Le 01/08/2021 à 03:21, Finn Thain a écrit :

On Sat, 31 Jul 2021, Christophe Leroy wrote:

quoted

quoted

Stan Johnson contacted me about a regression in mainline that he
observed on his G3 Powerbooks. Using 'git bisect' we determined that
this patch was the cause of the regression, i.e. commit 4c0104a83fc3
("powerpc/32: Dismantle EXC_XFER_STD/LITE/TEMPLATE").

When testing 4c0104a83fc and all subsequent builds, various user
processes were liable to segfault. Here is the console log that Stan
provided:

Hi, i will be able to look at that more in details next week, however I
have a few preliminary qurstions.

Can you reliabily reproduce the problem with the said commit, and can
you reliabily run without problem with the parent commit ?

Yes and yes. (I already asked Stan to establish those things before I
contacted the list.)

I think I found the problem with that commit. Can you retry with the 
following change:

diff --git a/arch/powerpc/kernel/head_book3s_32.S 

b/arch/powerpc/kernel/head_book3s_32.S
index 0a3d7d4a9ec4..a294103a91a1 100644

--- a/arch/powerpc/kernel/head_book3s_32.S
+++ b/arch/powerpc/kernel/head_book3s_32.S

@@ -299,7 +299,7 @@ ALT_MMU_FTR_SECTION_END_IFSET(MMU_FTR_HPTE_TABLE)
  	EXCEPTION_PROLOG_1
  	EXCEPTION_PROLOG_2 0x300 DataAccess handle_dar_dsisr=1
  	prepare_transfer_to_handler
-	lwz	r5, _DSISR(r11)
+	lwz	r5, _DSISR(r1)
  	andis.	r0, r5, DSISR_DABRMATCH@h
  	bne-	1f
  	bl	do_page_fault

---
Thanks
Christophe