[kvm-unit-tests PATCH v2 16/18] arm64: efi: Fix _start returns from failed _relocate

Andrew Jones
2024-02-27T19:22:22Z

If _relocate fails we need to restore the frame pointer and the link
register and return from _start. But we've pushed x0 and x1 on below
the fp and lr, so, as the code was, we'd restore the wrong values.
Revert parts of the code back to the way they are in gnu-efi and move
the stack alignment below the loading of x0 and x1, after we've
confirmed _relocate didn't fail.

Fixes: d231b539a41f ("arm64: Use code from the gnu-efi when booting with EFI")
Signed-off-by: Andrew Jones <andrew.jones@linux.dev>
---
arm/efi/crt0-efi-aarch64.S | 25 +++++++++++++------------
1 file changed, 13 insertions(+), 12 deletions(-)

diff --git a/arm/efi/crt0-efi-aarch64.S b/arm/efi/crt0-efi-aarch64.S
index 5d0dc04af54a..5fd3dc94dae8 100644
--- a/arm/efi/crt0-efi-aarch64.S
+++ b/arm/efi/crt0-efi-aarch64.S
@@ -111,17 +111,10 @@ section_table:

.align 12
_start:
- stp x29, x30, [sp, #-16]!
-
- /* Align sp; this is necessary due to way we store cpu0's thread_info */
+ stp x29, x30, [sp, #-32]!
mov x29, sp
- mov x30, sp
- and x30, x30, #THREAD_MASK
- mov sp, x30
- str x29, [sp, #-16]!
-
- stp x0, x1, [sp, #-16]!

+ stp x0, x1, [sp, #16]
mov x2, x0
mov x3, x1
adr x0, ImageBase
@@ -130,12 +123,20 @@ _start:
bl _relocate
cbnz x0, 0f

- ldp x0, x1, [sp], #16
+ ldp x0, x1, [sp, #16]
+
+ /* Align sp; this is necessary due to way we store cpu0's thread_info */
+ mov x29, sp
+ mov x30, sp
+ and x30, x30, #THREAD_MASK
+ mov sp, x30
+ str x29, [sp, #-16]!
+
bl efi_main

/* Restore sp */
ldr x30, [sp], #16
- mov sp, x30
+ mov sp, x30

-0: ldp x29, x30, [sp], #16
+0: ldp x29, x30, [sp], #32
ret
--
2.43.0