src: find .text section using dl_iterate_phdr

Use `dl_iterate_phdr(3)` to find the mapping containing
`__node_text_start` instead of parsing `/proc/self/maps`.
Signed-off-by: Gabriel Schulhof <gabriel.schulhof@intel.com>
Co-Authored-By: Ben Noordhuis <info@bnoordhuis.nl>
PR-URL: #32244
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: David Carlier <devnexen@gmail.com>

Author: 2 people

src/large_pages/node_large_page.cc

@@ -29,7 +29,12 @@
 #include"util.h"
 #include"uv.h"
 
-#include<fcntl.h>// _O_RDWR
+#if defined(__linux__)
+#ifndef _GNU_SOURCE
+#define_GNU_SOURCE
+#endif
+#include<link.h>
+#endif
 #include<sys/types.h>
 #include<sys/mman.h>
 #if defined(__FreeBSD__)
@@ -38,19 +43,17 @@
 #elif defined(__APPLE__)
 #include<mach/vm_map.h>
 #endif
-#include<unistd.h>//readlink
+#include<unistd.h>//getpid
 
 #include<climits>// PATH_MAX
 #include<clocale>
 #include<csignal>
-#include<cstdio>
 #include<cstdlib>
 #include<cstdint>
 #include<cstring>
 #include<string>
 #include<fstream>
 #include<iostream>
-#include<sstream>
 #include<vector>
 
 // The functions in this file map the text segment of node into 2M pages.
@@ -110,72 +113,63 @@ inline uintptr_t hugepage_align_down(uintptr_t addr) {
 return ((addr) & ~((hps) - 1));
 }
 
-// The format of the maps file is the following
-// address perms offset dev inode pathname
-// 00400000-00452000 r-xp 00000000 08:02 173521 /usr/bin/dbus-daemon
-// This is also handling the case where the first line is not the binary.
+structdl_iterate_params {
+uintptr_t start;
+uintptr_t end;
+uintptr_t reference_sym;
+};
+
+#if defined(__linux__)
+intFindMapping(structdl_phdr_info* info, size_t, void* data) {
+if (info->dlpi_name[0] == 0) {
+for (int idx = 0; idx < info->dlpi_phnum; idx++) {
+constElfW(Phdr)* phdr = &info->dlpi_phdr[idx];
+if (phdr->p_type == PT_LOAD && (phdr->p_flags & PF_X)) {
+auto dl_params = static_cast<dl_iterate_params*>(data);
+uintptr_t start = info->dlpi_addr + phdr->p_vaddr;
+uintptr_t end = start + phdr->p_memsz;
+
+if (dl_params->reference_sym >= start &&
+ dl_params->reference_sym <= end) {
+ dl_params->start = start;
+ dl_params->end = end;
+return1;
+ }
+ }
+ }
+ }
+return0;
+}
+#endif// defined(__linux__)
 
 structtext_regionFindNodeTextRegion() {
 structtext_region nregion;
  nregion.found_text_region = false;
 #if defined(__linux__)
- std::ifstream ifs;
- std::string map_line;
- std::string permission;
- std::string dev;
-char dash;
-uintptr_t start, end, offset, inode;
-uintptr_t node_text_start = reinterpret_cast<uintptr_t>(&__node_text_start);
+ dl_iterate_params dl_params = {
+0, 0, reinterpret_cast<uintptr_t>(&__node_text_start)
+ };
 uintptr_t lpstub_start = reinterpret_cast<uintptr_t>(&__start_lpstub);
 
- ifs.open("/proc/self/maps");
-if (!ifs) {
-PrintWarning("could not open /proc/self/maps");
-return nregion;
- }
-
-while (std::getline(ifs, map_line)) {
- std::istringstream iss(map_line);
- iss >> std::hex >> start;
- iss >> dash;
- iss >> std::hex >> end;
- iss >> permission;
- iss >> offset;
- iss >> dev;
- iss >> inode;
-
-if (inode == 0)
-continue;
-
- std::string pathname;
- iss >> pathname;
-
-if (permission != "r-xp")
-continue;
-
-if (node_text_start < start || node_text_start >= end)
-continue;
-
- start = node_text_start;
-if (lpstub_start > start && lpstub_start <= end)
- end = lpstub_start;
-
-char* from = reinterpret_cast<char*>(hugepage_align_up(start));
-char* to = reinterpret_cast<char*>(hugepage_align_down(end));
-
-if (from >= to)
-break;
-
-size_t size = to - from;
- nregion.found_text_region = true;
- nregion.from = from;
- nregion.to = to;
- nregion.total_hugepages = size / hps;
-
-break;
+if (dl_iterate_phdr(FindMapping, &dl_params) == 1) {
+ dl_params.start = dl_params.reference_sym;
+if (lpstub_start > dl_params.start && lpstub_start <= dl_params.end)
+ dl_params.end = lpstub_start;
+
+if (dl_params.start < dl_params.end) {
+char* from = reinterpret_cast<char*>(hugepage_align_up(dl_params.start));
+char* to = reinterpret_cast<char*>(hugepage_align_down(dl_params.end));
+if (from < to) {
+size_t pagecount = (to - from) / hps;
+if (pagecount > 0) {
+ nregion.found_text_region = true;
+ nregion.from = from;
+ nregion.to = to;
+ nregion.total_hugepages = pagecount;
+ }
+ }
+ }
  }
-
- ifs.close();
 #elif defined(__FreeBSD__)
  std::string exename;
  {
@@ -289,7 +283,7 @@ bool IsTransparentHugePagesEnabled() {
 return always == "[always]" || madvise == "[madvise]";
 }
 #elif defined(__FreeBSD__)
-staticboolIsSuperPagesEnabled() {
+boolIsSuperPagesEnabled() {
 // It is enabled by default on amd64.
 unsignedint super_pages = 0;
 size_t super_pages_length = sizeof(super_pages);