On 02/28/2017 11:34 AM, Jason Baron wrote:
On 02/28/2017 02:22 PM, David Daney wrote:
On 02/28/2017 11:05 AM, David Daney wrote:
On 02/28/2017 10:39 AM, Jason Baron wrote:
[...]
I suspect that the alignment of the __jump_table section in the .ko
files is not correct, and you are seeing some sort of problem due to
that.
Hi,
Yes, if you look at the trace that Sachin sent the module being loaded
that does the WARN_ON() is nfsd.ko.
That module from Sachin's trace has:
[31] __jump_table PROGBITS 0000000000000000 03fd77 0000c0
18 WAM 0 0 1
The problem is then the section alignment (last column) for power.
On mips with no patches applied, we get:
[17] __jump_table PROGBITS 0000000000000000 00d2c0 000048
00 WA 0 0 8
Look, proper alignment!
The question I have is why do the power ".llong" and ".long" assembler
directives not force section alignment? Is there an alternative that
could be used that would result in the proper alignment? Would ".word"
work?
If not, then I would say patch only power with your balign thing. 8-byte
alignment for 64-bit kernel, 4-byte alignment for 32-bit kernel
I think the proper fix is either:
A) Modify scripts/module-common.lds to force __jump_table alignment for
all architectures.
B) Add arch/powerpc/kernel/module.lds to force __jump_table alignment
for powerpc only.
David.
Ok, I can try adding it to the linger script.
FWIW, here is my before and after with the .balign thing for the nfsd.ko
module on powperc (using a cross-compiler):
before:
[31] __jump_table PROGBITS 0000000000000000 03ee3e 0000f0
00 WA 0 0 1
after:
[31] __jump_table PROGBITS 0000000000000000 03ee40 0000f0
00 WA 0 0 4
Try the (lightly tested) attached.
If it works and Steven likes it, perhaps someone can merge it.
David.
>From 89d4deafbc920351b93afb1ac4b4124995e1f19d Mon Sep 17 00:00:00 2001
From: David Daney <david.daney@xxxxxxxxxx>
Date: Tue, 28 Feb 2017 12:10:02 -0800
Subject: [PATCH] module: set __jump_table alignment to 8
For powerpc the __jump_table section in modules is not aligned, this
causes an OOPS when loading a module containing a __jump_table.
Fix by forcing __jump_table to 8, which is the same alignment used for
this section in the kernel proper.
Signed-off-by: David Daney <david.daney@xxxxxxxxxx>
---
scripts/module-common.lds | 2 ++
1 file changed, 2 insertions(+)
diff --git a/scripts/module-common.lds b/scripts/module-common.lds
index 73a2c7d..53234e8 100644
--- a/scripts/module-common.lds
+++ b/scripts/module-common.lds
@@ -19,4 +19,6 @@ SECTIONS {
. = ALIGN(8);
.init_array 0 : { *(SORT(.init_array.*)) *(.init_array) }
+
+ __jump_table 0 : ALIGN(8) { KEEP(*(__jump_table)) }
}
--
2.9.3
