rtld: add rudimentary support for procedure linkage tables (plt)

crt/elf.h

@@ -20,12 +20,14 @@ along with this program; see the file COPYING. If not, see
 #define PT_LOAD    1
 #define PT_DYNAMIC 2
 
-#define DT_NULL    0
-#define DT_NEEDED  1
-#define DT_STRTAB  5
-#define DT_SYMTAB  6
-#define DT_RELA    7
-#define DT_RELASZ  8
+#define DT_NULL     0
+#define DT_NEEDED   1
+#define DT_PLTRELSZ 2
+#define DT_STRTAB   5
+#define DT_SYMTAB   6
+#define DT_RELA     7
+#define DT_RELASZ   8
+#define DT_JMPREL   23
 #define DT_GNU_HASH 0x6ffffef5
 
 #define R_X86_64_64       1

crt/rtld_payload.c

@@ -244,8 +244,10 @@ dynsym_count(unsigned int *gnu_hash) {
 static int
 payload_load(void) {
   unsigned int *gnu_hash = 0;
+  unsigned long relasz = 0;
+  unsigned long pltsz = 0;
   Elf64_Rela* rela = 0;
-  long relasz = 0;
+  Elf64_Rela* plt = 0;
 
   // find lookup tables
   for(int i=0; _DYNAMIC[i].d_tag!=DT_NULL; i++) {
@@ -269,6 +271,14 @@ payload_load(void) {
     case DT_RELASZ:
       relasz = _DYNAMIC[i].d_un.d_val;
       break;
+
+    case DT_JMPREL:
+      plt = (Elf64_Rela*)(__image_start + _DYNAMIC[i].d_un.d_ptr);
+      break;
+
+    case DT_PLTRELSZ:
+      pltsz = _DYNAMIC[i].d_un.d_val;
+      break;
     }
   }
 
@@ -322,6 +332,21 @@ payload_load(void) {
     }
   }
 
+  for(int i=0; i<pltsz/sizeof(Elf64_Rela); i++) {
+    switch(plt[i].r_info & 0xffffffffl) {
+    case R_X86_64_JMP_SLOT:
+      if(r_jmp_slot(&plt[i])) {
+	return -1;
+      }
+      break;
+
+    default:
+      klog_printf("Unsupported plt type %x\n",
+                  plt[i].r_info);
+      break;
+    }
+  }
+
   return 0;
 }
 

crt/rtld_so.c

@@ -530,6 +530,15 @@ pt_dynamic(rtld_so_lib_t *lib, Elf64_Phdr *phdr) {
       lib->strtab = (char*)(lib->image + lib->phdr->p_offset +
                             dyn[i].d_un.d_ptr);
       break;
+
+    case DT_JMPREL:
+      lib->plt = (Elf64_Rela*)(lib->image + lib->phdr->p_offset +
+                               dyn[i].d_un.d_ptr);
+      break;
+
+    case DT_PLTRELSZ:
+      lib->plt_size = dyn[i].d_un.d_val;
+      break;
     }
   }
 
@@ -643,6 +652,21 @@ so_load(rtld_so_lib_t* lib, const char* path) {
     }
   }
 
+  for(int i=0; i<lib->plt_size/sizeof(Elf64_Rela); i++) {
+    switch(lib->plt[i].r_info & 0xffffffffl) {
+    case R_X86_64_JMP_SLOT:
+      if(r_jmp_slot(lib, &lib->plt[i])) {
+	return -1;
+      }
+      break;
+
+    default:
+      klog_printf("Unsupported plt relocation type %x\n",
+                  lib->plt[i].r_info);
+      break;
+    }
+  }
+
   // set protection bits on mapped memory
   for(int i=0; i<lib->ehdr->e_phnum && !error; i++) {
     if(lib->phdr[i].p_type != PT_LOAD || lib->phdr[i].p_memsz == 0) {

host/bin/prospero-clang

@@ -67,7 +67,7 @@ exec -a "${SCRIPT_NAME}" "${SCRIPT_DIR}/clang" \
      -isystem "${PS5_PAYLOAD_SDK}/target/include" \
      -L "${PS5_PAYLOAD_SDK}/target/lib" \
      -L "${PS5_PAYLOAD_HBROOT}/lib" \
-     -fno-stack-protector -fno-plt -femulated-tls \
+     -fno-stack-protector -femulated-tls \
      $LIBS_C \
      --end-no-unused-arguments \
      "$@" \

host/bin/prospero-clang++

@@ -73,7 +73,7 @@ exec -a "${SCRIPT_NAME}" "${SCRIPT_DIR}/clang++" \
      -stdlib++-isystem "${PS5_PAYLOAD_SDK}/target/include/c++/v1" \
      -L "${PS5_PAYLOAD_SDK}/target/lib" \
      -L "${PS5_PAYLOAD_HBROOT}/lib" \
-     -fno-stack-protector -fno-plt -femulated-tls \
+     -fno-stack-protector -femulated-tls \
      -frtti -fexceptions \
      $LIBS_CXX $LIBS_C \
      --end-no-unused-arguments \

host/elf_x86_64.x

@@ -33,6 +33,8 @@ SECTIONS {
 	    PROVIDE_HIDDEN (__text_end = .);
 	} : ph_text
 
+	.plt : { *(.plt) }
+
 	.rodata : ALIGN(CONSTANT(MAXPAGESIZE)) {
 	    *(.rodata .rodata.*)
 
@@ -47,6 +49,8 @@ SECTIONS {
 	    PROVIDE_HIDDEN(__fini_array_end = .);
 	} : ph_rodata
 
+	.gcc_except_table : { *(.gcc_except_table*) }
+
 	.eh_frame_hdr : ALIGN(CONSTANT(MAXPAGESIZE)) {
 	    PROVIDE_HIDDEN(__eh_frame_hdr_start = .);
 	    KEEP(*(.eh_frame_hdr))
@@ -59,7 +63,9 @@ SECTIONS {
 	    PROVIDE_HIDDEN(__eh_frame_end = .);
 	}
 
-	.rela : { *(.rela *.rela.*) }
+	.data.rel.ro : { *(.data.rel.ro .data.rel.ro.*); }
+	.got : { *(.got) }
+	.got.plt : { *(.got.plt) }
 
 	.data : ALIGN(CONSTANT(MAXPAGESIZE)) {
 	    *(.data .data.*)