On 9/27/20 10:40 AM, Bin Meng wrote:
> On Sun, Sep 27, 2020 at 4:24 PM Heinrich Schuchardt <xypron.g...@gmx.de>
> wrote:
>>
>> The gp register is used to store U-Boot's global data pointer. We should
>> not assume that an UEFI application leaves the gp register unchanged as
>> the UEFI specifications does not define who is the owner of the gp and tp
>> registers.
>>
>> So the following sequence should be followed in the trap handler:
>>
>> * save the caller's gp register
>> * restore the global data pointer
>> * serve interrupts or print crash dump and reset
>> * restore the caller's gp register
>>
>> Cc: Abner Chang <abner.ch...@hpe.com>
>> Signed-off-by: Heinrich Schuchardt <xypron.g...@gmx.de>
>> ---
>> v2:
>> Saving and restoring the caller's x3 is already handled in mtrap.S.
>> efi_loader.h provides an empty fallback efi_restore_gd() function
>> if CONFIG_EFI_LOADER=n.
>> ---
>> arch/riscv/lib/interrupts.c | 3 +++
>> 1 file changed, 3 insertions(+)
>>
>> diff --git a/arch/riscv/lib/interrupts.c b/arch/riscv/lib/interrupts.c
>> index cd47e64487..8ff40f0f36 100644
>> --- a/arch/riscv/lib/interrupts.c
>> +++ b/arch/riscv/lib/interrupts.c
>> @@ -111,6 +111,9 @@ ulong handle_trap(ulong cause, ulong epc, ulong tval,
>> struct pt_regs *regs)
>> {
>> ulong is_irq, irq;
>>
>> + /* An UEFI application may have changed gd. Restore U-Boot's gd. */
>> + efi_restore_gd();
>> +
>> is_irq = (cause & MCAUSE_INT);
>> irq = (cause & ~MCAUSE_INT);
>>
>
> Reviewed-by: Bin Meng <bin.m...@windriver.com>
>
> Does other arch suffer the same issue?
>
Hello Bin,
x86 does not use a register of gd.
arm has this statement already.
No further architectures support UEFI.
Best regards
Heinrich
