tools: add coredump.h header

Copy the coredump header so we can rely on it in the selftests.

Link: https://lore.kernel.org/20250603-work-coredump-socket-protocol-v2-4-05a5f0c18ecc@kernel.org
Acked-by: Lennart Poettering <lennart@poettering.net>
Reviewed-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@canonical.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>

Author: brauner

tools/include/uapi/linux/coredump.h

@@ -0,0 +1,104 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+
+#ifndef _UAPI_LINUX_COREDUMP_H
+#define _UAPI_LINUX_COREDUMP_H
+
+#include <linux/types.h>
+
+/**
+ * coredump_{req,ack} flags
+ * @COREDUMP_KERNEL: kernel writes coredump
+ * @COREDUMP_USERSPACE: userspace writes coredump
+ * @COREDUMP_REJECT: don't generate coredump
+ * @COREDUMP_WAIT: wait for coredump server
+ */
+enum {
+	COREDUMP_KERNEL		= (1ULL << 0),
+	COREDUMP_USERSPACE	= (1ULL << 1),
+	COREDUMP_REJECT		= (1ULL << 2),
+	COREDUMP_WAIT		= (1ULL << 3),
+};
+
+/**
+ * struct coredump_req - message kernel sends to userspace
+ * @size: size of struct coredump_req
+ * @size_ack: known size of struct coredump_ack on this kernel
+ * @mask: supported features
+ *
+ * When a coredump happens the kernel will connect to the coredump
+ * socket and send a coredump request to the coredump server. The @size
+ * member is set to the size of struct coredump_req and provides a hint
+ * to userspace how much data can be read. Userspace may use MSG_PEEK to
+ * peek the size of struct coredump_req and then choose to consume it in
+ * one go. Userspace may also simply read a COREDUMP_ACK_SIZE_VER0
+ * request. If the size the kernel sends is larger userspace simply
+ * discards any remaining data.
+ *
+ * The coredump_req->mask member is set to the currently know features.
+ * Userspace may only set coredump_ack->mask to the bits raised by the
+ * kernel in coredump_req->mask.
+ *
+ * The coredump_req->size_ack member is set by the kernel to the size of
+ * struct coredump_ack the kernel knows. Userspace may only send up to
+ * coredump_req->size_ack bytes to the kernel and must set
+ * coredump_ack->size accordingly.
+ */
+struct coredump_req {
+	__u32 size;
+	__u32 size_ack;
+	__u64 mask;
+};
+
+enum {
+	COREDUMP_REQ_SIZE_VER0 = 16U, /* size of first published struct */
+};
+
+/**
+ * struct coredump_ack - message userspace sends to kernel
+ * @size: size of the struct
+ * @spare: unused
+ * @mask: features kernel is supposed to use
+ *
+ * The @size member must be set to the size of struct coredump_ack. It
+ * may never exceed what the kernel returned in coredump_req->size_ack
+ * but it may of course be smaller (>= COREDUMP_ACK_SIZE_VER0 and <=
+ * coredump_req->size_ack).
+ *
+ * The @mask member must be set to the features the coredump server
+ * wants the kernel to use. Only bits the kernel returned in
+ * coredump_req->mask may be set.
+ */
+struct coredump_ack {
+	__u32 size;
+	__u32 spare;
+	__u64 mask;
+};
+
+enum {
+	COREDUMP_ACK_SIZE_VER0 = 16U, /* size of first published struct */
+};
+
+/**
+ * enum coredump_mark - Markers for the coredump socket
+ *
+ * The kernel will place a single byte on the coredump socket. The
+ * markers notify userspace whether the coredump ack succeeded or
+ * failed.
+ *
+ * @COREDUMP_MARK_MINSIZE: the provided coredump_ack size was too small
+ * @COREDUMP_MARK_MAXSIZE: the provided coredump_ack size was too big
+ * @COREDUMP_MARK_UNSUPPORTED: the provided coredump_ack mask was invalid
+ * @COREDUMP_MARK_CONFLICTING: the provided coredump_ack mask has conflicting options
+ * @COREDUMP_MARK_REQACK: the coredump request and ack was successful
+ * @__COREDUMP_MARK_MAX: the maximum coredump mark value
+ */
+enum coredump_mark {
+	COREDUMP_MARK_REQACK		= 0U,
+	COREDUMP_MARK_MINSIZE		= 1U,
+	COREDUMP_MARK_MAXSIZE		= 2U,
+	COREDUMP_MARK_UNSUPPORTED	= 3U,
+	COREDUMP_MARK_CONFLICTING	= 4U,
+	__COREDUMP_MARK_MAX		= (1U << 31),
+};
+
+#endif /* _UAPI_LINUX_COREDUMP_H */