[PATCH v2] x86/configs: add tiny_defconfig for minimal bootable systems

[Emir YILDIRIM <emir73503@gmail.com>]

Add a minimal yet boot-capable and usable configuration based on
tinyconfig.

It enables initramfs support, printk, TTY/PTY, ELF binary support,
scripts with shebang (#!) execution, and pseudo filesystems.

This configuration is intended for VM testing and experimentation with
ultra-minimal environments, providing a middle ground between
tinyconfig and standard defconfig.

Signed-off-by: Emir YILDIRIM <emir@emirpasha.com>

---
v2:
- Mention initramfs support in commit message
- Improve wording and formatting
---
 arch/x86/configs/tiny_defconfig | 91 +++++++++++++++++++++++++++++++++
 init/Kconfig                    |  6 +++
 2 files changed, 97 insertions(+)
 create mode 100644 arch/x86/configs/tiny_defconfig

diff --git a/arch/x86/configs/tiny_defconfig b/arch/x86/configs/tiny_defconfig
new file mode 100644
index 000000000..d5a96b15f
--- /dev/null
+++ b/arch/x86/configs/tiny_defconfig
@@ -0,0 +1,91 @@
+# CONFIG_LOCALVERSION_AUTO is not set
+CONFIG_KERNEL_XZ=y
+# CONFIG_CROSS_MEMORY_ATTACH is not set
+# CONFIG_PREEMPT_DYNAMIC is not set
+CONFIG_BLK_DEV_INITRD=y
+# CONFIG_RD_GZIP is not set
+# CONFIG_RD_BZIP2 is not set
+# CONFIG_RD_LZMA is not set
+# CONFIG_RD_XZ is not set
+# CONFIG_RD_LZO is not set
+# CONFIG_RD_LZ4 is not set
+# CONFIG_RD_ZSTD is not set
+CONFIG_CC_OPTIMIZE_FOR_SIZE=y
+CONFIG_EXPERT=y
+# CONFIG_MULTIUSER is not set
+# CONFIG_SGETMASK_SYSCALL is not set
+# CONFIG_FHANDLE is not set
+# CONFIG_POSIX_TIMERS is not set
+# CONFIG_BUG is not set
+# CONFIG_PCSPKR_PLATFORM is not set
+# CONFIG_FUTEX is not set
+# CONFIG_EPOLL is not set
+# CONFIG_SIGNALFD is not set
+# CONFIG_TIMERFD is not set
+# CONFIG_EVENTFD is not set
+# CONFIG_SHMEM is not set
+# CONFIG_AIO is not set
+# CONFIG_IO_URING is not set
+# CONFIG_ADVISE_SYSCALLS is not set
+# CONFIG_MEMBARRIER is not set
+# CONFIG_RSEQ is not set
+# CONFIG_CACHESTAT_SYSCALL is not set
+# CONFIG_KALLSYMS is not set
+# CONFIG_64BIT is not set
+# CONFIG_X86_EXTENDED_PLATFORM is not set
+# CONFIG_SCHED_OMIT_FRAME_POINTER is not set
+# CONFIG_DMI is not set
+# CONFIG_X86_MCE is not set
+# CONFIG_PERF_EVENTS_AMD_UNCORE is not set
+# CONFIG_X86_IOPL_IOPERM is not set
+# CONFIG_MTRR is not set
+# CONFIG_X86_UMIP is not set
+# CONFIG_RELOCATABLE is not set
+# CONFIG_MODIFY_LDT_SYSCALL is not set
+# CONFIG_X86_BUS_LOCK_DETECT is not set
+# CONFIG_CPU_MITIGATIONS is not set
+# CONFIG_SUSPEND is not set
+# CONFIG_ACPI is not set
+# CONFIG_VIRTUALIZATION is not set
+# CONFIG_SECCOMP is not set
+# CONFIG_STACKPROTECTOR is not set
+# CONFIG_COMPAT_32BIT_TIME is not set
+# CONFIG_RANDOMIZE_KSTACK_OFFSET is not set
+# CONFIG_BLOCK is not set
+# CONFIG_COREDUMP is not set
+CONFIG_SLUB_TINY=y
+# CONFIG_COMPAT_BRK is not set
+# CONFIG_COMPACTION is not set
+# CONFIG_ZONE_DMA is not set
+# CONFIG_VM_EVENT_COUNTERS is not set
+# CONFIG_SECRETMEM is not set
+CONFIG_DEVTMPFS=y
+# CONFIG_STANDALONE is not set
+# CONFIG_PREVENT_FIRMWARE_BUILD is not set
+# CONFIG_FW_LOADER is not set
+# CONFIG_ALLOW_DEV_COREDUMP is not set
+# CONFIG_FIRMWARE_MEMMAP is not set
+# CONFIG_HW_RANDOM is not set
+# CONFIG_DEVMEM is not set
+# CONFIG_DEVPORT is not set
+# CONFIG_HWMON is not set
+# CONFIG_USB_SUPPORT is not set
+# CONFIG_VIRTIO_MENU is not set
+# CONFIG_VHOST_MENU is not set
+# CONFIG_SURFACE_PLATFORMS is not set
+# CONFIG_X86_PLATFORM_DEVICES is not set
+# CONFIG_IOMMU_SUPPORT is not set
+# CONFIG_FILE_LOCKING is not set
+# CONFIG_DNOTIFY is not set
+# CONFIG_INOTIFY_USER is not set
+# CONFIG_MISC_FILESYSTEMS is not set
+# CONFIG_CRC_OPTIMIZATIONS is not set
+# CONFIG_SYMBOLIC_ERRNAME is not set
+# CONFIG_DEBUG_MISC is not set
+# CONFIG_SECTION_MISMATCH_WARN_ONLY is not set
+# CONFIG_FTRACE is not set
+# CONFIG_X86_VERBOSE_BOOTUP is not set
+# CONFIG_EARLY_PRINTK is not set
+# CONFIG_X86_DEBUG_FPU is not set
+CONFIG_UNWINDER_GUESS=y
+# CONFIG_RUNTIME_TESTING_MENU is not set
diff --git a/init/Kconfig b/init/Kconfig
index 2937c4d30..7f4f02128 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -2296,3 +2296,9 @@ config ARCH_HAS_SYNC_CORE_BEFORE_USERMODE
 # <asm/syscall_wrapper.h>.
 config ARCH_HAS_SYSCALL_WRAPPER
 	def_bool n
+
+config TINY_DEFCONFIG
+    bool "Tiny yet usable kernel configuration"
+    help
+      A minimal but bootable configuration intended for
+      testing and development in virtual machines.
-- 
2.47.3