pkg/architecture: Add architecture support validation#1783
pkg/architecture: Add architecture support validation#1783DaliborKr wants to merge 6 commits intocontainers:mainfrom
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The existing RunContextWithExitCode() wraps all errors from exec.Command in generic "failed to invoke" messages, which prevents callers from distinguishing between actual error types. Add RunContextWithExitCode2() and RunWithExitCode2() that return errors with their original types intact, including for ExitError. This allows callers to use errors.Is() and errors.As() to handle specific failure modes. For example, detecting a missing skopeo binary (exec.ErrNotFound) or an ENOEXEC error from inside non native containers, when an emulator is not set correctly. These new functions are meant to replace its original versions in the future. containers#1780 Signed-off-by: Dalibor Kricka <dalidalk@seznam.cz>
In /src/cmd/create.go, the same pattern of spinner creation and nil-safe stopping is repeated. Extract this into startSpinner() and stopSpinner() helper functions so that future callers can use spinners without duplicating the code. Replace the existing inline spinner code in createContainer() and pullImage() with calls to these new helpers. containers#1781 Signed-off-by: Dalibor Kricka <dalidalk@seznam.cz>
…atching Add IsSupportedDistroImage(), which iterates over all supported distros and checks if the image basename matches any of them. This will be used by the architecture resolution code to decide whether to parse architecture suffixes from image tags, as this should be done only for natively supported images [1]. [1] Toolbx supported distributions: https://containertoolbx.org/distros/ containers#1781 Signed-off-by: Dalibor Kricka <dalidalk@seznam.cz>
Introduce the architecture package that represents the core of the Toolbx cross-architecture support, which is based on user-mode emulation using QEMU and binfmt_misc. The Architecture struct collects all per-architecture data (ELF magic/mask, OCI and binfmt naming, aliases, binfmt registration parameters) into a single map. Architectures present in the supportedArchitectures map represent the set of supported architectures within Toolbx. Define architecture ID constants NotSpecified, Aarch64, Ppc64le, and X86_64, along with their supportedArchitectures entries. Add core query functions: - ParseArgArchValue() for resolving user-supplied architecture strings - GetArchNameBinfmt() and GetArchNameOCI() for name lookups (one architecture can have multiple valid names [1]) - HasContainerNativeArch() for comparing against the host - ImageReferenceGetArchFromTag() for extracting architecture from image tag suffixes like "42-aarch64" for architecture detection Expose the HostArchID package variable set by cmd/root.go at startup, and the Config struct for preserving the architecture ID and the QEMU emulator path, through the call chain. [1] https://itsfoss.com/arm-aarch64-x86_64/ containers#1782 Signed-off-by: Dalibor Kricka <dalidalk@seznam.cz>
Cross-architecture containers need QEMU binfmt_misc handlers registered within the container so that non-native architecture binaries can be executed via the host's kernel. Add the Registration struct that models a binfmt_misc registration entry, including name, magic type, offset, ELF magic/mask bytes, interpreter path, and flags. Add functions: - MountBinfmtMisc() to mount the sanboxed binfmt_misc filesystem inside a container, which enables setting the C flag in binfmt_misc registration without affecting the host system. The C flag presents a threat of privilege escalation when registered on the host, that why we want to have it isolated [1] - getDefaultRegistration() to fill a Registration struct containing all necessary binfmt_misc information taken from the architecture.supportedArchitectures data - RegisterBinfmtMisc() to write the registration string to /proc/sys/fs/binfmt_misc/register, which makes the non-native binary perception active - bytesToEscapedString() helper that formats byte slices into the \xHH-escaped string format required by the binfmt_misc register interface [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=21ca59b365c0 containers#1782 Signed-off-by: Dalibor Kricka <dalidalk@seznam.cz>
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Code Review
This pull request introduces a new architecture package to manage cross-architecture support, including binfmt_misc registration and QEMU emulation checks. It also refactors the spinner logic into reusable helper functions and adds host architecture detection to the root command. Feedback focuses on improving maintainability by avoiding generic function suffixes like '2', ensuring consistent logging by using logrus instead of direct stderr writes, and adding validation for architecture IDs to prevent confusing error messages.
| func RunContextWithExitCode2(ctx context.Context, | ||
| name string, | ||
| stdin io.Reader, | ||
| stdout, stderr io.Writer, | ||
| arg ...string) (int, error) { | ||
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| logLevel := logrus.GetLevel() | ||
| if stderr == nil && logLevel >= logrus.DebugLevel { | ||
| stderr = os.Stderr | ||
| } | ||
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| cmd := exec.CommandContext(ctx, name, arg...) | ||
| cmd.Stdin = stdin | ||
| cmd.Stdout = stdout | ||
| cmd.Stderr = stderr | ||
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| if err := cmd.Run(); err != nil { | ||
| exitCode := 1 | ||
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| if ctxErr := ctx.Err(); ctxErr != nil { | ||
| return 1, ctxErr | ||
| } | ||
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| var exitErr *exec.ExitError | ||
| if errors.As(err, &exitErr) { | ||
| exitCode = exitErr.ExitCode() | ||
| return exitCode, err | ||
| } | ||
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| return exitCode, err | ||
| } | ||
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| return 0, nil | ||
| } | ||
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| func RunWithExitCode(name string, stdin io.Reader, stdout, stderr io.Writer, arg ...string) (int, error) { | ||
| ctx := context.Background() | ||
| exitCode, err := RunContextWithExitCode(ctx, name, stdin, stdout, stderr, arg...) | ||
| return exitCode, err | ||
| } | ||
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| func RunWithExitCode2(name string, stdin io.Reader, stdout, stderr io.Writer, arg ...string) (int, error) { | ||
| ctx := context.Background() | ||
| exitCode, err := RunContextWithExitCode2(ctx, name, stdin, stdout, stderr, arg...) | ||
| return exitCode, err | ||
| } |
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Adding new functions with a 2 suffix (e.g., RunContextWithExitCode2 and RunWithExitCode2) is poor practice for maintainability. It's unclear how they differ from the original versions without inspecting the implementation.
If a different error handling behavior is required, consider using a more descriptive name (e.g., RunContextWithExitError) or refactoring the existing functions to be more flexible. Furthermore, these functions appear to be unused in the current PR and should be removed if not strictly necessary.
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| // Fallback: check standard locations on the host | ||
| logrus.Debugf("Interpreter at %s not found or not statically linked, checking fallback locations in '/run/host/usr/bin/'", interpreterPath) | ||
| fmt.Fprintf(os.Stderr, "Warning: QEMU emulator not found at expected path '%s', using fallback at '/run/host/usr/bin/'\n", interpreterPath) |
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Bypassing the logging system by writing directly to os.Stderr is inconsistent with the rest of the codebase. Using logrus.Warnf ensures that the message follows the configured log format and level.
| fmt.Fprintf(os.Stderr, "Warning: QEMU emulator not found at expected path '%s', using fallback at '/run/host/usr/bin/'\n", interpreterPath) | |
| logrus.Warnf("QEMU emulator not found at expected path '%s', using fallback at '/run/host/usr/bin/'", interpreterPath) |
| func IsArchSupportedOnCreation(archID int) (string, error) { | ||
| archName := getArchNameBinfmt(archID) |
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If archID is NotSpecified, this function proceeds to look for a binary named qemu-arch_not_specified-static, which will fail and result in a confusing error message for the user. It would be better to validate that archID is a supported architecture at the beginning of the function.
Before creating or initializing a cross-architecture container, the system must be checked for the required QEMU emulator and binfmt_misc registration. This prevents users from creating or running non-native containers when their host system doesn't meet the requirements, and provides users with an informative error message referring to the problem. Add IsArchSupportedOnCreation(), which searches for a statically linked QEMU binary on the host using exec.LookPath() and verifies that a matching binfmt_misc registration exists. It returns the path to the QEMU binary for use during container creation, which is meant to be passed to the init-container and registered through sandboxed binfmt_misc within the container. Add IsArchSupportedOnInitialization() which performs similar checks from inside the container, looking at the interpreter path passed from the host and falling back to standard host-mounted locations under /run/host/usr/bin/. Add isStaticallyLinkedELF() helper that uses debug/elf to verify a binary is statically linked. Only a statically linked QEMU interpreter can be used, because a dynamically linked one would cause the kernel to attempt to resolve its host-native shared libraries (such as libc.so) within the container, resulting in an immediate crash. Add validateBinfmtRegistration(), which checks for the presence of qemu-<arch> entries in binfmt_misc (or qemu-<arch>-static, since it can differ based on the system). containers#1783 Signed-off-by: Dalibor Kricka <dalidalk@seznam.cz>
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This is PR 4/10 in a series adding cross-architecture container support using QEMU and binfmt_misc.
Depends on: #1782 (cmd/create, pkg/utils: Add spinner helpers and distro image matching)
Please review #1782 first. The new commit in this PR is:
Summary
Before creating or initializing a cross-architecture container, the system must be verified to have the required QEMU emulator and
binfmt_miscregistration in place, and provide a user with an appropriate message. Without these checks, container creation would silently fail or produce broken containers.Add:
Host-side validation (
IsArchSupportedOnCreation()) that locates a statically linked QEMU binary viaexec.LookPathand verifies that a matching binfmt_misc registration exists. Returns the path to the QEMU binary for use during container initializationContainer-side validation (
IsArchSupportedOnInitialization()) that verifies QEMU support from inside the container using the interpreter path passed from the host, with fallback to the standard host-mounted locations under/run/host/usr/bin/ELF binary inspection (
isStaticallyLinkedELF()) that confirms the QEMU binary is statically linked, because a dynamically linked one would cause the kernel to attempt to resolve its host-native shared libraries (such aslibc.so) within the container, resulting in an immediate crash.