Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1337298

Re: [PATCH] lkdtm: add test for executing .rodata

Show all headers | View raw

On 18 February 2016 at 12:34, Ard Biesheuvel <ard.biesheuvel@linaro.org> wrote:
> On 18 February 2016 at 11:32, PaX Team <pageexec@freemail.hu> wrote:
>> On 17 Feb 2016 at 12:29, Kees Cook wrote:
>>
>>> >> +static void __attribute__((__section__(".rodata,\"a\",@progbits#")))
>>> >> +do_nothing_rodata(void)
>>> >> +{
>>> >> +       return;
>>> >> +}
>>> >> +
>>> >
>>> >
>>> >>
>>> >
>>> > This doesn't cross compile for me on arm64 with two different toolchains
>>> >
>>> > CC drivers/misc/lkdtm.o
>>> > /tmp/ccHzIWIx.s: Assembler messages:
>>> > /tmp/ccHzIWIx.s:21: Error: junk at end of line, first unrecognized character
>>> > is `#'
>>> > /tmp/ccHzIWIx.s: Error: unaligned opcodes detected in executable segment
>>> > scripts/Makefile.build:258: recipe for target 'drivers/misc/lkdtm.o' failed
>>> > make[2]: *** [drivers/misc/lkdtm.o] Error 1
>>> > scripts/Makefile.build:407: recipe for target 'drivers/misc' failed
>>> > make[1]: *** [drivers/misc] Error 2
>>> > Makefile:950: recipe for target 'drivers' failed
>>> > make: *** [drivers] Error 2
>>> >
>>> > I don't know the assembler well enough to give any insight.
>>>
>>> Hm, bummer. I was trying to get fancy with the function forced into
>>> .rodata by trying to force the bits. Looks like "#" is not seen as a
>>> comment character by the toolchain you're using.
>>>
>>> Anyone else successfully done tricks like this?
>>
>> wouldn't it be a better and more generic/reusable approach to
>>
>> #define __ro_text __attribute__((__section__(".rodata.text")))
>>
>> and move this function there by the linker script similar to how it's done
>> for other code that goes into special sections?
>>
>
> We have __section() as an alias for __attribute__((__section__())), so
> we could use that instead.
>
> However, that does not fix the issue Kees is trying to solve, where a
> .rodata section is emitted with the "x" bit set, which causes the
> linker to complain:
>
> /tmp/cc50ffWw.s: Assembler messages:
> /tmp/cc50ffWw.s:2: Warning: setting incorrect section attributes for
> .rodata.text
>
> I wonder if we could get away with doing something like
>
> AFLAGS_lkdtm.o += -Wa,-W
>
> here? This just hides the warnings, but may result in the .rodata
> section in the vmlinux file to have X permissions as well. I don't
> think anyone uses an ELF loader to load their kernel, but who knows
> ...
>
> That only matters when lkdtm is a module, btw

... is NOT a module, obviously

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

[PATCH] lkdtm: add test for executing .rodata Kees Cook <keescook@chromium.org> - 2016-02-16 22:50 +0100
  Re: [PATCH] lkdtm: add test for executing .rodata Laura Abbott <labbott@redhat.com> - 2016-02-17 02:10 +0100
    Re: [PATCH] lkdtm: add test for executing .rodata Kees Cook <keescook@chromium.org> - 2016-02-17 21:30 +0100
      Re: [PATCH] lkdtm: add test for executing .rodata Kees Cook <keescook@chromium.org> - 2016-02-17 22:10 +0100
      Re: [PATCH] lkdtm: add test for executing .rodata "PaX Team" <pageexec@freemail.hu> - 2016-02-18 11:40 +0100
        Re: [PATCH] lkdtm: add test for executing .rodata Ard Biesheuvel <ard.biesheuvel@linaro.org> - 2016-02-18 12:40 +0100
          Re: [PATCH] lkdtm: add test for executing .rodata Ard Biesheuvel <ard.biesheuvel@linaro.org> - 2016-02-18 13:00 +0100
          Re: [PATCH] lkdtm: add test for executing .rodata Arnd Bergmann <arnd@arndb.de> - 2016-02-18 13:10 +0100
            Re: [PATCH] lkdtm: add test for executing .rodata Ard Biesheuvel <ard.biesheuvel@linaro.org> - 2016-02-18 13:50 +0100
              Re: [PATCH] lkdtm: add test for executing .rodata Kees Cook <keescook@chromium.org> - 2016-02-18 21:10 +0100
          Re: [PATCH] lkdtm: add test for executing .rodata "PaX Team" <pageexec@freemail.hu> - 2016-02-18 22:30 +0100
            Re: [PATCH] lkdtm: add test for executing .rodata Kees Cook <keescook@chromium.org> - 2016-02-22 21:50 +0100
  Re: [PATCH] lkdtm: add test for executing .rodata Arnd Bergmann <arnd@arndb.de> - 2016-02-17 22:50 +0100
  Re: [PATCH] lkdtm: add test for executing .rodata Arnd Bergmann <arnd@arndb.de> - 2016-02-17 22:50 +0100

csiph-web