From ca92bfc3c64128872793c167de3a58a78b9a1299 Mon Sep 17 00:00:00 2001
From: grischka <grischka>
Date: Thu, 15 Dec 2016 17:01:22 +0100
Subject: tccelf: some linker cleanup

- generate and use SYM@PLT for plt addresses
- get rid of patch_dynsym_undef hack (no idea what it did on FreeBSD)
- use sym_attrs instead of symtab_to_dynsym
- special case for function pointers into .so on i386
- libtcc_test: test tcc_add_symbol with data object
- move target specicic code to *-link.c files
- add R_XXX_RELATIVE (needed for PE)
---
 x86_64-link.c | 76 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 73 insertions(+), 3 deletions(-)

(limited to 'x86_64-link.c')

diff --git a/x86_64-link.c b/x86_64-link.c
index 92404e4..9ff234b 100644
--- a/x86_64-link.c
+++ b/x86_64-link.c
@@ -14,8 +14,8 @@
 #define ELF_START_ADDR 0x400000
 #define ELF_PAGE_SIZE  0x200000
 
-#define HAVE_SECTION_RELOC
 #define PCRELATIVE_DLLPLT 1
+#define RELOCATE_DLLPLT 1
 
 #else /* !TARGET_DEFS_ONLY */
 
@@ -36,6 +36,7 @@ int code_reloc (int reloc_type)
         case R_X86_64_GOT32:
         case R_X86_64_GLOB_DAT:
         case R_X86_64_COPY:
+	case R_X86_64_RELATIVE:
             return 0;
 
         case R_X86_64_PC32:
@@ -57,6 +58,7 @@ int gotplt_entry_type (int reloc_type)
         case R_X86_64_GLOB_DAT:
         case R_X86_64_JUMP_SLOT:
         case R_X86_64_COPY:
+	case R_X86_64_RELATIVE:
             return NO_GOTPLT_ENTRY;
 
         case R_X86_64_32:
@@ -80,6 +82,71 @@ int gotplt_entry_type (int reloc_type)
     return -1;
 }
 
+ST_FUNC unsigned create_plt_entry(TCCState *s1, unsigned got_offset, struct sym_attr *attr)
+{
+    Section *plt = s1->plt;
+    uint8_t *p;
+    int modrm;
+    unsigned plt_offset, relofs;
+
+    modrm = 0x25;
+
+    /* empty PLT: create PLT0 entry that pushes the library indentifier
+       (GOT + PTR_SIZE) and jumps to ld.so resolution routine
+       (GOT + 2 * PTR_SIZE) */
+    if (plt->data_offset == 0) {
+        p = section_ptr_add(plt, 16);
+        p[0] = 0xff; /* pushl got + PTR_SIZE */
+        p[1] = modrm + 0x10;
+        write32le(p + 2, PTR_SIZE);
+        p[6] = 0xff; /* jmp *(got + PTR_SIZE * 2) */
+        p[7] = modrm;
+        write32le(p + 8, PTR_SIZE * 2);
+    }
+    plt_offset = plt->data_offset;
+
+    /* The PLT slot refers to the relocation entry it needs via offset.
+       The reloc entry is created below, so its offset is the current
+       data_offset */
+    relofs = s1->got->reloc ? s1->got->reloc->data_offset : 0;
+
+    /* Jump to GOT entry where ld.so initially put the address of ip + 4 */
+    p = section_ptr_add(plt, 16);
+    p[0] = 0xff; /* jmp *(got + x) */
+    p[1] = modrm;
+    write32le(p + 2, got_offset);
+    p[6] = 0x68; /* push $xxx */
+    /* On x86-64, the relocation is referred to by _index_ */
+    write32le(p + 7, relofs / sizeof (ElfW_Rel));
+    p[11] = 0xe9; /* jmp plt_start */
+    write32le(p + 12, -(plt->data_offset));
+    return plt_offset;
+}
+
+/* relocate the PLT: compute addresses and offsets in the PLT now that final
+   address for PLT and GOT are known (see fill_program_header) */
+ST_FUNC void relocate_plt(TCCState *s1)
+{
+    uint8_t *p, *p_end;
+
+    if (!s1->plt)
+      return;
+
+    p = s1->plt->data;
+    p_end = p + s1->plt->data_offset;
+
+    if (p < p_end) {
+        int x = s1->got->sh_addr - s1->plt->sh_addr - 6;
+        add32le(p + 2, x);
+        add32le(p + 8, x - 6);
+        p += 16;
+        while (p < p_end) {
+            add32le(p + 2, x + s1->plt->data - p);
+            p += 16;
+        }
+    }
+}
+
 static ElfW_Rel *qrel; /* ptr to next reloc entry reused */
 
 void relocate_init(Section *sr)
@@ -96,7 +163,7 @@ void relocate(TCCState *s1, ElfW_Rel *rel, int type, char *ptr, addr_t addr, add
     switch (type) {
         case R_X86_64_64:
             if (s1->output_type == TCC_OUTPUT_DLL) {
-                esym_index = s1->symtab_to_dynsym[sym_index];
+                esym_index = s1->sym_attrs[sym_index].dyn_index;
                 qrel->r_offset = rel->r_offset;
                 if (esym_index) {
                     qrel->r_info = ELFW(R_INFO)(esym_index, R_X86_64_64);
@@ -127,7 +194,7 @@ void relocate(TCCState *s1, ElfW_Rel *rel, int type, char *ptr, addr_t addr, add
         case R_X86_64_PC32:
             if (s1->output_type == TCC_OUTPUT_DLL) {
                 /* DLL relocation */
-                esym_index = s1->symtab_to_dynsym[sym_index];
+                esym_index = s1->sym_attrs[sym_index].dyn_index;
                 if (esym_index) {
                     qrel->r_offset = rel->r_offset;
                     qrel->r_info = ELFW(R_INFO)(esym_index, R_X86_64_PC32);
@@ -170,6 +237,9 @@ void relocate(TCCState *s1, ElfW_Rel *rel, int type, char *ptr, addr_t addr, add
             /* we load the got offset */
             add32le(ptr, s1->sym_attrs[sym_index].got_offset);
             break;
+        case R_X86_64_RELATIVE:
+            /* do nothing */
+            break;
     }
 }
 
-- 
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