modlib:support modlib can load PIC elf

Signed-off-by: anjiahao <anjiahao@xiaomi.com>

arch/arm/src/common/Toolchain.defs

@@ -502,11 +502,21 @@ LDMODULEFLAGS = -r -T $(call CONVERT_PATH,$(TOPDIR)/libs/libc/modlib/gnu-elf.ld)
 
 # ELF module definitions
 
-CELFFLAGS = $(CFLAGS) -fvisibility=hidden -mlong-calls # --target1-abs
+ifeq ($(CONFIG_PIC),y)
-CXXELFFLAGS = $(CXXFLAGS) -fvisibility=hidden
+  CFLAGS += --fixed-r10
+  PICFLAGS = -fpic -fPIE -mno-pic-data-is-text-relative \
+             -msingle-pic-base -mpic-register=r10
 
-LDELFFLAGS = -r -e main
+  # Generate an executable elf, need to ignore undefined symbols
-LDELFFLAGS += -T $(call CONVERT_PATH,$(TOPDIR)$(DELIM)libs$(DELIM)libc$(DELIM)modlib$(DELIM)gnu-elf.ld)
+  LDELFFLAGS += --unresolved-symbols=ignore-in-object-files --emit-relocs
+else
+  LDELFFLAGS += -r
+endif
+
+CELFFLAGS = $(CFLAGS) $(PICFLAGS) -fvisibility=hidden -mlong-calls # --target1-abs
+CXXELFFLAGS = $(CXXFLAGS) $(PICFLAGS) -fvisibility=hidden
+
+LDELFFLAGS +=  -e main -T $(call CONVERT_PATH,$(TOPDIR)$(DELIM)libs$(DELIM)libc$(DELIM)modlib$(DELIM)gnu-elf.ld)
 
 # Zig toolchain
 

binfmt/Kconfig

@@ -28,7 +28,7 @@ config BINFMT_LOADABLE
 		Automatically selected if a loadable binary format is selected.
 
 config PIC
-	bool
+	bool "Executable elf position-independent support"
 	default n
 	---help---
 		Automatically selected if the binary format requires position

binfmt/elf.c

@@ -33,6 +33,7 @@
 
 #include <nuttx/arch.h>
 #include <nuttx/binfmt/binfmt.h>
+#include <nuttx/kmalloc.h>
 
 #ifdef CONFIG_ELF
 
@@ -119,7 +120,7 @@ static int elf_loadbinary(FAR struct binary_s *binp,
 
   /* Bind the program to the exported symbol table */
 
-  if (loadinfo.ehdr.e_type == ET_REL)
+  if (loadinfo.ehdr.e_type == ET_REL || loadinfo.gotindex >= 0)
     {
       ret = modlib_bind(&binp->mod, &loadinfo, exports, nexports);
       if (ret != 0)
@@ -207,6 +208,23 @@ static int elf_loadbinary(FAR struct binary_s *binp,
 #endif
 
   modlib_dumpentrypt(&loadinfo);
+#ifdef CONFIG_PIC
+  if (loadinfo.gotindex >= 0)
+    {
+      FAR struct dspace_s *dspaces = kmm_zalloc(sizeof(struct dspace_s));
+
+      if (dspaces == NULL)
+        {
+          ret = -ENOMEM;
+          goto errout_with_load;
+        }
+
+      dspaces->region = (FAR void *)loadinfo.shdr[loadinfo.gotindex].sh_addr;
+      dspaces->crefs = 1;
+      binp->picbase = (FAR void *)dspaces;
+    }
+#endif
+
   modlib_uninitialize(&loadinfo);
   return OK;
 

include/nuttx/lib/modlib.h

@@ -231,6 +231,7 @@ struct mod_loadinfo_s
   uint16_t      buflen;      /* size of iobuffer[] */
   int           filfd;       /* Descriptor for the file being loaded */
   int           nexports;    /* ET_DYN - Number of symbols exported */
+  int           gotindex;    /* Index to the GOT section */
 
   /* Address environment.
    *

libs/libc/modlib/gnu-elf.ld

@@ -35,7 +35,9 @@ SECTIONS
 
   .init_array :
     {
+      _sinit = .;
       *(.init_array)
+      _einit = .;
     }
 
   .fini_array :
@@ -77,6 +79,11 @@ SECTIONS
       _ebss = . ;
     }
 
+  .got :
+    {
+      *(.got*)
+    }
+
     /* Stabs debugging sections.    */
 
     .stab 0 : { *(.stab) }

libs/libc/modlib/modlib_bind.c

@@ -292,8 +292,8 @@ static int modlib_relocate(FAR struct module_s *modp,
           /* Get the value of the symbol (in sym.st_value) */
 
           ret = modlib_symvalue(modp, loadinfo, sym,
-                           loadinfo->shdr[loadinfo->strtabidx].sh_offset,
+                  loadinfo->shdr[loadinfo->strtabidx].sh_offset,
-                            exports, nexports);
+                  exports, nexports);
           if (ret < 0)
             {
               /* The special error -ESRCH is returned only in one condition:
@@ -333,19 +333,75 @@ static int modlib_relocate(FAR struct module_s *modp,
 
       /* Calculate the relocation address. */
 
-      if (rel->r_offset < 0 ||
+      if (loadinfo->gotindex >= 0)
-          rel->r_offset > dstsec->sh_size)
         {
-          berr("ERROR: Section %d reloc %d: "
+          if (sym->st_shndx == SHN_UNDEF)
-               "Relocation address out of range, "
+            {
-               "offset %" PRIuPTR " size %ju\n",
+              /* Symbol type is undefined, we need to set the address
-               relidx, i, (uintptr_t)rel->r_offset,
+               * to the value of the symbol.
-               (uintmax_t)dstsec->sh_size);
+               */
-          ret = -EINVAL;
-          break;
-        }
 
-      addr = dstsec->sh_addr + rel->r_offset;
+              FAR Elf_Shdr *gotsec = &loadinfo->shdr[loadinfo->gotindex];
+              FAR uintptr_t *gotaddr = (FAR uintptr_t *)(gotsec->sh_addr +
+                *((FAR uintptr_t *)(dstsec->sh_addr + rel->r_offset)));
+
+              *gotaddr = sym->st_value;
+              continue;
+            }
+
+          if ((dstsec->sh_flags & SHF_WRITE) == 0)
+            {
+              /* Skip relocations for read-only sections */
+
+              continue;
+            }
+
+          /* Use the GOT to store the address */
+
+          if (rel->r_offset - dstsec->sh_offset >
+              dstsec->sh_size)
+            {
+              berr("ERROR: Section %d reloc %d: "
+                   "Relocation address out of range, "
+                   "offset %" PRIuPTR " size %ju\n",
+                   relidx, i, (uintptr_t)rel->r_offset,
+                   (uintmax_t)dstsec->sh_size);
+              ret = -EINVAL;
+              break;
+            }
+
+          addr = dstsec->sh_addr + rel->r_offset - dstsec->sh_offset;
+          if (ELF_ST_TYPE(sym->st_info) == STT_SECTION)
+            {
+              /* Symbol type is section, we need clear the address
+               * and keep the original value.
+               */
+
+              *(FAR uintptr_t *)addr -=
+                 loadinfo->shdr[sym->st_shndx].sh_offset;
+            }
+          else
+            {
+              /* Normal symbol, just keep it zero */
+
+              *(FAR uintptr_t *)addr = 0;
+            }
+        }
+      else
+        {
+          if (rel->r_offset > dstsec->sh_size)
+            {
+              berr("ERROR: Section %d reloc %d: "
+                   "Relocation address out of range, "
+                   "offset %" PRIuPTR " size %ju\n",
+                   relidx, i, (uintptr_t)rel->r_offset,
+                   (uintmax_t)dstsec->sh_size);
+              ret = -EINVAL;
+              break;
+            }
+
+          addr = dstsec->sh_addr + rel->r_offset;
+        }
 
       /* Now perform the architecture-specific relocation */
 

libs/libc/modlib/modlib_load.c

@@ -62,7 +62,7 @@
 static int modlib_section_alloc(FAR struct mod_loadinfo_s *loadinfo,
                                 FAR Elf_Shdr *shdr, uint8_t idx)
 {
-  if (loadinfo->ehdr.e_type != ET_REL)
+  if (loadinfo->ehdr.e_type != ET_DYN)
     {
       return -EINVAL;
     }
@@ -339,7 +339,8 @@ static inline int modlib_loadfile(FAR struct mod_loadinfo_s *loadinfo)
             }
 
 #ifdef CONFIG_ARCH_USE_SEPARATED_SECTION
-          if (loadinfo->ehdr.e_type == ET_REL)
+          if (loadinfo->ehdr.e_type == ET_REL ||
+              loadinfo->ehdr.e_type == ET_EXEC)
             {
               pptr = (FAR uint8_t **)&loadinfo->sectalloc[i];
             }
@@ -410,6 +411,9 @@ static inline int modlib_loadfile(FAR struct mod_loadinfo_s *loadinfo)
           binfo("%d. %08lx->%08lx\n", i,
                 (unsigned long)shdr->sh_addr, (unsigned long)*pptr);
 
+          /* Use offset to remember the original file address */
+
+          shdr->sh_offset = (uintptr_t)shdr->sh_addr;
           shdr->sh_addr = (uintptr_t)*pptr;
 
 #ifdef CONFIG_ARCH_USE_SEPARATED_SECTION
@@ -425,6 +429,34 @@ static inline int modlib_loadfile(FAR struct mod_loadinfo_s *loadinfo)
         }
     }
 
+  /* Update GOT table */
+
+  if (loadinfo->gotindex >= 0)
+    {
+      FAR Elf_Shdr *gotshdr = &loadinfo->shdr[loadinfo->gotindex];
+      FAR uintptr_t *got = (FAR uintptr_t *)gotshdr->sh_addr;
+      FAR uintptr_t *end = got + gotshdr->sh_size / sizeof(uintptr_t);
+
+      for (; got < end; got++)
+        {
+          for (i = 0; i < loadinfo->ehdr.e_shnum; i++)
+            {
+              FAR Elf_Shdr *shdr = &loadinfo->shdr[i];
+
+              if ((shdr->sh_flags & SHF_ALLOC) == 0)
+                {
+                  continue;
+                }
+
+              if (*got >= shdr->sh_offset &&
+                  *got < shdr->sh_offset + shdr->sh_size)
+                {
+                  *got += shdr->sh_addr - shdr->sh_offset;
+                }
+            }
+        }
+    }
+
   return OK;
 }
 
@@ -461,6 +493,12 @@ int modlib_load(FAR struct mod_loadinfo_s *loadinfo)
       goto errout_with_buffers;
     }
 
+  loadinfo->gotindex = modlib_findsection(loadinfo, ".got");
+  if (loadinfo->gotindex >= 0)
+    {
+      binfo("GOT section found! index %d\n", loadinfo->gotindex);
+    }
+
   /* Determine total size to allocate */
 
   modlib_elfsize(loadinfo, true);
@@ -474,21 +512,23 @@ int modlib_load(FAR struct mod_loadinfo_s *loadinfo)
    * GOT. Therefore we cannot do two different allocations.
    */
 
-  if (loadinfo->ehdr.e_type == ET_REL)
+#ifndef CONFIG_MODLIB_LOADTO_LMA
+
+  if (loadinfo->ehdr.e_type == ET_REL || loadinfo->ehdr.e_type == ET_EXEC)
     {
-#ifndef CONFIG_ARCH_USE_SEPARATED_SECTION
+#  ifndef CONFIG_ARCH_USE_SEPARATED_SECTION
       if (loadinfo->textsize > 0)
         {
-#  ifdef CONFIG_ARCH_USE_TEXT_HEAP
+#    ifdef CONFIG_ARCH_USE_TEXT_HEAP
           loadinfo->textalloc = (uintptr_t)
                                 up_textheap_memalign(loadinfo->textalign,
                                                      loadinfo->textsize +
                                                      loadinfo->segpad);
-#  else
+#    else
           loadinfo->textalloc = (uintptr_t)lib_memalign(loadinfo->textalign,
                                                         loadinfo->textsize +
                                                         loadinfo->segpad);
-#  endif
+#    endif
           if (!loadinfo->textalloc)
             {
               berr("ERROR: Failed to allocate memory for the module text\n");
@@ -499,14 +539,14 @@ int modlib_load(FAR struct mod_loadinfo_s *loadinfo)
 
       if (loadinfo->datasize > 0)
         {
-#  ifdef CONFIG_ARCH_USE_DATA_HEAP
+#    ifdef CONFIG_ARCH_USE_DATA_HEAP
           loadinfo->datastart = (uintptr_t)
                                  up_dataheap_memalign(loadinfo->dataalign,
                                                       loadinfo->datasize);
-#  else
+#    else
           loadinfo->datastart = (uintptr_t)lib_memalign(loadinfo->dataalign,
                                                         loadinfo->datasize);
-#  endif
+#    endif
           if (!loadinfo->datastart)
             {
               berr("ERROR: Failed to allocate memory for the module data\n");
@@ -514,7 +554,7 @@ int modlib_load(FAR struct mod_loadinfo_s *loadinfo)
               goto errout_with_buffers;
             }
         }
-#endif
+#  endif
     }
   else if (loadinfo->ehdr.e_type == ET_DYN)
     {
@@ -535,6 +575,8 @@ int modlib_load(FAR struct mod_loadinfo_s *loadinfo)
                             loadinfo->segpad;
     }
 
+#endif /* CONFIG_MODLIB_LOADTO_LMA */
+
   /* Load ELF section data into memory */
 
   ret = modlib_loadfile(loadinfo);
@@ -597,6 +639,12 @@ int modlib_load_with_addrenv(FAR struct mod_loadinfo_s *loadinfo)
       goto errout_with_buffers;
     }
 
+  loadinfo->gotindex = modlib_findsection(loadinfo, ".got");
+  if (loadinfo->gotindex >= 0)
+    {
+      binfo("GOT section found! index %d\n", loadinfo->gotindex);
+    }
+
   /* Determine total size to allocate */
 
   modlib_elfsize(loadinfo, false);

libs/libc/modlib/modlib_symbols.c

@@ -445,6 +445,10 @@ int modlib_symvalue(FAR struct module_s *modp,
               (uintptr_t)(sym->st_value + secbase));
 
         sym->st_value += secbase;
+        if (loadinfo->gotindex >= 0)
+          {
+            sym->st_value -= loadinfo->shdr[sym->st_shndx].sh_offset;
+          }
       }
       break;
     }