[llvm] [BOLT] Support instrumentation hook via DT_FINI_ARRAY (PR #67348)

[Job Noorman via llvm-commits]

================
@@ -0,0 +1,80 @@
+## Test the different ways of hooking the fini function for instrumentation (via
+## DT_FINI and via DT_FINI_ARRAY). We test the latter for both PIE and non-PIE
+## binaries because of the different ways of handling relocations (static or
+## dynamic).
+## All tests perform the following steps:
+## - Compile and link for the case to be tested
+## - Some sanity-checks on the dynamic section and relocations in the binary to
+##   verify it has the shape we want for testing:
+##   - DT_FINI or DT_FINI_ARRAY in dynamic section
+##   - No relative relocations for non-PIE
+## - Instrument
+## - Verify generated binary
+# REQUIRES: system-linux,bolt-runtime
+
+# RUN: %clang  %s -Wl,-q -o %t.exe
+# RUN: llvm-readelf -d %t.exe | FileCheck --check-prefix=DYN-FINI %s
+# RUN: llvm-readelf -r %t.exe | FileCheck --check-prefix=RELOC-PIE %s
+# RUN: llvm-bolt %t.exe -o %t --instrument
+# RUN: llvm-readelf -ds %t | FileCheck --check-prefix=CHECK-FINI %s
+
+# RUN: %clang  %s -Wl,-q,-fini=0 -o %t-no-fini.exe
+# RUN: llvm-readelf -d %t-no-fini.exe | FileCheck --check-prefix=DYN-NO-FINI %s
+# RUN: llvm-readelf -r %t-no-fini.exe | FileCheck --check-prefix=RELOC-PIE %s
+# RUN: llvm-bolt %t-no-fini.exe -o %t-no-fini --instrument
+# RUN: llvm-readelf -drs %t-no-fini | FileCheck --check-prefix=CHECK-NO-FINI %s
+
+# RUN: %clang  %s -no-pie -Wl,-q,-fini=0 -o %t-no-pie-no-fini.exe
+# RUN: llvm-readelf -d %t-no-pie-no-fini.exe | FileCheck --check-prefix=DYN-NO-FINI %s
+# RUN: llvm-readelf -r %t-no-pie-no-fini.exe | FileCheck --check-prefix=RELOC-NO-PIE %s
+# RUN: llvm-bolt %t-no-pie-no-fini.exe -o %t-no-pie-no-fini --instrument
+# RUN: llvm-readelf -ds -x .fini_array %t-no-pie-no-fini | FileCheck --check-prefix=CHECK-NO-PIE-NO-FINI %s
+
+## With fini: dynamic section should contain DT_FINI
+# DYN-FINI: (FINI)
+
+## Without fini: dynamic section should only contain DT_FINI_ARRAY
+# DYN-NO-FINI-NOT: (FINI)
+# DYN-NO-FINI:     (FINI_ARRAY)
+# DYN-NO-FINI:     (FINI_ARRAYSZ)
+
+## With PIE: binary should have relative relocations
+# RELOC-PIE: R_AARCH64_RELATIVE
+
+## Without PIE: binary should not have relative relocations
+# RELOC-NO-PIE-NOT: R_AARCH64_RELATIVE
+
+## Check that DT_FINI is set to __bolt_runtime_fini
+# CHECK-FINI: Dynamic section at offset {{.*}} contains {{.*}} entries:
+# CHECK-FINI: (FINI) 0x[[FINI:[[:xdigit:]]+]]
+# CHECK-FINI: Symbol table '.symtab' contains {{.*}} entries:
+# CHECK-FINI: {{0+}}[[FINI]] {{.*}} __bolt_runtime_fini
+
+## Check that DT_FINI_ARRAY has a dynamic relocation for __bolt_runtime_fini
+# CHECK-NO-FINI:     Dynamic section at offset {{.*}} contains {{.*}} entries:
+# CHECK-NO-FINI-NOT: (FINI)
+# CHECK-NO-FINI:     (FINI_ARRAY) 0x[[FINI_ARRAY:[[:xdigit:]]+]]
+# CHECK-NO-FINI:     Relocation section '.rela.dyn' at offset {{.*}} contains {{.*}} entries
+# CHECK-NO-FINI:     {{0+}}[[FINI_ARRAY]] {{.*}} R_AARCH64_RELATIVE [[FINI_ADDR:[[:xdigit:]]+]]
+# CHECK-NO-FINI:     Symbol table '.symtab' contains {{.*}} entries:
+# CHECK-NO-FINI:     {{0+}}[[FINI_ADDR]] {{.*}} __bolt_runtime_fini
----------------
mtvec wrote:

Done. I've added this through a separate `readelf` invocation to keep things readable.

https://github.com/llvm/llvm-project/pull/67348