binfmt_misc: add detection for 386

Detects x86 32-bit architectures

Signed-off-by: Tibor Vass <tibor@docker.com>

util/binfmt_misc/386_binary.go

@@ -0,0 +1,8 @@
+// +build !386
+
+package binfmt_misc
+
+// This file is generated by running make inside the binfmt_misc package.
+// Do not edit manually.
+
+const Binary386 = "\x1f\x8b\x08\x00\x00\x00\x00\x00\x02\xff\xec\xd8\x31\x6e\xc2\x30\x14\x06\xe0\xdf\x8d\xdb\x26\x6a\x07\x1f\x20\xaa\x3a\x74\xe8\x64\xb5\x52\xae\x00\x2c\x88\x8d\x03\x80\x14\xc1\x94\x44\x89\x91\x60\x22\x47\x60\xe0\x20\x8c\x8c\x5c\x80\x13\x70\x19\xf4\xe2\x67\x91\x81\x25\xfb\xfb\xa4\x5f\x16\xcf\xe6\x29\xeb\x7b\xfb\xd1\x74\xac\x94\x42\xf0\x82\x08\xdd\xaf\x83\x8e\x33\x00\x7f\xc6\xd7\x33\x7c\x23\xc2\x2f\x74\xb8\x27\xad\x8e\x29\x27\x00\x14\x4d\x35\x03\x7f\x6f\x7c\x0f\x4a\x02\x80\xf2\xca\x75\x7a\x77\xa4\xb4\x3a\xa6\xa4\x00\x52\xfe\x7f\xc8\x27\xbf\x9f\xcc\xe6\xd4\xef\x42\xb5\xc7\x57\x0a\x21\x84\x10\x42\x08\x21\x84\x10\x62\x88\x33\x0d\xd5\xff\xb7\x6b\x0b\xdb\xac\x1b\x57\xbb\xc5\x12\xb6\x28\x5d\x6e\x57\xc5\xc6\x56\x75\x59\xe5\xb5\xdb\xc1\xba\x7c\xeb\x86\xf4\xfd\x00\xf0\xde\xed\x13\x78\xce\xe7\x19\x3f\xd0\x7c\x7e\xf1\x5c\xff\xc6\x3b\x07\x18\xbf\x2b\x08\x54\xef\x8c\x7a\xf5\xc4\x00\x3f\x4f\xde\xdd\x03\x00\x00\xff\xff\x8d\xf7\xd2\x72\xd0\x10\x00\x00"

util/binfmt_misc/386_check.go

@@ -0,0 +1,7 @@
+// +build !386
+
+package binfmt_misc
+
+func i386Supported() error {
+	return check(Binary386)
+}

util/binfmt_misc/386_check_386.go

@@ -0,0 +1,7 @@
+// +build 386
+
+package binfmt_misc
+
+func i386Supported() error {
+	return nil
+}

util/binfmt_misc/Dockerfile

@@ -3,6 +3,7 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
   binutils-arm-linux-gnueabihf \
   binutils-aarch64-linux-gnu \
   binutils-x86-64-linux-gnu \
+  binutils-i686-linux-gnu \
   binutils-riscv64-linux-gnu \
   binutils-s390x-linux-gnu \
   binutils-powerpc64le-linux-gnu
@@ -13,6 +14,10 @@ FROM base AS exit-amd64
 COPY fixtures/exit.amd64.s .
 RUN x86_64-linux-gnu-as -o exit.o exit.amd64.s && x86_64-linux-gnu-ld -o exit -s exit.o
 
+FROM base AS exit-386
+COPY fixtures/exit.386.s .
+RUN i686-linux-gnu-as -o exit.o exit.386.s && i686-linux-gnu-ld -o exit -s exit.o
+
 FROM base AS exit-arm64
 COPY fixtures/exit.arm64.s .
 RUN aarch64-linux-gnu-as -o exit.o exit.arm64.s && aarch64-linux-gnu-ld -o exit -s exit.o
@@ -36,6 +41,7 @@ RUN powerpc64le-linux-gnu-as -o exit.o exit.ppc64le.s && powerpc64le-linux-gnu-l
 FROM golang:1.12-alpine AS generate
 WORKDIR /src
 COPY --from=exit-amd64 /src/exit amd64
+COPY --from=exit-386 /src/exit 386
 COPY --from=exit-arm64 /src/exit arm64
 COPY --from=exit-arm /src/exit arm
 COPY --from=exit-riscv64 /src/exit riscv64
@@ -43,7 +49,7 @@ COPY --from=exit-s390x /src/exit s390x
 COPY --from=exit-ppc64le /src/exit ppc64le
 COPY generate.go .
 
-RUN go run generate.go amd64 arm64 arm riscv64 s390x ppc64le && ls -l
+RUN go run generate.go amd64 386 arm64 arm riscv64 s390x ppc64le && ls -l
 
 
 FROM scratch

util/binfmt_misc/detect.go

@@ -30,6 +30,9 @@ func SupportedPlatforms() []string {
 		if p := "linux/s390x"; def != p && s390xSupported() == nil {
 			arr = append(arr, p)
 		}
+		if p := "linux/386"; def != p && i386Supported() == nil {
+			arr = append(arr, p)
+		}
 		if !strings.HasPrefix(def, "linux/arm/") && armSupported() == nil {
 			arr = append(arr, "linux/arm/v7", "linux/arm/v6")
 		} else if def == "linux/arm/v7" {
@@ -71,6 +74,11 @@ func WarnIfUnsupported(pfs []string) {
 					printPlatfromWarning(p, err)
 				}
 			}
+			if p == "linux/386" {
+				if err := i386Supported(); err != nil {
+					printPlatfromWarning(p, err)
+				}
+			}
 			if strings.HasPrefix(p, "linux/arm/v6") || strings.HasPrefix(p, "linux/arm/v7") {
 				if err := armSupported(); err != nil {
 					printPlatfromWarning(p, err)

util/binfmt_misc/fixtures/exit.386.s

@@ -0,0 +1,6 @@
+	.global _start
+	.text
+_start:
+	mov $1, %eax
+	xor %ebx, %ebx
+	int $0x80