Date:   Thu, 16 Nov 2023 15:46:54 +0100
From:   Thomas Weißschuh <linux@...ssschuh.net>
To:     Willy Tarreau <w@....eu>
Cc:     Shuah Khan <shuah@...nel.org>, linux-kernel@...r.kernel.org,
        linux-kselftest@...r.kernel.org
Subject: Re: [PATCH RFC 2/3] selftests/nolibc: migrate startup tests to new
 harness

On 2023-11-16 08:33:27+0100, Willy Tarreau wrote:
> On Wed, Nov 15, 2023 at 10:08:20PM +0100, Thomas Weißschuh wrote:
> > Migrate part of nolibc-test.c to the new test harness.
> > 
> > Signed-off-by: Thomas Weißschuh <linux@...ssschuh.net>
> 
> A few points, mostly questions and food for thoughts.
> 
> > -static void putcharn(char c, size_t n)
> > -{
> > -	char buf[64];
> > -
> > -	memset(buf, c, n);
> > -	buf[n] = '\0';
> > -	fputs(buf, stdout);
> > -}
> > -
> 
> Ah now I see how the other one came from :-)  My comment about the size
> check still stands anyway, especially when placed in an include file.
> 
> > +#if defined(NOLIBC)
> > +
> > +#define ASSUME_NOLIBC(stmt)
> > +
> > +#else /* defined(NOLIBC) */
> > +
> > +/* differ from nolibc, both glibc and musl have no global _auxv */
> > +unsigned long *_auxv = (void *)-1;
> > +#define ASSUME_NOLIBC(stmt) SKIP(stmt)
> > +
> > +#endif /* defined(NOLIBC) */
> > +
> 
> I've seen below how it's used and don't find this very clear. In general,
> passing a statement as an argument to a macro, especially control statements
> such as "return" is a bit difficult to grasp. If the macro is only used for
> this, maybe it should integrate the return statement and be called something
> like "RETURN_UNLESS_NOLIBC()" which is quite explicit this time. If you really
> need to keep the statement adjustable, then most likely that calling the
> macro "UNLESS_NOLIBC()" would help, because I understand more naturally
> that the following will perform a return if we're not on nolibc:
> 
>     UNLESS_NOLIBC(return);
> 
> than:
> 
>     ASSUME_NOLIBC(return);

The statement arguments is modelled after SKIP() from
kselftest_harness.h.

But the wrapper you proposed is indeed much better,
I'll switch to that.

> 
> > -	for (test = min; test >= 0 && test <= max; test++) {
> > -		int llen = 0; /* line length */
> > +	if (brk)
> > +		return brk;
> >  
> > -		/* avoid leaving empty lines below, this will insert holes into
> > -		 * test numbers.
> > -		 */
> > -		switch (test + __LINE__ + 1) {
> > -		CASE_TEST(argc);             EXPECT_GE(1, test_argc, 1); break;
> > -		CASE_TEST(argv_addr);        EXPECT_PTRGT(1, test_argv, brk); break;
> > -		CASE_TEST(argv_environ);     EXPECT_PTRLT(1, test_argv, environ); break;
> > -		CASE_TEST(argv_total);       EXPECT_EQ(1, environ - test_argv - 1, test_argc ?: 1); break;
> > -		CASE_TEST(argv0_addr);       EXPECT_PTRGT(1, argv0, brk); break;
> > -		CASE_TEST(argv0_str);        EXPECT_STRNZ(1, argv0 > brk ? argv0 : NULL); break;
> > -		CASE_TEST(argv0_len);        EXPECT_GE(1,  argv0 > brk ? strlen(argv0) : 0, 1); break;
> > -		CASE_TEST(environ_addr);     EXPECT_PTRGT(1, environ, brk); break;
> > -		CASE_TEST(environ_envp);     EXPECT_PTREQ(1, environ, test_envp); break;
> > -		CASE_TEST(environ_auxv);     EXPECT_PTRLT(test_auxv != (void *)-1, environ, test_auxv); break;
> > -		CASE_TEST(environ_total);    EXPECT_GE(test_auxv != (void *)-1, (void *)test_auxv - (void *)environ - 1, env_total); break;
> > -		CASE_TEST(environ_HOME);     EXPECT_PTRNZ(1, getenv("HOME")); break;
> > -		CASE_TEST(auxv_addr);        EXPECT_PTRGT(test_auxv != (void *)-1, test_auxv, brk); break;
> > -		CASE_TEST(auxv_AT_UID);      EXPECT_EQ(1, getauxval(AT_UID), getuid()); break;
> > -		CASE_TEST(constructor);      EXPECT_EQ(1, constructor_test_value, 2); break;
> > -		CASE_TEST(linkage_errno);    EXPECT_PTREQ(1, linkage_test_errno_addr(), &errno); break;
> > -		CASE_TEST(linkage_constr);   EXPECT_EQ(1, linkage_test_constructor_test_value, 6); break;
> > -		case __LINE__:
> > -			return ret; /* must be last */
> > -		/* note: do not set any defaults so as to permit holes above */
> > -		}
> > -	}
> > -	return ret;
> > +	brk = sbrk(0);
> > +
> > +	if (brk == (void *)-1)
> > +		brk = &end;
> > +
> > +	return brk;
> >  }
> >  
> > +TEST(startup, argc)           { ASSERT_GE(test_argc, 1); }
> > +TEST(startup, argv_addr)      { ASSERT_GT((void *)test_argv, pbrk()); }
> > +TEST(startup, argv_environ)   { ASSERT_LT(test_argv, environ); }
> > +TEST(startup, argv_total)     { ASSERT_EQ(environ - test_argv - 1, test_argc ?: 1); }
> > +TEST(startup, argv0_addr)     { ASSERT_GT((void *)argv0, pbrk()); }
> > +TEST(startup, argv0_str)      { ASSERT_STRNZ((void *)argv0 > pbrk() ? argv0 : NULL); }
> > +TEST(startup, argv0_len)      { ASSERT_GE((void *)argv0 > pbrk() ? strlen(argv0) : 0U, 1U); }
> > +TEST(startup, environ_addr)   { ASSERT_GT((void *)environ, pbrk()); }
> > +TEST(startup, environ_envp)   { ASSERT_EQ(environ, test_envp); }
> > +TEST(startup, environ_auxv)   {
> > +	ASSUME_NOLIBC(return);
> > +	ASSERT_LT((void *)environ, (void *)_auxv);
> > +}
> > +TEST(startup, environ_total)  {
> > +	ASSUME_NOLIBC(return);
> > +	/* kernel at least passes HOME and TERM, shell passes more */
> > +	ASSERT_GE((void *)_auxv - (void *)environ - 1, 2);
> > +}
> > +TEST(startup, environ_HOME)   { ASSERT_NE(getenv("HOME"), NULL); }
> > +TEST(startup, auxv_addr)      {
> > +	ASSUME_NOLIBC(return);
> > +	ASSERT_GT((void *)_auxv, pbrk());
> > +}
> > +TEST(startup, auxv_AT_UID)    { ASSERT_EQ(getauxval(AT_UID), getuid()); }
> > +TEST(startup, constructor)    { ASSERT_EQ(constructor_test_value, 2); }
> > +TEST(startup, linkage_errno)  { ASSERT_EQ(linkage_test_errno_addr(), &errno); }
> > +TEST(startup, linkage_constr) { ASSERT_EQ(linkage_test_constructor_test_value, 6); }
> 
> I do appreciate the much lower indent level that still manages to
> enumerate tests easily. But given that test suites are grouped, shouldn't
> we go a bit further and state that TEST() operates on the suite defined
> by the TEST_SUITE macro that must be defined before it ? This way you would
> have:
> 
>   #define TEST_SUITE startup
>   TEST(argc)           { ASSERT_GE(test_argc, 1); }
>   TEST(argv_addr)      { ASSERT_GT((void *)test_argv, pbrk()); }
>   ...
>   #undef TEST_SUITE
> 
> One thing that was not immediately obvious to me upon first read was
> if TEST() defines or executes a test (i.e. "test" is both a noun and a
> verb). Of course, spending 10 more seconds on the patch makes it obvious
> it's a definition, but maybe following the same logic we have with
> run_test_suite(), we should place the verb in front, for example
> "DEF_TEST()" which then makes it quite unambiguous. Any opinion ?

The TEST() macro is modelled after kselftest_harness
(which only takes one argument, as it doesn't support suites)
and google test which works the same as the new TEST().

So I would prefer to keep the name.

As for specifying the suite via a macro:
I like that it saves even more indentation but at the same time it feels
a bit too implicit.

I'm not sure...

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