[PATCH v2] arm64/efi: prefer AllocatePages() over efi_low_alloc() for vmlinux

[PATCH v2] arm64/efi: prefer AllocatePages() over efi_low_alloc() for vmlinux

[Ard Biesheuvel]

When allocating memory for the kernel image, try the AllocatePages()
boot service to obtain memory at the preferred offset of
'dram_base + TEXT_OFFSET', and only revert to efi_low_alloc() if that
fails. This is the only way to allocate at the base of DRAM if DRAM
starts at 0x0, since efi_low_alloc() refuses to allocate at 0x0.

Tested-by: Haojian Zhuang <haojian.zhuang@linaro.org>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
v2:
- reshuffle code flow to make it more logical, and have only a single
  memcpy() invocation at the end of the function
---
 arch/arm64/kernel/efi-stub.c | 41 ++++++++++++++++++++++++++++++++---------
 1 file changed, 32 insertions(+), 9 deletions(-)

diff --git a/arch/arm64/kernel/efi-stub.c b/arch/arm64/kernel/efi-stub.c
index f5374065ad53..816120ece6bc 100644
--- a/arch/arm64/kernel/efi-stub.c
+++ b/arch/arm64/kernel/efi-stub.c
@@ -13,7 +13,7 @@
 #include <asm/efi.h>
 #include <asm/sections.h>
 
-efi_status_t __init handle_kernel_image(efi_system_table_t *sys_table,
+efi_status_t __init handle_kernel_image(efi_system_table_t *sys_table_arg,
 					unsigned long *image_addr,
 					unsigned long *image_size,
 					unsigned long *reserve_addr,
@@ -23,21 +23,44 @@ efi_status_t __init handle_kernel_image(efi_system_table_t *sys_table,
 {
 	efi_status_t status;
 	unsigned long kernel_size, kernel_memsize = 0;
+	unsigned long nr_pages;
+	void *old_image_addr = (void *)*image_addr;
 
 	/* Relocate the image, if required. */
 	kernel_size = _edata - _text;
 	if (*image_addr != (dram_base + TEXT_OFFSET)) {
 		kernel_memsize = kernel_size + (_end - _edata);
-		status = efi_low_alloc(sys_table, kernel_memsize + TEXT_OFFSET,
-				       SZ_2M, reserve_addr);
+
+		/*
+		 * First, try a straight allocation at the preferred offset.
+		 * This will work around the issue where, if dram_base == 0x0,
+		 * efi_low_alloc() refuses to allocate at 0x0 (to prevent the
+		 * address of the allocation to be mistaken for a FAIL return
+		 * value or a NULL pointer). It will also ensure that, on
+		 * platforms where the [dram_base, dram_base + TEXT_OFFSET)
+		 * interval is partially occupied by the firmware (like on APM
+		 * Mustang), we can still place the kernel at the address
+		 * 'dram_base + TEXT_OFFSET'.
+		 */
+		*image_addr = *reserve_addr = dram_base + TEXT_OFFSET;
+		nr_pages = round_up(kernel_memsize, EFI_ALLOC_ALIGN) /
+			   EFI_PAGE_SIZE;
+		status = efi_call_early(allocate_pages, EFI_ALLOCATE_ADDRESS,
+					EFI_LOADER_DATA, nr_pages,
+					(efi_physical_addr_t *)reserve_addr);
 		if (status != EFI_SUCCESS) {
-			pr_efi_err(sys_table, "Failed to relocate kernel\n");
-			return status;
+			kernel_memsize += TEXT_OFFSET;
+			status = efi_low_alloc(sys_table_arg, kernel_memsize,
+					       SZ_2M, reserve_addr);
+
+			if (status != EFI_SUCCESS) {
+				pr_efi_err(sys_table_arg, "Failed to relocate kernel\n");
+				return status;
+			}
+			*image_addr = *reserve_addr + TEXT_OFFSET;
 		}
-		memcpy((void *)*reserve_addr + TEXT_OFFSET, (void *)*image_addr,
-		       kernel_size);
-		*image_addr = *reserve_addr + TEXT_OFFSET;
-		*reserve_size = kernel_memsize + TEXT_OFFSET;
+		memcpy((void *)*image_addr, old_image_addr, kernel_size);
+		*reserve_size = kernel_memsize;
 	}
 
 
-- 
1.9.1

[PATCH v2] arm64/efi: prefer AllocatePages() over efi_low_alloc() for vmlinux

[Mark Rutland]

On Fri, Jul 24, 2015 at 12:38:27PM +0100, Ard Biesheuvel wrote:
> When allocating memory for the kernel image, try the AllocatePages()
> boot service to obtain memory at the preferred offset of
> 'dram_base + TEXT_OFFSET', and only revert to efi_low_alloc() if that
> fails. This is the only way to allocate at the base of DRAM if DRAM
> starts at 0x0, since efi_low_alloc() refuses to allocate at 0x0.
> 
> Tested-by: Haojian Zhuang <haojian.zhuang@linaro.org>
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

Reviewed-by: Mark Rutland <mark.rutland@arm.com>

Mark.

> ---
> v2:
> - reshuffle code flow to make it more logical, and have only a single
>   memcpy() invocation at the end of the function
> ---
>  arch/arm64/kernel/efi-stub.c | 41 ++++++++++++++++++++++++++++++++---------
>  1 file changed, 32 insertions(+), 9 deletions(-)
> 
> diff --git a/arch/arm64/kernel/efi-stub.c b/arch/arm64/kernel/efi-stub.c
> index f5374065ad53..816120ece6bc 100644
> --- a/arch/arm64/kernel/efi-stub.c
> +++ b/arch/arm64/kernel/efi-stub.c
> @@ -13,7 +13,7 @@
>  #include <asm/efi.h>
>  #include <asm/sections.h>
>  
> -efi_status_t __init handle_kernel_image(efi_system_table_t *sys_table,
> +efi_status_t __init handle_kernel_image(efi_system_table_t *sys_table_arg,
>  					unsigned long *image_addr,
>  					unsigned long *image_size,
>  					unsigned long *reserve_addr,
> @@ -23,21 +23,44 @@ efi_status_t __init handle_kernel_image(efi_system_table_t *sys_table,
>  {
>  	efi_status_t status;
>  	unsigned long kernel_size, kernel_memsize = 0;
> +	unsigned long nr_pages;
> +	void *old_image_addr = (void *)*image_addr;
>  
>  	/* Relocate the image, if required. */
>  	kernel_size = _edata - _text;
>  	if (*image_addr != (dram_base + TEXT_OFFSET)) {
>  		kernel_memsize = kernel_size + (_end - _edata);
> -		status = efi_low_alloc(sys_table, kernel_memsize + TEXT_OFFSET,
> -				       SZ_2M, reserve_addr);
> +
> +		/*
> +		 * First, try a straight allocation at the preferred offset.
> +		 * This will work around the issue where, if dram_base == 0x0,
> +		 * efi_low_alloc() refuses to allocate at 0x0 (to prevent the
> +		 * address of the allocation to be mistaken for a FAIL return
> +		 * value or a NULL pointer). It will also ensure that, on
> +		 * platforms where the [dram_base, dram_base + TEXT_OFFSET)
> +		 * interval is partially occupied by the firmware (like on APM
> +		 * Mustang), we can still place the kernel at the address
> +		 * 'dram_base + TEXT_OFFSET'.
> +		 */
> +		*image_addr = *reserve_addr = dram_base + TEXT_OFFSET;
> +		nr_pages = round_up(kernel_memsize, EFI_ALLOC_ALIGN) /
> +			   EFI_PAGE_SIZE;
> +		status = efi_call_early(allocate_pages, EFI_ALLOCATE_ADDRESS,
> +					EFI_LOADER_DATA, nr_pages,
> +					(efi_physical_addr_t *)reserve_addr);
>  		if (status != EFI_SUCCESS) {
> -			pr_efi_err(sys_table, "Failed to relocate kernel\n");
> -			return status;
> +			kernel_memsize += TEXT_OFFSET;
> +			status = efi_low_alloc(sys_table_arg, kernel_memsize,
> +					       SZ_2M, reserve_addr);
> +
> +			if (status != EFI_SUCCESS) {
> +				pr_efi_err(sys_table_arg, "Failed to relocate kernel\n");
> +				return status;
> +			}
> +			*image_addr = *reserve_addr + TEXT_OFFSET;
>  		}
> -		memcpy((void *)*reserve_addr + TEXT_OFFSET, (void *)*image_addr,
> -		       kernel_size);
> -		*image_addr = *reserve_addr + TEXT_OFFSET;
> -		*reserve_size = kernel_memsize + TEXT_OFFSET;
> +		memcpy((void *)*image_addr, old_image_addr, kernel_size);
> +		*reserve_size = kernel_memsize;
>  	}
>  
>  
> -- 
> 1.9.1
> 

[PATCH v2] arm64/efi: prefer AllocatePages() over efi_low_alloc() for vmlinux

[Matt Fleming]

On Fri, 24 Jul, at 01:38:27PM, Ard Biesheuvel wrote:
> When allocating memory for the kernel image, try the AllocatePages()
> boot service to obtain memory at the preferred offset of
> 'dram_base + TEXT_OFFSET', and only revert to efi_low_alloc() if that
> fails. This is the only way to allocate at the base of DRAM if DRAM
> starts at 0x0, since efi_low_alloc() refuses to allocate at 0x0.
> 
> Tested-by: Haojian Zhuang <haojian.zhuang@linaro.org>
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> ---
> v2:
> - reshuffle code flow to make it more logical, and have only a single
>   memcpy() invocation at the end of the function
> ---
>  arch/arm64/kernel/efi-stub.c | 41 ++++++++++++++++++++++++++++++++---------
>  1 file changed, 32 insertions(+), 9 deletions(-)

Would it be easier if we allow efi_low_alloc() to return 0x0 for some
uses? If you don't need the preference for low allocations, probably
not, but I don't want to see us working around limitations in
efi_low_alloc() instead of just fixing it.

-- 
Matt Fleming, Intel Open Source Technology Center

[PATCH v2] arm64/efi: prefer AllocatePages() over efi_low_alloc() for vmlinux

[Ard Biesheuvel]

On 28 July 2015 at 23:17, Matt Fleming <matt@codeblueprint.co.uk> wrote:
> On Fri, 24 Jul, at 01:38:27PM, Ard Biesheuvel wrote:
>> When allocating memory for the kernel image, try the AllocatePages()
>> boot service to obtain memory at the preferred offset of
>> 'dram_base + TEXT_OFFSET', and only revert to efi_low_alloc() if that
>> fails. This is the only way to allocate at the base of DRAM if DRAM
>> starts at 0x0, since efi_low_alloc() refuses to allocate at 0x0.
>>
>> Tested-by: Haojian Zhuang <haojian.zhuang@linaro.org>
>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
>> ---
>> v2:
>> - reshuffle code flow to make it more logical, and have only a single
>>   memcpy() invocation at the end of the function
>> ---
>>  arch/arm64/kernel/efi-stub.c | 41 ++++++++++++++++++++++++++++++++---------
>>  1 file changed, 32 insertions(+), 9 deletions(-)
>
> Would it be easier if we allow efi_low_alloc() to return 0x0 for some
> uses? If you don't need the preference for low allocations, probably
> not, but I don't want to see us working around limitations in
> efi_low_alloc() instead of just fixing it.
>

This workaround fixes another issue as well: the arm64 kernel needs to
be loaded 512 KB above a 2MB aligned boundary, and using
efi_low_alloc() as we do loses (2 MB - 512 KB) at the bottom if part
of that 512 KB is occupied, since efi_low_alloc() is not aware of the
fact that the first 512 KB will remain unused.

What would be most helpful is if efi_low_alloc() could take an offset
param in addition to the alignment, i.e., alignment == 2MB and offset
== 512 KB. The offset would default to 0, reverting to the original
behavior.

If you'd be ok with such a change, I can propose it instead, and wire
it up into this function.

-- 
Ard.

[PATCH v2] arm64/efi: prefer AllocatePages() over efi_low_alloc() for vmlinux

[Matt Fleming]

On Tue, 28 Jul, at 11:24:23PM, Ard Biesheuvel wrote:
> 
> This workaround fixes another issue as well: the arm64 kernel needs to
> be loaded 512 KB above a 2MB aligned boundary, and using
> efi_low_alloc() as we do loses (2 MB - 512 KB) at the bottom if part
> of that 512 KB is occupied, since efi_low_alloc() is not aware of the
> fact that the first 512 KB will remain unused.
> 
> What would be most helpful is if efi_low_alloc() could take an offset
> param in addition to the alignment, i.e., alignment == 2MB and offset
> == 512 KB. The offset would default to 0, reverting to the original
> behavior.
> 
> If you'd be ok with such a change, I can propose it instead, and wire
> it up into this function.

It's probably because it's late but I'm having trouble thinking this
change through fully.

If it's not too much work, sure, please go ahead and propose a patch,
even the untested, uncompiled "this is what I'm thinking" type.

-- 
Matt Fleming, Intel Open Source Technology Center

[PATCH v2] arm64/efi: prefer AllocatePages() over efi_low_alloc() for vmlinux

[Will Deacon]

On Tue, Jul 28, 2015 at 10:24:23PM +0100, Ard Biesheuvel wrote:
> On 28 July 2015 at 23:17, Matt Fleming <matt@codeblueprint.co.uk> wrote:
> > On Fri, 24 Jul, at 01:38:27PM, Ard Biesheuvel wrote:
> >> When allocating memory for the kernel image, try the AllocatePages()
> >> boot service to obtain memory at the preferred offset of
> >> 'dram_base + TEXT_OFFSET', and only revert to efi_low_alloc() if that
> >> fails. This is the only way to allocate at the base of DRAM if DRAM
> >> starts at 0x0, since efi_low_alloc() refuses to allocate at 0x0.
> >>
> >> Tested-by: Haojian Zhuang <haojian.zhuang@linaro.org>
> >> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
> >> ---
> >> v2:
> >> - reshuffle code flow to make it more logical, and have only a single
> >>   memcpy() invocation at the end of the function
> >> ---
> >>  arch/arm64/kernel/efi-stub.c | 41 ++++++++++++++++++++++++++++++++---------
> >>  1 file changed, 32 insertions(+), 9 deletions(-)
> >
> > Would it be easier if we allow efi_low_alloc() to return 0x0 for some
> > uses? If you don't need the preference for low allocations, probably
> > not, but I don't want to see us working around limitations in
> > efi_low_alloc() instead of just fixing it.
> >
> 
> This workaround fixes another issue as well: the arm64 kernel needs to
> be loaded 512 KB above a 2MB aligned boundary, and using
> efi_low_alloc() as we do loses (2 MB - 512 KB) at the bottom if part
> of that 512 KB is occupied, since efi_low_alloc() is not aware of the
> fact that the first 512 KB will remain unused.
> 
> What would be most helpful is if efi_low_alloc() could take an offset
> param in addition to the alignment, i.e., alignment == 2MB and offset
> == 512 KB. The offset would default to 0, reverting to the original
> behavior.
> 
> If you'd be ok with such a change, I can propose it instead, and wire
> it up into this function.

I already merged the original patch, so if you propose anything extra,
please do it on top of that!

Will

[PATCH v2] arm64/efi: prefer AllocatePages() over efi_low_alloc() for vmlinux

[Timur Tabi]

On Fri, Jul 24, 2015 at 6:38 AM, Ard Biesheuvel
<ard.biesheuvel@linaro.org> wrote:
>
> +               /*
> +                * First, try a straight allocation at the preferred offset.
> +                * This will work around the issue where, if dram_base == 0x0,
> +                * efi_low_alloc() refuses to allocate at 0x0 (to prevent the
> +                * address of the allocation to be mistaken for a FAIL return
> +                * value or a NULL pointer). It will also ensure that, on
> +                * platforms where the [dram_base, dram_base + TEXT_OFFSET)
> +                * interval is partially occupied by the firmware (like on APM
> +                * Mustang), we can still place the kernel at the address
> +                * 'dram_base + TEXT_OFFSET'.
> +                */
> +               *image_addr = *reserve_addr = dram_base + TEXT_OFFSET;
> +               nr_pages = round_up(kernel_memsize, EFI_ALLOC_ALIGN) /
> +                          EFI_PAGE_SIZE;
> +               status = efi_call_early(allocate_pages, EFI_ALLOCATE_ADDRESS,
> +                                       EFI_LOADER_DATA, nr_pages,
> +                                       (efi_physical_addr_t *)reserve_addr);

This causes our kernel to crash, because on our system, dram_base is
not 2MB aligned.  I'll be posting a patch soon that fixes this.

-- 
Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project.