On 24 July 2015 at 12:49, Mark Rutland <mark.rutland@xxxxxxx> wrote:
> Hi Ard,
>
> On Fri, Jul 24, 2015 at 10:41:53AM +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@xxxxxxxxxx>
>> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
>> ---
>> arch/arm64/kernel/efi-stub.c | 47 ++++++++++++++++++++++++++++++++++++--------
>> 1 file changed, 39 insertions(+), 8 deletions(-)
>>
>> diff --git a/arch/arm64/kernel/efi-stub.c b/arch/arm64/kernel/efi-stub.c
>> index f5374065ad53..c8df74d14368 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,
>
> Any reason for the _arg addition?
>
Yes. Unfortunately, the efi_call_early() macro has a hidden
'efi_system_table_t *' parameter which it refers to by the name
'sys_table_arg'
>> unsigned long *image_addr,
>> unsigned long *image_size,
>> unsigned long *reserve_addr,
>> @@ -23,21 +23,52 @@ 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;
>>
>> /* 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'.
>> + //
>
> /*
> * Nit: please use the standard comment style
> */
>
Absolutely. EDK2 development must be really screwing with my brain if
I am unconsciously using C++ style comments in C code. Time to move
back to the light side for a while :-)
>> + *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) {
>> + memcpy((void *)*reserve_addr, (void *)*image_addr,
>> + kernel_size);
>> + *image_addr = *reserve_addr;
>> + *reserve_size = kernel_memsize;
>> + } else {
>> + status = efi_low_alloc(sys_table_arg,
>> + kernel_memsize + TEXT_OFFSET,
>> + SZ_2M, reserve_addr);
>> +
>> + if (status == EFI_SUCCESS) {
>> + memcpy((void *)*reserve_addr + TEXT_OFFSET,
>> + (void *)*image_addr,
>> + kernel_size);
>> + *image_addr = *reserve_addr + TEXT_OFFSET;
>> + *reserve_size = kernel_memsize + TEXT_OFFSET;
>> + }
>> + }
>> if (status != EFI_SUCCESS) {
>> - pr_efi_err(sys_table, "Failed to relocate kernel\n");
>> + pr_efi_err(sys_table_arg, "Failed to relocate kernel\n");
>> return status;
>> }
>> - memcpy((void *)*reserve_addr + TEXT_OFFSET, (void *)*image_addr,
>> - kernel_size);
>
> Could we have a new_image_addr assigned in each case, and keep the
> common memcpy here, followed by assignment to *image_addr? That would
> save a couple of lines and guarantee the two cases stay in sync.
>
Well, the memcpy() occurs before the assignment of *image_addr, which
is also used as the src arg. So I could record the value of
*image_addr in a temp, I suppose. I will do that in the next version.
> Otherwise this looks good to me.
>
Thanks,
Ard.
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