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SubjectRe: [PATCH] Modify UEFI anti-bricking code
On Thu, Jun 06, 2013 at 10:25:42AM +0100, Matt Fleming wrote:
> On Thu, 06 Jun, at 03:40:26PM, joeyli wrote:
> > OK, I moved volatile checking to the top of the function.
> > New version, version 3 diff result like the following.
>
> Thanks. This is what I've now got queued up.
>
> ---
>
> >From 118428bf3b207d9b390a27f32dfef6dc2979078d Mon Sep 17 00:00:00 2001
> From: Matthew Garrett <matthew.garrett@nebula.com>
> Date: Sat, 1 Jun 2013 16:06:20 -0400
> Subject: [PATCH] Modify UEFI anti-bricking code
>
> This patch reworks the UEFI anti-bricking code, including an effective
> reversion of cc5a080c and 31ff2f20. It turns out that calling
> QueryVariableInfo() from boot services results in some firmware
> implementations jumping to physical addresses even after entering virtual
> mode, so until we have 1:1 mappings for UEFI runtime space this isn't
> going to work so well.
>
> Reverting these gets us back to the situation where we'd refuse to create
> variables on some systems because they classify deleted variables as "used"
> until the firmware triggers a garbage collection run, which they won't do
> until they reach a lower threshold. This results in it being impossible to
> install a bootloader, which is unhelpful.
>
> Feedback from Samsung indicates that the firmware doesn't need more than
> 5KB of storage space for its own purposes, so that seems like a reasonable
> threshold. However, there's still no guarantee that a platform will attempt
> garbage collection merely because it drops below this threshold. It seems
> that this is often only triggered if an attempt to write generates a
> genuine EFI_OUT_OF_RESOURCES error. We can force that by attempting to
> create a variable larger than the remaining space. This should fail, but if
> it somehow succeeds we can then immediately delete it.
>
> I've tested this on the UEFI machines I have available, but I don't have
> a Samsung and so can't verify that it avoids the bricking problem.
>
> Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>
> Signed-off-by: Lee, Chun-Y <jlee@suse.com> [ dummy variable cleanup ]
> Signed-off-by: Matt Fleming <matt.fleming@intel.com>
> ---
> arch/x86/boot/compressed/eboot.c | 47 ---------
> arch/x86/include/asm/efi.h | 7 --
> arch/x86/include/uapi/asm/bootparam.h | 1 -
> arch/x86/platform/efi/efi.c | 188 ++++++++++++----------------------
> 4 files changed, 65 insertions(+), 178 deletions(-)
>
> diff --git a/arch/x86/boot/compressed/eboot.c b/arch/x86/boot/compressed/eboot.c
> index 35ee62f..c205035 100644
> --- a/arch/x86/boot/compressed/eboot.c
> +++ b/arch/x86/boot/compressed/eboot.c
> @@ -251,51 +251,6 @@ static void find_bits(unsigned long mask, u8 *pos, u8 *size)
> *size = len;
> }
>
> -static efi_status_t setup_efi_vars(struct boot_params *params)
> -{
> - struct setup_data *data;
> - struct efi_var_bootdata *efidata;
> - u64 store_size, remaining_size, var_size;
> - efi_status_t status;
> -
> - if (sys_table->runtime->hdr.revision < EFI_2_00_SYSTEM_TABLE_REVISION)
> - return EFI_UNSUPPORTED;
> -
> - data = (struct setup_data *)(unsigned long)params->hdr.setup_data;
> -
> - while (data && data->next)
> - data = (struct setup_data *)(unsigned long)data->next;
> -
> - status = efi_call_phys4((void *)sys_table->runtime->query_variable_info,
> - EFI_VARIABLE_NON_VOLATILE |
> - EFI_VARIABLE_BOOTSERVICE_ACCESS |
> - EFI_VARIABLE_RUNTIME_ACCESS, &store_size,
> - &remaining_size, &var_size);
> -
> - if (status != EFI_SUCCESS)
> - return status;
> -
> - status = efi_call_phys3(sys_table->boottime->allocate_pool,
> - EFI_LOADER_DATA, sizeof(*efidata), &efidata);
> -
> - if (status != EFI_SUCCESS)
> - return status;
> -
> - efidata->data.type = SETUP_EFI_VARS;
> - efidata->data.len = sizeof(struct efi_var_bootdata) -
> - sizeof(struct setup_data);
> - efidata->data.next = 0;
> - efidata->store_size = store_size;
> - efidata->remaining_size = remaining_size;
> - efidata->max_var_size = var_size;
> -
> - if (data)
> - data->next = (unsigned long)efidata;
> - else
> - params->hdr.setup_data = (unsigned long)efidata;
> -
> -}
> -
> static efi_status_t setup_efi_pci(struct boot_params *params)
> {
> efi_pci_io_protocol *pci;
> @@ -1202,8 +1157,6 @@ struct boot_params *efi_main(void *handle, efi_system_table_t *_table,
>
> setup_graphics(boot_params);
>
> - setup_efi_vars(boot_params);
> -
> setup_efi_pci(boot_params);
>
> status = efi_call_phys3(sys_table->boottime->allocate_pool,
> diff --git a/arch/x86/include/asm/efi.h b/arch/x86/include/asm/efi.h
> index 2fb5d58..60c89f3 100644
> --- a/arch/x86/include/asm/efi.h
> +++ b/arch/x86/include/asm/efi.h
> @@ -102,13 +102,6 @@ extern void efi_call_phys_epilog(void);
> extern void efi_unmap_memmap(void);
> extern void efi_memory_uc(u64 addr, unsigned long size);
>
> -struct efi_var_bootdata {
> - struct setup_data data;
> - u64 store_size;
> - u64 remaining_size;
> - u64 max_var_size;
> -};
> -
> #ifdef CONFIG_EFI
>
> static inline bool efi_is_native(void)
> diff --git a/arch/x86/include/uapi/asm/bootparam.h b/arch/x86/include/uapi/asm/bootparam.h
> index 0874424..c15ddaf 100644
> --- a/arch/x86/include/uapi/asm/bootparam.h
> +++ b/arch/x86/include/uapi/asm/bootparam.h
> @@ -6,7 +6,6 @@
> #define SETUP_E820_EXT 1
> #define SETUP_DTB 2
> #define SETUP_PCI 3
> -#define SETUP_EFI_VARS 4
>
> /* ram_size flags */
> #define RAMDISK_IMAGE_START_MASK 0x07FF
> diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
> index 82089d8..5ae2eb0 100644
> --- a/arch/x86/platform/efi/efi.c
> +++ b/arch/x86/platform/efi/efi.c
> @@ -42,7 +42,6 @@
> #include <linux/io.h>
> #include <linux/reboot.h>
> #include <linux/bcd.h>
> -#include <linux/ucs2_string.h>
>
> #include <asm/setup.h>
> #include <asm/efi.h>
> @@ -54,12 +53,12 @@
>
> #define EFI_DEBUG 1
>
> -/*
> - * There's some additional metadata associated with each
> - * variable. Intel's reference implementation is 60 bytes - bump that
> - * to account for potential alignment constraints
> - */
> -#define VAR_METADATA_SIZE 64
> +#define EFI_MIN_RESERVE 5120
> +
> +#define EFI_DUMMY_GUID \
> + EFI_GUID(0x4424ac57, 0xbe4b, 0x47dd, 0x9e, 0x97, 0xed, 0x50, 0xf0, 0x9f, 0x92, 0xa9)
> +
> +static efi_char16_t efi_dummy_name[6] = { 'D', 'U', 'M', 'M', 'Y', 0 };
>
> struct efi __read_mostly efi = {
> .mps = EFI_INVALID_TABLE_ADDR,
> @@ -79,13 +78,6 @@ struct efi_memory_map memmap;
> static struct efi efi_phys __initdata;
> static efi_system_table_t efi_systab __initdata;
>
> -static u64 efi_var_store_size;
> -static u64 efi_var_remaining_size;
> -static u64 efi_var_max_var_size;
> -static u64 boot_used_size;
> -static u64 boot_var_size;
> -static u64 active_size;
> -
> unsigned long x86_efi_facility;
>
> /*
> @@ -188,53 +180,8 @@ static efi_status_t virt_efi_get_next_variable(unsigned long *name_size,
> efi_char16_t *name,
> efi_guid_t *vendor)
> {
> - efi_status_t status;
> - static bool finished = false;
> - static u64 var_size;
> -
> - status = efi_call_virt3(get_next_variable,
> - name_size, name, vendor);
> -
> - if (status == EFI_NOT_FOUND) {
> - finished = true;
> - if (var_size < boot_used_size) {
> - boot_var_size = boot_used_size - var_size;
> - active_size += boot_var_size;
> - } else {
> - printk(KERN_WARNING FW_BUG "efi: Inconsistent initial sizes\n");
> - }
> - }
> -
> - if (boot_used_size && !finished) {
> - unsigned long size = 0;
> - u32 attr;
> - efi_status_t s;
> - void *tmp;
> -
> - s = virt_efi_get_variable(name, vendor, &attr, &size, NULL);
> -
> - if (s != EFI_BUFFER_TOO_SMALL || !size)
> - return status;
> -
> - tmp = kmalloc(size, GFP_ATOMIC);
> -
> - if (!tmp)
> - return status;
> -
> - s = virt_efi_get_variable(name, vendor, &attr, &size, tmp);
> -
> - if (s == EFI_SUCCESS && (attr & EFI_VARIABLE_NON_VOLATILE)) {
> - var_size += size;
> - var_size += ucs2_strsize(name, 1024);
> - active_size += size;
> - active_size += VAR_METADATA_SIZE;
> - active_size += ucs2_strsize(name, 1024);
> - }
> -
> - kfree(tmp);
> - }
> -
> - return status;
> + return efi_call_virt3(get_next_variable,
> + name_size, name, vendor);
> }
>
> static efi_status_t virt_efi_set_variable(efi_char16_t *name,
> @@ -243,34 +190,9 @@ static efi_status_t virt_efi_set_variable(efi_char16_t *name,
> unsigned long data_size,
> void *data)
> {
> - efi_status_t status;
> - u32 orig_attr = 0;
> - unsigned long orig_size = 0;
> -
> - status = virt_efi_get_variable(name, vendor, &orig_attr, &orig_size,
> - NULL);
> -
> - if (status != EFI_BUFFER_TOO_SMALL)
> - orig_size = 0;
> -
> - status = efi_call_virt5(set_variable,
> - name, vendor, attr,
> - data_size, data);
> -
> - if (status == EFI_SUCCESS) {
> - if (orig_size) {
> - active_size -= orig_size;
> - active_size -= ucs2_strsize(name, 1024);
> - active_size -= VAR_METADATA_SIZE;
> - }
> - if (data_size) {
> - active_size += data_size;
> - active_size += ucs2_strsize(name, 1024);
> - active_size += VAR_METADATA_SIZE;
> - }
> - }
> -
> - return status;
> + return efi_call_virt5(set_variable,
> + name, vendor, attr,
> + data_size, data);
> }
>
> static efi_status_t virt_efi_query_variable_info(u32 attr,
> @@ -786,9 +708,6 @@ void __init efi_init(void)
> char vendor[100] = "unknown";
> int i = 0;
> void *tmp;
> - struct setup_data *data;
> - struct efi_var_bootdata *efi_var_data;
> - u64 pa_data;
>
> #ifdef CONFIG_X86_32
> if (boot_params.efi_info.efi_systab_hi ||
> @@ -806,22 +725,6 @@ void __init efi_init(void)
> if (efi_systab_init(efi_phys.systab))
> return;
>
> - pa_data = boot_params.hdr.setup_data;
> - while (pa_data) {
> - data = early_ioremap(pa_data, sizeof(*efi_var_data));
> - if (data->type == SETUP_EFI_VARS) {
> - efi_var_data = (struct efi_var_bootdata *)data;
> -
> - efi_var_store_size = efi_var_data->store_size;
> - efi_var_remaining_size = efi_var_data->remaining_size;
> - efi_var_max_var_size = efi_var_data->max_var_size;
> - }
> - pa_data = data->next;
> - early_iounmap(data, sizeof(*efi_var_data));
> - }
> -
> - boot_used_size = efi_var_store_size - efi_var_remaining_size;
> -
> set_bit(EFI_SYSTEM_TABLES, &x86_efi_facility);
>
> /*
> @@ -1085,6 +988,13 @@ void __init efi_enter_virtual_mode(void)
> runtime_code_page_mkexec();
>
> kfree(new_memmap);
> +
> + /* clean DUMMY object */
> + efi.set_variable(efi_dummy_name, &EFI_DUMMY_GUID,
> + EFI_VARIABLE_NON_VOLATILE |
> + EFI_VARIABLE_BOOTSERVICE_ACCESS |
> + EFI_VARIABLE_RUNTIME_ACCESS,
> + 0, NULL);
> }
>
> /*
> @@ -1136,33 +1046,65 @@ efi_status_t efi_query_variable_store(u32 attributes, unsigned long size)
> efi_status_t status;
> u64 storage_size, remaining_size, max_size;
>
> + if (!(attributes & EFI_VARIABLE_NON_VOLATILE))
> + return 0;
> +
> status = efi.query_variable_info(attributes, &storage_size,
> &remaining_size, &max_size);
> if (status != EFI_SUCCESS)
> return status;
>
> - if (!max_size && remaining_size > size)
> - printk_once(KERN_ERR FW_BUG "Broken EFI implementation"
> - " is returning MaxVariableSize=0\n");
> /*
> * Some firmware implementations refuse to boot if there's insufficient
> * space in the variable store. We account for that by refusing the
> * write if permitting it would reduce the available space to under
> - * 50%. However, some firmware won't reclaim variable space until
> - * after the used (not merely the actively used) space drops below
> - * a threshold. We can approximate that case with the value calculated
> - * above. If both the firmware and our calculations indicate that the
> - * available space would drop below 50%, refuse the write.
> + * 5KB. This figure was provided by Samsung, so should be safe.
> */
> + if ((remaining_size - size < EFI_MIN_RESERVE) &&
> + !efi_no_storage_paranoia) {
> +
> + /*
> + * Triggering garbage collection may require that the firmware
> + * generate a real EFI_OUT_OF_RESOURCES error. We can force
> + * that by attempting to use more space than is available.
> + */
> + unsigned long dummy_size = remaining_size + 1024;

This looks like it will try to allocate more than the remaining size.
Is that intended?


> + void *dummy = kmalloc(dummy_size, GFP_ATOMIC);
> +
> + status = efi.set_variable(efi_dummy_name, &EFI_DUMMY_GUID,
> + EFI_VARIABLE_NON_VOLATILE |
> + EFI_VARIABLE_BOOTSERVICE_ACCESS |
> + EFI_VARIABLE_RUNTIME_ACCESS,
> + dummy_size, dummy);
> +
> + if (status == EFI_SUCCESS) {
> + /*
> + * This should have failed, so if it didn't make sure
> + * that we delete it...
> + */
> + efi.set_variable(efi_dummy_name, &EFI_DUMMY_GUID,
> + EFI_VARIABLE_NON_VOLATILE |
> + EFI_VARIABLE_BOOTSERVICE_ACCESS |
> + EFI_VARIABLE_RUNTIME_ACCESS,
> + 0, dummy);
> + }
>
> - if (!storage_size || size > remaining_size ||
> - (max_size && size > max_size))
> - return EFI_OUT_OF_RESOURCES;
> + /*
> + * The runtime code may now have triggered a garbage collection
> + * run, so check the variable info again
> + */
> + status = efi.query_variable_info(attributes, &storage_size,
> + &remaining_size, &max_size);
>
> - if (!efi_no_storage_paranoia &&
> - ((active_size + size + VAR_METADATA_SIZE > storage_size / 2) &&
> - (remaining_size - size < storage_size / 2)))
> - return EFI_OUT_OF_RESOURCES;
> + if (status != EFI_SUCCESS)
> + return status;
> +
> + /*
> + * There still isn't enough room, so return an error
> + */
> + if (remaining_size - size < EFI_MIN_RESERVE)
> + return EFI_OUT_OF_RESOURCES;
> + }
>
> return EFI_SUCCESS;
> }
> --
> 1.8.1.4
>
> --
> Matt Fleming, Intel Open Source Technology Center

--
Russ Anderson, OS RAS/Partitioning Project Lead
SGI - Silicon Graphics Inc rja@sgi.com


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