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https://github.com/carbon-language/carbon-lang.git
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Jon Ross-Perkins
3070e5cfc6
When finding an executable, this validates that the returned binary is a symlink back to the same thing as /proc/self/exe, also using that as a fallback for different things. Looking back at #3912, we started using `findProgramByName` in order to avoid path canonicalization done by `GetMainExecutable`. That created issues as in #5096, wherein an `argv[0]` that's not explicit enough (`llvm-symbolizer` instead of the full path, done in [LLVM's Signals.cpp](https://github.com/llvm/llvm-project/blob/4f60f45130c6bd96c79e468fe9927a29af760f56/llvm/lib/Support/Signals.cpp#L198)) leads to incorrect results (finding an `llvm-symbolizer` in `$PATH`). One option to fix this would be to patch LLVM to provide an absolute path for `llvm-symbolizer`. However, I'll suggest that passing a filename in `argv[0]` is not terribly uncommon, and could be a migration limitation if we force it. The failure mode is also opaque; for example: ``` $ /bin/sh -c "exec -a llvm-symbolizer ./bazel-bin/toolchain/carbon" error: expected carbon-busybox symlink at `/usr/lib/llvm-19/bin/llvm-symbolizer` ``` Combined with the `setenv` of `LLVM_SYMBOLIZER_PATH` in `busybox_main.cpp`, this is intended to fix #5096.
102 lines
3.8 KiB
C++
102 lines
3.8 KiB
C++
// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
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// Exceptions. See /LICENSE for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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#include "toolchain/install/busybox_info.h"
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#include <iterator>
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#include "common/exe_path.h"
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#include "llvm/ADT/StringRef.h"
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namespace Carbon {
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// The mode is set to the initial filename used for `argv[0]`.
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static auto GetMode(const std::filesystem::path& argv0)
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-> std::optional<std::string> {
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std::string filename = argv0.filename();
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if (filename != "carbon" && filename != "carbon-busybox") {
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return filename;
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}
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return std::nullopt;
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}
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auto GetBusyboxInfo(const char* argv0) -> ErrorOr<BusyboxInfo> {
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// Need storage due to `unsetenv` affecting `getenv` lifetime; using `path`
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// for `GetMode`.
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std::filesystem::path argv0_path = argv0;
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// Check for an override of `argv[0]` from the environment and apply it.
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if (const char* argv0_override = getenv(Argv0OverrideEnv)) {
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argv0_path = argv0_override;
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unsetenv(Argv0OverrideEnv);
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}
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BusyboxInfo info = {.bin_path = FindExecutablePath(argv0_path.c_str()),
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.mode = GetMode(argv0_path)};
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if (info.bin_path.filename() == "carbon-busybox") {
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// Check for bazel structure. For example, this makes work:
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// /bin/sh -c "exec -a carbon ./bazel-bin/toolchain/carbon"
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// /bin/sh -c "exec -a llvm-symbolizer ./bazel-bin/toolchain/carbon"
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if (std::filesystem::exists(info.bin_path.string() + ".runfiles")) {
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std::string prefix_root = info.bin_path.parent_path().string() +
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"/prefix_root/lib/carbon/carbon-busybox";
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if (std::filesystem::exists(prefix_root)) {
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info.bin_path = prefix_root;
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}
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}
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return info;
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}
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// Now search through any symlinks to locate the installed busybox binary.
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while (true) {
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// If we've not already reached the busybox, look for it relative to the
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// current binary path. This can help more immediately locate an
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// installation tree, and avoids walking through a final layer of symlinks
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// which may point to content-addressed storage or other parts of a build
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// output tree.
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//
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// We break this into two cases we need to handle:
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// - Carbon's CLI will be: `<prefix>/bin/carbon`
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// - Other tools will be: `<prefix>/lib/carbon/<group>/bin/<tool>`
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//
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// We also check that the current path is within a `bin` directory to
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// provide best-effort checking for accidentally walking up from symlinks
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// that aren't within an installation-shaped tree.
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auto parent_path = info.bin_path.parent_path();
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// Strip any `.` path components at the end to simplify processing.
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while (parent_path.filename() == ".") {
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parent_path = parent_path.parent_path();
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}
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if (parent_path.filename() == "bin") {
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auto lib_path = info.bin_path.filename() == "carbon"
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? parent_path / ".." / "lib" / "carbon"
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: parent_path / ".." / "..";
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auto busybox_path = lib_path / "carbon-busybox";
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std::error_code ec;
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if (std::filesystem::exists(busybox_path, ec)) {
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info.bin_path = busybox_path;
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return info;
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}
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}
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// Try to walk through another layer of symlinks and see if we can find the
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// installation there or are linked directly to the busybox.
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std::error_code ec;
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auto symlink_target = std::filesystem::read_symlink(info.bin_path, ec);
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if (ec) {
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return ErrorBuilder()
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<< "expected carbon-busybox symlink at `" << info.bin_path << "`";
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}
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// Do a path join, to handle relative symlinks.
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info.bin_path = parent_path / symlink_target;
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if (info.bin_path.filename() == "carbon-busybox") {
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return info;
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}
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}
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}
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} // namespace Carbon
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