Use sysinfo(2) to implement more of <sys/sysinfo.h>.

We already had implementations of some of the functions, and I didn't
bother rewriting them when we added sysinfo(2). Ross Anderson said in
https://www.lightbluetouchpaper.org/2016/07/29/yet-another-android-side-channel/
that we should "simply disable access to all procfs files", which made
me curious how many places we use /proc in bionic. This is the one that's
obviously unnecessary. The others I'm not aware of alternative APIs for.

Change-Id: Ia64f36b76f29a7a1dd67845270a5472e121aae10

diff --git a/libc/bionic/sysinfo.cpp b/libc/bionic/sysinfo.cpp
index 1cb5c79..304634a 100644 (file)
--- a/libc/bionic/sysinfo.cpp
+++ b/libc/bionic/sysinfo.cpp
@@ -76,29 +76,14 @@ int get_nprocs() {
   return cpu_count;
 }
 
-static int __get_meminfo_page_count(const char* pattern) {
-  FILE* fp = fopen("/proc/meminfo", "re");
-  if (fp == NULL) {
-    return -1;
-  }
-
-  int page_count = -1;
-  char buf[256];
-  while (fgets(buf, sizeof(buf), fp) != NULL) {
-    long total;
-    if (sscanf(buf, pattern, &total) == 1) {
-      page_count = static_cast<int>(total / (sysconf(_SC_PAGE_SIZE) / 1024));
-      break;
-    }
-  }
-  fclose(fp);
-  return page_count;
-}
-
 long get_phys_pages() {
-  return __get_meminfo_page_count("MemTotal: %ld kB");
+  struct sysinfo si;
+  sysinfo(&si);
+  return (si.totalram * si.mem_unit) / sysconf(_SC_PAGE_SIZE);
 }
 
 long get_avphys_pages() {
-  return __get_meminfo_page_count("MemFree: %ld kB");
+  struct sysinfo si;
+  sysinfo(&si);
+  return ((si.freeram + si.bufferram) * si.mem_unit) / sysconf(_SC_PAGE_SIZE);
 }

diff --git a/tests/sys_sysinfo_test.cpp b/tests/sys_sysinfo_test.cpp
index b00e13f..d7d0f6e 100644 (file)
--- a/tests/sys_sysinfo_test.cpp
+++ b/tests/sys_sysinfo_test.cpp
@@ -17,17 +17,28 @@
 #include <gtest/gtest.h>
 
 #include <sys/sysinfo.h>
+#include <unistd.h>
 
 TEST(sys_sysinfo, smoke) {
-  int nprocessor = get_nprocs();
-  ASSERT_GT(nprocessor, 0);
+  int nprocs = get_nprocs();
+  ASSERT_GT(nprocs, 0);
+  ASSERT_EQ(sysconf(_SC_NPROCESSORS_ONLN), nprocs);
 
-  int nprocessor_conf = get_nprocs_conf();
-  ASSERT_GE(nprocessor_conf, nprocessor);
+  int nprocs_conf = get_nprocs_conf();
+  ASSERT_GE(nprocs_conf, nprocs);
+  ASSERT_EQ(sysconf(_SC_NPROCESSORS_CONF), nprocs_conf);
 
   long avail_phys_pages = get_avphys_pages();
   ASSERT_GT(avail_phys_pages, 0);
+  ASSERT_EQ(sysconf(_SC_AVPHYS_PAGES), avail_phys_pages);
 
   long phys_pages = get_phys_pages();
   ASSERT_GE(phys_pages, avail_phys_pages);
+  ASSERT_EQ(sysconf(_SC_PHYS_PAGES), phys_pages);
+}
+
+TEST(sys_sysinfo, sysinfo) {
+  struct sysinfo si;
+  memset(&si, 0, sizeof(si));
+  ASSERT_EQ(0, sysinfo(&si));
 }