Revert "Generate PLT thumb stub only when necessary"
authorThomas Preud'homme <robotux@celest.fr>
Mon, 12 Nov 2012 22:14:21 +0000 (12 23:14 +0100)
committerThomas Preud'homme <robotux@celest.fr>
Mon, 12 Nov 2012 22:14:21 +0000 (12 23:14 +0100)
Revert commit 891dfcdf3fc441a1863c43d179dc6e0e4d65836f since it assumes
*all* architectures supported by tcc have GOT offsets aligned on 2. A
rework of this commit is being done since without it all PLT entries
grow by 4 bytes.

tcc.h
tccelf.c

diff --git a/tcc.h b/tcc.h
index fd4e8da..4e88782 100644 (file)
--- a/tcc.h
+++ b/tcc.h
@@ -33,7 +33,6 @@
 
 #include <stdlib.h>
 #include <stdio.h>
-#include <limits.h>
 #include <stdarg.h>
 #include <string.h>
 #include <errno.h>
@@ -525,15 +524,11 @@ struct TCCState {
     Section **priv_sections;
     int nb_priv_sections; /* number of private sections */
 
-    /* got & plt handling */
+    /* got handling */
     Section *got;
     Section *plt;
-    struct {
-        unsigned long plt_thumb_stub:1;
-        /* mult by 2 (or left shift by 1) before use */
-        unsigned long got_offset:(sizeof(long)*CHAR_BIT-1);
-    } *sym_infos;
-    int nb_sym_infos;
+    unsigned long *got_offsets;
+    int nb_got_offsets;
     /* give the correspondance from symtab indexes to dynsym indexes */
     int *symtab_to_dynsym;
 
index a2559ee..c5690dd 100644 (file)
--- a/tccelf.c
+++ b/tccelf.c
@@ -581,7 +581,7 @@ ST_FUNC void relocate_section(TCCState *s1, Section *s)
             break;
         case R_386_GOT32:
             /* we load the got offset */
-            *(int *)ptr += s1->sym_infos[sym_index].got_offset << 1;
+            *(int *)ptr += s1->got_offsets[sym_index];
             break;
         case R_386_16:
             if (s1->output_format != TCC_OUTPUT_FORMAT_BINARY) {
@@ -760,7 +760,7 @@ ST_FUNC void relocate_section(TCCState *s1, Section *s)
             break;
         case R_ARM_GOT_BREL:
             /* we load the got offset */
-            *(int *)ptr += s1->sym_infos[sym_index].got_offset << 1;
+            *(int *)ptr += s1->got_offsets[sym_index];
             break;
         case R_ARM_COPY:
             break;
@@ -866,14 +866,14 @@ ST_FUNC void relocate_section(TCCState *s1, Section *s)
             }
 #endif
             *(int *)ptr += (s1->got->sh_addr - addr +
-                            (s1->sym_infos[sym_index].got_offset << 1) - 4);
+                            s1->got_offsets[sym_index] - 4);
             break;
         case R_X86_64_GOTTPOFF:
             *(int *)ptr += val - s1->got->sh_addr;
             break;
         case R_X86_64_GOT32:
             /* we load the got offset */
-            *(int *)ptr += s1->sym_infos[sym_index].got_offset << 1;
+            *(int *)ptr += s1->got_offsets[sym_index];
             break;
 #else
 #error unsupported processor
@@ -943,36 +943,23 @@ static int prepare_dynamic_rel(TCCState *s1, Section *sr)
     return count;
 }
 
-static void put_sym_info(TCCState *s1, int index)
+static void put_got_offset(TCCState *s1, int index, unsigned long val)
 {
     int n;
-    typeof(s1->sym_infos) tab;
+    unsigned long *tab;
 
-    if (index >= s1->nb_sym_infos) {
+    if (index >= s1->nb_got_offsets) {
         /* find immediately bigger power of 2 and reallocate array */
         n = 1;
         while (index >= n)
             n *= 2;
-        tab = tcc_realloc(s1->sym_infos, n * sizeof(unsigned long));
-        s1->sym_infos = tab;
-        memset(s1->sym_infos + s1->nb_sym_infos, 0,
-               (n - s1->nb_sym_infos) * sizeof(unsigned long));
-        s1->nb_sym_infos = n;
+        tab = tcc_realloc(s1->got_offsets, n * sizeof(unsigned long));
+        s1->got_offsets = tab;
+        memset(s1->got_offsets + s1->nb_got_offsets, 0,
+               (n - s1->nb_got_offsets) * sizeof(unsigned long));
+        s1->nb_got_offsets = n;
     }
-}
-
-#ifdef TCC_TARGET_ARM
-static void put_plt_thumb_stub(TCCState *s1, int index, unsigned char bit)
-{
-    put_sym_info(s1, index);
-    s1->sym_infos[index].plt_thumb_stub = bit;
-}
-#endif
-
-static void put_got_offset(TCCState *s1, int index, unsigned long val)
-{
-    put_sym_info(s1, index);
-    s1->sym_infos[index].got_offset = val >> 1;
+    s1->got_offsets[index] = val;
 }
 
 /* XXX: suppress that */
@@ -1036,8 +1023,8 @@ static void put_got_entry(TCCState *s1,
         build_got(s1);
 
     /* if a got entry already exists for that symbol, no need to add one */
-    if (sym_index < s1->nb_sym_infos &&
-        s1->sym_infos[sym_index].got_offset << 1)
+    if (sym_index < s1->nb_got_offsets &&
+        s1->got_offsets[sym_index] != 0)
         return;
     
     put_got_offset(s1, sym_index, s1->got->data_offset);
@@ -1117,13 +1104,10 @@ static void put_got_entry(TCCState *s1,
                 put32(p + 12, 0xe5bef008);
             }
 
-            if (s1->sym_infos[sym_index].plt_thumb_stub) {
-                p = section_ptr_add(plt, 20);
-                put32(p  , 0x4778); // bx pc
-                put32(p+2, 0x46c0); // nop
-                p += 4;
-            } else
-                p = section_ptr_add(plt, 16);
+            p = section_ptr_add(plt, 20);
+            put32(p  , 0x4778); // bx pc
+            put32(p+2, 0x46c0); // nop
+            p += 4;
             put32(p  , 0xe59fc004); // ldr ip, [pc, #4] // offset in GOT
             put32(p+4, 0xe08fc00c); // add ip, pc, ip // absolute address or offset
             put32(p+8, 0xe59cf000); // ldr pc, [ip] // load absolute address or load offset
@@ -1510,9 +1494,9 @@ ST_FUNC void fill_got_entry(TCCState *s1, ElfW_Rel *rel)
        ElfW(Sym) *sym = &((ElfW(Sym) *) symtab_section->data)[sym_index];
        unsigned long offset;
 
-       if (sym_index >= s1->nb_sym_infos)
+       if (sym_index >= s1->nb_got_offsets)
                return;
-       offset = s1->sym_infos[sym_index].got_offset << 1;
+       offset = s1->got_offsets[sym_index];
        section_reserve(s1->got, offset + PTR_SIZE);
 #ifdef TCC_TARGET_X86_64
        /* only works for x86-64 */
@@ -2086,8 +2070,7 @@ static int elf_output_file(TCCState *s1, const char *filename)
                     x=s1->got->sh_addr - s1->plt->sh_addr - 12;
                     p += 16;
                     while (p < p_end) {
-                        if (get32(p) == 0x46c04778) /* PLT Thumb stub present */
-                            p += 4;
+                        p += 4;
                         put32(p + 12, x + get32(p + 12) + s1->plt->data - p);
                         p += 16;
                     }
@@ -2321,7 +2304,7 @@ static int elf_output_file(TCCState *s1, const char *filename)
     tcc_free(s1->symtab_to_dynsym);
     tcc_free(section_order);
     tcc_free(phdr);
-    tcc_free(s1->sym_infos);
+    tcc_free(s1->got_offsets);
     return ret;
 }
 
@@ -2616,19 +2599,6 @@ ST_FUNC int tcc_load_object_file(TCCState *s1,
                 rel->r_info = ELFW(R_INFO)(sym_index, type);
                 /* offset the relocation offset */
                 rel->r_offset += offseti;
-#ifdef TCC_TARGET_ARM
-                /* Jumps and branches from a Thumb code to a PLT entry need
-                   special handling since PLT entries are ARM code.
-                   Unconditional bl instructions referencing PLT entries are
-                   handled by converting these instructions into blx
-                   instructions. Other case of instructions referencing a PLT
-                   entry require to add a Thumb stub before the PLT entry to
-                   switch to ARM mode. We set bit 0 of the got offset of a
-                   symbol to indicate such a case. */
-                if (type == R_ARM_THM_JUMP24) {
-                    put_plt_thumb_stub(s1, sym_index, 1);
-                }
-#endif
             }
             break;
         default: