From: Jessica Yu <jeyu@kernel.org>
To: Nicholas Piggin <npiggin@gmail.com>
Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
"Michael Ellerman" <mpe@ellerman.id.au>,
"Michal Suchánek" <msuchanek@suse.de>
Subject: Re: [PATCH v4 1/2] module: add elf_check_module_arch for module specific elf arch checks
Date: Tue, 15 Jun 2021 14:17:40 +0200 [thread overview]
Message-ID: <YMiaZOqhHck9iy0n@p200300cbcf109700df096d564fe976c3.dip0.t-ipconnect.de> (raw)
In-Reply-To: <1623722110.amu32mwaqs.astroid@bobo.none>
+++ Nicholas Piggin [15/06/21 12:05 +1000]:
>Excerpts from Jessica Yu's message of June 14, 2021 10:06 pm:
>> +++ Nicholas Piggin [11/06/21 19:39 +1000]:
>>>The elf_check_arch() function is used to test usermode binaries, but
>>>kernel modules may have more specific requirements. powerpc would like
>>>to test for ABI version compatibility.
>>>
>>>Add an arch-overridable function elf_check_module_arch() that defaults
>>>to elf_check_arch() and use it in elf_validity_check().
>>>
>>>Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
>>>[np: split patch, added changelog]
>>>Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
>>>---
>>> include/linux/moduleloader.h | 5 +++++
>>> kernel/module.c | 2 +-
>>> 2 files changed, 6 insertions(+), 1 deletion(-)
>>>
>>>diff --git a/include/linux/moduleloader.h b/include/linux/moduleloader.h
>>>index 9e09d11ffe5b..fdc042a84562 100644
>>>--- a/include/linux/moduleloader.h
>>>+++ b/include/linux/moduleloader.h
>>>@@ -13,6 +13,11 @@
>>> * must be implemented by each architecture.
>>> */
>>>
>>>+// Allow arch to optionally do additional checking of module ELF header
>>>+#ifndef elf_check_module_arch
>>>+#define elf_check_module_arch elf_check_arch
>>>+#endif
>>
>> Hi Nicholas,
>>
>> Why not make elf_check_module_arch() consistent with the other
>> arch-specific functions? Please see module_frob_arch_sections(),
>> module_{init,exit}_section(), etc in moduleloader.h. That is, they are
>> all __weak functions that are overridable by arches. We can maybe make
>> elf_check_module_arch() a weak symbol, available for arches to
>> override if they want to perform additional elf checks. Then we don't
>> have to have this one-off #define.
>
>
>Like this? I like it. Good idea.
Yeah! Also, maybe we can alternatively make elf_check_module_arch() a
separate check entirely so that the powerpc implementation doesn't
have to include that extra elf_check_arch() call. Something like this maybe?
diff --git a/include/linux/moduleloader.h b/include/linux/moduleloader.h
index 9e09d11ffe5b..2f9ebd593b4f 100644
--- a/include/linux/moduleloader.h
+++ b/include/linux/moduleloader.h
@@ -39,6 +39,9 @@ bool module_init_section(const char *name);
*/
bool module_exit_section(const char *name);
+/* Arch may override to do additional checking of ELF header architecture */
+int elf_check_module_arch(Elf_Ehdr *hdr);
+
/*
* Apply the given relocation to the (simplified) ELF. Return -error
* or 0.
diff --git a/kernel/module.c b/kernel/module.c
index fdd6047728df..9963a979ed54 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2923,6 +2923,11 @@ static int validate_section_offset(struct load_info *info, Elf_Shdr *shdr)
return 0;
}
+int __weak elf_check_module_arch(Elf_Ehdr *hdr)
+{
+ return 1;
+}
+
/*
* Sanity checks against invalid binaries, wrong arch, weird elf version.
*
@@ -2941,6 +2946,7 @@ static int elf_validity_check(struct load_info *info)
if (memcmp(info->hdr->e_ident, ELFMAG, SELFMAG) != 0
|| info->hdr->e_type != ET_REL
|| !elf_check_arch(info->hdr)
+ || !elf_check_module_arch(info->hdr)
|| info->hdr->e_shentsize != sizeof(Elf_Shdr))
return -ENOEXEC;
next prev parent reply other threads:[~2021-06-15 12:17 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-11 9:39 [PATCH v4 0/2] powerpc/64: Option to use ELF V2 ABI for big-endian Nicholas Piggin
2021-06-11 9:39 ` [PATCH v4 1/2] module: add elf_check_module_arch for module specific elf arch checks Nicholas Piggin
2021-06-14 12:06 ` Jessica Yu
2021-06-15 2:05 ` Nicholas Piggin
2021-06-15 12:17 ` Jessica Yu [this message]
2021-06-15 12:50 ` Segher Boessenkool
2021-06-15 13:41 ` Jessica Yu
2021-06-15 14:30 ` Segher Boessenkool
2021-06-16 2:39 ` Michael Ellerman
2021-06-16 1:18 ` Nicholas Piggin
2021-06-16 12:54 ` Jessica Yu
2021-06-17 5:21 ` Nicholas Piggin
2021-06-16 2:37 ` Michael Ellerman
2021-06-16 13:49 ` Jessica Yu
2021-06-11 9:39 ` [PATCH v4 2/2] powerpc/64: Option to use ELF V2 ABI for big-endian kernels Nicholas Piggin
2021-06-11 9:58 ` Michal Suchánek
2021-06-11 10:20 ` Michal Suchánek
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