From c160a3a4002e69b4b0696ae7d3ee33a84c905db7 Mon Sep 17 00:00:00 2001
From: Rui Ueyama <ruiu@google.com>
Date: Tue, 4 Dec 2018 18:47:44 +0000
Subject: ELF: allow non allocated sections to go into allocated sections

Patch from Andrew Kelley.

For context, see https://bugs.llvm.org/show_bug.cgi?id=39862

The use case is embedded / OS programming where the kernel wants
access to its own debug info via mapped dwarf info. I have a proof of
concept of this working, using this linker script snippet:

  .rodata : ALIGN(4K) {
    *(.rodata)
    __debug_info_start = .;
    KEEP(*(.debug_info))
    __debug_info_end = .;
    __debug_abbrev_start = .;
    KEEP(*(.debug_abbrev))
    __debug_abbrev_end = .;
    __debug_str_start = .;
    KEEP(*(.debug_str))
    __debug_str_end = .;
    __debug_line_start = .;
    KEEP(*(.debug_line))
    __debug_line_end =
    .;
    __debug_ranges_start
    = .;
    KEEP(*(.debug_ranges))
    __debug_ranges_end
    = .;
  }

Differential revision: https://reviews.llvm.org/D55276
---
 lld/ELF/OutputSections.cpp                 |  2 +-
 lld/test/ELF/linkerscript/merge-nonalloc.s | 14 ++++++++++++++
 2 files changed, 15 insertions(+), 1 deletion(-)
 create mode 100644 lld/test/ELF/linkerscript/merge-nonalloc.s

(limited to 'lld')

diff --git a/lld/ELF/OutputSections.cpp b/lld/ELF/OutputSections.cpp
index 8ad01e34654..c1442c07873 100644
--- a/lld/ELF/OutputSections.cpp
+++ b/lld/ELF/OutputSections.cpp
@@ -95,7 +95,7 @@ void OutputSection::addSection(InputSection *IS) {
     Flags = IS->Flags;
   } else {
     // Otherwise, check if new type or flags are compatible with existing ones.
-    unsigned Mask = SHF_ALLOC | SHF_TLS | SHF_LINK_ORDER;
+    unsigned Mask = SHF_TLS | SHF_LINK_ORDER;
     if ((Flags & Mask) != (IS->Flags & Mask))
       error("incompatible section flags for " + Name + "\n>>> " + toString(IS) +
             ": 0x" + utohexstr(IS->Flags) + "\n>>> output section " + Name +
diff --git a/lld/test/ELF/linkerscript/merge-nonalloc.s b/lld/test/ELF/linkerscript/merge-nonalloc.s
new file mode 100644
index 00000000000..7c48d3bc6cd
--- /dev/null
+++ b/lld/test/ELF/linkerscript/merge-nonalloc.s
@@ -0,0 +1,14 @@
+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t.o
+# RUN: echo "SECTIONS { .text : { *(.text) *(.nonalloc) } }" > %t.script
+# RUN: ld.lld -shared -o %t.exe %t.script %t.o
+# RUN: llvm-objdump -syms %t.exe | FileCheck %s
+
+# CHECK: .text 00000000 nonalloc_start
+
+_start:
+  nop
+
+.section .nonalloc,"",@progbits
+nonalloc_start:
+  .long 0xcafe
-- 
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