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1## This reproduces a bug when rewriting dynamic relocations in X86 as2## BOLT incorrectly attributes R_X86_64_64 dynamic relocations3## to the wrong section when the -jump-tables=move flag is used. We4## expect the relocations to belong to the .bolt.org.rodata section but5## it is attributed to a new .rodata section that only contains jump6## table entries, created by BOLT. BOLT will only create this new .rodata7## section if both -jump-tables=move is used and a hot function with8## jt is present in the input binary, triggering a scenario where the9## dynamic relocs rewriting gets confused on where to put .rodata relocs.10 11## It is uncommon to end up with dynamic relocations against .rodata,12## but it can happen. In these cases we cannot corrupt the13## output binary by writing out dynamic relocs incorrectly. The linker14## avoids emitting relocs against read-only sections but we override15## this behavior with the -z notext flag. During runtime, these pages16## are mapped with write permission and then changed to read-only after17## the dynamic linker finishes processing the dynamic relocs.18 19## In this test, we create a reference to a dynamic object that will20## imply in R_X86_64_64 being used for .rodata. Now BOLT, when creating21## a new .rodata to hold jump table entries, needs to remember to emit22## these dynamic relocs against the original .rodata, and not the new23## one it just created.24 25# REQUIRES: system-linux26 27# RUN: llvm-mc -filetype=obj -triple x86_64-unknown-linux \28# RUN: %s -o %t.o29# RUN: link_fdata %s %t.o %t.fdata30# RUN: llvm-mc -filetype=obj -triple x86_64-unknown-linux \31# RUN: %p/Inputs/define_bar.s -o %t.2.o32# RUN: llvm-strip --strip-unneeded %t.o33# RUN: ld.lld %t.2.o -o %t.so -shared34# RUN: ld.lld -z notext %t.o -o %t.exe -q %t.so35# RUN: llvm-bolt -data %t.fdata %t.exe -relocs -o %t.out -lite=0 \36# RUN: -jump-tables=move37# RUN: llvm-readobj -rs %t.out | FileCheck --check-prefix=READOBJ %s38 39## Verify that BOLT outputs the dynamic reloc at the correct address,40## which is the start of the .bolt.org.rodata section.41# READOBJ: Relocations [42# READOBJ: Section ([[#]]) .rela.dyn {43# READOBJ-NEXT: 0x[[#%X,ADDR:]] R_X86_64_64 bar 0x1044# READOBJ: Symbols [45# READOBJ: Name: .bolt.org.rodata46# READOBJ-NEXT: Value: 0x[[#ADDR]]47 48 # Create a hot function with jump table49 .text50 .globl _start51 .type _start, %function52_start:53 .cfi_startproc54# FDATA: 0 [unknown] 0 1 _start 0 0 655 movq .LJUMPTABLE(,%rdi,8), %rax56b: jmpq *%rax57# FDATA: 1 _start #b# 1 _start #c# 0 358c:59 mov $1, %rax60d:61 xorq %rax, %rax62 ret63 .cfi_endproc64 .size _start, .-_start65 66 # This is the section that needs to be tested.67 .section .rodata68 .align 469 # We will have a R_X86_64_64 here or R_X86_64_COPY if this section70 # is non-writable. We use -z notext to force the linker to accept dynamic71 # relocations in read-only sections and make it a R_X86_64_64.72 .quad bar + 16 # Reference a dynamic object (such as a vtable ref)73 # Add other contents to this section: a hot jump table that will be74 # copied by BOLT into a new section.75.LJUMPTABLE:76 .quad c77 .quad c78 .quad d79 .quad d80