Hi Ard,
On 22-12-2019 13:02, Ard Biesheuvel wrote:
On Sat, 21 Dec 2019 at 22:22, Hans de Goede <hdegoede@xxxxxxxxxx> wrote:
Hi Ard,
On 18-12-2019 18:01, Ard Biesheuvel wrote:
We use special wrapper routines to invoke firmware services in the
native case as well as the mixed mode case. For mixed mode, the need
is obvious, but for the native cases, we can simply rely on the
compiler to generate the indirect call, given that GCC now has
support for the MS calling convention (and has had it for quite some
time now). Note that on i386, the decompressor and the EFI stub are not
built with -mregparm=3 like the rest of the i386 kernel, so we can
safely allow the compiler to emit the indirect calls here as well.
So drop all the wrappers and indirection, and switch to either native
calls, or direct calls into the thunk routine for mixed mode.
Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
I'm afraid that this patch breaks the boot on one of my machines.
Specifically this patch breaks my GDP pocket machine. This is a Cherry
Trail device with a 64 UEFI running a 64 bit kernel build.
As soon as I cherry pick this patch into my personal 5.5.0-rc2 based
tree, the GPD pocket stops booting and it stop so early on that I get 0
debug output. I guess I could try adding a few pr_efi_err calls
and see if those still do something.
I noticed that you have made some changes to this patch, I've
tried updating it to the version from your efistub-x86-cleanup-v3
branch, commit id a37d90a2c570a25926fd1645482cb9f3c1d042a0
and I have also cherry-picked the latest version of all preceding
commits, unfortunately even with the new version, the GPD pocket
still hangs at boot.
Unfortunately the nature of this patch makes it hard to figure
out the root cause of this issue...
I've also tried another Cherry Trail device with 64 bit UEFI and
that does not suffer from this problem.
Thanks Hans.
There are a number of things that change in the way the calls are
made, but the most obvious thing to check is whether the stack needs
to be aligned, since that is no longer being done.
If you have time to experiment a bit more, could you check whether
doing 'and $~0xf %rsp' before 'call efi_main' in the .S stub code for
x86_64 makes a difference?
Ok, so I made this change on top of a37d90a2c570a25926fd1645482cb9f3c1d042a0
(the last "efi/libstub/x86: avoid thunking for native firmware calls" version
I tried before reporting this problem) :
--- a/arch/x86/boot/compressed/head_64.S
+++ b/arch/x86/boot/compressed/head_64.S
@@ -464,6 +464,7 @@ SYM_FUNC_START(efi_pe_entry)
handover_entry:
movq efi_config(%rip), %rdi
+ and $~0xf, %rsp
call efi_main
movq %rax,%rsi
cmpq $0,%rax
And that does the trick, the GPD pocket boots successfully with commit
a37d90a2c570a25926fd1645482cb9f3c1d042a0 + the above change.
So it looks like your first hunch on how to fix this is correct :)
Regards,
Hans
