[ELF] Write IPLT header in -static -z retpolineplt mode
Summary:
This fixes PR39711: -static -z retpolineplt does not produce retpoline PLT header.
-z now is not relevant.
Statically linked executable does not have PLT, but may have IPLT with no header. When -z retpolineplt is specified, however, the repoline PLT header should still be emitted.
I've checked that this fixes the FreeBSD reproduce in PR39711 and a Linux program statically linked against glibc. The programm print "Hi" rather than SIGILL/SIGSEGV.
getPltEntryOffset may look dirty after this patch, but it can be cleaned up later.
Another possible improvement is that when there are non-preemptible IFUNC symbols (rare case, e.g. -Bsymbolic), both In.Plt and In.Iplt can be non-empty and we'll emit the retpoline PLT header twice.
Reviewers: espindola, emaste, chandlerc, ruiu
Reviewed By: emaste
Subscribers: emaste, arichardson, krytarowski, llvm-commits
Differential Revision: https://reviews.llvm.org/D54782
llvm-svn: 347404
2018-11-22 02:10:00 +08:00
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# REQUIRES: x86
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# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t.o
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# RUN: ld.lld -z retpolineplt -z now %t.o -o %t
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2020-03-16 08:47:44 +08:00
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# RUN: llvm-objdump -d --no-show-raw-insn %t | FileCheck %s
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[ELF] Write IPLT header in -static -z retpolineplt mode
Summary:
This fixes PR39711: -static -z retpolineplt does not produce retpoline PLT header.
-z now is not relevant.
Statically linked executable does not have PLT, but may have IPLT with no header. When -z retpolineplt is specified, however, the repoline PLT header should still be emitted.
I've checked that this fixes the FreeBSD reproduce in PR39711 and a Linux program statically linked against glibc. The programm print "Hi" rather than SIGILL/SIGSEGV.
getPltEntryOffset may look dirty after this patch, but it can be cleaned up later.
Another possible improvement is that when there are non-preemptible IFUNC symbols (rare case, e.g. -Bsymbolic), both In.Plt and In.Iplt can be non-empty and we'll emit the retpoline PLT header twice.
Reviewers: espindola, emaste, chandlerc, ruiu
Reviewed By: emaste
Subscribers: emaste, arichardson, krytarowski, llvm-commits
Differential Revision: https://reviews.llvm.org/D54782
llvm-svn: 347404
2018-11-22 02:10:00 +08:00
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2019-09-16 15:05:34 +08:00
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#0x2011a9+5 + 34 = 0x2011d0 (foo@plt)
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2020-03-06 06:18:38 +08:00
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# CHECK: <_start>:
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2020-03-23 06:03:10 +08:00
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# CHECK-NEXT: 2011a9: callq 0x2011d0
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[ELF] Write IPLT header in -static -z retpolineplt mode
Summary:
This fixes PR39711: -static -z retpolineplt does not produce retpoline PLT header.
-z now is not relevant.
Statically linked executable does not have PLT, but may have IPLT with no header. When -z retpolineplt is specified, however, the repoline PLT header should still be emitted.
I've checked that this fixes the FreeBSD reproduce in PR39711 and a Linux program statically linked against glibc. The programm print "Hi" rather than SIGILL/SIGSEGV.
getPltEntryOffset may look dirty after this patch, but it can be cleaned up later.
Another possible improvement is that when there are non-preemptible IFUNC symbols (rare case, e.g. -Bsymbolic), both In.Plt and In.Iplt can be non-empty and we'll emit the retpoline PLT header twice.
Reviewers: espindola, emaste, chandlerc, ruiu
Reviewed By: emaste
Subscribers: emaste, arichardson, krytarowski, llvm-commits
Differential Revision: https://reviews.llvm.org/D54782
llvm-svn: 347404
2018-11-22 02:10:00 +08:00
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#Static IPLT header due to -z retpolineplt
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2020-03-06 06:18:38 +08:00
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# CHECK: 00000000002011b0 <.plt>:
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2020-03-23 06:03:10 +08:00
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# CHECK-NEXT: 2011b0: callq 0x2011c0 <.plt+0x10>
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2019-09-16 15:05:34 +08:00
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# CHECK-NEXT: 2011b5: pause
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# CHECK-NEXT: 2011b7: lfence
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[ELF] Write IPLT header in -static -z retpolineplt mode
Summary:
This fixes PR39711: -static -z retpolineplt does not produce retpoline PLT header.
-z now is not relevant.
Statically linked executable does not have PLT, but may have IPLT with no header. When -z retpolineplt is specified, however, the repoline PLT header should still be emitted.
I've checked that this fixes the FreeBSD reproduce in PR39711 and a Linux program statically linked against glibc. The programm print "Hi" rather than SIGILL/SIGSEGV.
getPltEntryOffset may look dirty after this patch, but it can be cleaned up later.
Another possible improvement is that when there are non-preemptible IFUNC symbols (rare case, e.g. -Bsymbolic), both In.Plt and In.Iplt can be non-empty and we'll emit the retpoline PLT header twice.
Reviewers: espindola, emaste, chandlerc, ruiu
Reviewed By: emaste
Subscribers: emaste, arichardson, krytarowski, llvm-commits
Differential Revision: https://reviews.llvm.org/D54782
llvm-svn: 347404
2018-11-22 02:10:00 +08:00
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#foo@plt
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2019-09-16 15:05:34 +08:00
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# CHECK: 2011d0: movq 4105(%rip), %r11
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2020-03-23 06:03:10 +08:00
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# CHECK-NEXT: 2011d7: jmp 0x2011b0 <.plt>
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[ELF] Write IPLT header in -static -z retpolineplt mode
Summary:
This fixes PR39711: -static -z retpolineplt does not produce retpoline PLT header.
-z now is not relevant.
Statically linked executable does not have PLT, but may have IPLT with no header. When -z retpolineplt is specified, however, the repoline PLT header should still be emitted.
I've checked that this fixes the FreeBSD reproduce in PR39711 and a Linux program statically linked against glibc. The programm print "Hi" rather than SIGILL/SIGSEGV.
getPltEntryOffset may look dirty after this patch, but it can be cleaned up later.
Another possible improvement is that when there are non-preemptible IFUNC symbols (rare case, e.g. -Bsymbolic), both In.Plt and In.Iplt can be non-empty and we'll emit the retpoline PLT header twice.
Reviewers: espindola, emaste, chandlerc, ruiu
Reviewed By: emaste
Subscribers: emaste, arichardson, krytarowski, llvm-commits
Differential Revision: https://reviews.llvm.org/D54782
llvm-svn: 347404
2018-11-22 02:10:00 +08:00
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.type foo STT_GNU_IFUNC
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.globl foo
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foo:
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ret
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.globl _start
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_start:
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call foo
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