git: 187492ef639f - stable/13 - powerpc64: Fix boot on virtual-mode OF (PowerMac G5)

[Brandon Bergren]

The branch stable/13 has been updated by bdragon:

URL: https://cgit.FreeBSD.org/src/commit/?id=187492ef639fecde6c122838cfff0a75d8b94608

commit 187492ef639fecde6c122838cfff0a75d8b94608
Author:     Brandon Bergren <bdragon at FreeBSD.org>
AuthorDate: 2021-02-07 22:05:41 +0000
Commit:     Brandon Bergren <bdragon at FreeBSD.org>
CommitDate: 2021-02-10 03:19:45 +0000

    powerpc64: Fix boot on virtual-mode OF (PowerMac G5)
    
    In 78599c32efed3247d165302a1fbe8d9203e38974, CFI endproc decoration was
    added to locore64.S. However, it missed the subtle detail that
    __restartkernel_virtual() falls through to __restartkernel(). This was
    causing boot failure on PowerMac G5, as it tried to execute the
    epilogue as code.
    
    Fix this by branching to __restartkernel() instead of intentionally
    running off the end of the function.
    
    While here, add some additional notes on how the virtual mode restart
    works.
    
    (cherry picked from commit d26f2a50ff48dacd38ba358d658882d51f7bdbc4)
---
 sys/powerpc/aim/locore64.S | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/sys/powerpc/aim/locore64.S b/sys/powerpc/aim/locore64.S
index 0bc0619620d9..f0a183c4b331 100644
--- a/sys/powerpc/aim/locore64.S
+++ b/sys/powerpc/aim/locore64.S
@@ -255,6 +255,16 @@ ASENTRY_NOPROF(__restartkernel_virtual)
 	addi	%r14, %r14, 1
 	cmpdi	%r14, 16
 	blt	1b
+
+	/*
+	 * Now that we are set up with a temporary direct map, we can
+	 * continue with __restartkernel. Translation will be switched
+	 * back on at the rfid, at which point we will be executing from
+	 * the temporary direct map we just installed, until the kernel
+	 * takes over responsibility for the MMU.
+	 */
+	bl	__restartkernel
+	nop
 ASEND(__restartkernel_virtual)
 
 ASENTRY_NOPROF(__restartkernel)