Support new interpreter requirements in test

Refactoring in 0036d1f7eb95bcc52977f15507f00dd07018e7e2 (v4.10) caused Linux to
start unconditionally zeroing the remainder of the last page in the
interpreter. Previously it did not due so if filesz == memsz, and *still* does
not do so when filesz == memsz for loading binaries, only interpreter.

This inconsistency is not worth replicating in gVisor, as it is arguably a bug,
but our tests must ensure we create interpreter ELFs compatible with this new
requirement.

PiperOrigin-RevId: 272266401

1 files changed, 32 insertions, 19 deletions

diff --git a/test/syscalls/linux/exec_binary.cc b/test/syscalls/linux/exec_binary.cc
index 68af882bb..0a3931e5a 100644
--- a/test/syscalls/linux/exec_binary.cc
+++ b/test/syscalls/linux/exec_binary.cc
@@ -859,6 +859,11 @@ TEST(ElfTest, ELFInterpreter) {
   // The first segment really needs to start at 0 for a normal PIE binary, and
   // thus includes the headers.
   uint64_t const offset = interpreter.phdrs[1].p_offset;
+  // N.B. Since Linux 4.10 (0036d1f7eb95b "binfmt_elf: fix calculations for bss
+  // padding"), Linux unconditionally zeroes the remainder of the highest mapped
+  // page in an interpreter, failing if the protections don't allow write. Thus
+  // we must mark this writeable.
+  interpreter.phdrs[1].p_flags = PF_R | PF_W | PF_X;
   interpreter.phdrs[1].p_offset = 0x0;
   interpreter.phdrs[1].p_vaddr = 0x0;
   interpreter.phdrs[1].p_filesz += offset;
@@ -908,15 +913,15 @@ TEST(ElfTest, ELFInterpreter) {
 
   const uint64_t interp_load_addr = regs.rip & ~(kPageSize - 1);
 
-  EXPECT_THAT(child,
-              ContainsMappings(std::vector<ProcMapsEntry>({
-                  // Main binary
-                  {0x40000, 0x41000, true, false, true, true, 0, 0, 0, 0,
-                   binary_file.path().c_str()},
-                  // Interpreter
-                  {interp_load_addr, interp_load_addr + 0x1000, true, false,
-                   true, true, 0, 0, 0, 0, interpreter_file.path().c_str()},
-              })));
+  EXPECT_THAT(
+      child, ContainsMappings(std::vector<ProcMapsEntry>({
+                 // Main binary
+                 {0x40000, 0x41000, true, false, true, true, 0, 0, 0, 0,
+                  binary_file.path().c_str()},
+                 // Interpreter
+                 {interp_load_addr, interp_load_addr + 0x1000, true, true, true,
+                  true, 0, 0, 0, 0, interpreter_file.path().c_str()},
+             })));
 }
 
 // Test parameter to ElfInterpterStaticTest cases. The first item is a suffix to
@@ -933,6 +938,8 @@ TEST_P(ElfInterpreterStaticTest, Test) {
   const int expected_errno = std::get<1>(GetParam());
 
   ElfBinary<64> interpreter = StandardElf();
+  // See comment in ElfTest.ELFInterpreter.
+  interpreter.phdrs[1].p_flags = PF_R | PF_W | PF_X;
   interpreter.UpdateOffsets();
   TempPath interpreter_file =
       ASSERT_NO_ERRNO_AND_VALUE(CreateElfWith(interpreter));
@@ -962,7 +969,7 @@ TEST_P(ElfInterpreterStaticTest, Test) {
 
     EXPECT_THAT(child, ContainsMappings(std::vector<ProcMapsEntry>({
                            // Interpreter.
-                           {0x40000, 0x41000, true, false, true, true, 0, 0, 0,
+                           {0x40000, 0x41000, true, true, true, true, 0, 0, 0,
                             0, interpreter_file.path().c_str()},
                        })));
   }
@@ -1040,6 +1047,8 @@ TEST(ElfTest, ELFInterpreterRelative) {
   // The first segment really needs to start at 0 for a normal PIE binary, and
   // thus includes the headers.
   uint64_t const offset = interpreter.phdrs[1].p_offset;
+  // See comment in ElfTest.ELFInterpreter.
+  interpreter.phdrs[1].p_flags = PF_R | PF_W | PF_X;
   interpreter.phdrs[1].p_offset = 0x0;
   interpreter.phdrs[1].p_vaddr = 0x0;
   interpreter.phdrs[1].p_filesz += offset;
@@ -1078,15 +1087,15 @@ TEST(ElfTest, ELFInterpreterRelative) {
 
   const uint64_t interp_load_addr = regs.rip & ~(kPageSize - 1);
 
-  EXPECT_THAT(child,
-              ContainsMappings(std::vector<ProcMapsEntry>({
-                  // Main binary
-                  {0x40000, 0x41000, true, false, true, true, 0, 0, 0, 0,
-                   binary_file.path().c_str()},
-                  // Interpreter
-                  {interp_load_addr, interp_load_addr + 0x1000, true, false,
-                   true, true, 0, 0, 0, 0, interpreter_file.path().c_str()},
-              })));
+  EXPECT_THAT(
+      child, ContainsMappings(std::vector<ProcMapsEntry>({
+                 // Main binary
+                 {0x40000, 0x41000, true, false, true, true, 0, 0, 0, 0,
+                  binary_file.path().c_str()},
+                 // Interpreter
+                 {interp_load_addr, interp_load_addr + 0x1000, true, true, true,
+                  true, 0, 0, 0, 0, interpreter_file.path().c_str()},
+             })));
 }
 
 // ELF interpreter architecture doesn't match the binary.
@@ -1100,6 +1109,8 @@ TEST(ElfTest, ELFInterpreterWrongArch) {
   // The first segment really needs to start at 0 for a normal PIE binary, and
   // thus includes the headers.
   uint64_t const offset = interpreter.phdrs[1].p_offset;
+  // See comment in ElfTest.ELFInterpreter.
+  interpreter.phdrs[1].p_flags = PF_R | PF_W | PF_X;
   interpreter.phdrs[1].p_offset = 0x0;
   interpreter.phdrs[1].p_vaddr = 0x0;
   interpreter.phdrs[1].p_filesz += offset;
@@ -1179,6 +1190,8 @@ TEST(ElfTest, ElfInterpreterNoExecute) {
   // The first segment really needs to start at 0 for a normal PIE binary, and
   // thus includes the headers.
   uint64_t const offset = interpreter.phdrs[1].p_offset;
+  // See comment in ElfTest.ELFInterpreter.
+  interpreter.phdrs[1].p_flags = PF_R | PF_W | PF_X;
   interpreter.phdrs[1].p_offset = 0x0;
   interpreter.phdrs[1].p_vaddr = 0x0;
   interpreter.phdrs[1].p_filesz += offset;