Collect .openbsd.syscalls sections into a new PT_OPENBSD_SYSCALLS seg…

…ment.

This will be used soon to pin system calls to designated call sites.

ok deraadt@

gnu/llvm/lld/ELF/ScriptParser.cpp

@@ -1577,6 +1577,7 @@ unsigned ScriptParser::readPhdrType() {
                      .Case("PT_GNU_RELRO", PT_GNU_RELRO)
                      .Case("PT_OPENBSD_MUTABLE", PT_OPENBSD_MUTABLE)
                      .Case("PT_OPENBSD_RANDOMIZE", PT_OPENBSD_RANDOMIZE)
+                     .Case("PT_OPENBSD_SYSCALLS", PT_OPENBSD_SYSCALLS)
                      .Case("PT_OPENBSD_WXNEEDED", PT_OPENBSD_WXNEEDED)
                      .Case("PT_OPENBSD_BOOTDATA", PT_OPENBSD_BOOTDATA)
                      .Default(-1);

gnu/llvm/lld/ELF/Writer.cpp

@@ -2388,6 +2388,11 @@ SmallVector<PhdrEntry *, 0> Writer<ELFT>::createPhdrs(Partition &part) {
   if (OutputSection *cmd = findSection(".openbsd.randomdata", partNo))
     addHdr(PT_OPENBSD_RANDOMIZE, cmd->getPhdrFlags())->add(cmd);
 
+  // PT_OPENBSD_SYSCALLS is an OpenBSD-specific feature. That makes
+  // the kernel and dynamic linker register system call sites.
+  if (OutputSection *cmd = findSection(".openbsd.syscalls", partNo))
+    addHdr(PT_OPENBSD_SYSCALLS, cmd->getPhdrFlags())->add(cmd);
+
   if (config->zGnustack != GnuStackKind::None) {
     // PT_GNU_STACK is a special section to tell the loader to make the
     // pages for the stack non-executable. If you really want an executable

gnu/llvm/llvm/include/llvm/BinaryFormat/ELF.h

@@ -1405,6 +1405,7 @@ enum {
   PT_OPENBSD_RANDOMIZE = 0x65a3dbe6, // Fill with random data.
   PT_OPENBSD_WXNEEDED = 0x65a3dbe7,  // Program does W^X violations.
   PT_OPENBSD_NOBTCFI = 0x65a3dbe8,   // Do not enforce branch target CFI
+  PT_OPENBSD_SYSCALLS = 0x65a3dbe9,  // System call sites.
   PT_OPENBSD_BOOTDATA = 0x65a41be6,  // Section for boot arguments.
 
   // ARM program header types.

gnu/llvm/llvm/tools/llvm-objdump/ELFDump.cpp

@@ -259,6 +259,9 @@ static void printProgramHeaders(const ELFFile<ELFT> &Obj, StringRef FileName) {
     case ELF::PT_OPENBSD_RANDOMIZE:
       outs() << "OPENBSD_RANDOMIZE ";
       break;
+    case ELF::PT_OPENBSD_SYSCALLS:
+      outs() << "OPENBSD_SYSCALLS ";
+      break;
     case ELF::PT_OPENBSD_WXNEEDED:
       outs() << "OPENBSD_WXNEEDED ";
       break;

gnu/llvm/llvm/tools/llvm-readobj/ELFDumper.cpp

@@ -1411,6 +1411,7 @@ static StringRef segmentTypeToString(unsigned Arch, unsigned Type) {
 
     LLVM_READOBJ_ENUM_CASE(ELF, PT_OPENBSD_MUTABLE);
     LLVM_READOBJ_ENUM_CASE(ELF, PT_OPENBSD_RANDOMIZE);
+    LLVM_READOBJ_ENUM_CASE(ELF, PT_OPENBSD_SYSCALLS);
     LLVM_READOBJ_ENUM_CASE(ELF, PT_OPENBSD_WXNEEDED);
     LLVM_READOBJ_ENUM_CASE(ELF, PT_OPENBSD_NOBTCFI);
     LLVM_READOBJ_ENUM_CASE(ELF, PT_OPENBSD_BOOTDATA);