Nitro Enclaves can only boot EIF files which are a combination of
kernel, initramfs and cmdline in a single file. When the kernel image is
not an EIF, treat it like a kernel image and assemble an EIF image on
the fly. This way, users can call QEMU with a direct
kernel/initrd/cmdline combination and everything "just works".
Signed-off-by: Alexander Graf <graf@amazon.com>
---
hw/core/eif.h | 3 ++
hw/nitro/machine.c | 116 +++++++++++++++++++++++++++++++++++++++++++
hw/nitro/meson.build | 2 +-
3 files changed, 120 insertions(+), 1 deletion(-)
diff --git a/hw/core/eif.h b/hw/core/eif.h
index a3412377a9..0c432dbc2d 100644
--- a/hw/core/eif.h
+++ b/hw/core/eif.h
@@ -12,6 +12,7 @@
#define HW_CORE_EIF_H
#define MAX_SECTIONS 32
+#define EIF_HDR_ARCH_ARM64 0x1
/* members are ordered according to field order in .eif file */
typedef struct EifHeader {
@@ -49,6 +50,8 @@ enum EifSectionTypes {
EIF_SECTION_MAX = 6,
};
+#define EIF_MAGIC { '.', 'e', 'i', 'f' }
+
bool read_eif_file(const char *eif_path, const char *machine_initrd,
char **kernel_path, char **initrd_path,
char **kernel_cmdline, uint8_t *image_sha384,
diff --git a/hw/nitro/machine.c b/hw/nitro/machine.c
index e28c8e9bf5..8849959359 100644
--- a/hw/nitro/machine.c
+++ b/hw/nitro/machine.c
@@ -32,9 +32,104 @@
#include "system/nitro-accel.h"
#include "qemu/accel.h"
#include "hw/arm/machines-qom.h"
+#include "hw/core/eif.h"
+#include <zlib.h> /* for crc32 */
#define EIF_LOAD_ADDR (8 * 1024 * 1024)
+static bool is_eif(char *eif, gsize len)
+{
+ const char eif_magic[] = EIF_MAGIC;
+
+ return len >= sizeof(eif_magic) &&
+ !memcmp(eif, eif_magic, sizeof(eif_magic));
+}
+
+static void build_eif_section(EifHeader *hdr, GByteArray *buf, uint16_t type,
+ const char *data, uint64_t size)
+{
+ uint16_t section = be16_to_cpu(hdr->section_cnt);
+ EifSectionHeader shdr = {
+ .section_type = cpu_to_be16(type),
+ .flags = 0,
+ .section_size = cpu_to_be64(size),
+ };
+
+ hdr->section_offsets[section] = cpu_to_be64(buf->len);
+ hdr->section_sizes[section] = cpu_to_be64(size);
+
+ g_byte_array_append(buf, (const uint8_t *)&shdr, sizeof(shdr));
+ if (size) {
+ g_byte_array_append(buf, (const uint8_t *)data, size);
+ }
+
+ hdr->section_cnt = cpu_to_be16(section + 1);
+}
+
+/*
+ * Nitro Enclaves only support loading EIF files. When the user provides
+ * a Linux kernel, initrd and cmdline, convert them into EIF format.
+ */
+static char *build_eif(const char *kernel_data, gsize kernel_size,
+ const char *initrd_path, const char *cmdline,
+ gsize *out_size, Error **errp)
+{
+ g_autofree char *initrd_data = NULL;
+ static const char metadata[] = "{}";
+ size_t metadata_len = sizeof(metadata) - 1;
+ gsize initrd_size = 0;
+ GByteArray *buf;
+ EifHeader hdr;
+ uint32_t crc = 0;
+ size_t cmdline_len;
+
+ if (initrd_path) {
+ if (!g_file_get_contents(initrd_path, &initrd_data,
+ &initrd_size, NULL)) {
+ error_setg(errp, "Failed to read initrd '%s'", initrd_path);
+ return NULL;
+ }
+ }
+
+ buf = g_byte_array_new();
+
+ cmdline_len = cmdline ? strlen(cmdline) : 0;
+
+ hdr = (EifHeader) {
+ .magic = EIF_MAGIC,
+ .version = cpu_to_be16(4),
+ .flags = cpu_to_be16(target_aarch64() ? EIF_HDR_ARCH_ARM64 : 0),
+ };
+
+ g_byte_array_append(buf, (const uint8_t *)&hdr, sizeof(hdr));
+
+ /* Kernel */
+ build_eif_section(&hdr, buf, EIF_SECTION_KERNEL, kernel_data, kernel_size);
+
+ /* Command line */
+ build_eif_section(&hdr, buf, EIF_SECTION_CMDLINE, cmdline, cmdline_len);
+
+ /* Initramfs */
+ build_eif_section(&hdr, buf, EIF_SECTION_RAMDISK, initrd_data, initrd_size);
+
+ /* Metadata */
+ build_eif_section(&hdr, buf, EIF_SECTION_METADATA, metadata, metadata_len);
+
+ /*
+ * Patch the header into the buffer first (with real section offsets
+ * and sizes), then compute CRC over everything except the CRC field.
+ */
+ memcpy(buf->data, &hdr, sizeof(hdr));
+ crc = crc32(crc, buf->data, offsetof(EifHeader, eif_crc32));
+ crc = crc32(crc, &buf->data[sizeof(hdr)], buf->len - sizeof(hdr));
+
+ /* Finally write the CRC into the in-buffer header */
+ ((EifHeader *)buf->data)->eif_crc32 = cpu_to_be32(crc);
+
+ *out_size = buf->len;
+ return (char *)g_byte_array_free(buf, false);
+}
+
static void nitro_machine_init(MachineState *machine)
{
const char *eif_path = machine->kernel_filename;
@@ -74,6 +169,27 @@ static void nitro_machine_init(MachineState *machine)
error_report("nitro: failed to read EIF '%s'", eif_path);
exit(1);
}
+
+ if (!is_eif(eif_data, eif_size)) {
+ char *kernel_data = eif_data;
+ gsize kernel_size = eif_size;
+ Error *err = NULL;
+
+ /*
+ * The user gave us a non-EIF kernel, likely a Linux kernel image.
+ * Assemble an EIF file from it, the -initrd and the -append arguments,
+ * so that users can perform a natural direct kernel boot.
+ */
+ eif_data = build_eif(kernel_data, kernel_size, machine->initrd_filename,
+ machine->kernel_cmdline, &eif_size, &err);
+ if (!eif_data) {
+ error_report_err(err);
+ exit(1);
+ }
+
+ g_free(kernel_data);
+ }
+
address_space_write(&address_space_memory, EIF_LOAD_ADDR,
MEMTXATTRS_UNSPECIFIED, eif_data, eif_size);
diff --git a/hw/nitro/meson.build b/hw/nitro/meson.build
index e3f1895890..b9bd0d4300 100644
--- a/hw/nitro/meson.build
+++ b/hw/nitro/meson.build
@@ -1,4 +1,4 @@
system_ss.add(when: 'CONFIG_NITRO_VSOCK_BUS', if_true: files('nitro-vsock-bus.c'))
system_ss.add(when: 'CONFIG_NITRO_SERIAL_VSOCK', if_true: files('serial-vsock.c'))
system_ss.add(when: 'CONFIG_NITRO_HEARTBEAT', if_true: files('heartbeat.c'))
-system_ss.add(when: 'CONFIG_NITRO_MACHINE', if_true: files('machine.c'))
+system_ss.add(when: 'CONFIG_NITRO_MACHINE', if_true: [files('machine.c'), zlib])
--
2.47.1
Amazon Web Services Development Center Germany GmbH
Tamara-Danz-Str. 13
10243 Berlin
Geschaeftsfuehrung: Christof Hellmis, Andreas Stieger
Eingetragen am Amtsgericht Charlottenburg unter HRB 257764 B
Sitz: Berlin
Ust-ID: DE 365 538 597On Thu, Feb 26, 2026 at 4:09 AM Alexander Graf <graf@amazon.com> wrote:
>
> Nitro Enclaves can only boot EIF files which are a combination of
> kernel, initramfs and cmdline in a single file. When the kernel image is
> not an EIF, treat it like a kernel image and assemble an EIF image on
> the fly. This way, users can call QEMU with a direct
> kernel/initrd/cmdline combination and everything "just works".
>
> Signed-off-by: Alexander Graf <graf@amazon.com>
> ---
> hw/core/eif.h | 3 ++
> hw/nitro/machine.c | 116 +++++++++++++++++++++++++++++++++++++++++++
> hw/nitro/meson.build | 2 +-
> 3 files changed, 120 insertions(+), 1 deletion(-)
>
Reviewed-by: Dorjoy Chowdhury <dorjoychy111@gmail.com>
> diff --git a/hw/core/eif.h b/hw/core/eif.h
> index a3412377a9..0c432dbc2d 100644
> --- a/hw/core/eif.h
> +++ b/hw/core/eif.h
> @@ -12,6 +12,7 @@
> #define HW_CORE_EIF_H
>
> #define MAX_SECTIONS 32
> +#define EIF_HDR_ARCH_ARM64 0x1
>
> /* members are ordered according to field order in .eif file */
> typedef struct EifHeader {
> @@ -49,6 +50,8 @@ enum EifSectionTypes {
> EIF_SECTION_MAX = 6,
> };
>
> +#define EIF_MAGIC { '.', 'e', 'i', 'f' }
> +
> bool read_eif_file(const char *eif_path, const char *machine_initrd,
> char **kernel_path, char **initrd_path,
> char **kernel_cmdline, uint8_t *image_sha384,
> diff --git a/hw/nitro/machine.c b/hw/nitro/machine.c
> index e28c8e9bf5..8849959359 100644
> --- a/hw/nitro/machine.c
> +++ b/hw/nitro/machine.c
> @@ -32,9 +32,104 @@
> #include "system/nitro-accel.h"
> #include "qemu/accel.h"
> #include "hw/arm/machines-qom.h"
> +#include "hw/core/eif.h"
> +#include <zlib.h> /* for crc32 */
>
> #define EIF_LOAD_ADDR (8 * 1024 * 1024)
>
> +static bool is_eif(char *eif, gsize len)
> +{
> + const char eif_magic[] = EIF_MAGIC;
> +
> + return len >= sizeof(eif_magic) &&
> + !memcmp(eif, eif_magic, sizeof(eif_magic));
> +}
> +
> +static void build_eif_section(EifHeader *hdr, GByteArray *buf, uint16_t type,
> + const char *data, uint64_t size)
> +{
> + uint16_t section = be16_to_cpu(hdr->section_cnt);
> + EifSectionHeader shdr = {
> + .section_type = cpu_to_be16(type),
> + .flags = 0,
> + .section_size = cpu_to_be64(size),
> + };
> +
> + hdr->section_offsets[section] = cpu_to_be64(buf->len);
> + hdr->section_sizes[section] = cpu_to_be64(size);
> +
> + g_byte_array_append(buf, (const uint8_t *)&shdr, sizeof(shdr));
> + if (size) {
> + g_byte_array_append(buf, (const uint8_t *)data, size);
> + }
> +
> + hdr->section_cnt = cpu_to_be16(section + 1);
> +}
> +
> +/*
> + * Nitro Enclaves only support loading EIF files. When the user provides
> + * a Linux kernel, initrd and cmdline, convert them into EIF format.
> + */
> +static char *build_eif(const char *kernel_data, gsize kernel_size,
> + const char *initrd_path, const char *cmdline,
> + gsize *out_size, Error **errp)
> +{
> + g_autofree char *initrd_data = NULL;
> + static const char metadata[] = "{}";
> + size_t metadata_len = sizeof(metadata) - 1;
> + gsize initrd_size = 0;
> + GByteArray *buf;
> + EifHeader hdr;
> + uint32_t crc = 0;
> + size_t cmdline_len;
> +
> + if (initrd_path) {
> + if (!g_file_get_contents(initrd_path, &initrd_data,
> + &initrd_size, NULL)) {
> + error_setg(errp, "Failed to read initrd '%s'", initrd_path);
> + return NULL;
> + }
> + }
> +
> + buf = g_byte_array_new();
> +
> + cmdline_len = cmdline ? strlen(cmdline) : 0;
> +
> + hdr = (EifHeader) {
> + .magic = EIF_MAGIC,
> + .version = cpu_to_be16(4),
> + .flags = cpu_to_be16(target_aarch64() ? EIF_HDR_ARCH_ARM64 : 0),
> + };
> +
> + g_byte_array_append(buf, (const uint8_t *)&hdr, sizeof(hdr));
> +
> + /* Kernel */
> + build_eif_section(&hdr, buf, EIF_SECTION_KERNEL, kernel_data, kernel_size);
> +
> + /* Command line */
> + build_eif_section(&hdr, buf, EIF_SECTION_CMDLINE, cmdline, cmdline_len);
> +
> + /* Initramfs */
> + build_eif_section(&hdr, buf, EIF_SECTION_RAMDISK, initrd_data, initrd_size);
> +
> + /* Metadata */
> + build_eif_section(&hdr, buf, EIF_SECTION_METADATA, metadata, metadata_len);
> +
> + /*
> + * Patch the header into the buffer first (with real section offsets
> + * and sizes), then compute CRC over everything except the CRC field.
> + */
> + memcpy(buf->data, &hdr, sizeof(hdr));
> + crc = crc32(crc, buf->data, offsetof(EifHeader, eif_crc32));
> + crc = crc32(crc, &buf->data[sizeof(hdr)], buf->len - sizeof(hdr));
> +
> + /* Finally write the CRC into the in-buffer header */
> + ((EifHeader *)buf->data)->eif_crc32 = cpu_to_be32(crc);
> +
> + *out_size = buf->len;
> + return (char *)g_byte_array_free(buf, false);
> +}
> +
> static void nitro_machine_init(MachineState *machine)
> {
> const char *eif_path = machine->kernel_filename;
> @@ -74,6 +169,27 @@ static void nitro_machine_init(MachineState *machine)
> error_report("nitro: failed to read EIF '%s'", eif_path);
> exit(1);
> }
> +
> + if (!is_eif(eif_data, eif_size)) {
> + char *kernel_data = eif_data;
> + gsize kernel_size = eif_size;
> + Error *err = NULL;
> +
> + /*
> + * The user gave us a non-EIF kernel, likely a Linux kernel image.
> + * Assemble an EIF file from it, the -initrd and the -append arguments,
> + * so that users can perform a natural direct kernel boot.
> + */
> + eif_data = build_eif(kernel_data, kernel_size, machine->initrd_filename,
> + machine->kernel_cmdline, &eif_size, &err);
> + if (!eif_data) {
> + error_report_err(err);
> + exit(1);
> + }
> +
> + g_free(kernel_data);
> + }
> +
> address_space_write(&address_space_memory, EIF_LOAD_ADDR,
> MEMTXATTRS_UNSPECIFIED, eif_data, eif_size);
>
> diff --git a/hw/nitro/meson.build b/hw/nitro/meson.build
> index e3f1895890..b9bd0d4300 100644
> --- a/hw/nitro/meson.build
> +++ b/hw/nitro/meson.build
> @@ -1,4 +1,4 @@
> system_ss.add(when: 'CONFIG_NITRO_VSOCK_BUS', if_true: files('nitro-vsock-bus.c'))
> system_ss.add(when: 'CONFIG_NITRO_SERIAL_VSOCK', if_true: files('serial-vsock.c'))
> system_ss.add(when: 'CONFIG_NITRO_HEARTBEAT', if_true: files('heartbeat.c'))
> -system_ss.add(when: 'CONFIG_NITRO_MACHINE', if_true: files('machine.c'))
> +system_ss.add(when: 'CONFIG_NITRO_MACHINE', if_true: [files('machine.c'), zlib])
> --
> 2.47.1
>
>
>
>
> Amazon Web Services Development Center Germany GmbH
> Tamara-Danz-Str. 13
> 10243 Berlin
> Geschaeftsfuehrung: Christof Hellmis, Andreas Stieger
> Eingetragen am Amtsgericht Charlottenburg unter HRB 257764 B
> Sitz: Berlin
> Ust-ID: DE 365 538 597
>
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