Created student weenix repository

1 files changed, 184 insertions, 0 deletions

diff --git a/user/lib/ld-weenix/ldreloc_x86_64.c b/user/lib/ld-weenix/ldreloc_x86_64.c
new file mode 100644
index 0000000..dddd418
--- /dev/null
+++ b/user/lib/ld-weenix/ldreloc_x86_64.c
@@ -0,0 +1,184 @@
+/*
+ *  File: ldreloc_x86_64.c
+ *  Date: Mar 26 2019
+ *  Acct: Sandy Harvie (charvie)
+ *  Desc: x86-64 ELF dynamic linker
+ */
+
+#include "stdio.h"
+#include "stdlib.h"
+#include "string.h"
+#include "sys/types.h"
+
+#include "ldresolve.h"
+#include "ldtypes.h"
+#include "ldutil.h"
+
+extern void _ld_bind(void);
+
+ldinit_t _ldloadrtld(int argc, char **argv, char **envp, Elf64_auxv_t *auxv)
+{
+    /* Find our own base address in the auxiliary vector */
+    Elf64_Addr base = 0;
+    for (size_t i = 0; auxv[i].a_type != AT_NULL; i++)
+    {
+        if (auxv[i].a_type == AT_BASE)
+        {
+            base = (Elf64_Addr)auxv[i].a_un.a_val;
+            break;
+        }
+    }
+    if (!base)
+        exit(1);
+
+    /* Make sure we are ourselves */
+    Elf64_Ehdr *hdr = (Elf64_Ehdr *)base;
+    if (hdr->e_ident[EI_MAG0] != ELFMAG0 || hdr->e_ident[EI_MAG1] != ELFMAG1 ||
+        hdr->e_ident[EI_MAG2] != ELFMAG2 || hdr->e_ident[EI_MAG3] != ELFMAG3)
+    {
+        exit(1);
+    }
+
+    /* Find our program header */
+    Elf64_Phdr *phdr = (Elf64_Phdr *)(base + hdr->e_phoff);
+
+    /* Find our dynamic segment */
+    while (phdr->p_type != PT_DYNAMIC)
+    {
+        phdr++;
+    }
+
+    /* Find relocation entries in the dynamic segment */
+    size_t d_reloff = 0;
+    size_t d_relcount = 0;
+    Elf64_Dyn *dyn = (Elf64_Dyn *)(base + phdr->p_vaddr);
+    for (; dyn->d_tag != DT_NULL; dyn++)
+    {
+        if (dyn->d_tag == DT_RELA)
+        {
+            d_reloff = dyn->d_un.d_ptr;
+        }
+        else if (dyn->d_tag == DT_RELACOUNT)
+        {
+            d_relcount = dyn->d_un.d_val;
+        }
+    }
+
+    /* Relocate ourselves */
+    Elf64_Rela *rel = (Elf64_Rela *)(base + d_reloff);
+    for (size_t i = 0; i < d_relcount; i++)
+    {
+        size_t type = ELF64_R_TYPE(rel[i].r_info);
+        if (type == R_X86_64_RELATIVE)
+        {
+            Elf64_Addr *addr = (Elf64_Addr *)(base + rel[i].r_offset);
+            *addr = base + rel[i].r_addend;
+        }
+        else
+        {
+            fprintf(stderr, "_ldloadrtld: unsupported relocation type: %lu\n",
+                    type);
+            exit(1);
+        }
+    }
+
+    /* Relocate the executable */
+    return _ldstart(envp, auxv);
+}
+
+void _ldrelocobj(module_t *module)
+{
+    Elf64_Addr base = module->base;
+
+    for (size_t i = 0; i < module->nreloc; i++)
+    {
+        Elf64_Rela rel = module->reloc[i];
+
+        uint64_t sym = ELF64_R_SYM(rel.r_info);
+        uint64_t type = ELF64_R_TYPE(rel.r_info);
+        const char *name = module->dynstr + module->dynsym[sym].st_name;
+        void *addr = (void *)(base + rel.r_offset);
+
+        Elf64_Word size;
+        ldsym_t symbol;
+        switch (type)
+        {
+        case R_X86_64_RELATIVE:
+            *(Elf64_Addr *)addr = base + rel.r_addend;
+            break;
+        case R_X86_64_COPY:
+            symbol = _ldresolve(module, name, -1, &size, 1);
+            memcpy(addr, symbol, size);
+            break;
+        case R_X86_64_JUMP_SLOT:
+        case R_X86_64_GLOB_DAT:
+            symbol = _ldresolve(module, name, -1, 0, 0);
+            *(Elf64_Addr *)addr = (Elf64_Addr)symbol;
+            break;
+        case R_X86_64_32:
+            symbol = _ldresolve(module, name, -1, 0, 0);
+            *(Elf64_Addr *)addr = (Elf64_Addr)symbol + rel.r_addend;
+            break;
+        case R_X86_64_PC32:
+            symbol = _ldresolve(module, name, -1, 0, 0);
+            *(Elf64_Addr *)addr =
+                (Elf64_Addr)symbol + rel.r_addend - (Elf64_Addr)addr;
+            break;
+        default:
+            fprintf(stderr,
+                    "_ldrelocobj: unsupported relocation type: %lu\n",
+                    type);
+            exit(1);
+        }
+    }
+}
+
+void _ldrelocplt(module_t *module)
+{
+    for (size_t i = 0; i < module->npltreloc; i++)
+    {
+        Elf64_Rela rel = module->pltreloc[i];
+
+        uint64_t type = ELF64_R_TYPE(rel.r_info);
+        if (type != R_X86_64_JUMP_SLOT)
+        {
+            fprintf(stderr, "_ldrelocplt: unsupported relocation type: %lu\n",
+                    type);
+            exit(1);
+        }
+
+        *(Elf64_Addr *)(module->base + rel.r_offset) += module->base;
+    }
+}
+
+void _ldpltgot_init(module_t *module)
+{
+    Elf64_Addr *pltbase = module->pltgot;
+    pltbase[1] = (Elf64_Addr)module;
+    pltbase[2] = (Elf64_Addr)&_ld_bind;
+}
+
+void _ldbindnow(module_t *module)
+{
+    Elf64_Addr base = module->base;
+
+    for (size_t i = 0; i < module->npltreloc; i++)
+    {
+        Elf64_Rela rel = module->pltreloc[i];
+
+        uint64_t sym = ELF64_R_SYM(rel.r_info);
+        uint64_t type = ELF64_R_TYPE(rel.r_info);
+        const char *name = module->dynstr + module->dynsym[sym].st_name;
+        void *addr = (void *)(base + rel.r_offset);
+
+        if (type != R_X86_64_JUMP_SLOT)
+        {
+            fprintf(stderr, "_ldbindnow: unsupported relocation type: %lu\n",
+                    type);
+            exit(1);
+        }
+
+        ldsym_t symbol = _ldresolve(module, name, -1, 0, 0);
+        *(Elf64_Addr *)addr = (Elf64_Addr)symbol;
+    }
+}