Thread (12 messages) 12 messages, 3 authors, 2020-10-12

Re: [PATCH 1/6] efistub: pass uefi secureboot flag via fdt params

From: Ard Biesheuvel <ardb@kernel.org>
Date: 2020-09-11 17:06:16
Also in: linux-doc, linux-efi, linux-integrity, lkml

On Fri, 4 Sep 2020 at 10:29, Chester Lin [off-list ref] wrote:
Add a new UEFI parameter: "linux,uefi-secure-boot" in fdt boot params
as other architectures have done in their own boot data. For example,
the boot_params->secure_boot in x86.

Signed-off-by: Chester Lin <redacted>
Why do we need this flag? Can't the OS simply check the variable directly?
quoted hunk ↗ jump to hunk
---
 drivers/firmware/efi/libstub/fdt.c | 39 +++++++++++++++++++++++++++++-
 1 file changed, 38 insertions(+), 1 deletion(-)
diff --git a/drivers/firmware/efi/libstub/fdt.c b/drivers/firmware/efi/libstub/fdt.c
index 11ecf3c4640e..c9a341e4715f 100644
--- a/drivers/firmware/efi/libstub/fdt.c
+++ b/drivers/firmware/efi/libstub/fdt.c
@@ -136,6 +136,10 @@ static efi_status_t update_fdt(void *orig_fdt, unsigned long orig_fdt_size,
        if (status)
                goto fdt_set_fail;

+       status = fdt_setprop_var(fdt, node, "linux,uefi-secure-boot", fdt_val32);
+       if (status)
+               goto fdt_set_fail;
+
        if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) {
                efi_status_t efi_status;
@@ -199,6 +203,24 @@ static efi_status_t update_fdt_memmap(void *fdt, struct efi_boot_memmap *map)
        return EFI_SUCCESS;
 }

+static efi_status_t update_fdt_secboot(void *fdt, u32 secboot)
+{
+       int node = fdt_path_offset(fdt, "/chosen");
+       u32 fdt_val32;
+       int err;
+
+       if (node < 0)
+               return EFI_LOAD_ERROR;
+
+       fdt_val32 = cpu_to_fdt32(secboot);
+
+       err = fdt_setprop_inplace_var(fdt, node, "linux,uefi-secure-boot", fdt_val32);
+       if (err)
+               return EFI_LOAD_ERROR;
+
+       return EFI_SUCCESS;
+}
+
 struct exit_boot_struct {
        efi_memory_desc_t       *runtime_map;
        int                     *runtime_entry_count;
@@ -208,6 +230,9 @@ struct exit_boot_struct {
 static efi_status_t exit_boot_func(struct efi_boot_memmap *map,
                                   void *priv)
 {
+       efi_status_t status;
+       enum efi_secureboot_mode secboot_status;
+       u32 secboot_var = 0;
        struct exit_boot_struct *p = priv;
        /*
         * Update the memory map with virtual addresses. The function will also
@@ -217,7 +242,19 @@ static efi_status_t exit_boot_func(struct efi_boot_memmap *map,
        efi_get_virtmap(*map->map, *map->map_size, *map->desc_size,
                        p->runtime_map, p->runtime_entry_count);

-       return update_fdt_memmap(p->new_fdt_addr, map);
+       status = update_fdt_memmap(p->new_fdt_addr, map);
+
+       if (status != EFI_SUCCESS)
+               return status;
+
+       secboot_status = efi_get_secureboot();
+
+       if (secboot_status == efi_secureboot_mode_enabled)
+               secboot_var = 1;
+
+       status = update_fdt_secboot(p->new_fdt_addr, secboot_var);
+
+       return status;
 }

 #ifndef MAX_FDT_SIZE
--
2.26.1
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