[PATCH v2] erofs-utils: lib: oci: support auto-detecting host platform

[Gao Xiang]

On 2026/1/15 11:38, ChengyuZhu6 wrote:
> From: Chengyu Zhu <hudsonzhu at tencent.com>
> 
> Currently, the platform is hard-coded to "linux/amd64" if not specified.
> This patch introduces `ocierofs_get_platform_spec` helper to detect the
> host platform (OS, architecture, and variant) at compile time using
> preprocessor macros.
> 
> Signed-off-by: Chengyu Zhu <hudsonzhu at tencent.com>
> ---
>   lib/remotes/oci.c | 68 ++++++++++++++++++++++++++++++++++++++++++++---
>   1 file changed, 64 insertions(+), 4 deletions(-)
> 
> diff --git a/lib/remotes/oci.c b/lib/remotes/oci.c
> index c8711ea..4c4568f 100644
> --- a/lib/remotes/oci.c
> +++ b/lib/remotes/oci.c
> @@ -694,10 +694,20 @@ static char *ocierofs_get_manifest_digest(struct ocierofs_ctx *ctx,
>   		    json_object_object_get_ex(manifest, "digest", &digest_obj)) {
>   			const char *arch = json_object_get_string(arch_obj);
>   			const char *os = json_object_get_string(os_obj);
> +			json_object *variant_obj;
> +			const char *variant = NULL;
>   			char manifest_platform[64];
>   
> -			snprintf(manifest_platform, sizeof(manifest_platform),
> -				 "%s/%s", os, arch);
> +			if (json_object_object_get_ex(platform_obj, "variant", &variant_obj))
> +				variant = json_object_get_string(variant_obj);
> +
> +			if (variant)
> +				snprintf(manifest_platform, sizeof(manifest_platform),
> +					 "%s/%s/%s", os, arch, variant);
> +			else
> +				snprintf(manifest_platform, sizeof(manifest_platform),
> +					 "%s/%s", os, arch);
> +
>   			if (!strcmp(manifest_platform, platform)) {
>   				digest = strdup(json_object_get_string(digest_obj));
>   				break;
> @@ -1089,13 +1099,63 @@ static int ocierofs_parse_ref(struct ocierofs_ctx *ctx, const char *ref_str)
>   	return 0;
>   }
>   
> +static char *ocierofs_get_platform_spec(void)
> +{
> +	const char *os = NULL, *arch = NULL, *variant = NULL;
> +	char *platform;
> +
> +#if defined(__linux__)
> +	os = "linux";
> +#elif defined(__APPLE__)
> +	os = "darwin";
> +#elif defined(_WIN32)
> +	os = "windows";
> +#elif defined(__FreeBSD__)
> +	os = "freebsd";
> +#endif
> +
> +#if defined(__x86_64__) || defined(__amd64__)
> +	arch = "amd64";
> +#elif defined(__aarch64__) || defined(__arm64__)
> +	arch = "arm64";
> +	variant = "v8";
> +#elif defined(__i386__)
> +	arch = "386";
> +#elif defined(__arm__)
> +	arch = "arm";
> +	variant = "v7";
> +#elif defined(__riscv) && (__riscv_xlen == 64)
> +	arch = "riscv64";
> +#elif defined(__ppc64__)
> +#if defined(__BYTE_ORDER__) && (__BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__)
> +	arch = "ppc64le";
> +#else
> +	arch = "ppc64";
> +#endif
> +#elif defined(__s390x__)
> +	arch = "s390x";
> +#endif
> +
> +	if (!os || !arch)
> +		return NULL;
> +
> +	if (variant) {
> +		if (asprintf(&platform, "%s/%s/%s", os, arch, variant) < 0)
> +			return NULL;
> +	} else {
> +		if (asprintf(&platform, "%s/%s", os, arch) < 0)
> +			return NULL;
> +	}
> +	return platform;
> +}
> +
>   /**
>    * ocierofs_init - Initialize OCI context
>    * @ctx: OCI context structure to initialize
>    * @config: OCI configuration
>    *
>    * Initialize OCI context structure, set up CURL handle, and configure
> - * default parameters including platform (linux/amd64), registry
> + * default parameters including platform (host platform), registry
>    * (registry-1.docker.io), and tag (latest).
>    *
>    * Return: 0 on success, negative errno on failure
> @@ -1120,7 +1180,7 @@ static int ocierofs_init(struct ocierofs_ctx *ctx, const struct ocierofs_config
>   	if (config->platform)
>   		ctx->platform = strdup(config->platform);
>   	else
> -		ctx->platform = strdup("linux/amd64");
> +		ctx->platform = ocierofs_get_platform_spec();

	if (!ctx->platform)
		return -EOPNOTSUPP;

I will update this part manually, otherwise it looks good to me.

Thanks,
Gao Xiang