Introduce cosmo_futex_wait and cosmo_futex_wake

Cosmopolitan Futexes are now exposed as a public API.
2025-06-27 06:48:31 +00:00 · 2024-11-22 11:08:29 -08:00 · 2024-11-22 11:08:29 -08:00 · 9ddbfd921e
commit 9ddbfd921e
parent 729f7045e3
66 changed files with 886 additions and 917 deletions
--- a/libc/intrin/vdsofunc.c
+++ b/libc/intrin/vdsofunc.c
@ -0,0 +1,153 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│ vi: set et ft=c ts=2 sts=2 sw=2 fenc=utf-8                               :vi │
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2022 Justine Alexandra Roberts Tunney                              │
+│                                                                              │
+│ Permission to use, copy, modify, and/or distribute this software for         │
+│ any purpose with or without fee is hereby granted, provided that the         │
+│ above copyright notice and this permission notice appear in all copies.      │
+│                                                                              │
+│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
+│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
+│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
+│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
+│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
+│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
+│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
+│ PERFORMANCE OF THIS SOFTWARE.                                                │
+╚─────────────────────────────────────────────────────────────────────────────*/
+#include "libc/calls/calls.h"
+#include "libc/dce.h"
+#include "libc/elf/def.h"
+#include "libc/elf/scalar.h"
+#include "libc/elf/struct/ehdr.h"
+#include "libc/elf/struct/phdr.h"
+#include "libc/elf/struct/shdr.h"
+#include "libc/elf/struct/sym.h"
+#include "libc/elf/struct/verdaux.h"
+#include "libc/elf/struct/verdef.h"
+#include "libc/intrin/getauxval.h"
+#include "libc/intrin/strace.h"
+#include "libc/runtime/runtime.h"
+#include "libc/str/str.h"
+#include "libc/sysv/consts/auxv.h"
+
+// needed to avoid asan restrictions on strcmp
+static int StrCmp(const char *l, const char *r) {
+  size_t i = 0;
+  while (l[i] == r[i] && r[i])
+    ++i;
+  return (l[i] & 255) - (r[i] & 255);
+}
+
+static inline int CheckDsoSymbolVersion(Elf64_Verdef *vd, int sym,
+                                        const char *name, char *strtab) {
+  Elf64_Verdaux *aux;
+  for (;; vd = (Elf64_Verdef *)((char *)vd + vd->vd_next)) {
+    if (!(vd->vd_flags & VER_FLG_BASE) &&
+        (vd->vd_ndx & 0x7fff) == (sym & 0x7fff)) {
+      aux = (Elf64_Verdaux *)((char *)vd + vd->vd_aux);
+      return !StrCmp(name, strtab + aux->vda_name);
+    }
+    if (!vd->vd_next) {
+      return 0;
+    }
+  }
+}
+
+/**
+ * Returns address of "Virtual Dynamic Shared Object" function on Linux.
+ */
+void *__vdsosym(const char *version, const char *name) {
+  void *p;
+  size_t i;
+  Elf64_Ehdr *ehdr;
+  Elf64_Phdr *phdr;
+  char *strtab = 0;
+  size_t *dyn, base;
+  Elf64_Sym *symtab = 0;
+  uint16_t *versym = 0;
+  Elf_Symndx *hashtab = 0;
+  Elf64_Verdef *verdef = 0;
+  struct AuxiliaryValue av;
+
+  av = __getauxval(AT_SYSINFO_EHDR);
+  if (!av.isfound) {
+    KERNTRACE("__vdsosym() → missing AT_SYSINFO_EHDR");
+    return 0;
+  }
+
+  ehdr = (void *)av.value;
+  phdr = (void *)((char *)ehdr + ehdr->e_phoff);
+  for (base = -1, dyn = 0, i = 0; i < ehdr->e_phnum;
+       i++, phdr = (void *)((char *)phdr + ehdr->e_phentsize)) {
+    switch (phdr->p_type) {
+      case PT_LOAD:
+        // modern linux uses the base address zero, but elders
+        // e.g. rhel7 uses the base address 0xffffffffff700000
+        base = (size_t)ehdr + phdr->p_offset - phdr->p_vaddr;
+        break;
+      case PT_DYNAMIC:
+        dyn = (void *)((char *)ehdr + phdr->p_offset);
+        break;
+      default:
+        break;
+    }
+  }
+  if (!dyn || base == -1) {
+    KERNTRACE("__vdsosym() → missing program headers");
+    return 0;
+  }
+
+  for (i = 0; dyn[i]; i += 2) {
+    p = (void *)(base + dyn[i + 1]);
+    switch (dyn[i]) {
+      case DT_STRTAB:
+        strtab = p;
+        break;
+      case DT_SYMTAB:
+        symtab = p;
+        break;
+      case DT_HASH:
+        hashtab = p;
+        break;
+      case DT_VERSYM:
+        versym = p;
+        break;
+      case DT_VERDEF:
+        verdef = p;
+        break;
+    }
+  }
+  if (!strtab || !symtab || !hashtab) {
+    KERNTRACE("__vdsosym() → tables not found");
+    return 0;
+  }
+  if (!verdef) {
+    versym = 0;
+  }
+
+  for (i = 0; i < hashtab[1]; i++) {
+    if (ELF64_ST_TYPE(symtab[i].st_info) != STT_FUNC &&
+        ELF64_ST_TYPE(symtab[i].st_info) != STT_OBJECT &&
+        ELF64_ST_TYPE(symtab[i].st_info) != STT_NOTYPE) {
+      continue;
+    }
+    if (ELF64_ST_BIND(symtab[i].st_info) != STB_GLOBAL) {
+      continue;
+    }
+    if (!symtab[i].st_shndx) {
+      continue;
+    }
+    if (StrCmp(name, strtab + symtab[i].st_name)) {
+      continue;
+    }
+    if (versym && !CheckDsoSymbolVersion(verdef, versym[i], version, strtab)) {
+      continue;
+    }
+    return (void *)(base + symtab[i].st_value);
+  }
+
+  KERNTRACE("__vdsosym() → symbol not found");
+  return 0;
+}