diff --git a/hw/top_earlgrey/BUILD b/hw/top_earlgrey/BUILD
index 1b2288c35271d..e2ae56c5a1249 100644
--- a/hw/top_earlgrey/BUILD
+++ b/hw/top_earlgrey/BUILD
@@ -2,6 +2,10 @@
 # Licensed under the Apache License, Version 2.0, see LICENSE for details.
 # SPDX-License-Identifier: Apache-2.0
 
+load(
+    "//rules:manifest.bzl",
+    "manifest",
+)
 load(
     "//rules/opentitan:defs.bzl",
     "CLEAR_KEY_SET",
@@ -27,6 +31,14 @@ filegroup(
     ],
 )
 
+# The following definition is used to define a null manifest in the signing
+# configuration for execution environments (exec_env) and opentitan_test
+# and opentitan_binary rules. When building the binaries, if the manifest equals
+# to this null manifest, then the signing will be skipped.
+CLEAR_MANIFEST = manifest(d = {
+    "name": "none_manifest",
+})
+
 ###########################################################################
 # FPGA CW310 Environments
 ###########################################################################
diff --git a/rules/opentitan/cc.bzl b/rules/opentitan/cc.bzl
index 96047ee8b55dc..e29e993f4f1a7 100644
--- a/rules/opentitan/cc.bzl
+++ b/rules/opentitan/cc.bzl
@@ -182,6 +182,9 @@ def _build_binary(ctx, exec_env, name, deps, kind):
     )
 
     manifest = get_fallback(ctx, "file.manifest", exec_env)
+    if manifest and str(manifest.owner) == "@@//hw/top_earlgrey:none_manifest":
+        manifest = None
+
     ecdsa_key = get_fallback(ctx, "attr.ecdsa_key", exec_env)
     rsa_key = get_fallback(ctx, "attr.rsa_key", exec_env)
     spx_key = get_fallback(ctx, "attr.spx_key", exec_env)
@@ -226,10 +229,20 @@ def _opentitan_binary(ctx):
     providers = []
     default_info = []
     groups = {}
-    for exec_env in ctx.attr.exec_env:
-        exec_env = exec_env[ExecEnvInfo]
+    for exec_env_target in ctx.attr.exec_env:
+        exec_env = exec_env_target[ExecEnvInfo]
         name = _binary_name(ctx, exec_env)
         deps = ctx.attr.deps + exec_env.libs
+
+        imm_rom_ext_deps = []
+        for dep in ctx.attr.immutable_rom_ext_sections:
+            if exec_env_target.label.name not in dep.label.name:
+                continue
+            imm_rom_ext_deps.append(dep)
+        if ctx.attr.immutable_rom_ext_sections and len(imm_rom_ext_deps) != 1:
+            fail("When building for exec_env {}, found zero or more than one immutable ROM_EXT sections to link: {}".format(imm_rom_ext_deps, exec_env_target))
+        deps += imm_rom_ext_deps
+
         kind = ctx.attr.kind
         provides, signed = _build_binary(ctx, exec_env, name, deps, kind)
         providers.append(exec_env.provider(kind = kind, **provides))
@@ -329,6 +342,10 @@ common_binary_attrs = {
         doc = "Indicates whether the binary is intended for a chip with the immutable ROM_EXT feature enabled.",
         default = False,
     ),
+    "immutable_rom_ext_sections": attr.label_list(
+        providers = [CcInfo],
+        doc = "The list of immutable ROM_EXT sections to be linked in to the binary target.  Only the deps matched with the specific exec_env will be kept.",
+    ),
 }
 
 opentitan_binary = rv_rule(
diff --git a/sw/device/silicon_creator/imm_rom_ext/BUILD b/sw/device/silicon_creator/imm_rom_ext/BUILD
index 86d8cb1f26b6e..a55fefff49c26 100644
--- a/sw/device/silicon_creator/imm_rom_ext/BUILD
+++ b/sw/device/silicon_creator/imm_rom_ext/BUILD
@@ -2,17 +2,26 @@
 # Licensed under the Apache License, Version 2.0, see LICENSE for details.
 # SPDX-License-Identifier: Apache-2.0
 
+load("@lowrisc_opentitan//rules/opentitan:exec_env.bzl", "ExecEnvInfo")
 load("@lowrisc_opentitan//rules/opentitan:transform.bzl", "obj_transform")
 load("//rules/opentitan:defs.bzl", "OPENTITAN_CPU", "opentitan_binary")
 load("//rules:linker.bzl", "ld_library")
-load("//sw/device/silicon_creator/imm_rom_ext:utils.bzl", "imm_rom_ext_section")
+load("//sw/device/silicon_creator/imm_rom_ext:defs.bzl", "DEFAULT_EXEC_ENV")
+load(
+    "//sw/device/silicon_creator/imm_rom_ext:utils.bzl",
+    "create_imm_rom_ext_targets",
+)
 
 package(default_visibility = ["//visibility:public"])
 
 cc_library(
     name = "main_lib",
-    srcs = ["imm_rom_ext.c"],
+    srcs = [
+        "imm_rom_ext.c",
+        "imm_rom_ext_start.S",
+    ],
     hdrs = ["imm_rom_ext.h"],
+    target_compatible_with = [OPENTITAN_CPU],
     deps = [
         ":imm_rom_ext_epmp",
         "//hw/top:flash_ctrl_c_regs",
@@ -52,43 +61,110 @@ cc_library(
 )
 
 ld_library(
-    name = "ld_hello_world",
-    script = "hello_world.ld",
+    name = "ld_common",
+    includes = ["imm_rom_ext_common.ld"],
     deps = [
         "//hw/top_earlgrey/sw/autogen:top_earlgrey_memory",
         "//sw/device:info_sections",
+        "//sw/device/silicon_creator/lib/base:static_critical_sections",
     ],
 )
 
-cc_library(
-    name = "hello_world",
-    srcs = [
-        "hello_world.c",
-        "hello_world_start.S",
+ld_library(
+    name = "ld_slot_a",
+    script = "imm_rom_ext_slot_a.ld",
+    deps = [
+        ":ld_common",
+        "//hw/top_earlgrey/sw/autogen:top_earlgrey_memory",
     ],
-    hdrs = ["hello_world.h"],
-    target_compatible_with = [OPENTITAN_CPU],
+)
+
+ld_library(
+    name = "ld_slot_b",
+    script = "imm_rom_ext_slot_b.ld",
     deps = [
-        "//sw/device/silicon_creator/lib/drivers:uart",
+        ":ld_common",
+        "//hw/top_earlgrey/sw/autogen:top_earlgrey_memory",
+    ],
+)
+
+ld_library(
+    name = "ld_slot_virtual",
+    script = "imm_rom_ext_slot_virtual.ld",
+    deps = [
+        ":ld_common",
+        "//hw/top_earlgrey/sw/autogen:top_earlgrey_memory",
     ],
 )
 
 opentitan_binary(
-    name = "hello_world_binaries",
-    # TODO(#24368): Support multiple executing environments. Currently all
-    # environments derive the same binary so only one environment is kept here,
-    # but we need to support multiple executing environments and make sure
-    # ROM_EXT targets choose the matched environment when linking IMM_ROM_EXT.
-    exec_env = [
-        "//hw/top_earlgrey:fpga_cw340",
+    name = "main_binaries_slot_a",
+    exec_env = DEFAULT_EXEC_ENV,
+    extra_bazel_features = [
+        "minsize",
+        "use_lld",
     ],
-    linker_script = ":ld_hello_world",
+    linker_script = ":ld_slot_a",
+    manifest = "//hw/top_earlgrey:none_manifest",
     deps = [
-        ":hello_world",
+        ":main_lib",
+        "//sw/device/lib/crt",
     ],
 )
 
-imm_rom_ext_section(
-    name = "hello_world_section",
-    srcs = [":hello_world_binaries"],
+[
+    create_imm_rom_ext_targets(
+        src = ":main_binaries_slot_a",
+        base_name = "main_section_slot_a",
+        exec_env = env,
+    )
+    for env in DEFAULT_EXEC_ENV
+]
+
+opentitan_binary(
+    name = "main_binaries_slot_b",
+    exec_env = DEFAULT_EXEC_ENV,
+    extra_bazel_features = [
+        "minsize",
+        "use_lld",
+    ],
+    linker_script = ":ld_slot_b",
+    manifest = "//hw/top_earlgrey:none_manifest",
+    deps = [
+        ":main_lib",
+        "//sw/device/lib/crt",
+    ],
 )
+
+[
+    create_imm_rom_ext_targets(
+        src = ":main_binaries_slot_b",
+        base_name = "main_section_slot_b",
+        exec_env = env,
+    )
+    for env in DEFAULT_EXEC_ENV
+]
+
+opentitan_binary(
+    name = "main_binaries_slot_virtual",
+    exec_env = DEFAULT_EXEC_ENV,
+    extra_bazel_features = [
+        "minsize",
+        "use_lld",
+    ],
+    linker_script = ":ld_slot_virtual",
+    manifest = "//hw/top_earlgrey:none_manifest",
+    deps = [
+        ":main_lib",
+        "//sw/device/lib/crt",
+    ],
+)
+
+[
+    create_imm_rom_ext_targets(
+        src = ":main_binaries_slot_virtual",
+        base_name = "main_section_slot_virtual",
+        exec_env = env,
+    )
+    for env in DEFAULT_EXEC_ENV
+]
diff --git a/sw/device/silicon_creator/imm_rom_ext/defs.bzl b/sw/device/silicon_creator/imm_rom_ext/defs.bzl
index 04ada7e14b651..01d2937c42a5b 100644
--- a/sw/device/silicon_creator/imm_rom_ext/defs.bzl
+++ b/sw/device/silicon_creator/imm_rom_ext/defs.bzl
@@ -2,8 +2,41 @@
 # Licensed under the Apache License, Version 2.0, see LICENSE for details.
 # SPDX-License-Identifier: Apache-2.0
 
+DEFAULT_EXEC_ENV = [
+    "//hw/top_earlgrey:fpga_cw310",
+    "//hw/top_earlgrey:fpga_cw340",
+    "//hw/top_earlgrey:sim_dv_base",
+    "//hw/top_earlgrey:sim_verilator_base",
+    "//hw/top_earlgrey:silicon_creator",
+]
+
 # The target list should contian prebuilt artifacts and run-time build targets.
-IMM_ROM_EXT_TARGETS = {
-    "nop": "//sw/device/silicon_creator/imm_rom_ext/prebuilts:nop_imm_rom_ext",
-    "hello_world": "//sw/device/silicon_creator/imm_rom_ext:hello_world_section",
+SLOT_A_IMM_ROM_EXT_SECTIONS = {
+    "main": [
+        "//sw/device/silicon_creator/imm_rom_ext:main_section_slot_a_fpga_cw310",
+        "//sw/device/silicon_creator/imm_rom_ext:main_section_slot_a_fpga_cw340",
+        "//sw/device/silicon_creator/imm_rom_ext:main_section_slot_a_sim_dv_base",
+        "//sw/device/silicon_creator/imm_rom_ext:main_section_slot_a_sim_verilator_base",
+        "//sw/device/silicon_creator/imm_rom_ext:main_section_slot_a_silicon_creator",
+    ],
+}
+
+SLOT_B_IMM_ROM_EXT_SECTIONS = {
+    "main": [
+        "//sw/device/silicon_creator/imm_rom_ext:main_section_slot_b_fpga_cw310",
+        "//sw/device/silicon_creator/imm_rom_ext:main_section_slot_b_fpga_cw340",
+        "//sw/device/silicon_creator/imm_rom_ext:main_section_slot_b_sim_dv_base",
+        "//sw/device/silicon_creator/imm_rom_ext:main_section_slot_b_sim_verilator_base",
+        "//sw/device/silicon_creator/imm_rom_ext:main_section_slot_b_silicon_creator",
+    ],
+}
+
+SLOT_VIRTUAL_IMM_ROM_EXT_SECTIONS = {
+    "main": [
+        "//sw/device/silicon_creator/imm_rom_ext:main_section_slot_virtual_fpga_cw310",
+        "//sw/device/silicon_creator/imm_rom_ext:main_section_slot_virtual_fpga_cw340",
+        "//sw/device/silicon_creator/imm_rom_ext:main_section_slot_virtual_sim_dv_base",
+        "//sw/device/silicon_creator/imm_rom_ext:main_section_slot_virtual_sim_verilator_base",
+        "//sw/device/silicon_creator/imm_rom_ext:main_section_slot_virtual_silicon_creator",
+    ],
 }
diff --git a/sw/device/silicon_creator/imm_rom_ext/hello_world.c b/sw/device/silicon_creator/imm_rom_ext/hello_world.c
deleted file mode 100644
index 81b350269f418..0000000000000
--- a/sw/device/silicon_creator/imm_rom_ext/hello_world.c
+++ /dev/null
@@ -1,25 +0,0 @@
-// Copyright lowRISC contributors (OpenTitan project).
-// Licensed under the Apache License, Version 2.0, see LICENSE for details.
-// SPDX-License-Identifier: Apache-2.0
-
-#include "sw/device/silicon_creator/imm_rom_ext/hello_world.h"
-
-#include "sw/device/silicon_creator/lib/drivers/uart.h"
-
-void imm_rom_ext_main(void) {
-  // Print "Immutable" to the UART console.
-  //                        l b a t u m m I
-  const uint64_t kStr1 = 0x6c626174756d6d49;
-  //                        e
-  const uint32_t kStr2 = 0x65;
-  const uint32_t kNewline = 0x0a0d;
-  uart_write_imm(kStr1);
-  uart_write_imm(kStr2);
-  uart_write_imm(kNewline);
-
-  // Wait until the UART is done transmitting.
-  while (!uart_tx_idle()) {
-  }
-
-  return;
-}
diff --git a/sw/device/silicon_creator/imm_rom_ext/hello_world.h b/sw/device/silicon_creator/imm_rom_ext/hello_world.h
deleted file mode 100644
index 2932989cb8e76..0000000000000
--- a/sw/device/silicon_creator/imm_rom_ext/hello_world.h
+++ /dev/null
@@ -1,18 +0,0 @@
-// Copyright lowRISC contributors (OpenTitan project).
-// Licensed under the Apache License, Version 2.0, see LICENSE for details.
-// SPDX-License-Identifier: Apache-2.0
-
-#ifndef OPENTITAN_SW_DEVICE_SILICON_CREATOR_IMM_ROM_EXT_HELLO_WORLD_H_
-#define OPENTITAN_SW_DEVICE_SILICON_CREATOR_IMM_ROM_EXT_HELLO_WORLD_H_
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
-void imm_rom_ext_main(void);
-
-#ifdef __cplusplus
-}  // extern "C"
-#endif
-
-#endif  // OPENTITAN_SW_DEVICE_SILICON_CREATOR_IMM_ROM_EXT_HELLO_WORLD_H_
diff --git a/sw/device/silicon_creator/imm_rom_ext/hello_world.ld b/sw/device/silicon_creator/imm_rom_ext/hello_world.ld
deleted file mode 100644
index 47b757cded97d..0000000000000
--- a/sw/device/silicon_creator/imm_rom_ext/hello_world.ld
+++ /dev/null
@@ -1,46 +0,0 @@
-/* Copyright lowRISC contributors (OpenTitan project). */
-/* Licensed under the Apache License, Version 2.0, see LICENSE for details. */
-/* SPDX-License-Identifier: Apache-2.0 */
-
-/**
- * TODO(#24368): Adapt the linker script for real IMM_ROM_EXT. This linker
- * script only works for hello-world IMM_ROM_EXT.
- */
-OUTPUT_ARCH(riscv)
-
-/**
- * Indicate that there are no dynamic libraries, whatsoever.
- */
-__DYNAMIC = 0;
-
-/* DV Log offset (has to be different to other boot stages). */
-_dv_log_offset = 0x10000;
-
-ENTRY(_imm_rom_ext_start_boot)
-
-SECTIONS {
-  .rom_ext_immutable : ALIGN(4) {
-    /* Ibex */
-    *(.vectors)
-    . = ALIGN(256);
-    /* CRT */
-    *(.crt)
-    . = ALIGN(4);
-    /* Text */
-    *(.text)
-    *(.text.*)
-    . = ALIGN(4);
-    /* Read-only Data */
-    *(.srodata)
-    *(.srodata.*)
-    *(.rodata)
-    *(.rodata.*)
-    . = ALIGN(4);
-    *(.data)
-    . = ALIGN(4);
-    *(.bss)
-    . = ALIGN(4);
-  }
-
-  INCLUDE sw/device/info_sections.ld
-}
diff --git a/sw/device/silicon_creator/imm_rom_ext/hello_world_start.S b/sw/device/silicon_creator/imm_rom_ext/hello_world_start.S
deleted file mode 100644
index f90d7a861da8c..0000000000000
--- a/sw/device/silicon_creator/imm_rom_ext/hello_world_start.S
+++ /dev/null
@@ -1,14 +0,0 @@
-// Copyright lowRISC contributors (OpenTitan project).
-// Licensed under the Apache License, Version 2.0, see LICENSE for details.
-// SPDX-License-Identifier: Apache-2.0
-
-// TODO(#24368): Adapt the startup assembly for real IMM_ROM_EXT. This startup
-// assembly only works for hello-world IMM_ROM_EXT.
-#include "hw/top_earlgrey/sw/autogen/top_earlgrey_memory.h"
-
-  .balign 4
-  .global _imm_rom_ext_start_boot
-  .type _imm_rom_ext_start_boot, @function
-_imm_rom_ext_start_boot:
-  tail imm_rom_ext_main
-  .size _imm_rom_ext_start_boot, .-_imm_rom_ext_start_boot
diff --git a/sw/device/silicon_creator/imm_rom_ext/imm_rom_ext_common.ld b/sw/device/silicon_creator/imm_rom_ext/imm_rom_ext_common.ld
new file mode 100644
index 0000000000000..03731afd856fd
--- /dev/null
+++ b/sw/device/silicon_creator/imm_rom_ext/imm_rom_ext_common.ld
@@ -0,0 +1,150 @@
+/* Copyright lowRISC contributors (OpenTitan project). */
+/* Licensed under the Apache License, Version 2.0, see LICENSE for details. */
+/* SPDX-License-Identifier: Apache-2.0 */
+
+/**
+ * TODO(#24368): Adapt the linker script for real IMM_ROM_EXT. This linker
+ * script only works for hello-world IMM_ROM_EXT.
+ */
+
+OUTPUT_ARCH(riscv)
+
+/**
+ * Indicate that there are no dynamic libraries, whatsoever.
+ */
+__DYNAMIC = 0;
+
+/* DV Log offset (has to be different to other boot stages). */
+_dv_log_offset = 0x10000;
+
+ENTRY(_imm_rom_ext_start_boot)
+
+SECTIONS {
+  /**
+   * Ibex interrupt vector.
+   *
+   * This has to be set up at a 256-byte offset, so that we can use it with
+   * Ibex.
+   */
+  .vectors : ALIGN(256) {
+    _text_start = .;
+    _rom_ext_immutable_start = .;
+    KEEP(*(.vectors))
+  } > rom_ext_flash
+
+  /**
+   * C runtime (CRT) section, containing program initialization code.
+   */
+  .crt : ALIGN(4) {
+    KEEP(*(.crt))
+  } > rom_ext_flash
+
+  /**
+   * Standard text section, containing program code.
+   */
+  .text : ALIGN(4) {
+    *(.text)
+    *(.text.*)
+
+    /* Ensure section end is word-aligned. */
+    . = ALIGN(4);
+  } > rom_ext_flash
+
+  /**
+   * Shutdown text section, containing shutdown function(s).
+   *
+   * This must be the last executable section in the ROM_EXT flash image.
+   */
+  .shutdown : ALIGN(4) {
+    *(.shutdown)
+    *(.shutdown.*)
+
+    /* Ensure section end is word-aligned. */
+    . = ALIGN(4);
+    _text_end = .;
+  } > rom_ext_flash
+
+  /**
+   * Read-only data section, containing all large compile-time constants, like
+   * strings.
+   */
+  .rodata : ALIGN(4) {
+    /* Small read-only data comes before regular read-only data for the same
+     * reasons as in the data section */
+    *(.srodata)
+    *(.srodata.*)
+    *(.rodata)
+    *(.rodata.*)
+  } > rom_ext_flash
+
+  /**
+   * Critical static data that is accessible by both the ROM and the ROM
+   * extension.
+   */
+  INCLUDE sw/device/silicon_creator/lib/base/static_critical.ld
+
+  /**
+   * Mutable data section, at the bottom of ram_main. This will be initialized
+   * from flash at runtime by the CRT.
+   *
+   * Load this by copying the bytes from [_data_init_start, _data_init_end] into
+   * the range [_data_start, _data_end].
+   */
+  .data : ALIGN(4) {
+    _data_start = .;
+    _data_init_start = LOADADDR(.data);
+
+    /* This will get loaded into `gp`, and the linker will use that register for
+     * accessing data within [-2048,2047] of `__global_pointer$`.
+     *
+     * This is much cheaper (for small data) than materializing the
+     * address and loading from that (which will take one extra instruction).
+     */
+    __global_pointer$ = . + 2048;
+
+    /* Small data should come before larger data. This helps to ensure small
+     * globals are within 2048 bytes of the value of `gp`, making their accesses
+     * hopefully only take one instruction. */
+    *(.sdata)
+    *(.sdata.*)
+
+    /* Other data will likely need multiple instructions to load, so we're less
+     * concerned about address materialisation taking more than one instruction.
+     */
+    *(.data)
+    *(.data.*)
+
+    /* Ensure section end is word-aligned. */
+    . = ALIGN(4);
+    _data_end = .;
+    _data_init_end = LOADADDR(.data) + SIZEOF(.data);
+    _rom_ext_immutable_end = LOADADDR(.data) + SIZEOF(.data);
+
+    /* This puts it in ram_main at runtime (for the VMA), but puts the section
+     * into flash for load time (for the LMA). This is why `_data_init_*` uses
+     * `LOADADDR`.
+     *
+     * Using `AT>` means we don't have to keep track of the next free part of
+     * flash, as we do in our other linker scripts. */
+  } > ram_main AT> rom_ext_flash
+
+  /**
+   * Standard BSS section. This will be zeroed at runtime by the CRT.
+   */
+  .bss : ALIGN(4) {
+    _bss_start = .;
+
+    /* Small BSS comes before regular BSS for the same reasons as in the data
+     * section */
+    *(.sbss)
+    *(.sbss.*)
+    *(.bss)
+    *(.bss.*)
+
+    /* Ensure section end is word-aligned. */
+    . = ALIGN(4);
+    _bss_end = .;
+  } > ram_main
+
+  INCLUDE sw/device/info_sections.ld
+}
diff --git a/sw/device/silicon_creator/imm_rom_ext/imm_rom_ext_slot_a.ld b/sw/device/silicon_creator/imm_rom_ext/imm_rom_ext_slot_a.ld
new file mode 100644
index 0000000000000..e7751d59bf4fc
--- /dev/null
+++ b/sw/device/silicon_creator/imm_rom_ext/imm_rom_ext_slot_a.ld
@@ -0,0 +1,27 @@
+/* Copyright lowRISC contributors (OpenTitan project). */
+/* Licensed under the Apache License, Version 2.0, see LICENSE for details. */
+/* SPDX-License-Identifier: Apache-2.0 */
+
+/**
+ * Linker script for an OpenTitan IMM_ROM_EXT.
+ *
+ * Portions of this file are Ibex-specific.
+ *
+ * The IMM_ROM_EXT is kept in the .rom_ext_immutable section in ROM, after the
+ * .manifest section. This linker script targets to use slot A address, and
+ * the addresses are similar to the linker script rom_ext_slot_a.ld that ROM_EXT
+ * is using.
+ */
+
+INCLUDE hw/top_earlgrey/sw/autogen/top_earlgrey_memory.ld
+
+/**
+ * Symbols to be used in the setup of the address translation for IMM_ROM_EXT.
+ */
+
+MEMORY {
+  imm_rom_ext_slot_a(rx) : ORIGIN = ORIGIN(eflash) + 0x400, LENGTH = LENGTH(eflash) / 2 - 0x400
+}
+REGION_ALIAS("rom_ext_flash", imm_rom_ext_slot_a);
+
+INCLUDE sw/device/silicon_creator/imm_rom_ext/imm_rom_ext_common.ld
diff --git a/sw/device/silicon_creator/imm_rom_ext/imm_rom_ext_slot_b.ld b/sw/device/silicon_creator/imm_rom_ext/imm_rom_ext_slot_b.ld
new file mode 100644
index 0000000000000..35540731a9888
--- /dev/null
+++ b/sw/device/silicon_creator/imm_rom_ext/imm_rom_ext_slot_b.ld
@@ -0,0 +1,28 @@
+/* Copyright lowRISC contributors (OpenTitan project). */
+/* Licensed under the Apache License, Version 2.0, see LICENSE for details. */
+/* SPDX-License-Identifier: Apache-2.0 */
+
+/**
+ * Linker script for an OpenTitan IMM_ROM_EXT.
+ *
+ * Portions of this file are Ibex-specific.
+ *
+ * The IMM_ROM_EXT is kept in the .rom_ext_immutable section in ROM, after the
+ * .manifest section. This linker script targets to use slot B address, and
+ * the addresses are similar to the linker script rom_ext_slot_b.ld that ROM_EXT
+ * is using.
+ */
+
+INCLUDE hw/top_earlgrey/sw/autogen/top_earlgrey_memory.ld
+
+/**
+ * Symbols to be used in the setup of the address translation for IMM_ROM_EXT.
+ */
+
+/* Slot B starts at the half-size mark of the eFlash. */
+MEMORY {
+  imm_rom_ext_slot_b(rx) : ORIGIN = ORIGIN(eflash) + LENGTH(eflash) / 2 + 0x400, LENGTH = LENGTH(eflash) / 2 - 0x400
+}
+REGION_ALIAS("rom_ext_flash", imm_rom_ext_slot_b);
+
+INCLUDE sw/device/silicon_creator/imm_rom_ext/imm_rom_ext_common.ld
diff --git a/sw/device/silicon_creator/imm_rom_ext/imm_rom_ext_slot_virtual.ld b/sw/device/silicon_creator/imm_rom_ext/imm_rom_ext_slot_virtual.ld
new file mode 100644
index 0000000000000..47d3dcd372bfd
--- /dev/null
+++ b/sw/device/silicon_creator/imm_rom_ext/imm_rom_ext_slot_virtual.ld
@@ -0,0 +1,27 @@
+/* Copyright lowRISC contributors (OpenTitan project). */
+/* Licensed under the Apache License, Version 2.0, see LICENSE for details. */
+/* SPDX-License-Identifier: Apache-2.0 */
+
+/**
+ * Linker script for an OpenTitan IMM_ROM_EXT.
+ *
+ * Portions of this file are Ibex-specific.
+ *
+ * The IMM_ROM_EXT is kept in the .rom_ext_immutable section in ROM, after the
+ * .manifest section. This linker script targets to use virtual address, and
+ * the addresses are similar to the linker script rom_ext_slot_virtual.ld that
+ * ROM_EXT is using.
+ */
+
+INCLUDE hw/top_earlgrey/sw/autogen/top_earlgrey_memory.ld
+
+/**
+ * Symbols to be used in the setup of the address translation for IMM_ROM_EXT.
+ */
+
+MEMORY {
+  imm_rom_ext_virtual(rx) : ORIGIN = ORIGIN(rom_ext_virtual) + 0x400, LENGTH = 0x80000 - 0x400
+}
+REGION_ALIAS("rom_ext_flash", imm_rom_ext_virtual);
+
+INCLUDE sw/device/silicon_creator/imm_rom_ext/imm_rom_ext_common.ld
diff --git a/sw/device/silicon_creator/imm_rom_ext/imm_rom_ext_start.S b/sw/device/silicon_creator/imm_rom_ext/imm_rom_ext_start.S
new file mode 100644
index 0000000000000..cf382cf8cd5ae
--- /dev/null
+++ b/sw/device/silicon_creator/imm_rom_ext/imm_rom_ext_start.S
@@ -0,0 +1,91 @@
+// Copyright lowRISC contributors (OpenTitan project).
+// Licensed under the Apache License, Version 2.0, see LICENSE for details.
+// SPDX-License-Identifier: Apache-2.0
+
+#include "hw/top_earlgrey/sw/autogen/top_earlgrey_memory.h"
+#include "sw/device/lib/base/hardened_asm.h"
+
+  /**
+   * NOTE: The "ax" flag below is necessary to ensure that this section
+   * is allocated executable space in ROM by the linker.
+   */
+  .section .crt, "ax"
+
+  /**
+   * Entry point.
+   *
+   * This symbol is jumped to from `rom_boot` using the `entry_point` field
+   * of the manifest.
+   */
+  .balign 4
+  .global _imm_rom_ext_start_boot
+  .type _imm_rom_ext_start_boot, @function
+_imm_rom_ext_start_boot:
+
+  .option push
+  .option norelax
+
+  /**
+   * Set up the global pointer `gp`.
+   */
+  la gp, __global_pointer$
+
+  .option pop
+
+  /**
+   * Save registers.
+   */
+  addi sp, sp, -8
+  sw ra, 4(sp)
+
+  /**
+   * Disable Interrupts.
+   *
+   * We cannot disable exceptions, or Ibex's non-maskable interrupts (interrupt
+   * 31), so we still need to be careful.
+   */
+
+  // Clear `MIE` field of `mstatus` (disable interrupts globally).
+  csrci mstatus, 0x8
+
+  /**
+   * Clear all the machine-defined interrupts, `MEIE`, `MTIE`, and `MSIE` fields
+   * of `mie`.
+   */
+  li   t0, 0xFFFF0888
+  csrc mie, t0
+
+  /**
+   * Setup C Runtime
+   */
+  /**
+   * Initialize the `.data` section in RAM from ROM.
+   */
+  la   a0, _data_start
+  la   a1, _data_end
+  la   a2, _data_init_start
+  jal  ra, crt_section_copy
+
+  /**
+   * Initialize the `.bss` section.
+   *
+   * We do this despite zeroing all of SRAM above, so that we still zero `.bss`
+   * once we've enabled SRAM scrambling.
+   */
+  la   a0, _bss_start
+  la   a1, _bss_end
+  jal  ra, crt_section_clear
+
+
+  /**
+   * Restore registers.
+   */
+  lw ra, 4(sp)
+  addi sp, sp, 8
+
+  /**
+   * Jump to IMM_ROM_EXT.
+   */
+  tail imm_rom_ext_main
+
+  .size _imm_rom_ext_start_boot, .-_imm_rom_ext_start_boot
diff --git a/sw/device/silicon_creator/imm_rom_ext/utils.bzl b/sw/device/silicon_creator/imm_rom_ext/utils.bzl
index 1c881c2860ae2..d013047f20f72 100644
--- a/sw/device/silicon_creator/imm_rom_ext/utils.bzl
+++ b/sw/device/silicon_creator/imm_rom_ext/utils.bzl
@@ -5,6 +5,7 @@
 load("@rules_cc//cc:action_names.bzl", "OBJ_COPY_ACTION_NAME")
 load("@rules_cc//cc:find_cc_toolchain.bzl", "find_cc_toolchain")
 load("@lowrisc_opentitan//rules:rv.bzl", "rv_rule")
+load("@lowrisc_opentitan//rules/opentitan:exec_env.bzl", "ExecEnvInfo")
 
 def _bin_to_imm_rom_ext_object_impl(ctx):
     cc_toolchain = find_cc_toolchain(ctx)
@@ -20,9 +21,8 @@ def _bin_to_imm_rom_ext_object_impl(ctx):
     )
 
     outputs = []
-    for src in ctx.files.srcs:
-        if src.extension != "bin":
-            continue
+    exec_env_name = ctx.attr.exec_env[ExecEnvInfo].exec_env
+    for src in ctx.attr.src.output_groups[exec_env_name + "_binary"].to_list():
         object = ctx.actions.declare_file(
             "{}.{}".format(
                 src.basename.replace("." + src.extension, ""),
@@ -45,23 +45,40 @@ def _bin_to_imm_rom_ext_object_impl(ctx):
             executable = objcopy,
         )
         outputs.append(object)
-    return [DefaultInfo(files = depset(outputs), runfiles = ctx.runfiles(files = outputs))]
+    if len(outputs) != 1:
+        fail("Generated zero or more than one binary: {}".format(outputs))
+    return [
+        DefaultInfo(
+            files = depset(outputs),
+            runfiles = ctx.runfiles(files = outputs),
+        ),
+    ]
 
 bin_to_imm_rom_ext_object = rv_rule(
     implementation = _bin_to_imm_rom_ext_object_impl,
     attrs = {
-        "srcs": attr.label_list(allow_files = True),
+        "src": attr.label(allow_files = True),
+        "exec_env": attr.label(
+            providers = [ExecEnvInfo],
+            doc = "The execution environment for this target.",
+        ),
         "_cc_toolchain": attr.label(default = Label("@bazel_tools//tools/cpp:current_cc_toolchain")),
     },
     fragments = ["cpp"],
     toolchains = ["@rules_cc//cc:toolchain_type"],
 )
 
-def imm_rom_ext_section(name, srcs):
-    object_target_name = name + "_object"
-    bin_to_imm_rom_ext_object(name = object_target_name, srcs = srcs)
+def create_imm_rom_ext_targets(src, exec_env, base_name):
+    exec_env_name = Label(exec_env).name
+    object_target_name = "{}_{}_object".format(base_name, exec_env_name)
+    cc_import_name = "{}_{}".format(base_name, exec_env_name)
+    bin_to_imm_rom_ext_object(
+        name = object_target_name,
+        src = src,
+        exec_env = exec_env,
+    )
     native.cc_import(
-        name = name,
+        name = cc_import_name,
         objects = [object_target_name],
         data = [object_target_name],
         alwayslink = 1,
diff --git a/sw/device/silicon_creator/rom_ext/BUILD b/sw/device/silicon_creator/rom_ext/BUILD
index 97b9bc066606f..1e145f06a9279 100644
--- a/sw/device/silicon_creator/rom_ext/BUILD
+++ b/sw/device/silicon_creator/rom_ext/BUILD
@@ -14,7 +14,9 @@ load(
 )
 load(
     "//sw/device/silicon_creator/imm_rom_ext:defs.bzl",
-    "IMM_ROM_EXT_TARGETS",
+    "SLOT_A_IMM_ROM_EXT_SECTIONS",
+    "SLOT_B_IMM_ROM_EXT_SECTIONS",
+    "SLOT_VIRTUAL_IMM_ROM_EXT_SECTIONS",
 )
 
 package(default_visibility = ["//visibility:public"])
@@ -233,7 +235,6 @@ cc_library(
         "//sw/device/lib/base:memory",
         "//sw/device/lib/base:stdasm",
         "//sw/device/lib/runtime:hart",
-        "//sw/device/silicon_creator/imm_rom_ext:main_lib",
         "//sw/device/silicon_creator/lib:boot_data",
         "//sw/device/silicon_creator/lib:boot_log",
         "//sw/device/silicon_creator/lib:dbg_print",
@@ -291,6 +292,7 @@ opentitan_binary(
         "minsize",
         "use_lld",
     ],
+    immutable_rom_ext_sections = SLOT_A_IMM_ROM_EXT_SECTIONS["main"],
     linker_script = ":ld_slot_a",
     manifest = ":manifest",
     spx_key = {"//sw/device/silicon_creator/rom/keys/fake/spx:prod_key_0_spx": "prod_key_0"},
@@ -319,6 +321,7 @@ opentitan_binary(
         "minsize",
         "use_lld",
     ],
+    immutable_rom_ext_sections = SLOT_B_IMM_ROM_EXT_SECTIONS["main"],
     linker_script = ":ld_slot_b",
     manifest = ":manifest",
     spx_key = {"//sw/device/silicon_creator/rom/keys/fake/spx:prod_key_0_spx": "prod_key_0"},
@@ -347,6 +350,7 @@ opentitan_binary(
         "minsize",
         "use_lld",
     ],
+    immutable_rom_ext_sections = SLOT_VIRTUAL_IMM_ROM_EXT_SECTIONS["main"],
     linker_script = ":ld_slot_virtual",
     manifest = ":manifest",
     deps = [
@@ -374,6 +378,7 @@ opentitan_binary(
             "minsize",
             "use_lld",
         ],
+        immutable_rom_ext_sections = imm_rom_ext_sections,
         linker_script = ":ld_slot_virtual",
         manifest = ":manifest",
         deps = [
@@ -382,11 +387,9 @@ opentitan_binary(
             "//sw/device/silicon_creator/lib:manifest_def",
             "//sw/device/silicon_creator/lib/ownership:test_owner",
             "//sw/device/silicon_creator/lib/ownership/keys/fake",
-        ] + [
-            imm_rom_ext_target,
         ],
     )
-    for name, imm_rom_ext_target in IMM_ROM_EXT_TARGETS.items()
+    for name, imm_rom_ext_sections in SLOT_VIRTUAL_IMM_ROM_EXT_SECTIONS.items()
 ]
 
 manifest(d = {
diff --git a/sw/device/silicon_creator/rom_ext/e2e/verified_boot/BUILD b/sw/device/silicon_creator/rom_ext/e2e/verified_boot/BUILD
index a25d750ab8c4a..bb69b14a06d69 100644
--- a/sw/device/silicon_creator/rom_ext/e2e/verified_boot/BUILD
+++ b/sw/device/silicon_creator/rom_ext/e2e/verified_boot/BUILD
@@ -23,7 +23,7 @@ load(
 )
 load(
     "//sw/device/silicon_creator/imm_rom_ext:defs.bzl",
-    "IMM_ROM_EXT_TARGETS",
+    "SLOT_VIRTUAL_IMM_ROM_EXT_SECTIONS",
 )
 
 package(default_visibility = ["//visibility:public"])
@@ -48,7 +48,7 @@ filegroup(
         rom_ext = "//sw/device/silicon_creator/rom_ext:rom_ext_with_{}_imm_slot_virtual".format(name),
         visibility = ["//visibility:private"],
     )
-    for name in IMM_ROM_EXT_TARGETS
+    for name in SLOT_VIRTUAL_IMM_ROM_EXT_SECTIONS
 ]
 
 [
@@ -62,7 +62,7 @@ filegroup(
         ],
         visibility = ["//visibility:private"],
     )
-    for name in IMM_ROM_EXT_TARGETS
+    for name in SLOT_VIRTUAL_IMM_ROM_EXT_SECTIONS
 ]
 
 _POSITIONS = {
@@ -139,7 +139,7 @@ _POSITIONS = {
         "success": "rom_ext_slot = AA__\r\n",
         "otp_img": ":otp_img_with_{}_imm_romext_enabled".format(name),
     }
-    for name in IMM_ROM_EXT_TARGETS
+    for name in SLOT_VIRTUAL_IMM_ROM_EXT_SECTIONS
 }
 
 [
diff --git a/sw/device/silicon_creator/rom_ext/rom_ext.c b/sw/device/silicon_creator/rom_ext/rom_ext.c
index c9df0d54c3cad..1cd63a1f2ee09 100644
--- a/sw/device/silicon_creator/rom_ext/rom_ext.c
+++ b/sw/device/silicon_creator/rom_ext/rom_ext.c
@@ -10,7 +10,6 @@
 #include "sw/device/lib/base/memory.h"
 #include "sw/device/lib/base/stdasm.h"
 #include "sw/device/lib/runtime/hart.h"
-#include "sw/device/silicon_creator/imm_rom_ext/imm_rom_ext.h"
 #include "sw/device/silicon_creator/lib/base/boot_measurements.h"
 #include "sw/device/silicon_creator/lib/base/chip.h"
 #include "sw/device/silicon_creator/lib/base/sec_mmio.h"
@@ -602,11 +601,6 @@ static rom_error_t rom_ext_start(boot_data_t *boot_data, boot_log_t *boot_log) {
 }
 
 void rom_ext_main(void) {
-  // TODO(opentitan#24368): Call immutable main in .rom_ext_immutable.
-  // The immutable rom_ext startup code is not ready yet, so we call it here
-  // to avoid breaking tests.
-  imm_rom_ext_main();
-
   rom_ext_check_rom_expectations();
   boot_data_t boot_data;
   boot_log_t *boot_log = &retention_sram_get()->creator.boot_log;
@@ -632,10 +626,3 @@ void rom_ext_exception_handler(void);
 OT_USED
 OT_ALIAS("rom_ext_interrupt_handler")
 void rom_ext_nmi_handler(void);
-
-// A no-op immutable rom_ext fallback to avoid breaking tests before the
-// proper bazel target is ready.
-// TODO(opentitan#24368): Remove this nop fallback.
-OT_USED
-OT_SECTION(".rom_ext_immutable.fallback")
-void imm_rom_ext_placeholder(void) {}
diff --git a/sw/device/silicon_creator/rom_ext/sival/BUILD b/sw/device/silicon_creator/rom_ext/sival/BUILD
index 7db34c0cd79df..ac2a597615e20 100644
--- a/sw/device/silicon_creator/rom_ext/sival/BUILD
+++ b/sw/device/silicon_creator/rom_ext/sival/BUILD
@@ -11,6 +11,11 @@ load(
     "ROM_EXT_VERSION",
 )
 load("@rules_pkg//pkg:tar.bzl", "pkg_tar")
+load(
+    "//sw/device/silicon_creator/imm_rom_ext:defs.bzl",
+    "SLOT_A_IMM_ROM_EXT_SECTIONS",
+    "SLOT_B_IMM_ROM_EXT_SECTIONS",
+)
 
 package(default_visibility = ["//visibility:public"])
 
@@ -49,6 +54,7 @@ opentitan_binary(
         "minsize",
         "use_lld",
     ],
+    immutable_rom_ext_sections = SLOT_A_IMM_ROM_EXT_SECTIONS["main"],
     linker_script = "//sw/device/silicon_creator/rom_ext:ld_slot_a",
     linkopts = LINK_ORDER,
     manifest = ":manifest_sival",
@@ -75,6 +81,7 @@ opentitan_binary(
         "minsize",
         "use_lld",
     ],
+    immutable_rom_ext_sections = SLOT_B_IMM_ROM_EXT_SECTIONS["main"],
     linker_script = "//sw/device/silicon_creator/rom_ext:ld_slot_b",
     linkopts = LINK_ORDER,
     manifest = ":manifest_sival",
@@ -97,6 +104,7 @@ opentitan_binary(
         "minsize",
         "use_lld",
     ],
+    immutable_rom_ext_sections = SLOT_A_IMM_ROM_EXT_SECTIONS["main"],
     linker_script = "//sw/device/silicon_creator/rom_ext:ld_slot_a",
     linkopts = LINK_ORDER,
     deps = [
@@ -117,6 +125,7 @@ opentitan_binary(
         "minsize",
         "use_lld",
     ],
+    immutable_rom_ext_sections = SLOT_B_IMM_ROM_EXT_SECTIONS["main"],
     linker_script = "//sw/device/silicon_creator/rom_ext:ld_slot_b",
     linkopts = LINK_ORDER,
     deps = [