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[libunwind][test][AIX] Add C API test for unwinding from AIX VAPI (non-signal-handler case) (llvm#209306)
Test detection, during stepping, of the backchain mutation introduced by a VAPI call (see llvm#209280). Further, test resumption of contexts using cursors obtained while a VAPI is active on the thread. Testing is done via FileCheck inspection of trace output enabled by `LIBUNWIND_PRINT_UNWINDING=1`. When Live Library Update is not enabled, synthetic trace output is generated by the test program itself. --------- Assisted-by: IBM Bob (cherry picked from commit 861efe0)
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‎libunwind/test/CMakeLists.txt‎

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pythonize_bool(HAVE_GETAUXVAL)
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pythonize_bool(HAVE_ELF_AUX_INFO)
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pythonize_bool(LIBUNWIND_ENABLE_ASSERTIONS)
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pythonize_bool(LIBUNWIND_ENABLE_CET)
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pythonize_bool(LIBUNWIND_ENABLE_GCS)
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pythonize_bool(LIBUNWIND_ENABLE_THREADS)

‎libunwind/test/aix_vapi_unw_resume.pass.cpp‎

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//===----------------------------------------------------------------------===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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// REQUIRES: target={{.+}}-aix{{.*}}
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// REQUIRES: has-filecheck
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// ADDITIONAL_COMPILE_FLAGS: -fno-inline -fno-exceptions
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// RUN: %{build}
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// RUN: %{exec} %t.exe 2>&1 \
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// RUN: | FileCheck --check-prefix=CHECK \
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// RUN: %if libunwind-assertions-enabled %{ --check-prefix=DEBUG %} \
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// RUN: %s
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// Tests use of the libunwind C API to step up from a context where the VAPI is
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// active and to resume contexts where
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// - the VAPI is active (and thus VAPI return glue is not called) and
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// - where the VAPI is not active (and thus VAPI return glue _is_ called).
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//
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// In the latter case, which applies not just to the caller of the Virtual API
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// but also to its ancestors, the return glue should always be called (i.e.,
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// each time, without regard for whether the VAPI is currently active).
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#include <assert.h>
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#include <libunwind.h>
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#include <stdio.h>
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#include <stdlib.h>
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#ifdef __64BIT__
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#define R3 UNW_PPC64_R3
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#else
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#define R3 UNW_PPC_R3
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#endif
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extern "C" void *returns_twice_bsearch
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[[gnu::returns_twice]] (const void *, const void *, size_t, size_t,
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int (*)(const void *,
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const void *)) __asm__("bsearch");
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static bool llu_enabled;
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static unw_cursor_t bsearch_cursor;
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static unw_cursor_t bsearch_caller_cursor;
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static unw_cursor_t main_cursor;
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extern "C" int cmp(const void *pa, const void *pb) {
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(void)pa;
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(void)pb;
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fprintf(
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stderr,
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"Populate global cursors for `bsearch`, `bsearch_caller`, and `main`.\n");
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// CHECK-LABEL: Populate global cursors
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unw_context_t context;
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unw_cursor_t cursor;
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unw_getcontext(&context);
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unw_init_local(&cursor, &context);
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// Step from `cmp` up to `bsearch`.
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unw_step(&cursor);
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if (!llu_enabled)
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fprintf(stderr,
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"libunwind: the next return address=VAPI_NOT_ENABLED from VAPI\n");
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// DEBUG-LABEL: libunwind: stepWithTBTable: Look up traceback table of func=cmp
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// DEBUG: libunwind: the next return address=[[VAPI_RA:[^ ]*]] from VAPI
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bsearch_cursor = cursor;
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// Step from `bsearch` up to `bsearch_caller`.
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unw_step(&cursor);
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if (!llu_enabled)
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fprintf(stderr, "libunwind: return address=VAPI_NOT_ENABLED from VAPI\n");
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// DEBUG-LABEL: libunwind: stepWithTBTable: Look up traceback table of func=bsearch
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// DEBUG: libunwind: return address=[[VAPI_RA]] from VAPI
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bsearch_caller_cursor = cursor;
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// Step from `bsearch_caller` up to `main`.
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unw_step(&cursor);
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// DEBUG-LABEL: libunwind: stepWithTBTable: Look up traceback table of func=_Z14bsearch_callerv
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// DEBUG-NOT: VAPI
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main_cursor = cursor;
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// Test resuming context where VAPI is active.
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fprintf(stderr,
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"Return to `bsearch` with r3 set to 0 using the global cursor.\n");
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unw_set_reg(&bsearch_cursor, R3, (unw_word_t)0);
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unw_resume(&bsearch_cursor);
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__builtin_unreachable();
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// CHECK-LABEL: Return to `bsearch`
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// DEBUG-NOT: VAPI: executing return glue
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}
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char bsearch_caller_ret;
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void *bsearch_caller(void) {
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volatile int state = 0;
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char c;
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char buf[3];
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#pragma clang diagnostic push
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#pragma clang diagnostic ignored "-Wuninitialized-const-pointer"
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void *result = returns_twice_bsearch(&c, buf, 1, 1, cmp);
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#pragma clang diagnostic pop
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assert(result == &buf[state]);
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// Test resuming context where VAPI is not active. The VAPI return glue should
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// be used each time without regard for whether the VAPI is currently active.
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// `state` is volatile to observe changes in the value between the multiple
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// returns in `setjmp`/`longjmp`-like usage. We need to spell out the
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// `volatile` accesses very explicitly thanks to changes in the C++ standard.
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if ((state = state + 1, state) < 3) {
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fprintf(stderr,
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"Return to `bsearch_caller` at the invocation of "
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"`returns_twice_bsearch` (really `bsearch`) with r3 set to "
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"&buf[%d] using the global cursor.\n",
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state);
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if (!llu_enabled)
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fprintf(stderr,
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"libunwind: VAPI: executing return glue VAPI_NOT_ENABLED\n");
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unw_set_reg(&bsearch_caller_cursor, R3, (unw_word_t)&buf[state]);
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unw_resume(&bsearch_caller_cursor);
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__builtin_unreachable();
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// CHECK-LABEL: Return to `bsearch_caller` {{.*}}&buf[1]
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// DEBUG: libunwind: VAPI: executing return glue
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// CHECK-LABEL: Return to `bsearch_caller` {{.*}}&buf[2]
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// DEBUG: libunwind: VAPI: executing return glue
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}
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// Test resuming context where VAPI is not active, one frame up from the VAPI
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// caller.
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fprintf(stderr, "Return to `main` at the invocation of `bsearch_caller` with "
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"r3 set to `&bsearch_caller_ret` using the global cursor.\n");
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if (!llu_enabled)
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fprintf(stderr,
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"libunwind: VAPI: executing return glue VAPI_NOT_ENABLED\n");
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unw_set_reg(&main_cursor, R3, (unw_word_t)&bsearch_caller_ret);
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unw_resume(&main_cursor);
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__builtin_unreachable();
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// CHECK-LABEL: Return to `main`
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// DEBUG: libunwind: VAPI: executing return glue
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}
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// VAPI glue addresses
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constexpr uintptr_t vapi_glue_addr_ext_32 = 0x8b80;
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constexpr uintptr_t vapi_addr_64 = 0x8e00;
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constexpr size_t vapi_size_64 = 0x0200;
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constexpr uintptr_t vapi_glue_addr_begin = vapi_glue_addr_ext_32;
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constexpr uintptr_t vapi_glue_addr_end = vapi_addr_64 + vapi_size_64;
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struct FunctionDescriptor {
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uintptr_t entry;
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uintptr_t toc;
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uintptr_t env;
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};
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int main(void) {
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if (setenv("LIBUNWIND_PRINT_UNWINDING", "1", true) != 0) {
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perror("setenv");
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abort();
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}
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FunctionDescriptor *fd = reinterpret_cast<FunctionDescriptor *>(bsearch);
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llu_enabled =
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vapi_glue_addr_begin <= fd->entry && fd->entry < vapi_glue_addr_end;
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assert(bsearch_caller() == &bsearch_caller_ret);
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}

‎libunwind/test/configs/cmake-bridge.cfg.in‎

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# Add a few features that are common to all the configurations
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if @LIBUNWIND_USES_ARM_EHABI@:
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config.available_features.add('libunwind-arm-ehabi')
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if @LIBUNWIND_ENABLE_ASSERTIONS@:
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config.available_features.add('libunwind-assertions-enabled')
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if not @LIBUNWIND_ENABLE_THREADS@:
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config.available_features.add('libunwind-no-threads')
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