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authorRui Ueyama <ruiu@google.com>2016-11-23 22:41:00 +0000
committerRui Ueyama <ruiu@google.com>2016-11-23 22:41:00 +0000
commit2eda6d16330ed1d27783544c7ae7595f65cc4189 (patch)
treea4d6295a8791c61019d372f6037af6e8c8764a45
parent3ce6a545c7be2603bac2fa5c94e7f8eb02d123e0 (diff)
downloadbcm5719-llvm-2eda6d16330ed1d27783544c7ae7595f65cc4189.tar.gz
bcm5719-llvm-2eda6d16330ed1d27783544c7ae7595f65cc4189.zip
Set default entry point to .text if no entry point is found.
Previously, if a symbol specified by -e or ENTRY() is not found, we didn't set entry point address. That is incompatible with GNU because GNU linkers set the first address of .text to entry. This patch implement that behavior. llvm-svn: 287836
-rw-r--r--lld/ELF/Writer.cpp25
-rw-r--r--lld/test/ELF/entry.s41
2 files changed, 51 insertions, 15 deletions
diff --git a/lld/ELF/Writer.cpp b/lld/ELF/Writer.cpp
index 39ece191d8c..5329514cdef 100644
--- a/lld/ELF/Writer.cpp
+++ b/lld/ELF/Writer.cpp
@@ -82,6 +82,7 @@ private:
void addRelIpltSymbols();
void addStartEndSymbols();
void addStartStopSymbols(OutputSectionBase *Sec);
+ uintX_t getEntryAddr();
OutputSectionBase *findSection(StringRef Name);
std::vector<Phdr> Phdrs;
@@ -1360,12 +1361,30 @@ template <class ELFT> void Writer<ELFT>::setPhdrs() {
}
}
-template <class ELFT> static typename ELFT::uint getEntryAddr() {
+// The entry point address is chosen in the following ways.
+//
+// 1. the '-e' entry command-line option;
+// 2. the ENTRY(symbol) command in a linker control script;
+// 3. the value of the symbol start, if present;
+// 4. the address of the first byte of the .text section, if present;
+// 5. the address 0.
+template <class ELFT> typename ELFT::uint Writer<ELFT>::getEntryAddr() {
+ // Case 1, 2 or 3
if (Config->Entry.empty())
return Config->EntryAddr;
if (SymbolBody *B = Symtab<ELFT>::X->find(Config->Entry))
return B->getVA<ELFT>();
- warn("entry symbol " + Config->Entry + " not found, assuming 0");
+
+ // Case 4
+ if (OutputSectionBase *Sec = findSection(".text")) {
+ warn("cannot find entry symbol " + Config->Entry + "; defaulting to 0x" +
+ utohexstr(Sec->Addr));
+ return Sec->Addr;
+ }
+
+ // Case 5
+ warn("cannot find entry symbol " + Config->Entry +
+ "; not setting start address");
return 0;
}
@@ -1438,7 +1457,7 @@ template <class ELFT> void Writer<ELFT>::writeHeader() {
EHdr->e_type = getELFType();
EHdr->e_machine = Config->EMachine;
EHdr->e_version = EV_CURRENT;
- EHdr->e_entry = getEntryAddr<ELFT>();
+ EHdr->e_entry = getEntryAddr();
EHdr->e_shoff = SectionHeaderOff;
EHdr->e_ehsize = sizeof(Elf_Ehdr);
EHdr->e_phnum = Phdrs.size();
diff --git a/lld/test/ELF/entry.s b/lld/test/ELF/entry.s
index 34a55ababff..cf08073025c 100644
--- a/lld/test/ELF/entry.s
+++ b/lld/test/ELF/entry.s
@@ -1,33 +1,50 @@
# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t1
-# RUN: ld.lld -e foobar %t1 -o %t2 2>&1 | FileCheck -check-prefix=WARN %s
-# RUN: llvm-readobj -file-headers %t2 | FileCheck -check-prefix=NOENTRY %s
+# RUN: ld.lld -e foobar %t1 -o %t2 2>&1 | FileCheck -check-prefix=WARN1 %s
+# RUN: llvm-readobj -file-headers %t2 | FileCheck -check-prefix=TEXT %s
+
+# WARN1: warning: cannot find entry symbol foobar; defaulting to 0x201000
+# TEXT: Entry: 0x201000
+
# RUN: ld.lld %t1 -o %t2 2>&1 | FileCheck -check-prefix=WARN2 %s
+# WARN2: warning: cannot find entry symbol _start; defaulting to 0x201000
+
+# RUN: ld.lld -shared -e foobar %t1 -o %t2 2>&1 | FileCheck -check-prefix=WARN3 %s
+# WARN3: warning: cannot find entry symbol foobar; defaulting to 0x1000
-# RUN: ld.lld -shared -e foobar %t1 -o %t2 2>&1 | FileCheck -check-prefix=WARN %s
# RUN: ld.lld -shared --fatal-warnings -e entry %t1 -o %t2
# RUN: ld.lld -shared --fatal-warnings %t1 -o %t2
+# RUN: echo .data > %t.s
+# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux -n %t.s -o %t3
+# RUN: ld.lld %t3 -o %t4 2>&1 | FileCheck -check-prefix=WARN4 %s
+# RUN: llvm-readobj -file-headers %t4 | FileCheck -check-prefix=NOENTRY %s
+
+# WARN4: cannot find entry symbol _start; not setting start address
+# NOENTRY: Entry: 0x0
+
# RUN: ld.lld %t1 -o %t2 -e entry
# RUN: llvm-readobj -file-headers %t2 | FileCheck -check-prefix=SYM %s
+# SYM: Entry: 0x201008
+
# RUN: ld.lld %t1 --fatal-warnings -shared -o %t2 -e entry
# RUN: llvm-readobj -file-headers %t2 | FileCheck -check-prefix=DSO %s
+# DSO: Entry: 0x1008
+
# RUN: ld.lld %t1 -o %t2 --entry=4096
# RUN: llvm-readobj -file-headers %t2 | FileCheck -check-prefix=DEC %s
+# DEC: Entry: 0x1000
+
# RUN: ld.lld %t1 -o %t2 --entry 0xcafe
# RUN: llvm-readobj -file-headers %t2 | FileCheck -check-prefix=HEX %s
+# HEX: Entry: 0xCAFE
+
# RUN: ld.lld %t1 -o %t2 -e 0777
# RUN: llvm-readobj -file-headers %t2 | FileCheck -check-prefix=OCT %s
-
-# WARN: warning: entry symbol foobar not found, assuming 0
-# WARN2: warning: entry symbol _start not found, assuming 0
-
-# NOENTRY: Entry: 0x0
-# SYM: Entry: 0x201000
-# DSO: Entry: 0x1000
-# DEC: Entry: 0x1000
-# HEX: Entry: 0xCAFE
# OCT: Entry: 0x1FF
.globl entry
+.text
+ .quad 0
entry:
+ ret
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