linux-kernel - Re: [PATCH v3 linux-kselftest-test 3/6] kunit: add kunit_find

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
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <CAFd5g46s=zgJXKRKj8iw5Bng=a06wb-PmDs_7-c7c-MiryrnAg@mail.gmail.com>
Date:   Thu, 7 Nov 2019 17:24:21 -0800
From:   Brendan Higgins <brendanhiggins@...gle.com>
To:     Alan Maguire <alan.maguire@...cle.com>
Cc:     "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        KUnit Development <kunit-dev@...glegroups.com>,
        Kees Cook <keescook@...omium.org>,
        Iurii Zaikin <yzaikin@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        catalin.marinas@....com, joe.lawrence@...hat.com,
        penguin-kernel@...ove.sakura.ne.jp, schowdary@...dia.com,
        urezki@...il.com, andriy.shevchenko@...ux.intel.com,
        Jonathan Corbet <corbet@....net>,
        "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
        Knut Omang <knut.omang@...cle.com>
Subject: Re: [PATCH v3 linux-kselftest-test 3/6] kunit: add
 kunit_find_symbol() function for symbol lookup

On Thu, Oct 17, 2019 at 11:08 AM Alan Maguire <alan.maguire@...cle.com> wrote:
>
> In preparation for module support for kunit and kunit tests,
> we need a way of retrieving non-exported symbols from the
> core kernel and modules.  kunit_find_symbol() supports this.
>
> Signed-off-by: Alan Maguire <alan.maguire@...cle.com>
> Signed-off-by: Knut Omang <knut.omang@...cle.com>

I think you suggested on another thread that splitting this patch out
of this patchset might be a good idea. I agree with that. Can you send
this patch separately?

> ---
>  include/kunit/test.h  |  8 ++++++++
>  lib/kunit/test-test.c | 19 +++++++++++++++++++
>  lib/kunit/test.c      | 36 ++++++++++++++++++++++++++++++++++++
>  3 files changed, 63 insertions(+)
>
> diff --git a/include/kunit/test.h b/include/kunit/test.h
> index dba4830..c645d18 100644
> --- a/include/kunit/test.h
> +++ b/include/kunit/test.h
> @@ -339,6 +339,14 @@ static inline void *kunit_kzalloc(struct kunit *test, size_t size, gfp_t gfp)
>
>  void kunit_cleanup(struct kunit *test);
>
> +/**
> + * kunit_find_symbol() - lookup un-exported symbol in kernel or modules.
> + * @sym: symbol name.
> + *
> + * Returns symbol or ERR_PTR value on error.

Can you document which ERR_PTRs it returns?

> + */
> +void *kunit_find_symbol(const char *sym);
> +
>  #define kunit_printk(lvl, test, fmt, ...) \
>         printk(lvl "\t# %s: " fmt, (test)->name, ##__VA_ARGS__)
>
> diff --git a/lib/kunit/test-test.c b/lib/kunit/test-test.c
> index c4162a9..7f09dd0 100644
> --- a/lib/kunit/test-test.c
> +++ b/lib/kunit/test-test.c
> @@ -330,3 +330,22 @@ static void kunit_resource_test_exit(struct kunit *test)
>         .test_cases = kunit_resource_test_cases,
>  };
>  kunit_test_suite(kunit_resource_test_suite);
> +
> +/*
> + * Find non-exported kernel symbol; we use the modules list as a safe
> + * choice that should always be present.
> + */
> +static void kunit_find_symbol_kernel(struct kunit *test)
> +{
> +       KUNIT_ASSERT_NOT_ERR_OR_NULL(test, kunit_find_symbol("modules"));

I think this should be a KUNIT_EXPECT_... here since nothing in this
test case depends on this check passing.

> +}
> +
> +static struct kunit_case kunit_find_symbol_test_cases[] = {
> +       KUNIT_CASE(kunit_find_symbol_kernel),
> +};
> +
> +static struct kunit_suite kunit_find_symbol_test_suite = {
> +       .name = "kunit-find-symbol",
> +       .test_cases = kunit_find_symbol_test_cases,
> +};
> +kunit_test_suite(kunit_find_symbol_test_suite);
> diff --git a/lib/kunit/test.c b/lib/kunit/test.c
> index 49ac5fe..a2b1b46 100644
> --- a/lib/kunit/test.c
> +++ b/lib/kunit/test.c
> @@ -8,6 +8,7 @@
>
>  #include <kunit/test.h>
>  #include <kunit/try-catch.h>
> +#include <linux/kallsyms.h>
>  #include <linux/kernel.h>
>  #include <linux/sched/debug.h>
>  #include "string-stream-impl.h"
> @@ -478,3 +479,38 @@ void kunit_cleanup(struct kunit *test)
>                 kunit_resource_free(test, resource);
>         }
>  }
> +
> +/*
> + * Support for looking up kernel/module internal symbols to enable testing.
> + */
> +void *kunit_find_symbol(const char *sym)
> +{
> +       unsigned long (*modlookup)(const char *name);
> +       unsigned long addr = 0;
> +
> +       if (!sym || strlen(sym) > KSYM_NAME_LEN)
> +               return ERR_PTR(-EINVAL);
> +
> +       /*
> +        * Try for kernel-internal symbol first; fall back to modules
> +        * if that fails.
> +        */
> +       addr = kallsyms_lookup_name(sym);
> +       if (addr)
> +               return (void *)addr;

nit: please add a newline here.

> +       modlookup = (void *)kallsyms_lookup_name("module_kallsyms_lookup_name");

Can you add a comment here explaining what module_kallsyms_lookup_name
is and why you need to look it up this way?

> +       if (modlookup)
> +               addr = modlookup(sym);
> +       if (addr)
> +               return (void *)addr;
> +
> +#ifndef CONFIG_KALLSYMS_ALL
> +       WARN_ONCE(true,
> +                 "CONFIG_KALLSYMS_ALL is not set, so unexported symbols like '%s' are not available\n",
> +                 sym);
> +       return ERR_PTR(-ENOTSUPP);
> +#else
> +       WARN_ONCE(true, "symbol '%s' is not available\n", sym);
> +#endif
> +       return ERR_PTR(-ENOENT);
> +}
> --
> 1.8.3.1
>