* Re: [PATCH] efi: stub: prefer mirrored memory for randomized allocations
@ 2022-05-05 13:43 ` Kefeng Wang
0 siblings, 0 replies; 12+ messages in thread
From: Kefeng Wang @ 2022-05-05 13:43 UTC (permalink / raw)
To: Ard Biesheuvel, linux-efi; +Cc: linux-arm-kernel, mawupeng1, linux-mm
On 2022/5/3 23:21, Ard Biesheuvel wrote:
> If the system exposes memory regions with the EFI_MORE_RELIABLE
> attribute, it is implied that it is intended to be used for allocations
> that are relatively important, such as the kernel's static image.
>
> Since efi_random_alloc() is mostly (only) used for allocating space for
> the kernel image, let's update it to take this into account, and
> disregard all memory without the EFI_MORE_RELIABLE attribute if there is
> sufficient memory available that does have this attribute.
>
> Note that this change only affects booting with randomization enabled.
> In other cases, the EFI stub runs the kernel image in place unless its
> placement is unsuitable for some reason (i.e., misaligned, or its BSS
> overlaps with another allocation), and it is left to the bootloader to
> ensure that the kernel was loaded into EFI_MORE_RELIABLE memory if this
> is desired.
>
> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> ---
> drivers/firmware/efi/libstub/randomalloc.c | 11 +++++++++++
> 1 file changed, 11 insertions(+)
>
> diff --git a/drivers/firmware/efi/libstub/randomalloc.c b/drivers/firmware/efi/libstub/randomalloc.c
> index 724155b9e10d..07a762910312 100644
> --- a/drivers/firmware/efi/libstub/randomalloc.c
> +++ b/drivers/firmware/efi/libstub/randomalloc.c
> @@ -56,6 +56,7 @@ efi_status_t efi_random_alloc(unsigned long size,
> unsigned long random_seed)
> {
> unsigned long map_size, desc_size, total_slots = 0, target_slot;
> + unsigned long total_mirrored_slots = 0;
> unsigned long buff_size;
> efi_status_t status;
> efi_memory_desc_t *memory_map;
> @@ -86,8 +87,14 @@ efi_status_t efi_random_alloc(unsigned long size,
> slots = get_entry_num_slots(md, size, ilog2(align));
> MD_NUM_SLOTS(md) = slots;
> total_slots += slots;
> + if (md->attribute & EFI_MEMORY_MORE_RELIABLE)
> + total_mirrored_slots += slots;
> }
>
> + /* only consider mirrored slots for randomization if any exist */
> + if (total_mirrored_slots > 0)
> + total_slots = total_mirrored_slots;
> +
The kernel will check 4G lower limit to enable kernelcore=mirror feature.
Do we need some fallback mechanism in case of small mirror slots which
leads to fail allocation for Image?
> /* find a random number between 0 and total_slots */
> target_slot = (total_slots * (u64)(random_seed & U32_MAX)) >> 32;
>
> @@ -107,6 +114,10 @@ efi_status_t efi_random_alloc(unsigned long size,
> efi_physical_addr_t target;
> unsigned long pages;
>
> + if (total_mirrored_slots > 0 &&
> + !(md->attribute & EFI_MEMORY_MORE_RELIABLE))
> + continue;
> +
> if (target_slot >= MD_NUM_SLOTS(md)) {
> target_slot -= MD_NUM_SLOTS(md);
> continue;
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH] efi: stub: prefer mirrored memory for randomized allocations
2022-05-05 13:43 ` Kefeng Wang
@ 2022-05-05 16:12 ` Ard Biesheuvel
-1 siblings, 0 replies; 12+ messages in thread
From: Ard Biesheuvel @ 2022-05-05 16:12 UTC (permalink / raw)
To: Kefeng Wang; +Cc: linux-efi, Linux ARM, Wupeng Ma, Linux Memory Management List
On Thu, 5 May 2022 at 15:43, Kefeng Wang <wangkefeng.wang@huawei.com> wrote:
>
>
> On 2022/5/3 23:21, Ard Biesheuvel wrote:
> > If the system exposes memory regions with the EFI_MORE_RELIABLE
> > attribute, it is implied that it is intended to be used for allocations
> > that are relatively important, such as the kernel's static image.
> >
> > Since efi_random_alloc() is mostly (only) used for allocating space for
> > the kernel image, let's update it to take this into account, and
> > disregard all memory without the EFI_MORE_RELIABLE attribute if there is
> > sufficient memory available that does have this attribute.
> >
> > Note that this change only affects booting with randomization enabled.
> > In other cases, the EFI stub runs the kernel image in place unless its
> > placement is unsuitable for some reason (i.e., misaligned, or its BSS
> > overlaps with another allocation), and it is left to the bootloader to
> > ensure that the kernel was loaded into EFI_MORE_RELIABLE memory if this
> > is desired.
> >
> > Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> > ---
> > drivers/firmware/efi/libstub/randomalloc.c | 11 +++++++++++
> > 1 file changed, 11 insertions(+)
> >
> > diff --git a/drivers/firmware/efi/libstub/randomalloc.c b/drivers/firmware/efi/libstub/randomalloc.c
> > index 724155b9e10d..07a762910312 100644
> > --- a/drivers/firmware/efi/libstub/randomalloc.c
> > +++ b/drivers/firmware/efi/libstub/randomalloc.c
> > @@ -56,6 +56,7 @@ efi_status_t efi_random_alloc(unsigned long size,
> > unsigned long random_seed)
> > {
> > unsigned long map_size, desc_size, total_slots = 0, target_slot;
> > + unsigned long total_mirrored_slots = 0;
> > unsigned long buff_size;
> > efi_status_t status;
> > efi_memory_desc_t *memory_map;
> > @@ -86,8 +87,14 @@ efi_status_t efi_random_alloc(unsigned long size,
> > slots = get_entry_num_slots(md, size, ilog2(align));
> > MD_NUM_SLOTS(md) = slots;
> > total_slots += slots;
> > + if (md->attribute & EFI_MEMORY_MORE_RELIABLE)
> > + total_mirrored_slots += slots;
> > }
> >
> > + /* only consider mirrored slots for randomization if any exist */
> > + if (total_mirrored_slots > 0)
> > + total_slots = total_mirrored_slots;
> > +
>
> The kernel will check 4G lower limit to enable kernelcore=mirror feature.
>
Why? I mean, why is 4G a magic number also on arm64?
> Do we need some fallback mechanism in case of small mirror slots which
>
> leads to fail allocation for Image?
>
This code only counts slots that are large enough to hold the Image so
this can never happen. If total_mirrored_slots > 0, there is at least
one possible placement of the kernel where it falls entirely inside a
EFI_MORE_RELIABLE region.
>
> > /* find a random number between 0 and total_slots */
> > target_slot = (total_slots * (u64)(random_seed & U32_MAX)) >> 32;
> >
> > @@ -107,6 +114,10 @@ efi_status_t efi_random_alloc(unsigned long size,
> > efi_physical_addr_t target;
> > unsigned long pages;
> >
> > + if (total_mirrored_slots > 0 &&
> > + !(md->attribute & EFI_MEMORY_MORE_RELIABLE))
> > + continue;
> > +
> > if (target_slot >= MD_NUM_SLOTS(md)) {
> > target_slot -= MD_NUM_SLOTS(md);
> > continue;
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH] efi: stub: prefer mirrored memory for randomized allocations
@ 2022-05-05 16:12 ` Ard Biesheuvel
0 siblings, 0 replies; 12+ messages in thread
From: Ard Biesheuvel @ 2022-05-05 16:12 UTC (permalink / raw)
To: Kefeng Wang; +Cc: linux-efi, Linux ARM, Wupeng Ma, Linux Memory Management List
On Thu, 5 May 2022 at 15:43, Kefeng Wang <wangkefeng.wang@huawei.com> wrote:
>
>
> On 2022/5/3 23:21, Ard Biesheuvel wrote:
> > If the system exposes memory regions with the EFI_MORE_RELIABLE
> > attribute, it is implied that it is intended to be used for allocations
> > that are relatively important, such as the kernel's static image.
> >
> > Since efi_random_alloc() is mostly (only) used for allocating space for
> > the kernel image, let's update it to take this into account, and
> > disregard all memory without the EFI_MORE_RELIABLE attribute if there is
> > sufficient memory available that does have this attribute.
> >
> > Note that this change only affects booting with randomization enabled.
> > In other cases, the EFI stub runs the kernel image in place unless its
> > placement is unsuitable for some reason (i.e., misaligned, or its BSS
> > overlaps with another allocation), and it is left to the bootloader to
> > ensure that the kernel was loaded into EFI_MORE_RELIABLE memory if this
> > is desired.
> >
> > Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> > ---
> > drivers/firmware/efi/libstub/randomalloc.c | 11 +++++++++++
> > 1 file changed, 11 insertions(+)
> >
> > diff --git a/drivers/firmware/efi/libstub/randomalloc.c b/drivers/firmware/efi/libstub/randomalloc.c
> > index 724155b9e10d..07a762910312 100644
> > --- a/drivers/firmware/efi/libstub/randomalloc.c
> > +++ b/drivers/firmware/efi/libstub/randomalloc.c
> > @@ -56,6 +56,7 @@ efi_status_t efi_random_alloc(unsigned long size,
> > unsigned long random_seed)
> > {
> > unsigned long map_size, desc_size, total_slots = 0, target_slot;
> > + unsigned long total_mirrored_slots = 0;
> > unsigned long buff_size;
> > efi_status_t status;
> > efi_memory_desc_t *memory_map;
> > @@ -86,8 +87,14 @@ efi_status_t efi_random_alloc(unsigned long size,
> > slots = get_entry_num_slots(md, size, ilog2(align));
> > MD_NUM_SLOTS(md) = slots;
> > total_slots += slots;
> > + if (md->attribute & EFI_MEMORY_MORE_RELIABLE)
> > + total_mirrored_slots += slots;
> > }
> >
> > + /* only consider mirrored slots for randomization if any exist */
> > + if (total_mirrored_slots > 0)
> > + total_slots = total_mirrored_slots;
> > +
>
> The kernel will check 4G lower limit to enable kernelcore=mirror feature.
>
Why? I mean, why is 4G a magic number also on arm64?
> Do we need some fallback mechanism in case of small mirror slots which
>
> leads to fail allocation for Image?
>
This code only counts slots that are large enough to hold the Image so
this can never happen. If total_mirrored_slots > 0, there is at least
one possible placement of the kernel where it falls entirely inside a
EFI_MORE_RELIABLE region.
>
> > /* find a random number between 0 and total_slots */
> > target_slot = (total_slots * (u64)(random_seed & U32_MAX)) >> 32;
> >
> > @@ -107,6 +114,10 @@ efi_status_t efi_random_alloc(unsigned long size,
> > efi_physical_addr_t target;
> > unsigned long pages;
> >
> > + if (total_mirrored_slots > 0 &&
> > + !(md->attribute & EFI_MEMORY_MORE_RELIABLE))
> > + continue;
> > +
> > if (target_slot >= MD_NUM_SLOTS(md)) {
> > target_slot -= MD_NUM_SLOTS(md);
> > continue;
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH] efi: stub: prefer mirrored memory for randomized allocations
2022-05-05 16:12 ` Ard Biesheuvel
@ 2022-05-06 1:42 ` Kefeng Wang
-1 siblings, 0 replies; 12+ messages in thread
From: Kefeng Wang @ 2022-05-06 1:42 UTC (permalink / raw)
To: Ard Biesheuvel
Cc: linux-efi, Linux ARM, Wupeng Ma, Linux Memory Management List
On 2022/5/6 0:12, Ard Biesheuvel wrote:
> On Thu, 5 May 2022 at 15:43, Kefeng Wang <wangkefeng.wang@huawei.com> wrote:
>>
>> On 2022/5/3 23:21, Ard Biesheuvel wrote:
>>> If the system exposes memory regions with the EFI_MORE_RELIABLE
>>> attribute, it is implied that it is intended to be used for allocations
>>> that are relatively important, such as the kernel's static image.
>>>
>>> Since efi_random_alloc() is mostly (only) used for allocating space for
>>> the kernel image, let's update it to take this into account, and
>>> disregard all memory without the EFI_MORE_RELIABLE attribute if there is
>>> sufficient memory available that does have this attribute.
>>>
>>> Note that this change only affects booting with randomization enabled.
>>> In other cases, the EFI stub runs the kernel image in place unless its
>>> placement is unsuitable for some reason (i.e., misaligned, or its BSS
>>> overlaps with another allocation), and it is left to the bootloader to
>>> ensure that the kernel was loaded into EFI_MORE_RELIABLE memory if this
>>> is desired.
>>>
>>> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
>>> ---
>>> drivers/firmware/efi/libstub/randomalloc.c | 11 +++++++++++
>>> 1 file changed, 11 insertions(+)
>>>
>>> diff --git a/drivers/firmware/efi/libstub/randomalloc.c b/drivers/firmware/efi/libstub/randomalloc.c
>>> index 724155b9e10d..07a762910312 100644
>>> --- a/drivers/firmware/efi/libstub/randomalloc.c
>>> +++ b/drivers/firmware/efi/libstub/randomalloc.c
>>> @@ -56,6 +56,7 @@ efi_status_t efi_random_alloc(unsigned long size,
>>> unsigned long random_seed)
>>> {
>>> unsigned long map_size, desc_size, total_slots = 0, target_slot;
>>> + unsigned long total_mirrored_slots = 0;
>>> unsigned long buff_size;
>>> efi_status_t status;
>>> efi_memory_desc_t *memory_map;
>>> @@ -86,8 +87,14 @@ efi_status_t efi_random_alloc(unsigned long size,
>>> slots = get_entry_num_slots(md, size, ilog2(align));
>>> MD_NUM_SLOTS(md) = slots;
>>> total_slots += slots;
>>> + if (md->attribute & EFI_MEMORY_MORE_RELIABLE)
>>> + total_mirrored_slots += slots;
>>> }
>>>
>>> + /* only consider mirrored slots for randomization if any exist */
>>> + if (total_mirrored_slots > 0)
>>> + total_slots = total_mirrored_slots;
>>> +
>> The kernel will check 4G lower limit to enable kernelcore=mirror feature.
>>
> Why? I mean, why is 4G a magic number also on arm64?
Please ignore this, replied in the previous email.
>
>> Do we need some fallback mechanism in case of small mirror slots which
>>
>> leads to fail allocation for Image?
>>
> This code only counts slots that are large enough to hold the Image so
> this can never happen. If total_mirrored_slots > 0, there is at least
> one possible placement of the kernel where it falls entirely inside a
> EFI_MORE_RELIABLE region.
I see, slots = get_entry_num_slots(md, *size*, ilog2(align));
Thanks.
Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com>
>
>>> /* find a random number between 0 and total_slots */
>>> target_slot = (total_slots * (u64)(random_seed & U32_MAX)) >> 32;
>>>
>>> @@ -107,6 +114,10 @@ efi_status_t efi_random_alloc(unsigned long size,
>>> efi_physical_addr_t target;
>>> unsigned long pages;
>>>
>>> + if (total_mirrored_slots > 0 &&
>>> + !(md->attribute & EFI_MEMORY_MORE_RELIABLE))
>>> + continue;
>>> +
>>> if (target_slot >= MD_NUM_SLOTS(md)) {
>>> target_slot -= MD_NUM_SLOTS(md);
>>> continue;
> .
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH] efi: stub: prefer mirrored memory for randomized allocations
@ 2022-05-06 1:42 ` Kefeng Wang
0 siblings, 0 replies; 12+ messages in thread
From: Kefeng Wang @ 2022-05-06 1:42 UTC (permalink / raw)
To: Ard Biesheuvel
Cc: linux-efi, Linux ARM, Wupeng Ma, Linux Memory Management List
On 2022/5/6 0:12, Ard Biesheuvel wrote:
> On Thu, 5 May 2022 at 15:43, Kefeng Wang <wangkefeng.wang@huawei.com> wrote:
>>
>> On 2022/5/3 23:21, Ard Biesheuvel wrote:
>>> If the system exposes memory regions with the EFI_MORE_RELIABLE
>>> attribute, it is implied that it is intended to be used for allocations
>>> that are relatively important, such as the kernel's static image.
>>>
>>> Since efi_random_alloc() is mostly (only) used for allocating space for
>>> the kernel image, let's update it to take this into account, and
>>> disregard all memory without the EFI_MORE_RELIABLE attribute if there is
>>> sufficient memory available that does have this attribute.
>>>
>>> Note that this change only affects booting with randomization enabled.
>>> In other cases, the EFI stub runs the kernel image in place unless its
>>> placement is unsuitable for some reason (i.e., misaligned, or its BSS
>>> overlaps with another allocation), and it is left to the bootloader to
>>> ensure that the kernel was loaded into EFI_MORE_RELIABLE memory if this
>>> is desired.
>>>
>>> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
>>> ---
>>> drivers/firmware/efi/libstub/randomalloc.c | 11 +++++++++++
>>> 1 file changed, 11 insertions(+)
>>>
>>> diff --git a/drivers/firmware/efi/libstub/randomalloc.c b/drivers/firmware/efi/libstub/randomalloc.c
>>> index 724155b9e10d..07a762910312 100644
>>> --- a/drivers/firmware/efi/libstub/randomalloc.c
>>> +++ b/drivers/firmware/efi/libstub/randomalloc.c
>>> @@ -56,6 +56,7 @@ efi_status_t efi_random_alloc(unsigned long size,
>>> unsigned long random_seed)
>>> {
>>> unsigned long map_size, desc_size, total_slots = 0, target_slot;
>>> + unsigned long total_mirrored_slots = 0;
>>> unsigned long buff_size;
>>> efi_status_t status;
>>> efi_memory_desc_t *memory_map;
>>> @@ -86,8 +87,14 @@ efi_status_t efi_random_alloc(unsigned long size,
>>> slots = get_entry_num_slots(md, size, ilog2(align));
>>> MD_NUM_SLOTS(md) = slots;
>>> total_slots += slots;
>>> + if (md->attribute & EFI_MEMORY_MORE_RELIABLE)
>>> + total_mirrored_slots += slots;
>>> }
>>>
>>> + /* only consider mirrored slots for randomization if any exist */
>>> + if (total_mirrored_slots > 0)
>>> + total_slots = total_mirrored_slots;
>>> +
>> The kernel will check 4G lower limit to enable kernelcore=mirror feature.
>>
> Why? I mean, why is 4G a magic number also on arm64?
Please ignore this, replied in the previous email.
>
>> Do we need some fallback mechanism in case of small mirror slots which
>>
>> leads to fail allocation for Image?
>>
> This code only counts slots that are large enough to hold the Image so
> this can never happen. If total_mirrored_slots > 0, there is at least
> one possible placement of the kernel where it falls entirely inside a
> EFI_MORE_RELIABLE region.
I see, slots = get_entry_num_slots(md, *size*, ilog2(align));
Thanks.
Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com>
>
>>> /* find a random number between 0 and total_slots */
>>> target_slot = (total_slots * (u64)(random_seed & U32_MAX)) >> 32;
>>>
>>> @@ -107,6 +114,10 @@ efi_status_t efi_random_alloc(unsigned long size,
>>> efi_physical_addr_t target;
>>> unsigned long pages;
>>>
>>> + if (total_mirrored_slots > 0 &&
>>> + !(md->attribute & EFI_MEMORY_MORE_RELIABLE))
>>> + continue;
>>> +
>>> if (target_slot >= MD_NUM_SLOTS(md)) {
>>> target_slot -= MD_NUM_SLOTS(md);
>>> continue;
> .
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH] efi: stub: prefer mirrored memory for randomized allocations
2022-05-06 1:42 ` Kefeng Wang
@ 2022-05-06 6:19 ` Ard Biesheuvel
-1 siblings, 0 replies; 12+ messages in thread
From: Ard Biesheuvel @ 2022-05-06 6:19 UTC (permalink / raw)
To: Kefeng Wang; +Cc: linux-efi, Linux ARM, Wupeng Ma, Linux Memory Management List
On Fri, 6 May 2022 at 03:43, Kefeng Wang <wangkefeng.wang@huawei.com> wrote:
>
>
> On 2022/5/6 0:12, Ard Biesheuvel wrote:
> > On Thu, 5 May 2022 at 15:43, Kefeng Wang <wangkefeng.wang@huawei.com> wrote:
> >>
> >> On 2022/5/3 23:21, Ard Biesheuvel wrote:
> >>> If the system exposes memory regions with the EFI_MORE_RELIABLE
> >>> attribute, it is implied that it is intended to be used for allocations
> >>> that are relatively important, such as the kernel's static image.
> >>>
> >>> Since efi_random_alloc() is mostly (only) used for allocating space for
> >>> the kernel image, let's update it to take this into account, and
> >>> disregard all memory without the EFI_MORE_RELIABLE attribute if there is
> >>> sufficient memory available that does have this attribute.
> >>>
> >>> Note that this change only affects booting with randomization enabled.
> >>> In other cases, the EFI stub runs the kernel image in place unless its
> >>> placement is unsuitable for some reason (i.e., misaligned, or its BSS
> >>> overlaps with another allocation), and it is left to the bootloader to
> >>> ensure that the kernel was loaded into EFI_MORE_RELIABLE memory if this
> >>> is desired.
> >>>
> >>> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> >>> ---
> >>> drivers/firmware/efi/libstub/randomalloc.c | 11 +++++++++++
> >>> 1 file changed, 11 insertions(+)
> >>>
> >>> diff --git a/drivers/firmware/efi/libstub/randomalloc.c b/drivers/firmware/efi/libstub/randomalloc.c
> >>> index 724155b9e10d..07a762910312 100644
> >>> --- a/drivers/firmware/efi/libstub/randomalloc.c
> >>> +++ b/drivers/firmware/efi/libstub/randomalloc.c
> >>> @@ -56,6 +56,7 @@ efi_status_t efi_random_alloc(unsigned long size,
> >>> unsigned long random_seed)
> >>> {
> >>> unsigned long map_size, desc_size, total_slots = 0, target_slot;
> >>> + unsigned long total_mirrored_slots = 0;
> >>> unsigned long buff_size;
> >>> efi_status_t status;
> >>> efi_memory_desc_t *memory_map;
> >>> @@ -86,8 +87,14 @@ efi_status_t efi_random_alloc(unsigned long size,
> >>> slots = get_entry_num_slots(md, size, ilog2(align));
> >>> MD_NUM_SLOTS(md) = slots;
> >>> total_slots += slots;
> >>> + if (md->attribute & EFI_MEMORY_MORE_RELIABLE)
> >>> + total_mirrored_slots += slots;
> >>> }
> >>>
> >>> + /* only consider mirrored slots for randomization if any exist */
> >>> + if (total_mirrored_slots > 0)
> >>> + total_slots = total_mirrored_slots;
> >>> +
> >> The kernel will check 4G lower limit to enable kernelcore=mirror feature.
> >>
> > Why? I mean, why is 4G a magic number also on arm64?
> Please ignore this, replied in the previous email.
> >
> >> Do we need some fallback mechanism in case of small mirror slots which
> >>
> >> leads to fail allocation for Image?
> >>
> > This code only counts slots that are large enough to hold the Image so
> > this can never happen. If total_mirrored_slots > 0, there is at least
> > one possible placement of the kernel where it falls entirely inside a
> > EFI_MORE_RELIABLE region.
>
> I see, slots = get_entry_num_slots(md, *size*, ilog2(align));
>
> Thanks.
>
> Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com>
>
Thank you. I have queued this up now.
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH] efi: stub: prefer mirrored memory for randomized allocations
@ 2022-05-06 6:19 ` Ard Biesheuvel
0 siblings, 0 replies; 12+ messages in thread
From: Ard Biesheuvel @ 2022-05-06 6:19 UTC (permalink / raw)
To: Kefeng Wang; +Cc: linux-efi, Linux ARM, Wupeng Ma, Linux Memory Management List
On Fri, 6 May 2022 at 03:43, Kefeng Wang <wangkefeng.wang@huawei.com> wrote:
>
>
> On 2022/5/6 0:12, Ard Biesheuvel wrote:
> > On Thu, 5 May 2022 at 15:43, Kefeng Wang <wangkefeng.wang@huawei.com> wrote:
> >>
> >> On 2022/5/3 23:21, Ard Biesheuvel wrote:
> >>> If the system exposes memory regions with the EFI_MORE_RELIABLE
> >>> attribute, it is implied that it is intended to be used for allocations
> >>> that are relatively important, such as the kernel's static image.
> >>>
> >>> Since efi_random_alloc() is mostly (only) used for allocating space for
> >>> the kernel image, let's update it to take this into account, and
> >>> disregard all memory without the EFI_MORE_RELIABLE attribute if there is
> >>> sufficient memory available that does have this attribute.
> >>>
> >>> Note that this change only affects booting with randomization enabled.
> >>> In other cases, the EFI stub runs the kernel image in place unless its
> >>> placement is unsuitable for some reason (i.e., misaligned, or its BSS
> >>> overlaps with another allocation), and it is left to the bootloader to
> >>> ensure that the kernel was loaded into EFI_MORE_RELIABLE memory if this
> >>> is desired.
> >>>
> >>> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
> >>> ---
> >>> drivers/firmware/efi/libstub/randomalloc.c | 11 +++++++++++
> >>> 1 file changed, 11 insertions(+)
> >>>
> >>> diff --git a/drivers/firmware/efi/libstub/randomalloc.c b/drivers/firmware/efi/libstub/randomalloc.c
> >>> index 724155b9e10d..07a762910312 100644
> >>> --- a/drivers/firmware/efi/libstub/randomalloc.c
> >>> +++ b/drivers/firmware/efi/libstub/randomalloc.c
> >>> @@ -56,6 +56,7 @@ efi_status_t efi_random_alloc(unsigned long size,
> >>> unsigned long random_seed)
> >>> {
> >>> unsigned long map_size, desc_size, total_slots = 0, target_slot;
> >>> + unsigned long total_mirrored_slots = 0;
> >>> unsigned long buff_size;
> >>> efi_status_t status;
> >>> efi_memory_desc_t *memory_map;
> >>> @@ -86,8 +87,14 @@ efi_status_t efi_random_alloc(unsigned long size,
> >>> slots = get_entry_num_slots(md, size, ilog2(align));
> >>> MD_NUM_SLOTS(md) = slots;
> >>> total_slots += slots;
> >>> + if (md->attribute & EFI_MEMORY_MORE_RELIABLE)
> >>> + total_mirrored_slots += slots;
> >>> }
> >>>
> >>> + /* only consider mirrored slots for randomization if any exist */
> >>> + if (total_mirrored_slots > 0)
> >>> + total_slots = total_mirrored_slots;
> >>> +
> >> The kernel will check 4G lower limit to enable kernelcore=mirror feature.
> >>
> > Why? I mean, why is 4G a magic number also on arm64?
> Please ignore this, replied in the previous email.
> >
> >> Do we need some fallback mechanism in case of small mirror slots which
> >>
> >> leads to fail allocation for Image?
> >>
> > This code only counts slots that are large enough to hold the Image so
> > this can never happen. If total_mirrored_slots > 0, there is at least
> > one possible placement of the kernel where it falls entirely inside a
> > EFI_MORE_RELIABLE region.
>
> I see, slots = get_entry_num_slots(md, *size*, ilog2(align));
>
> Thanks.
>
> Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com>
>
Thank you. I have queued this up now.
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^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH] efi: stub: prefer mirrored memory for randomized allocations
2022-05-05 13:43 ` Kefeng Wang
@ 2022-05-06 1:06 ` Kefeng Wang
-1 siblings, 0 replies; 12+ messages in thread
From: Kefeng Wang @ 2022-05-06 1:06 UTC (permalink / raw)
To: Ard Biesheuvel, linux-efi; +Cc: linux-arm-kernel, mawupeng1, linux-mm
On 2022/5/5 21:43, Kefeng Wang wrote:
>
> On 2022/5/3 23:21, Ard Biesheuvel wrote:
>> If the system exposes memory regions with the EFI_MORE_RELIABLE
>> attribute, it is implied that it is intended to be used for allocations
>> that are relatively important, such as the kernel's static image.
>>
>> Since efi_random_alloc() is mostly (only) used for allocating space for
>> the kernel image, let's update it to take this into account, and
>> disregard all memory without the EFI_MORE_RELIABLE attribute if there is
>> sufficient memory available that does have this attribute.
>>
>> Note that this change only affects booting with randomization enabled.
>> In other cases, the EFI stub runs the kernel image in place unless its
>> placement is unsuitable for some reason (i.e., misaligned, or its BSS
>> overlaps with another allocation), and it is left to the bootloader to
>> ensure that the kernel was loaded into EFI_MORE_RELIABLE memory if this
>> is desired.
>>
>> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
>> ---
>> drivers/firmware/efi/libstub/randomalloc.c | 11 +++++++++++
>> 1 file changed, 11 insertions(+)
>>
>> diff --git a/drivers/firmware/efi/libstub/randomalloc.c
>> b/drivers/firmware/efi/libstub/randomalloc.c
>> index 724155b9e10d..07a762910312 100644
>> --- a/drivers/firmware/efi/libstub/randomalloc.c
>> +++ b/drivers/firmware/efi/libstub/randomalloc.c
>> @@ -56,6 +56,7 @@ efi_status_t efi_random_alloc(unsigned long size,
>> unsigned long random_seed)
>> {
>> unsigned long map_size, desc_size, total_slots = 0, target_slot;
>> + unsigned long total_mirrored_slots = 0;
>> unsigned long buff_size;
>> efi_status_t status;
>> efi_memory_desc_t *memory_map;
>> @@ -86,8 +87,14 @@ efi_status_t efi_random_alloc(unsigned long size,
>> slots = get_entry_num_slots(md, size, ilog2(align));
>> MD_NUM_SLOTS(md) = slots;
>> total_slots += slots;
>> + if (md->attribute & EFI_MEMORY_MORE_RELIABLE)
>> + total_mirrored_slots += slots;
>> }
>> + /* only consider mirrored slots for randomization if any exist */
>> + if (total_mirrored_slots > 0)
>> + total_slots = total_mirrored_slots;
>> +
>
> The kernel will check 4G lower limit to enable kernelcore=mirror feature.
Please ignore this, the kernel only check whether the memory below 4G are
all mirrored memory or not.
>
> Do we need some fallback mechanism in case of small mirror slots which
>
> leads to fail allocation for Image?
>
>
>> /* find a random number between 0 and total_slots */
>> target_slot = (total_slots * (u64)(random_seed & U32_MAX)) >> 32;
>> @@ -107,6 +114,10 @@ efi_status_t efi_random_alloc(unsigned long size,
>> efi_physical_addr_t target;
>> unsigned long pages;
>> + if (total_mirrored_slots > 0 &&
>> + !(md->attribute & EFI_MEMORY_MORE_RELIABLE))
>> + continue;
>> +
>> if (target_slot >= MD_NUM_SLOTS(md)) {
>> target_slot -= MD_NUM_SLOTS(md);
>> continue;
^ permalink raw reply [flat|nested] 12+ messages in thread
* Re: [PATCH] efi: stub: prefer mirrored memory for randomized allocations
@ 2022-05-06 1:06 ` Kefeng Wang
0 siblings, 0 replies; 12+ messages in thread
From: Kefeng Wang @ 2022-05-06 1:06 UTC (permalink / raw)
To: Ard Biesheuvel, linux-efi; +Cc: linux-arm-kernel, mawupeng1, linux-mm
On 2022/5/5 21:43, Kefeng Wang wrote:
>
> On 2022/5/3 23:21, Ard Biesheuvel wrote:
>> If the system exposes memory regions with the EFI_MORE_RELIABLE
>> attribute, it is implied that it is intended to be used for allocations
>> that are relatively important, such as the kernel's static image.
>>
>> Since efi_random_alloc() is mostly (only) used for allocating space for
>> the kernel image, let's update it to take this into account, and
>> disregard all memory without the EFI_MORE_RELIABLE attribute if there is
>> sufficient memory available that does have this attribute.
>>
>> Note that this change only affects booting with randomization enabled.
>> In other cases, the EFI stub runs the kernel image in place unless its
>> placement is unsuitable for some reason (i.e., misaligned, or its BSS
>> overlaps with another allocation), and it is left to the bootloader to
>> ensure that the kernel was loaded into EFI_MORE_RELIABLE memory if this
>> is desired.
>>
>> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
>> ---
>> drivers/firmware/efi/libstub/randomalloc.c | 11 +++++++++++
>> 1 file changed, 11 insertions(+)
>>
>> diff --git a/drivers/firmware/efi/libstub/randomalloc.c
>> b/drivers/firmware/efi/libstub/randomalloc.c
>> index 724155b9e10d..07a762910312 100644
>> --- a/drivers/firmware/efi/libstub/randomalloc.c
>> +++ b/drivers/firmware/efi/libstub/randomalloc.c
>> @@ -56,6 +56,7 @@ efi_status_t efi_random_alloc(unsigned long size,
>> unsigned long random_seed)
>> {
>> unsigned long map_size, desc_size, total_slots = 0, target_slot;
>> + unsigned long total_mirrored_slots = 0;
>> unsigned long buff_size;
>> efi_status_t status;
>> efi_memory_desc_t *memory_map;
>> @@ -86,8 +87,14 @@ efi_status_t efi_random_alloc(unsigned long size,
>> slots = get_entry_num_slots(md, size, ilog2(align));
>> MD_NUM_SLOTS(md) = slots;
>> total_slots += slots;
>> + if (md->attribute & EFI_MEMORY_MORE_RELIABLE)
>> + total_mirrored_slots += slots;
>> }
>> + /* only consider mirrored slots for randomization if any exist */
>> + if (total_mirrored_slots > 0)
>> + total_slots = total_mirrored_slots;
>> +
>
> The kernel will check 4G lower limit to enable kernelcore=mirror feature.
Please ignore this, the kernel only check whether the memory below 4G are
all mirrored memory or not.
>
> Do we need some fallback mechanism in case of small mirror slots which
>
> leads to fail allocation for Image?
>
>
>> /* find a random number between 0 and total_slots */
>> target_slot = (total_slots * (u64)(random_seed & U32_MAX)) >> 32;
>> @@ -107,6 +114,10 @@ efi_status_t efi_random_alloc(unsigned long size,
>> efi_physical_addr_t target;
>> unsigned long pages;
>> + if (total_mirrored_slots > 0 &&
>> + !(md->attribute & EFI_MEMORY_MORE_RELIABLE))
>> + continue;
>> +
>> if (target_slot >= MD_NUM_SLOTS(md)) {
>> target_slot -= MD_NUM_SLOTS(md);
>> continue;
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^ permalink raw reply [flat|nested] 12+ messages in thread