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?
