llvm-project/llvm
Xing GUO dd440675cf [BinaryFormat] Add DT_USED tag into dynamic section.
Summary:
This tag is documented in https://docs.oracle.com/cd/E19253-01/817-1984/chapter6-42444/index.html 
Though I could not find some docs that describe it in detail, I found some code snippets.

1.
```
	/*
	 * Look up the string in the string table and get its offset. If
	 * this succeeds, then it is possible that there is a DT_NEEDED
	 * dynamic entry that references it.
	 */
	have_string = elfedit_sec_findstr(argstate->str.sec,
	    strpad_elt.dn_dyn.d_un.d_val, arg, &str_offset) != 0;
	if (have_string) {
		dyn = argstate->dynamic.data;
		for (ndx = 0; ndx < numdyn; dyn++, ndx++) {
			if (((dyn->d_tag == DT_NEEDED) ||
			    (dyn->d_tag == DT_USED)) &&
			    (dyn->d_un.d_val == str_offset))
				goto done;
		}
	}
```
80192cd83b/usr/src/cmd/sgs/elfedit/modules/common/syminfo.c (L512)

2.
```
    case DT_USED:
    case DT_INIT_ARRAY:
    case DT_FINI_ARRAY:
      if (do_dynamic)
        {
          if (entry->d_tag == DT_USED
          && VALID_DYNAMIC_NAME (entry->d_un.d_val))
        {
          char *name = GET_DYNAMIC_NAME (entry->d_un.d_val);

          if (*name)
            {
              printf (_("Not needed object: [%s]\n"), name);
              break;
            }
        }

          print_vma (entry->d_un.d_val, PREFIX_HEX);
          putchar ('\n');
        }
      break;
```
http://web.mit.edu/freebsd/head/contrib/binutils/binutils/readelf.c

3.
```
#define DT_USED     0x7ffffffe  /* ignored - same as needed */
```
https://github.com/switchbrew/switch-tools/blob/master/src/elf_common.h

Reviewers: jhenderson, grimar

Reviewed By: jhenderson, grimar

Subscribers: emaste, krytarowski, fedor.sergeev, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D58762

llvm-svn: 355468
2019-03-06 01:28:40 +00:00
..
benchmarks
bindings [bindings/go] Fix building on 32-bit systems (ARM etc.) 2019-02-16 22:33:10 +00:00
cmake [OptRemarks] Make OptRemarks more generic: rename OptRemarks to Remarks 2019-03-05 20:45:17 +00:00
docs [LangRef] Add 'callbr' instruction to the 'blockaddress' section. 2019-03-05 05:23:37 +00:00
examples [Kaleidoscope] Fix symbol resolver to search in reverse order. 2019-02-21 16:53:04 +00:00
include [BinaryFormat] Add DT_USED tag into dynamic section. 2019-03-06 01:28:40 +00:00
lib Revert "[AtomicExpand] Allow libcall expansion for non-zero address spaces" for buildbot failures. 2019-03-06 00:25:40 +00:00
projects
resources
runtimes [build] Rename clang-headers to clang-resource-headers 2019-03-04 21:19:53 +00:00
test [BinaryFormat] Add DT_USED tag into dynamic section. 2019-03-06 01:28:40 +00:00
tools [opt] Report if the provided architecture is invalid. 2019-03-05 23:10:28 +00:00
unittests [OptRemarks] Make OptRemarks more generic: rename OptRemarks to Remarks 2019-03-05 20:45:17 +00:00
utils gn build: Add 32-bit Linux support. 2019-03-06 01:28:32 +00:00
.arcconfig
.clang-format
.clang-tidy Disable tidy checks with too many hits 2019-02-01 11:20:13 +00:00
.gitattributes
.gitignore [clangd] Store index in '.clangd/index' instead of '.clangd-index' 2019-02-20 19:08:06 +00:00
CMakeLists.txt [CMake] Honor LLVM_EXTERNAL_<proj>_SOURCE_DIR 2019-02-22 21:19:48 +00:00
CODE_OWNERS.TXT
CREDITS.TXT [NFC] Add to contributor list. 2019-02-26 05:46:45 +00:00
LICENSE.TXT
LLVMBuild.txt
README.txt Testing commit access 2019-02-19 20:38:51 +00:00
RELEASE_TESTERS.TXT
configure
llvm.spec.in

README.txt

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================================

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Please see the documentation provided in docs/ for further
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