Improve signals and memory protection

- Document sigaction() - Simplify New Technology fork() code - Testing and many bug fixes for mprotect() - Distribute Intel Xed ILD in the amalgamation - Turn Xed enums into defines to avoid DWARF bloat - Improve polyfilling of SA_SIGINFO on BSDs and fix bugs - setpgid(getpid(), getpid()) on Windows will ignore CTRL-C - Work around issues relating to NT mappings being executable - Permit automatic executable stack override via `ape_stack_pf`
2025-06-26 22:38:30 +00:00 · 2022-04-12 22:11:00 -07:00 · 2022-04-12 22:11:00 -07:00 · f684e348d4
commit f684e348d4
parent c95c9d9508
76 changed files with 1844 additions and 1121 deletions
--- a/libc/runtime/mprotect.greg.c
+++ b/libc/runtime/mprotect.greg.c
@ -0,0 +1,107 @@
+/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
+│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
+╞══════════════════════════════════════════════════════════════════════════════╡
+│ Copyright 2020 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/bits/asmflag.h"
+#include "libc/bits/likely.h"
+#include "libc/calls/internal.h"
+#include "libc/calls/strace.internal.h"
+#include "libc/dce.h"
+#include "libc/errno.h"
+#include "libc/intrin/describeflags.internal.h"
+#include "libc/macros.internal.h"
+#include "libc/nt/memory.h"
+#include "libc/nt/thunk/msabi.h"
+#include "libc/runtime/directmap.internal.h"
+#include "libc/runtime/memtrack.internal.h"
+#include "libc/sysv/consts/nr.h"
+#include "libc/sysv/consts/prot.h"
+#include "libc/sysv/errfuns.h"
+
+extern typeof(VirtualProtect) *const __imp_VirtualProtect __msabi;
+
+#define ADDR(x) ((char *)((int64_t)((uint64_t)(x) << 32) >> 16))
+
+/**
+ * Modifies restrictions on virtual memory address range.
+ *
+ * @param addr needs to be 4kb aligned
+ * @param prot can have PROT_{NONE,READ,WRITE,EXEC,GROWSDOWN,GROWSUP}
+ * @return 0 on success, or -1 w/ errno
+ * @see mmap()
+ */
+noasan noubsan privileged int mprotect(void *addr, size_t size, int prot) {
+  bool cf;
+  int64_t rc;
+  unsigned i;
+  uint32_t op;
+  char *a, *b, *x, *y, *p;
+  if (SupportsWindows() && (prot & ~(PROT_READ | PROT_WRITE | PROT_EXEC |
+                                     PROT_GROWSDOWN | PROT_GROWSUP))) {
+    rc = einval();  // unix checks prot before checking size
+  } else if (!size) {
+    return 0;  // make new technology consistent with unix
+  } else if (UNLIKELY((intptr_t)addr & 4095)) {
+    rc = einval();
+  } else if (!IsWindows()) {
+    asm volatile(CFLAG_ASM("clc\n\tsyscall")
+                 : CFLAG_CONSTRAINT(cf), "=a"(rc)
+                 : "1"(__NR_mprotect), "D"(addr), "S"(size), "d"(prot)
+                 : "rcx", "r11", "memory", "cc");
+    if (cf) {
+      errno = rc;
+      rc = -1;
+    } else if (rc > -4096ul) {
+      errno = -rc;
+      rc = -1;
+    }
+  } else {
+    rc = 0;
+    p = addr;
+    i = FindMemoryInterval(&_mmi, (intptr_t)p >> 16);
+    if (i == _mmi.i || (!i && p + size <= ADDR(_mmi.p[0].x))) {
+      // memory isn't in memtrack
+      // let's just trust the user then
+      // it's probably part of the executable
+      if (!VirtualProtect(addr, size, __prot2nt(prot, false), &op)) {
+        rc = -1;
+      }
+    } else {
+      // memory is in memtrack, so use memtrack, to do dimensioning
+      // we unfortunately must do something similar to this for cow
+      for (; i < _mmi.i; ++i) {
+        x = ADDR(_mmi.p[i].x);
+        y = x + _mmi.p[i].size;
+        if ((x <= p && p < y) || (x < p + size && p + size <= y) ||
+            (p < x && y < p + size)) {
+          a = MIN(MAX(p, x), y);
+          b = MAX(MIN(p + size, y), x);
+          if (!VirtualProtect(a, b - a, __prot2nt(prot, _mmi.p[i].iscow),
+                              &op)) {
+            rc = -1;
+            break;
+          }
+        } else {
+          break;
+        }
+      }
+    }
+  }
+  STRACE("mprotect(%p, %'zu, %s) → %d% m", addr, size, DescribeProtFlags(prot),
+         rc);
+  return rc;
+}