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<!--LLVM PR SUMMARY COMMENT--> @llvm/pr-subscribers-libunwind Author: Hubert Tong (hubert-reinterpretcast) <details> <summary>Changes</summary> Test detection, during stepping, of the backchain mutation introduced by a VAPI call (see https://github.com/llvm/llvm-project/pull/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 --- Full diff: https://github.com/llvm/llvm-project/pull/209306.diff 1 Files Affected: - (added) libunwind/test/aix_vapi_unw_resume.pass.cpp (+164) ``````````diff diff --git a/libunwind/test/aix_vapi_unw_resume.pass.cpp b/libunwind/test/aix_vapi_unw_resume.pass.cpp new file mode 100644 index 0000000000000..a1426487b4018 --- /dev/null +++ b/libunwind/test/aix_vapi_unw_resume.pass.cpp @@ -0,0 +1,164 @@ +//===----------------------------------------------------------------------===// +// +// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. +// See https://llvm.org/LICENSE.txt for license information. +// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception +// +//===----------------------------------------------------------------------===// + +// REQUIRES: target={{.+}}-aix{{.*}} +// REQUIRES: has-filecheck + +// ADDITIONAL_COMPILE_FLAGS: -fno-inline -fno-exceptions + +// RUN: %{build} +// RUN: %{exec} %t.exe 2>&1 | FileCheck %s + +// Tests use of the libunwind C API to step up from a context where the VAPI is +// active and to resume contexts where +// - the VAPI is active (and thus VAPI return glue is not called) and +// - where the VAPI is not active (and thus VAPI return glue _is_ called). +// +// In the latter case, which applies not just to the caller of the Virtual API +// but also to its ancestors, the return glue should always be called (i.e., +// each time, without regard for whether the VAPI is currently active). + +#include <assert.h> +#include <libunwind.h> +#include <stdio.h> +#include <stdlib.h> + +#ifdef __64BIT__ +#define R3 UNW_PPC64_R3 +#else +#define R3 UNW_PPC_R3 +#endif + +extern "C" void *returns_twice_bsearch + [[gnu::returns_twice]] (const void *, const void *, size_t, size_t, + int (*)(const void *, + const void *)) __asm__("bsearch"); + +static bool llu_enabled; +static unw_cursor_t bsearch_cursor; +static unw_cursor_t bsearch_caller_cursor; +static unw_cursor_t main_cursor; + +extern "C" int cmp(const void *pa, const void *pb) { + (void)pa; + (void)pb; + + fprintf( + stderr, + "Populate global cursors for `bsearch`, `bsearch_caller`, and `main`.\n"); + // CHECK-LABEL: Populate global cursors + unw_context_t context; + unw_cursor_t cursor; + unw_getcontext(&context); + unw_init_local(&cursor, &context); + // Step from `cmp` up to `bsearch`. + unw_step(&cursor); + if (!llu_enabled) + fprintf(stderr, + "libunwind: the next return address=VAPI_NOT_ENABLED from VAPI\n"); + // CHECK-LABEL: libunwind: stepWithTBTable: Look up traceback table of func=cmp + // CHECK: libunwind: the next return address=[[VAPI_RA:[^ ]*]] from VAPI + bsearch_cursor = cursor; + // Step from `bsearch` up to `bsearch_caller`. + unw_step(&cursor); + if (!llu_enabled) + fprintf(stderr, "libunwind: return address=VAPI_NOT_ENABLED from VAPI\n"); + // CHECK-LABEL: libunwind: stepWithTBTable: Look up traceback table of func=bsearch + // CHECK: libunwind: return address=[[VAPI_RA]] from VAPI + bsearch_caller_cursor = cursor; + // Step from `bsearch_caller` up to `main`. + unw_step(&cursor); + // CHECK-LABEL: libunwind: stepWithTBTable: Look up traceback table of func=_Z14bsearch_callerv + // CHECK-NOT: VAPI + main_cursor = cursor; + + // Test resuming context where VAPI is active. + fprintf(stderr, + "Return to `bsearch` with r3 set to 0 using the global cursor.\n"); + unw_set_reg(&bsearch_cursor, R3, (unw_word_t)0); + unw_resume(&bsearch_cursor); + __builtin_unreachable(); + // CHECK-LABEL: Return to `bsearch` + // CHECK-NOT: VAPI: executing return glue +} + +char bsearch_caller_ret; +void *bsearch_caller(void) { + volatile int state = 0; + + char c; + char buf[3]; +#pragma clang diagnostic push +#pragma clang diagnostic ignored "-Wuninitialized-const-pointer" + void *result = returns_twice_bsearch(&c, buf, 1, 1, cmp); +#pragma clang diagnostic pop + assert(result == &buf[state]); + + // Test resuming context where VAPI is not active. The VAPI return glue should + // be used each time without regard for whether the VAPI is currently active. + + // `state` is volatile to observe changes in the value between the multiple + // returns in `setjmp`/`longjmp`-like usage. We need to spell out the + // `volatile` accesses very explicitly thanks to changes in the C++ standard. + if ((state = state + 1, state) < 3) { + fprintf(stderr, + "Return to `bsearch_caller` at the invocation of " + "`returns_twice_bsearch` (really `bsearch`) with r3 set to " + "&buf[%d] using the global cursor.\n", + state); + if (!llu_enabled) + fprintf(stderr, + "libunwind: VAPI: executing return glue VAPI_NOT_ENABLED\n"); + unw_set_reg(&bsearch_caller_cursor, R3, (unw_word_t)&buf[state]); + unw_resume(&bsearch_caller_cursor); + __builtin_unreachable(); + // CHECK-LABEL: Return to `bsearch_caller` {{.*}}&buf[1] + // CHECK: libunwind: VAPI: executing return glue + // CHECK-LABEL: Return to `bsearch_caller` {{.*}}&buf[2] + // CHECK: libunwind: VAPI: executing return glue + } + + // Test resuming context where VAPI is not active, one frame up from the VAPI + // caller. + fprintf(stderr, "Return to `main` at the invocation of `bsearch_caller` with " + "r3 set to `&bsearch_caller_ret` using the global cursor.\n"); + if (!llu_enabled) + fprintf(stderr, + "libunwind: VAPI: executing return glue VAPI_NOT_ENABLED\n"); + unw_set_reg(&main_cursor, R3, (unw_word_t)&bsearch_caller_ret); + unw_resume(&main_cursor); + __builtin_unreachable(); + // CHECK-LABEL: Return to `main` + // CHECK: libunwind: VAPI: executing return glue +} + +// VAPI glue addresses +constexpr uintptr_t vapi_glue_addr_ext_32 = 0x8b80; +constexpr uintptr_t vapi_addr_64 = 0x8e00; +constexpr size_t vapi_size_64 = 0x0200; +constexpr uintptr_t vapi_glue_addr_begin = vapi_glue_addr_ext_32; +constexpr uintptr_t vapi_glue_addr_end = vapi_addr_64 + vapi_size_64; + +struct FunctionDescriptor { + uintptr_t entry; + uintptr_t toc; + uintptr_t env; +}; + +int main(void) { + if (setenv("LIBUNWIND_PRINT_UNWINDING", "1", true) != 0) { + perror("setenv"); + abort(); + } + + FunctionDescriptor *fd = reinterpret_cast<FunctionDescriptor *>(bsearch); + llu_enabled = + vapi_glue_addr_begin <= fd->entry && fd->entry < vapi_glue_addr_end; + + assert(bsearch_caller() == &bsearch_caller_ret); +} `````````` </details> https://github.com/llvm/llvm-project/pull/209306 _______________________________________________ cfe-commits mailing list [email protected] https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
