commit bc1a6191f124bce88f922c1d3e0f3154ff5d98c3
author Peter Collingbourne <pcc@google.com> Tue Mar 31 23:08:12 2020 +0000
committer Gerrit Code Review <noreply-gerritcodereview@google.com> Tue Mar 31 23:08:12 2020 +0000
tree 8fc51d481042a20974c1c37290bed6784756f554
parent fcf2d8b89b98f4ac09e5b849d9d27f8e63d97cef
parent a7b4c5d25aebc2c7e6156473dae98238c029e630

Merge "Fix off-by-one in ReadBuildIDFromMemory."

libunwindstack/ElfInterface.cpp

diff --git a/libunwindstack/ElfInterface.cpp b/libunwindstack/ElfInterface.cpp
index 341275d..821e042 100644
--- a/libunwindstack/ElfInterface.cpp
+++ b/libunwindstack/ElfInterface.cpp
@@ -662,7 +662,7 @@
         if (note_size - offset < hdr.n_descsz || hdr.n_descsz == 0) {
           return "";
         }
-        std::string build_id(hdr.n_descsz - 1, '\0');
+        std::string build_id(hdr.n_descsz, '\0');
         if (memory->ReadFully(note_offset + offset, &build_id[0], hdr.n_descsz)) {
           return build_id;
         }

libunwindstack/tests/MapInfoGetBuildIDTest.cpp

diff --git a/libunwindstack/tests/MapInfoGetBuildIDTest.cpp b/libunwindstack/tests/MapInfoGetBuildIDTest.cpp
index 6953e26..70e136b 100644
--- a/libunwindstack/tests/MapInfoGetBuildIDTest.cpp
+++ b/libunwindstack/tests/MapInfoGetBuildIDTest.cpp
@@ -142,15 +142,14 @@
 
   char note_section[128];
   Elf32_Nhdr note_header = {};
-  note_header.n_namesz = 4;   // "GNU"
-  note_header.n_descsz = 12;  // "ELF_BUILDID"
+  note_header.n_namesz = sizeof("GNU");
+  note_header.n_descsz = sizeof("ELF_BUILDID") - 1;
   note_header.n_type = NT_GNU_BUILD_ID;
   memcpy(&note_section, &note_header, sizeof(note_header));
   size_t note_offset = sizeof(note_header);
-  memcpy(&note_section[note_offset], "GNU", sizeof("GNU"));
-  note_offset += sizeof("GNU");
-  memcpy(&note_section[note_offset], "ELF_BUILDID", sizeof("ELF_BUILDID"));
-  note_offset += sizeof("ELF_BUILDID");
+  memcpy(&note_section[note_offset], "GNU", note_header.n_namesz);
+  note_offset += note_header.n_namesz;
+  memcpy(&note_section[note_offset], "ELF_BUILDID", note_header.n_descsz);
 
   Elf32_Shdr shdr = {};
   shdr.sh_type = SHT_NOTE;
@@ -195,4 +194,10 @@
   MultipleThreadTest("ELF_BUILDID");
 }
 
+TEST_F(MapInfoGetBuildIDTest, real_elf) {
+  MapInfo map_info(nullptr, nullptr, 0x1000, 0x20000, 0, PROT_READ | PROT_WRITE,
+                   TestGetFileDirectory() + "offline/empty_arm64/libc.so");
+  EXPECT_EQ("6df0590c4920f4c7b9f34fe833f37d54", map_info.GetPrintableBuildID());
+}
+
 }  // namespace unwindstack