On 25.12.18 09:26, Heinrich Schuchardt wrote:
> Refactor the switch from supervisor to hypervisor to a new function called at
> the beginning of do_bootefi().
Why?
>
> Signed-off-by: Heinrich Schuchardt <xypron.g...@gmx.de>
> ---
> With this patch I am just moving around the switch from supervisor to
> hypervisor mode within the EFI subsystem. Similar switching also occurs
> in all other boot commands (cf. arch/arm/lib/bootm.c).
>
> Why are we running the U-Boot console in supervisor mode at all? Wouldn't
> it be advisable for security reasons to switch to hypervisor mode before
> entering the console?
>
> Best regards
>
> Heinrich
> ---
> cmd/bootefi.c | 109 ++++++++++++++++++++++----------------------------
> 1 file changed, 47 insertions(+), 62 deletions(-)
>
> diff --git a/cmd/bootefi.c b/cmd/bootefi.c
> index 1aaf5319e13..277d4863953 100644
> --- a/cmd/bootefi.c
> +++ b/cmd/bootefi.c
> @@ -31,9 +31,9 @@ DECLARE_GLOBAL_DATA_PTR;
> #define OBJ_LIST_NOT_INITIALIZED 1
>
> static efi_status_t efi_obj_list_initialized = OBJ_LIST_NOT_INITIALIZED;
> -
> static struct efi_device_path *bootefi_image_path;
> static struct efi_device_path *bootefi_device_path;
> +struct jmp_buf_data hyp_jmp;
>
> /* Initialize and populate EFI object list */
> efi_status_t efi_init_obj_list(void)
> @@ -122,6 +122,50 @@ void __weak allow_unaligned(void)
> {
> }
>
> +/**
> + * entry_hyp() - entry point when switching to hypervisor mode
> + */
> +static void entry_hyp(void)
Potentially unused function depending on config settings?
> +{
> + dcache_enable();
> + debug("Reached HYP mode\n");
HYP is a 32bit ARM term. AArch64 does not know what HYP is - there it's EL2.
Also keep in mind that this is not 100% ARM specific. We might see
something along the lines of this logic on RISC-V eventually too.
> + longjmp(&hyp_jmp, 1);
> +}
> +
> +/**
> + * leave_supervisor() - switch to hypervisor mode
> + */
> +static void leave_supervisor(void)
That's not necessarily what this function does. It may switch from
EL1->EL2 or from EL3->EL2.
> +{
> +#ifdef CONFIG_ARMV7_NONSEC
> + static bool is_nonsec;
> +
> + if (armv7_boot_nonsec() && !is_nonsec) {
> + if (setjmp(&hyp_jmp))
> + return;
> + dcache_disable(); /* flush cache before switch to HYP */
> + armv7_init_nonsec();
> + is_nonsec = true;
> + secure_ram_addr(_do_nonsec_entry)(entry_hyp, 0, 0, 0);
> + }
> +#endif
> +
> +#ifdef CONFIG_ARM64
> + /* On AArch64 we need to make sure we call our payload in < EL3 */
> + if (current_el() == 3) {
> + if (setjmp(&hyp_jmp))
> + return;
> + smp_kick_all_cpus();
> + dcache_disable(); /* flush cache before switch to EL2 */
> +
> + /* Move into EL2 and keep running there */
> + armv8_switch_to_el2(0, 0, 0, 0, (uintptr_t)entry_hyp,
> + ES_TO_AARCH64);
> + }
> +#endif
> + return;
> +}
> +
> /*
> * Set the load options of an image from an environment variable.
> *
> @@ -233,34 +277,6 @@ static efi_status_t efi_do_enter(
> return ret;
> }
>
> -#ifdef CONFIG_ARM64
> -static efi_status_t efi_run_in_el2(EFIAPI efi_status_t (*entry)(
> - efi_handle_t image_handle, struct efi_system_table *st),
> - efi_handle_t image_handle, struct efi_system_table *st)
> -{
> - /* Enable caches again */
> - dcache_enable();
> -
> - return efi_do_enter(image_handle, st, entry);
> -}
> -#endif
> -
> -#ifdef CONFIG_ARMV7_NONSEC
> -static bool is_nonsec;
> -
> -static efi_status_t efi_run_in_hyp(EFIAPI efi_status_t (*entry)(
> - efi_handle_t image_handle, struct efi_system_table *st),
> - efi_handle_t image_handle, struct efi_system_table *st)
> -{
> - /* Enable caches again */
> - dcache_enable();
> -
> - is_nonsec = true;
> -
> - return efi_do_enter(image_handle, st, entry);
> -}
> -#endif
> -
> /*
> * efi_carve_out_dt_rsv() - Carve out DT reserved memory ranges
> *
> @@ -440,39 +456,6 @@ static efi_status_t do_bootefi_exec(void *efi,
> goto err_prepare;
> }
>
> -#ifdef CONFIG_ARM64
> - /* On AArch64 we need to make sure we call our payload in < EL3 */
> - if (current_el() == 3) {
> - smp_kick_all_cpus();
> - dcache_disable(); /* flush cache before switch to EL2 */
> -
> - /* Move into EL2 and keep running there */
> - armv8_switch_to_el2((ulong)entry,
> - (ulong)&image_obj->header,
> - (ulong)&systab, 0, (ulong)efi_run_in_el2,
> - ES_TO_AARCH64);
> -
> - /* Should never reach here, efi exits with longjmp */
> - while (1) { }
> - }
> -#endif
> -
> -#ifdef CONFIG_ARMV7_NONSEC
> - if (armv7_boot_nonsec() && !is_nonsec) {
> - dcache_disable(); /* flush cache before switch to HYP */
> -
> - armv7_init_nonsec();
> - secure_ram_addr(_do_nonsec_entry)(
> - efi_run_in_hyp,
> - (uintptr_t)entry,
> - (uintptr_t)&image_obj->header,
> - (uintptr_t)&systab);
> -
> - /* Should never reach here, efi exits with longjmp */
> - while (1) { }
> - }
> -#endif
> -
> ret = efi_do_enter(&image_obj->header, &systab, entry);
>
> err_prepare:
> @@ -558,6 +541,8 @@ static int do_bootefi(cmd_tbl_t *cmdtp, int flag, int
> argc, char * const argv[])
> /* Allow unaligned memory access */
> allow_unaligned();
>
> + leave_supervisor();
This means you're potentially executing object initialization code in a
mode it wasn't meant to be run in. Is that a smart thing to do? It's
definitely more than just refactoring.
If you just find the do_bootefi_exec() function too hard to read,
refactoring it into calling an arch_efi_do_enter() call is probably
smarter. Then aarch64 and 32bit arm can just provide their own "get be
into target mode" functions within their own arch directories.
Alex
> +
> /* Initialize EFI drivers */
> r = efi_init_obj_list();
> if (r != EFI_SUCCESS) {
>
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