From: Daniel Wagner <daniel.wagner@bmw-carit.de>
To: "Maciej W. Rozycki" <macro@imgtec.com>
Cc: <linux-mips@linux-mips.org>, <linux-kernel@vger.kernel.org>,
Ralf Baechle <ralf@linux-mips.org>
Subject: Re: [PATCH] MIPS: Differentiate between 32 and 64 bit ELF header
Date: Mon, 1 Feb 2016 17:07:07 +0100 [thread overview]
Message-ID: <56AF82AB.5010502@bmw-carit.de> (raw)
In-Reply-To: <alpine.DEB.2.00.1602010038230.5958@tp.orcam.me.uk>
On 02/01/2016 01:52 AM, Maciej W. Rozycki wrote:
> On Fri, 29 Jan 2016, Daniel Wagner wrote:
>
>> Depending on the configuration either the 32 or 64 bit version of
>> elf_check_arch() is defined. parse_crash_elf32_headers() does
>> some basic verification of the ELF header via elf_check_arch().
>> parse_crash_elf64_headers() does it via vmcore_elf64_check_arch()
>> which expands to the same elf_check_check().
>>
>> In file included from include/linux/elf.h:4:0,
>> from fs/proc/vmcore.c:13:
>> fs/proc/vmcore.c: In function 'parse_crash_elf64_headers':
>>>> arch/mips/include/asm/elf.h:228:23: error: initialization from incompatible pointer type [-Werror=incompatible-pointer-types]
>> struct elfhdr *__h = (hdr); \
>> ^
>> include/linux/crash_dump.h:41:37: note: in expansion of macro 'elf_check_arch'
>> #define vmcore_elf64_check_arch(x) (elf_check_arch(x) || vmcore_elf_check_arch_cross(x))
>> ^
>> fs/proc/vmcore.c:1015:4: note: in expansion of macro 'vmcore_elf64_check_arch'
>> !vmcore_elf64_check_arch(&ehdr) ||
>> ^
>>
>> Since the MIPS ELF header for 32 bit and 64 bit differ we need
>> to check accordingly.
>
> I fail to see how it can work as it stands given that `elf_check_arch' is
> called from the same source file both on a pointer to `Elf32_Ehdr' and one
> to `Elf64_Ehdr'. However the MIPS implementations of `elf_check_arch'
> only use an auxiliary variable to avoid multiple evaluation of a macro
> argument and therefore instead I recommend the use of the usual approach
> taken in such a situation within a statement expression, that is to
> declare the variable with `typeof' rather than an explicit type. As an
> upside this will minimise code disruption as well.
Good point on the type for hdr. Thought elf_check_arch() implementation
differ on 32 bit and 64 bit implementation. I played a bit around and the
simplest version I found was this here:
diff --git a/arch/mips/include/asm/elf.h b/arch/mips/include/asm/elf.h
index b01a6ff..8c88238 100644
--- a/arch/mips/include/asm/elf.h
+++ b/arch/mips/include/asm/elf.h
@@ -205,8 +205,6 @@ struct mips_elf_abiflags_v0 {
#define MIPS_ABI_FP_64 6 /* -mips32r2 -mfp64 */
#define MIPS_ABI_FP_64A 7 /* -mips32r2 -mfp64 -mno-odd-spreg */
-#ifdef CONFIG_32BIT
-
/*
* In order to be sure that we don't attempt to execute an O32 binary which
* requires 64 bit FP (FR=1) on a system which does not support it we refuse
@@ -225,23 +223,30 @@ struct mips_elf_abiflags_v0 {
#define elf_check_arch(hdr) \
({ \
int __res = 1; \
- struct elfhdr *__h = (hdr); \
+ typeof(*(hdr)) *__h = (hdr); \
\
if (__h->e_machine != EM_MIPS) \
__res = 0; \
- if (__h->e_ident[EI_CLASS] != ELFCLASS32) \
- __res = 0; \
- if ((__h->e_flags & EF_MIPS_ABI2) != 0) \
- __res = 0; \
- if (((__h->e_flags & EF_MIPS_ABI) != 0) && \
- ((__h->e_flags & EF_MIPS_ABI) != EF_MIPS_ABI_O32)) \
- __res = 0; \
- if (__h->e_flags & __MIPS_O32_FP64_MUST_BE_ZERO) \
- __res = 0; \
+ if (__same_type(hdr, Elf32_Ehdr *)) { \
+ if (__h->e_ident[EI_CLASS] != ELFCLASS32) \
+ __res = 0; \
+ if ((__h->e_flags & EF_MIPS_ABI2) != 0) \
+ __res = 0; \
+ if (((__h->e_flags & EF_MIPS_ABI) != 0) && \
+ ((__h->e_flags & EF_MIPS_ABI) != EF_MIPS_ABI_O32)) \
+ __res = 0; \
+ if (__h->e_flags & __MIPS_O32_FP64_MUST_BE_ZERO) \
+ __res = 0; \
+ } else if (__same_type(hdr, Elf64_Ehdr *)) { \
+ if (__h->e_ident[EI_CLASS] != ELFCLASS64) \
+ __res = 0; \
+ } \
\
__res; \
})
+#ifdef CONFIG_32BIT
+
/*
* These are used to set parameters in the core dumps.
*/
@@ -250,21 +255,6 @@ struct mips_elf_abiflags_v0 {
#endif /* CONFIG_32BIT */
#ifdef CONFIG_64BIT
-/*
- * This is used to ensure we don't load something for the wrong architecture.
- */
-#define elf_check_arch(hdr) \
-({ \
- int __res = 1; \
- struct elfhdr *__h = (hdr); \
- \
- if (__h->e_machine != EM_MIPS) \
- __res = 0; \
- if (__h->e_ident[EI_CLASS] != ELFCLASS64) \
- __res = 0; \
- \
- __res; \
-})
/*
* These are used to set parameters in the core dumps.
Not sure if that is what you had in mind.
cheers,
daniel
next prev parent reply other threads:[~2016-02-01 16:07 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-28 14:44 [PATCH tip v6 0/5] Simple wait queue support Daniel Wagner
2016-01-28 14:44 ` [PATCH tip v6 1/5] wait.[ch]: Introduce the simple waitqueue (swait) implementation Daniel Wagner
2016-01-28 14:44 ` [PATCH tip v6 2/5] kbuild: Add option to turn incompatible pointer check into error Daniel Wagner
2016-01-29 12:17 ` Daniel Wagner
2016-01-29 18:55 ` Paul Gortmaker
2016-02-01 6:49 ` Daniel Wagner
2016-02-05 8:16 ` Daniel Wagner
2016-02-07 4:39 ` Paul Gortmaker
2016-02-17 13:04 ` Daniel Wagner
2016-01-28 14:44 ` [PATCH tip v6 3/5] KVM: use simple waitqueue for vcpu->wq Daniel Wagner
2016-01-29 12:18 ` Daniel Wagner
2016-01-28 14:44 ` [PATCH tip v6 4/5] rcu: Do not call rcu_nocb_gp_cleanup() while holding rnp->lock Daniel Wagner
2016-01-28 14:44 ` [PATCH tip v6 5/5] rcu: use simple wait queues where possible in rcutree Daniel Wagner
2016-01-29 13:23 ` [PATCH] video: Use bool instead int pointer for get_opt_bool() argument Daniel Wagner
2016-01-29 13:28 ` [PATCH] MIPS: Differentiate between 32 and 64 bit ELF header Daniel Wagner
2016-02-01 0:52 ` Maciej W. Rozycki
2016-02-01 16:07 ` Daniel Wagner [this message]
2016-02-06 17:16 ` Maciej W. Rozycki
2016-02-08 15:44 ` [PATCH v3 0/3] " Daniel Wagner
2016-02-08 15:44 ` [PATCH v3 1/3] mips: Use arch specific auxvec.h instead of generic-asm version Daniel Wagner
2016-02-08 17:19 ` Maciej W. Rozycki
2016-02-09 7:01 ` Daniel Wagner
2016-02-09 11:46 ` Maciej W. Rozycki
2016-02-09 12:37 ` Daniel Wagner
2016-02-09 14:51 ` Maciej W. Rozycki
2016-02-10 8:51 ` Daniel Wagner
2016-02-08 15:44 ` [PATCH v3 2/3] crash_dump: Add vmcore_elf32_check_arch Daniel Wagner
2016-02-08 17:05 ` Maciej W. Rozycki
2016-02-08 15:44 ` [PATCH v3 3/3] mips: Differentiate between 32 and 64 bit ELF header Daniel Wagner
2016-02-08 16:22 ` kbuild test robot
2016-02-09 8:03 ` Daniel Wagner
2016-02-09 12:32 ` Maciej W. Rozycki
2016-02-09 12:38 ` Daniel Wagner
2016-02-09 19:44 ` Maciej W. Rozycki
2016-02-10 6:28 ` Daniel Wagner
2016-02-10 9:21 ` [PATCH v4 0/2] " Daniel Wagner
2016-02-10 9:21 ` [PATCH v4 1/2] crash_dump: Add vmcore_elf32_check_arch Daniel Wagner
2016-02-10 9:21 ` [PATCH v4 2/2] mips: Differentiate between 32 and 64 bit ELF header Daniel Wagner
2016-02-11 10:49 ` Ralf Baechle
2016-02-11 12:04 ` Maciej W. Rozycki
2016-02-11 12:14 ` Daniel Wagner
2016-02-11 14:58 ` Maciej W. Rozycki
2016-02-11 15:30 ` Ralf Baechle
2016-02-08 16:58 ` [PATCH v3 3/3] " Maciej W. Rozycki
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