On 7/5/2016 4:57 PM, Jason Baron wrote:
On 07/01/2016 03:30 PM, Chris Metcalf wrote:
On 6/10/2016 5:28 PM, Jason Baron wrote:
Hi Arnd,
Ok, I managed to reproduce this on tile and sparc64 by adding
static_branch_[un]likely() to __exit functions as you mentioned.
Although I didn't find the actual broken config.
I think its only an issue on those 2 arches b/c they have jump
label support and discard __exit text at build time (most
arches seem to do it at run-time). Thus, we can end up with
references in the __jump_table to addresses that may be in an
__exit section. The jump label code already protects itself
from touch code in the init sections after it has been freed.
Thus, simply having functions marked with __exit in the init
section is sufficient here.
How does this patch work instead?
diff --git a/arch/tile/kernel/vmlinux.lds.S
b/arch/tile/kernel/vmlinux.lds.S
index 378f5d8d1ec8..5e83d2689def 100644
--- a/arch/tile/kernel/vmlinux.lds.S
+++ b/arch/tile/kernel/vmlinux.lds.S
@@ -58,7 +58,15 @@ SECTIONS
_etext = .;
/* "Init" is divided into two areas with very different virtual
addresses. */
- INIT_TEXT_SECTION(PAGE_SIZE)
+ . = ALIGN(PAGE_SIZE);
+ .init.text : AT(ADDR(.init.text) - LOAD_OFFSET) {
+ VMLINUX_SYMBOL(_sinittext) = .;
+ INIT_TEXT
+#ifdef CONFIG_JUMP_LABEL /* __jump_table may reference __exit text */
+ EXIT_TEXT
+#endif
+ VMLINUX_SYMBOL(_einittext) = .;
+ }
/* Now we skip back to PAGE_OFFSET for the data. */
. = (. - TEXT_OFFSET + PAGE_OFFSET);
Hi Chris,
Thanks for the patch. I can confirm that it resolves the following
compilation issue:
`.exit.text' referenced in section `__jump_table' of fs/built-in.o:
defined in discarded section `.exit.text' of fs/built-in.o
`.exit.text' referenced in section `__jump_table' of fs/built-in.o:
defined in discarded section `.exit.text' of fs/built-in.o
I was able to create the issue by simply adding a
static_key_unlikely() branch to an __exit section that ends
up being built-in (non-module).
So this issue is really independent of this patch series...
Should I add your patch to my series when I re-post?
I'm happy to just take a version of this into the tile tree instead, since
you're right, it's a pre-existing problem. I'll post the revised change
shortly and cc you. Thanks!
--
Chris Metcalf, Mellanox Technologies
http://www.mellanox.com
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