On Fri, Aug 13, 2021 at 4:28 PM Andrii Nakryiko
<andrii.nakryiko@xxxxxxxxx> wrote:
>
> On Thu, Aug 12, 2021 at 9:47 AM Kuniyuki Iwashima <kuniyu@xxxxxxxxxxxx> wrote:
> >
> > This patch adds a "positive" pattern for "%c", which intentionally uses a
> > __u32 value (0x64636261, "dbca") to print a single character "a". If the
> > implementation went wrong, other 3 bytes might show up as the part of the
> > latter "%+05s".
> >
> > Also, this patch adds two "negative" patterns for wide character.
> >
> > Signed-off-by: Kuniyuki Iwashima <kuniyu@xxxxxxxxxxxx>
> > ---
> > tools/testing/selftests/bpf/prog_tests/snprintf.c | 4 +++-
> > tools/testing/selftests/bpf/progs/test_snprintf.c | 7 ++++---
> > 2 files changed, 7 insertions(+), 4 deletions(-)
> >
> > diff --git a/tools/testing/selftests/bpf/prog_tests/snprintf.c b/tools/testing/selftests/bpf/prog_tests/snprintf.c
> > index dffbcaa1ec98..f77d7def7fed 100644
> > --- a/tools/testing/selftests/bpf/prog_tests/snprintf.c
> > +++ b/tools/testing/selftests/bpf/prog_tests/snprintf.c
> > @@ -19,7 +19,7 @@
> > #define EXP_ADDR_OUT "0000000000000000 ffff00000add4e55 "
> > #define EXP_ADDR_RET sizeof(EXP_ADDR_OUT "unknownhashedptr")
> >
> > -#define EXP_STR_OUT "str1 longstr"
> > +#define EXP_STR_OUT "str1 a longstr"
> > #define EXP_STR_RET sizeof(EXP_STR_OUT)
> >
> > #define EXP_OVER_OUT "%over"
> > @@ -114,6 +114,8 @@ void test_snprintf_negative(void)
> > ASSERT_ERR(load_single_snprintf("%"), "invalid specifier 3");
> > ASSERT_ERR(load_single_snprintf("%12345678"), "invalid specifier 4");
> > ASSERT_ERR(load_single_snprintf("%--------"), "invalid specifier 5");
> > + ASSERT_ERR(load_single_snprintf("%lc"), "invalid specifier 6");
> > + ASSERT_ERR(load_single_snprintf("%llc"), "invalid specifier 7");
> > ASSERT_ERR(load_single_snprintf("\x80"), "non ascii character");
> > ASSERT_ERR(load_single_snprintf("\x1"), "non printable character");
> > }
> > diff --git a/tools/testing/selftests/bpf/progs/test_snprintf.c b/tools/testing/selftests/bpf/progs/test_snprintf.c
> > index e2ad26150f9b..afc2c583125b 100644
> > --- a/tools/testing/selftests/bpf/progs/test_snprintf.c
> > +++ b/tools/testing/selftests/bpf/progs/test_snprintf.c
> > @@ -40,6 +40,7 @@ int handler(const void *ctx)
> > /* Convenient values to pretty-print */
> > const __u8 ex_ipv4[] = {127, 0, 0, 1};
> > const __u8 ex_ipv6[] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1};
> > + const __u32 chr1 = 0x64636261; /* dcba */
> > static const char str1[] = "str1";
> > static const char longstr[] = "longstr";
> >
> > @@ -59,9 +60,9 @@ int handler(const void *ctx)
> > /* Kernel pointers */
> > addr_ret = BPF_SNPRINTF(addr_out, sizeof(addr_out), "%pK %px %p",
> > 0, 0xFFFF00000ADD4E55, 0xFFFF00000ADD4E55);
> > - /* Strings embedding */
> > - str_ret = BPF_SNPRINTF(str_out, sizeof(str_out), "%s %+05s",
> > - str1, longstr);
> > + /* Strings and single-byte character embedding */
> > + str_ret = BPF_SNPRINTF(str_out, sizeof(str_out), "%s % 9c %+05s",
> > + str1, chr1, longstr);
Can you also add tests for %+2c, %-3c, %04c, %0c? Think outside the box ;)
>
>
> Why this hackery with __u32? You are making an endianness assumption
> (it will break on big-endian), and you'd never write real code like
> that. Just pass 'a', what's wrong with that?
>
> > /* Overflow */
> > over_ret = BPF_SNPRINTF(over_out, sizeof(over_out), "%%overflow");
> > /* Padding of fixed width numbers */
> > --
> > 2.30.2
> >
