* Alex Thorlton <athorlton@xxxxxxx> wrote: > The efi_call assembly code has a slight error that prevents us from > using arguments 7 and higher, which will be passed in on the stack. > > mov (%rsp), %rax > mov 8(%rax), %rax > ... > mov %rax, 40(%rsp) > > This code goes and grabs the return address for the current stack frame, > and puts it on the stack, next the 5th argument for the EFI runtime > call. Considering the fact that having the return address in that > position on the stack makes no sense, I'm guessing that the intent of > this code was actually to grab an argument off the stack frame for this > call and place it into the frame for the next one. > > The small change to that offset (i.e. 8(%rax) to 16(%rax)) ensures that > we grab the 7th argument off the stack, and pass it as the 6th argument > to the EFI runtime function that we're about to call. This change gets > our EFI runtime calls that need to pass more than 6 arguments working > again. I suppose the SGI/UV code is the only one using 7 arguments or more? Might make sense to point that out in the changelog. > > Signed-off-by: Alex Thorlton <athorlton@xxxxxxx> > Cc: Dimitri Sivanich <sivanich@xxxxxxx> > Cc: Russ Anderson <rja@xxxxxxx> > Cc: Mike Travis <travis@xxxxxxx> > Cc: Matt Fleming <matt@xxxxxxxxxxxxxxxxxxx> > Cc: Borislav Petkov <bp@xxxxxxx> > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> > Cc: Ingo Molnar <mingo@xxxxxxxxxx> > Cc: "H. Peter Anvin" <hpa@xxxxxxxxx> > Cc: x86@xxxxxxxxxx > Cc: linux-efi@xxxxxxxxxxxxxxx > --- > arch/x86/platform/efi/efi_stub_64.S | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/x86/platform/efi/efi_stub_64.S b/arch/x86/platform/efi/efi_stub_64.S > index 92723ae..62938ff 100644 > --- a/arch/x86/platform/efi/efi_stub_64.S > +++ b/arch/x86/platform/efi/efi_stub_64.S > @@ -43,7 +43,7 @@ ENTRY(efi_call) > FRAME_BEGIN > SAVE_XMM > mov (%rsp), %rax > - mov 8(%rax), %rax > + mov 16(%rax), %rax > subq $48, %rsp > mov %r9, 32(%rsp) > mov %rax, 40(%rsp) Just curious, how did you find this bug? It's a pretty obscure one, of the 'developer tears out hairs from frustruation' type ... Thanks, Ingo -- To unsubscribe from this list: send the line "unsubscribe linux-efi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
