Created student weenix repository

1 files changed, 119 insertions, 0 deletions

diff --git a/user/lib/ld-weenix/ldresolve.c b/user/lib/ld-weenix/ldresolve.c
new file mode 100644
index 0000000..db1da80
--- /dev/null
+++ b/user/lib/ld-weenix/ldresolve.c
@@ -0,0 +1,119 @@
+/*
+ *  File: ldresolve.c
+ *  Date: 12 April 1998
+ *  Acct: David Powell (dep)
+ *  Desc: Various symbol resolution functions
+ *
+ *
+ *  Acct: Sandy Harvie (charvie)
+ *  Date: 27 March 2019
+ *  Desc: Modified for x86-64
+ */
+
+#include "string.h"
+
+#include "ldresolve.h"
+#include "ldutil.h"
+
+#define H_nbucket 0
+#define H_nchain 1
+#define H_bucket 2
+
+/* This function looks up the specified symbol in the specified
+ * module.  If the symbol is present, it returns the symbol's index in
+ * the dynamic symbol table, otherwise STN_UNDEF is returned. */
+
+int _ldlookup(module_t *module, const char *name)
+{
+    unsigned long hashval;
+    unsigned long y;
+
+    hashval = _ldelfhash(name);
+    hashval %= module->hash[H_nbucket];
+
+    y = module->hash[H_bucket + hashval];
+
+    while ((y != STN_UNDEF) &&
+           strcmp(module->dynstr + module->dynsym[y].st_name, name))
+    {
+        y = module->hash[H_bucket + module->hash[H_nbucket] + y];
+    }
+
+    return y;
+}
+
+/* This looks up the specified symbol in the given module, subject to
+ * the provided binding and type restrictions (a value of -1 will
+ * function as a wildcard for both the 'binding' and 'type'
+ * parameters).  The symbol's size will be placed in the memory
+ * location pointed to by 'size', if it is non-null.  0 is returned if
+ * a symbol matching all the requirements is not found. */
+
+ldsym_t _ldsymbol(module_t *module, const char *name, int binding, int type,
+                  Elf64_Word *size)
+{
+    int result;
+
+    /* LINTED */
+    if (((result = _ldlookup(module, name)) != STN_UNDEF) &&
+        ((binding < 0) ||
+         (ELF64_ST_BIND(module->dynsym[result].st_info) == binding)) &&
+        ((type < 0) ||
+         (ELF64_ST_TYPE(module->dynsym[result].st_info) == type)) &&
+        (module->dynsym[result].st_shndx != SHN_UNDEF))
+    {
+        if (size)
+            *size = module->dynsym[result].st_size;
+        return (ldsym_t)((uintptr_t)module->base +
+                         (uintptr_t)module->dynsym[result].st_value);
+    }
+
+    return 0;
+}
+
+/* Given a module and a symbol name, this function attempts to find the
+ * symbol through the process' link chain.  It first checks for its
+ * presence as a global symbol, then as a weak symbol, and finally as a
+ * local symbol in the specified module.  A type restriction can be
+ * specified, and if 'size' is non-null, the memory location to which
+ * it points will hold the size of the resolved symbol.  0 is returned
+ * if the symbol cannot be found. */
+
+ldsym_t _ldresolve(module_t *module, const char *name, int type,
+                   Elf64_Word *size, int exclude)
+{
+    module_t *curmod;
+    ldsym_t sym;
+
+    curmod = module->first;
+
+    while (curmod)
+    {
+        if (!exclude || curmod != module)
+        {
+            if ((sym = _ldsymbol(curmod, name, STB_GLOBAL, type, size)))
+                return sym;
+        }
+        curmod = curmod->next;
+    }
+
+    curmod = module->first;
+    while (curmod)
+    {
+        if ((sym = _ldsymbol(curmod, name, STB_WEAK, type, size)))
+            return sym;
+        curmod = curmod->next;
+    }
+
+    return _ldsymbol(module, name, STB_LOCAL, type, size);
+}
+
+Elf64_Addr _rtresolve(module_t *mod, Elf64_Word reloff)
+{
+    Elf64_Rela *rel = mod->pltreloc + reloff;
+    int sym = ELF64_R_SYM(rel->r_info);
+    const char *name = mod->dynstr + mod->dynsym[sym].st_name;
+    ldsym_t symbol = _ldresolve(mod, name, -1, 0, 0);
+    *(Elf64_Addr *)(mod->base + rel->r_offset) = (Elf64_Addr)symbol;
+    return (Elf64_Addr)symbol;
+}