Name anonymous memory allocations on Linux.

Use Linux's prctl(PR_SET_VMA) system call to name memory arenas being
allocated using mmap(MAP_ANONYMOUS).

This change allows Abseil's memory arena(s) to be distinguished from
other uses of anonymous memory within a process, which in turn helps
investigations into the memory usage of applications.

The change adds a new prctl() system call to the code paths that call
mmap(). This is not expected to add significant overhead to applications.

The call to prctl(PR_SET_VMA, ...) can fail if the Linux kernel in use was
not configured with the CONFIG_ANON_VMA_NAME kernel option.  This should
be OK since the naming memory regions is primarily a debugging aid.

PiperOrigin-RevId: 523687348
Change-Id: Ie404e5eeef0a6da53330b3a56149c4f3bc6bf5c7

absl/base/internal/low_level_alloc.cc

@@ -42,6 +42,10 @@
 #include <windows.h>
 #include <windows.h>
 #endif
 #endif
 
 
+#ifdef __linux__
+#include <sys/prctl.h>
+#endif
+
 #include <string.h>
 #include <string.h>
 #include <algorithm>
 #include <algorithm>
 #include <atomic>
 #include <atomic>
@@ -570,6 +574,18 @@ static void *DoAllocWithArena(size_t request, LowLevelAlloc::Arena *arena) {
         ABSL_RAW_LOG(FATAL, "mmap error: %d", errno);
         ABSL_RAW_LOG(FATAL, "mmap error: %d", errno);
       }
       }
 
 
+#ifdef __linux__
+#if defined(PR_SET_VMA) && defined(PR_SET_VMA_ANON_NAME)
+      // Attempt to name the allocated address range in /proc/$PID/smaps on
+      // Linux.
+      //
+      // This invocation of prctl() may fail if the Linux kernel was not
+      // configured with the CONFIG_ANON_VMA_NAME option.  This is OK since
+      // the naming of arenas is primarily a debugging aid.
+      prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, new_pages, new_pages_size,
+            "absl");
+#endif
+#endif  // __linux__
 #endif  // _WIN32
 #endif  // _WIN32
       arena->mu.Lock();
       arena->mu.Lock();
       s = reinterpret_cast<AllocList *>(new_pages);
       s = reinterpret_cast<AllocList *>(new_pages);

absl/debugging/failure_signal_handler.cc

@@ -33,6 +33,10 @@
 #include <sys/mman.h>
 #include <sys/mman.h>
 #endif
 #endif
 
 
+#ifdef __linux__
+#include <sys/prctl.h>
+#endif
+
 #include <algorithm>
 #include <algorithm>
 #include <atomic>
 #include <atomic>
 #include <cerrno>
 #include <cerrno>
@@ -172,6 +176,20 @@ static bool SetupAlternateStackOnce() {
   if (sigaltstack(&sigstk, nullptr) != 0) {
   if (sigaltstack(&sigstk, nullptr) != 0) {
     ABSL_RAW_LOG(FATAL, "sigaltstack() failed with errno=%d", errno);
     ABSL_RAW_LOG(FATAL, "sigaltstack() failed with errno=%d", errno);
   }
   }
+
+#ifdef __linux__
+#if defined(PR_SET_VMA) && defined(PR_SET_VMA_ANON_NAME)
+  // Make a best-effort attempt to name the allocated region in
+  // /proc/$PID/smaps.
+  //
+  // The call to prctl() may fail if the kernel was not configured with the
+  // CONFIG_ANON_VMA_NAME kernel option.  This is OK since the call is
+  // primarily a debugging aid.
+  prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, sigstk.ss_sp, sigstk.ss_size,
+        "absl-signalstack");
+#endif
+#endif  // __linux__
+
   return true;
   return true;
 }
 }