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# This reproduces a bug when rewriting dynamic relocations in X86 as
# BOLT incorrectly attributes R_X86_64_64 dynamic relocations
# to the wrong section when the -jump-tables=move flag is used. We
# expect the relocations to belong to the .bolt.org.rodata section but
# it is attributed to a new .rodata section that only contains jump
# table entries, created by BOLT. BOLT will only create this new .rodata
# section if both -jump-tables=move is used and a hot function with
# jt is present in the input binary, triggering a scenario where the
# dynamic relocs rewriting gets confused on where to put .rodata relocs.
# It is uncommon to end up with dynamic relocations against .rodata,
# but it can happen. In these cases we cannot corrupt the
# output binary by writing out dynamic relocs incorrectly. The linker
# avoids emitting relocs against read-only sections but we override
# this behvior with the -z notext flag. During runtime, these pages
# are mapped with write permission and then changed to read-only after
# the dynamic linker finishes processing the dynamic relocs.
# In this test, we create a reference to a dynamic object that will
# imply in R_X86_64_64 being used for .rodata. Now BOLT, when creating
# a new .rodata to hold jump table entries, needs to remember to emit
# these dynamic relocs against the original .rodata, and not the new
# one it just created.
# REQUIRES: system-linux
# RUN: llvm-mc -filetype=obj -triple x86_64-unknown-linux \
# RUN: %s -o %t.o
# RUN: link_fdata %s %t.o %t.fdata
# RUN: llvm-mc -filetype=obj -triple x86_64-unknown-linux \
# RUN: %p/Inputs/define_bar.s -o %t.2.o
# RUN: llvm-strip --strip-unneeded %t.o
# RUN: ld.lld %t.2.o -o %t.so -shared
# RUN: ld.lld -z notext %t.o -o %t.exe -q %t.so
# RUN: llvm-bolt -data %t.fdata %t.exe -relocs -o %t.out -lite=0 \
# RUN: -jump-tables=move
# RUN: llvm-readobj -rs %t.out | FileCheck --check-prefix=READOBJ %s
# Verify that BOLT outputs the dynamic reloc at the correct address,
# which is the start of the .bolt.org.rodata section.
# READOBJ: Relocations [
# READOBJ: Section ([[#]]) .rela.dyn {
# READOBJ-NEXT: 0x[[#%X,ADDR:]] R_X86_64_64 bar 0x10
# READOBJ: Symbols [
# READOBJ: Name: .bolt.org.rodata
# READOBJ-NEXT: Value: 0x[[#ADDR]]
# Create a hot function with jump table
.text
.globl _start
.type _start, %function
_start:
.cfi_startproc
# FDATA: 0 [unknown] 0 1 _start 0 0 6
movq .LJUMPTABLE(,%rdi,8), %rax
b: jmpq *%rax
# FDATA: 1 _start #b# 1 _start #c# 0 3
c:
mov $1, %rax
d:
xorq %rax, %rax
ret
.cfi_endproc
.size _start, .-_start
# This is the section that needs to be tested.
.section .rodata
.align 4
# We will have a R_X86_64_64 here or R_X86_64_COPY if this section
# is non-writable. We use -z notext to force the linker to accept dynamic
# relocations in read-only sections and make it a R_X86_64_64.
.quad bar + 16 # Reference a dynamic object (such as a vtable ref)
# Add other contents to this section: a hot jump table that will be
# copied by BOLT into a new section.
.LJUMPTABLE:
.quad c
.quad c
.quad d
.quad d
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