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package container
import (
"strings"
"unsafe"
"hakurei.app/check"
)
// escapeBinfmt escapes magic/mask sequences in a [BinfmtEntry].
func escapeBinfmt(buf *strings.Builder, s string) string {
const lowerhex = "0123456789abcdef"
buf.Reset()
for _, c := range unsafe.Slice(unsafe.StringData(s), len(s)) {
switch c {
case 0, '\\', ':':
buf.WriteString(`\x`)
buf.WriteByte(lowerhex[c>>4])
buf.WriteByte(lowerhex[c&0xf])
default:
buf.WriteByte(c)
}
}
return buf.String()
}
// BinfmtEntry is an entry to be registered by the init process.
type BinfmtEntry struct {
// The offset of the magic/mask in the file, counted in bytes.
Offset byte
// The byte sequence binfmt_misc is matching for.
Magic string
// An (optional, defaults to all 0xff) mask.
Mask string
// The program that should be invoked with the binary as first argument.
Interpreter *check.Absolute
}
// Valid returns whether e can be registered into the kernel.
func (e *BinfmtEntry) Valid() bool {
return e != nil &&
int(e.Offset)+max(len(e.Magic), len(e.Mask)) < 128 &&
e.Interpreter != nil && len(e.Interpreter.String()) < 128
}
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