| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <cce19b1c-449a-f306-533a-9edc855049aa@csgroup.eu>
Date: Wed, 29 Jun 2022 18:30:23 +0000
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: Sathvika Vasireddy <sv@...ux.vnet.ibm.com>,
Sathvika Vasireddy <sv@...ux.ibm.com>,
"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>
CC: "jpoimboe@...hat.com" <jpoimboe@...hat.com>,
"peterz@...radead.org" <peterz@...radead.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"aik@...abs.ru" <aik@...abs.ru>,
"mpe@...erman.id.au" <mpe@...erman.id.au>,
"mingo@...hat.com" <mingo@...hat.com>,
"rostedt@...dmis.org" <rostedt@...dmis.org>,
"naveen.n.rao@...ux.vnet.ibm.com" <naveen.n.rao@...ux.vnet.ibm.com>,
"mbenes@...e.cz" <mbenes@...e.cz>,
"benh@...nel.crashing.org" <benh@...nel.crashing.org>,
"paulus@...ba.org" <paulus@...ba.org>,
Chen Zhongjin <chenzhongjin@...wei.com>,
Marc Zyngier <maz@...nel.org>,
Linux ARM <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [RFC PATCH v3 11/12] powerpc: Remove unreachable() from WARN_ON()
Hi Sathvika,
Adding ARM people as they seem to face the same kind of problem (see
https://patchwork.kernel.org/project/linux-kbuild/patch/20220623014917.199563-33-chenzhongjin@huawei.com/)
Le 27/06/2022 à 17:35, Sathvika Vasireddy a écrit :
>
> On 25/06/22 12:16, Christophe Leroy wrote:
>>
>> Le 24/06/2022 à 20:32, Sathvika Vasireddy a écrit :
>>> objtool is throwing *unannotated intra-function call*
>>> warnings with a few instructions that are marked
>>> unreachable. Remove unreachable() from WARN_ON()
>>> to fix these warnings, as the codegen remains same
>>> with and without unreachable() in WARN_ON().
>> Did you try the two exemples described in commit 1e688dd2a3d6
>> ("powerpc/bug: Provide better flexibility to WARN_ON/__WARN_FLAGS() with
>> asm goto") ?
>>
>> Without your patch:
>>
>> 00000640 <test>:
>> 640: 81 23 00 84 lwz r9,132(r3)
>> 644: 71 29 40 00 andi. r9,r9,16384
>> 648: 40 82 00 0c bne 654 <test+0x14>
>> 64c: 80 63 00 0c lwz r3,12(r3)
>> 650: 4e 80 00 20 blr
>> 654: 0f e0 00 00 twui r0,0
>>
>> 00000658 <test9w>:
>> 658: 2c 04 00 00 cmpwi r4,0
>> 65c: 41 82 00 0c beq 668 <test9w+0x10>
>> 660: 7c 63 23 96 divwu r3,r3,r4
>> 664: 4e 80 00 20 blr
>> 668: 0f e0 00 00 twui r0,0
>> 66c: 38 60 00 00 li r3,0
>> 670: 4e 80 00 20 blr
>>
>>
>> With your patch:
>>
>> 00000640 <test>:
>> 640: 81 23 00 84 lwz r9,132(r3)
>> 644: 71 29 40 00 andi. r9,r9,16384
>> 648: 40 82 00 0c bne 654 <test+0x14>
>> 64c: 80 63 00 0c lwz r3,12(r3)
>> 650: 4e 80 00 20 blr
>> 654: 0f e0 00 00 twui r0,0
>> 658: 4b ff ff f4 b 64c <test+0xc> <==
>>
>> 0000065c <test9w>:
>> 65c: 2c 04 00 00 cmpwi r4,0
>> 660: 41 82 00 0c beq 66c <test9w+0x10>
>> 664: 7c 63 23 96 divwu r3,r3,r4
>> 668: 4e 80 00 20 blr
>> 66c: 0f e0 00 00 twui r0,0
>> 670: 38 60 00 00 li r3,0 <==
>> 674: 4e 80 00 20 blr <==
>> 678: 38 60 00 00 li r3,0
>> 67c: 4e 80 00 20 blr
>>
> The builtin variant of unreachable (__builtin_unreachable()) works.
>
> How about using that instead of unreachable() ?
>
>
In fact the problem comes from the macro annotate_unreachable() which is
called by unreachable() before calling __build_unreachable().
Seems like this macro adds (after the unconditional trap twui) a call to
an empty function whose address is listed in section .discard.unreachable
1c78: 00 00 e0 0f twui r0,0
1c7c: 55 e7 ff 4b bl 3d0
<qdisc_root_sleeping_lock.part.0>
RELOCATION RECORDS FOR [.discard.unreachable]:
OFFSET TYPE VALUE
0000000000000000 R_PPC64_REL32 .text+0x00000000000003d0
The problem is that that function has size 0:
00000000000003d0 l F .text 0000000000000000
qdisc_root_sleeping_lock.part.0
And objtool is not prepared for a function with size 0.
The following changes to objtool seem to fix the problem, most warning
are gone with that change.
diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index 63218f5799c2..37c0a268b7ea 100644
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -77,6 +77,8 @@ static int symbol_by_offset(const void *key, const
struct rb_node *node)
if (*o < s->offset)
return -1;
+ if (*o == s->offset && !s->len)
+ return 0;
if (*o >= s->offset + s->len)
return 1;
@@ -400,7 +402,7 @@ static void elf_add_symbol(struct elf *elf, struct
symbol *sym)
* Don't store empty STT_NOTYPE symbols in the rbtree. They
* can exist within a function, confusing the sorting.
*/
- if (!sym->len)
+ if (sym->type == STT_NOTYPE && !sym->len)
rb_erase(&sym->node, &sym->sec->symbol_tree);
}
---
I also had objtool running for ever on
arch/powerpc/sysdev/xics/icp-hv.o, which I fixed with the below hack:
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 51b6dcec8d6a..ef2303ad6381 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -529,7 +529,7 @@ static struct instruction *find_last_insn(struct
objtool_file *file,
unsigned int offset;
unsigned int end = (sec->sh.sh_size > 10) ? sec->sh.sh_size - 10 : 0;
- for (offset = sec->sh.sh_size - 1; offset >= end && !insn; offset--)
+ for (offset = sec->sh.sh_size - 1; offset && offset >= end && !insn;
offset--)
insn = find_insn(file, sec, offset);
return insn;
---
Now I only have the following two warnings:
arch/powerpc/sysdev/xics/icp-hv.o: warning: objtool: can't find
unreachable insn at .text.unlikely+0x0
drivers/crypto/vmx/aesp8-ppc.o: warning: objtool:
aes_p8_set_encrypt_key+0x44: unannotated intra-function call
The first one is linked to the infinite loop I hacked. So I now have to
understand what the problem really is.
The second one is an assembly file aesp8-ppc.S which lacks the changes
you did in other assembly files in patch 12.
Christophe
Powered by blists - more mailing lists