/cpukit/libdl/rtl-obj.h
index 9ec184be1a..6a35a72822 100644
--- a/cpukit/libdl/rtl-obj.h
+++ b/cpukit/libdl/rtl-obj.h
@@ -102,8 +102,19 @@ typedef struct rtems_rtl_loader_table_s
 #define RTEMS_RTL_OBJ_SECT_WRITE (1 << 11) /**< Section is writable, ie data. */
 #define RTEMS_RTL_OBJ_SECT_EXEC  (1 << 12) /**< Section is executable. */
 #define RTEMS_RTL_OBJ_SECT_ZERO  (1 << 13) /**< Section is preset to zero. */
-#define RTEMS_RTL_OBJ_SECT_CTOR  (1 << 14) /**< Section contains constructors. */
-#define RTEMS_RTL_OBJ_SECT_DTOR  (1 << 15) /**< Section contains destructors. */
+#define RTEMS_RTL_OBJ_SECT_LINK  (1 << 14) /**< Section is link-ordered. */
+#define RTEMS_RTL_OBJ_SECT_CTOR  (1 << 15) /**< Section contains constructors. */
+#define RTEMS_RTL_OBJ_SECT_DTOR  (1 << 16) /**< Section contains destructors. */
+#define RTEMS_RTL_OBJ_SECT_LOCD  (1 << 17) /**< Section has been located. */
+
+/**
+ * Section types mask.
+ */
+#define RTEMS_RTL_OBJ_SECT_TYPES (RTEMS_RTL_OBJ_SECT_TEXT | \
+                                  RTEMS_RTL_OBJ_SECT_CONST | \
+                                  RTEMS_RTL_OBJ_SECT_DATA | \
+                                  RTEMS_RTL_OBJ_SECT_BSS | \
+                                  RTEMS_RTL_OBJ_SECT_EH)
 
 /**
  * An object file is made up of sections and the can be more than
@@ -124,6 +135,7 @@ struct rtems_rtl_obj_sect_s
   uint32_t         flags;       /**< The section's flags. */
   void*            base;        /**< The base address of the section in
                                  *   memory. */
+  int              load_order;  /**< Order we load sections. */
 };
 
 /**