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[BOLT,test] Link against a shared object to test PLT (#125625)

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A few tests generate a statically-linked position-independent executable
with `-nostdlib -Wl,--unresolved-symbols=ignore-all -pie` (`%clang`) and
test PLT handling. (--unresolved-symbols=ignore-all suppresses undefined
symbol errors and serves as a convenience hack.)

This relies on an unguaranteed linker behavior: a statically-linked PIE
does not necessarily generate PLT entries.
While current lld generates a PLT entry, it will change to suppress the
PLT entry to simplify internal handling and improve consistency.

(The behavior has no consistency in GNU ld, some ports generated a
.dynsym entry while some don't. While most seem to generate a PLT entry
but some ports use a weird `R_*_NONE` relocation.)
This commit is contained in:
Fangrui Song
2025-02-05 09:31:58 -08:00
committed by GitHub
parent 19c3e2f7de
commit a907008bcb
7 changed files with 22 additions and 9 deletions
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4
bolt/test/AArch64/exceptions-plt.cpp
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@@ -2,7 +2,9 @@
// REQUIRES: system-linux
// RUN: %clangxx %cxxflags -O1 -Wl,-q,-znow %s -o %t.exe
// RUN: %clang %cflags -fpic -shared -xc /dev/null -o %t.so
// Link against a DSO to ensure PLT entries.
// RUN: %clangxx %cxxflags -O1 -Wl,-q,-znow %s %t.so -o %t.exe
// RUN: llvm-bolt %t.exe -o %t.bolt.exe --plt=all --print-only=.*main.* \
// RUN: --print-finalized 2>&1 | FileCheck %s

4
bolt/test/AArch64/plt-call.test
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@@ -1,6 +1,8 @@
// Verify that PLTCall optimization works.
RUN: %clang %cflags %p/../Inputs/plt-tailcall.c \
RUN: %clang %cflags -fpic -shared -xc /dev/null -o %t.so
// Link against a DSO to ensure PLT entries.
RUN: %clang %cflags %p/../Inputs/plt-tailcall.c %t.so \
RUN: -o %t -Wl,-q
RUN: llvm-bolt %t -o %t.bolt --plt=all --print-plt --print-only=foo | FileCheck %s

4
bolt/test/X86/callcont-fallthru.s
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@@ -1,7 +1,9 @@
## Ensures that a call continuation fallthrough count is set when using
## pre-aggregated perf data.
# RUN: %clangxx %cxxflags %s -o %t -Wl,-q -nostdlib
# RUN: %clang %cflags -fpic -shared -xc /dev/null -o %t.so
## Link against a DSO to ensure PLT entries.
# RUN: %clangxx %cxxflags %s %t.so -o %t -Wl,-q -nostdlib
# RUN: link_fdata %s %t %t.pa1 PREAGG
# RUN: link_fdata %s %t %t.pa2 PREAGG2
# RUN: link_fdata %s %t %t.pa3 PREAGG3

4
bolt/test/X86/cfi-instrs-reordered.s
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@@ -3,7 +3,9 @@
# RUN: llvm-mc -filetype=obj -triple x86_64-unknown-unknown %s -o %t.o
# RUN: llvm-strip --strip-unneeded %t.o
# RUN: %clangxx %cflags %t.o -o %t.exe
# RUN: %clang %cflags -fpic -shared -xc /dev/null -o %t.so
## Link against a DSO to ensure PLT entries.
# RUN: %clangxx %cflags %t.o %t.so -o %t.exe
# RUN: llvm-bolt %t.exe -o %t --reorder-blocks=cache --print-after-lowering \
# RUN: --print-only=_Z10SolveCubicddddPiPd 2>&1 | FileCheck %s
#

4
bolt/test/X86/plt-call.test
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@@ -1,6 +1,8 @@
// Verify that PLTCall optimization works.
RUN: %clang %cflags %p/../Inputs/plt-tailcall.c \
RUN: %clang %cflags -fpic -shared -xc /dev/null -o %t.so
// Link against a DSO to ensure PLT entries.
RUN: %clang %cflags %p/../Inputs/plt-tailcall.c %t.so \
RUN: -o %t -Wl,-q
RUN: llvm-bolt %t -o %t.bolt --plt=all --print-plt --print-only=foo | FileCheck %s

4
bolt/test/runtime/exceptions-plt.cpp
View File

@@ -2,7 +2,9 @@
// REQUIRES: system-linux
// RUN: %clangxx %cxxflags -O1 -Wl,-q,-znow %s -o %t.exe
// RUN: %clang %cflags -fpic -shared -xc /dev/null -o %t.so
// Link against a DSO to ensure PLT entries.
// RUN: %clangxx %cxxflags -O1 -Wl,-q,-znow %s %t.so -o %t.exe
// RUN: llvm-bolt %t.exe -o %t.bolt.exe --plt=all
// RUN: %t.bolt.exe

7
bolt/test/runtime/plt-lld.test
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@@ -1,14 +1,15 @@
// This test checks that the pointers to PLT are properly updated.
// The test is using lld linker.
// The test uses lld and links against a DSO to ensure PLT entries.
RUN: %clang %cflags -fpic -shared -xc /dev/null -o %t.so
// Non-PIE:
RUN: %clang %cflags -no-pie %p/../Inputs/plt.c -fuse-ld=lld \
RUN: %clang %cflags -no-pie %p/../Inputs/plt.c %t.so -fuse-ld=lld \
RUN: -o %t.lld.exe -Wl,-q
RUN: llvm-bolt %t.lld.exe -o %t.lld.bolt.exe --use-old-text=0 --lite=0
RUN: %t.lld.bolt.exe | FileCheck %s
// PIE:
RUN: %clang %cflags -fPIC -pie %p/../Inputs/plt.c -fuse-ld=lld \
RUN: %clang %cflags -fPIC -pie %p/../Inputs/plt.c %t.so -fuse-ld=lld \
RUN: -o %t.lld.pie.exe -Wl,-q
RUN: llvm-bolt %t.lld.pie.exe -o %t.lld.bolt.pie.exe --use-old-text=0 --lite=0
RUN: %t.lld.bolt.pie.exe | FileCheck %s