[LinkerScript] Support OR of FLAGS in PHDR directives

[ruiu]

https://sourceware.org/binutils/docs/ld/PHDRS.html says that "The value of flags must be an integer". Can you give me a pointer to a sample use case?

[davide]

Sorry, I found that in a linker script we use internally (can't share, alas). It seems not even ld.bfd accepts this syntax so I'll keep this patch private.

[ruiu]

Looks like you can easily replace it with 0x3.

[davide]

In D23031#502539, @ruiu wrote:

Looks like you can easily replace it with 0x3.

Yes. I can. I just don't have control over these linker scripts, so it's very hard.

ELF/LinkerScript.cpp

       Tok = next();
       if (Tok == ";")
         break;
       if (Tok == "FILEHDR")
         PhdrCmd.HasFilehdr = true;
       else if (Tok == "PHDRS")
         PhdrCmd.HasPhdrs = true;
       else if (Tok == "FLAGS") {
+        // This can contain a bitwise-OR of flags.
         expect("(");
-        next().getAsInteger(0, PhdrCmd.Flags);
+        uint8_t Flags;
+        PhdrCmd.Flags = 0;
+        do {
+          next().getAsInteger(0, Flags);
+          PhdrCmd.Flags |= Flags;
+        } while (skip("|"));
         expect(")");
       } else
         setError("unexpected header attribute: " + Tok);
     } while (!Error);
   }
 }
 
 void ScriptParser::readSearchDir() {

test/ELF/linkerscript/linkerscript-phdrs-flags.s

 # REQUIRES: x86
 # RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t
-# RUN: echo "PHDRS {all PT_LOAD FILEHDR PHDRS FLAGS (1);} \
+# RUN: echo "PHDRS {all PT_LOAD FILEHDR PHDRS FLAGS (0x1 | 0x2);} \
 # RUN:       SECTIONS { \
 # RUN:           . = 0x10000200; \
 # RUN:           .text : {*(.text.*)} :all \
 # RUN:           .foo : {*(.foo.*)} :all \
 # RUN:           .data : {*(.data.*)} :all}" > %t.script
 
 # RUN: ld.lld -o %t1 --script %t.script %t
 # RUN: llvm-readobj -program-headers %t1 | FileCheck %s
 # CHECK:     ProgramHeaders [
 # CHECK-NEXT:  ProgramHeader {
 # CHECK-NEXT:    Type: PT_LOAD (0x1)
 # CHECK-NEXT:    Offset: 0x0
 # CHECK-NEXT:    VirtualAddress: 0x10000000
 # CHECK-NEXT:    PhysicalAddress: 0x10000000
 # CHECK-NEXT:    FileSize: 521
 # CHECK-NEXT:    MemSize: 521
-# CHECK-NEXT:    Flags [ (0x1)
+# CHECK-NEXT:    Flags [ (0x3)
+# CHECK-NEXT:      PF_W (0x2)
 # CHECK-NEXT:      PF_X (0x1)
 # CHECK-NEXT:    ]
 
 .global _start
 _start:
  nop
 
 .section .foo.1,"a"
 foo1:
  .long 0
 
 .section .foo.2,"aw"
 foo2:
  .long 0