Add a "fork" of musl as //fusl.

fusl/src/internal/vdso.c

+#include <elf.h>
+#include <limits.h>
+#include <stdint.h>
+#include <string.h>
+#include "libc.h"
+#include "syscall.h"
+
+#ifdef VDSO_USEFUL
+
+#if ULONG_MAX == 0xffffffff
+typedef Elf32_Ehdr Ehdr;
+typedef Elf32_Phdr Phdr;
+typedef Elf32_Sym Sym;
+typedef Elf32_Verdef Verdef;
+typedef Elf32_Verdaux Verdaux;
+#else
+typedef Elf64_Ehdr Ehdr;
+typedef Elf64_Phdr Phdr;
+typedef Elf64_Sym Sym;
+typedef Elf64_Verdef Verdef;
+typedef Elf64_Verdaux Verdaux;
+#endif
+
+static int checkver(Verdef *def, int vsym, const char *vername, char *strings)
+{
+        vsym &= 0x7fff;
+        for (;;) {
+                if (!(def->vd_flags & VER_FLG_BASE)
+                  && (def->vd_ndx & 0x7fff) == vsym)
+                        break;
+                if (def->vd_next == 0)
+                        return 0;
+                def = (Verdef *)((char *)def + def->vd_next);
+        }
+        Verdaux *aux = (Verdaux *)((char *)def + def->vd_aux);
+        return !strcmp(vername, strings + aux->vda_name);
+}
+
+#define OK_TYPES (1<<STT_NOTYPE | 1<<STT_OBJECT | 1<<STT_FUNC | 1<<STT_COMMON)
+#define OK_BINDS (1<<STB_GLOBAL | 1<<STB_WEAK | 1<<STB_GNU_UNIQUE)
+
+void *__vdsosym(const char *vername, const char *name)
+{
+        size_t i;
+        for (i=0; libc.auxv[i] != AT_SYSINFO_EHDR; i+=2)
+                if (!libc.auxv[i]) return 0;
+        Ehdr *eh = (void *)libc.auxv[i+1];
+        Phdr *ph = (void *)((char *)eh + eh->e_phoff);
+        size_t *dynv=0, base=-1;
+        for (i=0; i<eh->e_phnum; i++, ph=(void *)((char *)ph+eh->e_phentsize)) {
+                if (ph->p_type == PT_LOAD)
+                        base = (size_t)eh + ph->p_offset - ph->p_vaddr;
+                else if (ph->p_type == PT_DYNAMIC)
+                        dynv = (void *)((char *)eh + ph->p_offset);
+        }
+        if (!dynv || base==(size_t)-1) return 0;
+
+        char *strings = 0;
+        Sym *syms = 0;
+        uint32_t *hashtab = 0;
+        uint16_t *versym = 0;
+        Verdef *verdef = 0;
+        
+        for (i=0; dynv[i]; i+=2) {
+                void *p = (void *)(base + dynv[i+1]);
+                switch(dynv[i]) {
+                case DT_STRTAB: strings = p; break;
+                case DT_SYMTAB: syms = p; break;
+                case DT_HASH: hashtab = p; break;
+                case DT_VERSYM: versym = p; break;
+                case DT_VERDEF: verdef = p; break;
+                }
+        }       
+
+        if (!strings || !syms || !hashtab) return 0;
+        if (!verdef) versym = 0;
+
+        for (i=0; i<hashtab[1]; i++) {
+                if (!(1<<(syms[i].st_info&0xf) & OK_TYPES)) continue;
+                if (!(1<<(syms[i].st_info>>4) & OK_BINDS)) continue;
+                if (!syms[i].st_shndx) continue;
+                if (strcmp(name, strings+syms[i].st_name)) continue;
+                if (versym && !checkver(verdef, versym[i], vername, strings))
+                        continue;
+                return (void *)(base + syms[i].st_value);
+        }
+
+        return 0;
+}
+
+#endif