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* [PATCH 2/2] selftests/bpf: add verifier test for PTR_TO_MEM spill
@ 2021-01-12  9:15 Gilad Reti
  2021-01-12 14:55 ` KP Singh
  0 siblings, 1 reply; 7+ messages in thread
From: Gilad Reti @ 2021-01-12  9:15 UTC (permalink / raw)
  To: bpf
  Cc: gilad.reti, Shuah Khan, Alexei Starovoitov, Daniel Borkmann,
	Andrii Nakryiko, Martin KaFai Lau, Song Liu, Yonghong Song,
	John Fastabend, KP Singh, linux-kselftest, netdev, linux-kernel

Add test to check that the verifier is able to recognize spilling of
PTR_TO_MEM registers.

The patch was partially contibuted by CyberArk Software, Inc.

Signed-off-by: Gilad Reti <gilad.reti@gmail.com>
---
 tools/testing/selftests/bpf/test_verifier.c   | 12 +++++++-
 .../selftests/bpf/verifier/spill_fill.c       | 30 +++++++++++++++++++
 2 files changed, 41 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c
index 777a81404fdb..f8569f04064b 100644
--- a/tools/testing/selftests/bpf/test_verifier.c
+++ b/tools/testing/selftests/bpf/test_verifier.c
@@ -50,7 +50,7 @@
 #define MAX_INSNS	BPF_MAXINSNS
 #define MAX_TEST_INSNS	1000000
 #define MAX_FIXUPS	8
-#define MAX_NR_MAPS	20
+#define MAX_NR_MAPS	21
 #define MAX_TEST_RUNS	8
 #define POINTER_VALUE	0xcafe4all
 #define TEST_DATA_LEN	64
@@ -87,6 +87,7 @@ struct bpf_test {
 	int fixup_sk_storage_map[MAX_FIXUPS];
 	int fixup_map_event_output[MAX_FIXUPS];
 	int fixup_map_reuseport_array[MAX_FIXUPS];
+	int fixup_map_ringbuf[MAX_FIXUPS];
 	const char *errstr;
 	const char *errstr_unpriv;
 	uint32_t insn_processed;
@@ -640,6 +641,7 @@ static void do_test_fixup(struct bpf_test *test, enum bpf_prog_type prog_type,
 	int *fixup_sk_storage_map = test->fixup_sk_storage_map;
 	int *fixup_map_event_output = test->fixup_map_event_output;
 	int *fixup_map_reuseport_array = test->fixup_map_reuseport_array;
+	int *fixup_map_ringbuf = test->fixup_map_ringbuf;
 
 	if (test->fill_helper) {
 		test->fill_insns = calloc(MAX_TEST_INSNS, sizeof(struct bpf_insn));
@@ -817,6 +819,14 @@ static void do_test_fixup(struct bpf_test *test, enum bpf_prog_type prog_type,
 			fixup_map_reuseport_array++;
 		} while (*fixup_map_reuseport_array);
 	}
+	if (*fixup_map_ringbuf) {
+		map_fds[20] = create_map(BPF_MAP_TYPE_RINGBUF, 0,
+					   0, 4096);
+		do {
+			prog[*fixup_map_ringbuf].imm = map_fds[20];
+			fixup_map_ringbuf++;
+		} while (*fixup_map_ringbuf);
+	}
 }
 
 struct libcap {
diff --git a/tools/testing/selftests/bpf/verifier/spill_fill.c b/tools/testing/selftests/bpf/verifier/spill_fill.c
index 45d43bf82f26..1833b6c730dd 100644
--- a/tools/testing/selftests/bpf/verifier/spill_fill.c
+++ b/tools/testing/selftests/bpf/verifier/spill_fill.c
@@ -28,6 +28,36 @@
 	.result = ACCEPT,
 	.result_unpriv = ACCEPT,
 },
+{
+	"check valid spill/fill, ptr to mem",
+	.insns = {
+	/* reserve 8 byte ringbuf memory */
+	BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0),
+	BPF_LD_MAP_FD(BPF_REG_1, 0),
+	BPF_MOV64_IMM(BPF_REG_2, 8),
+	BPF_MOV64_IMM(BPF_REG_3, 0),
+	BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_ringbuf_reserve),
+	/* store a pointer to the reserved memory in R6 */
+	BPF_MOV64_REG(BPF_REG_6, BPF_REG_0),
+	/* check whether the reservation was successful */
+	BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 6),
+	/* spill R6(mem) into the stack */
+	BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_6, -8),
+	/* fill it back in R7 */
+	BPF_LDX_MEM(BPF_DW, BPF_REG_7, BPF_REG_10, -8),
+	/* should be able to access *(R7) = 0 */
+	BPF_ST_MEM(BPF_DW, BPF_REG_7, 0, 0),
+	/* submit the reserved rungbuf memory */
+	BPF_MOV64_REG(BPF_REG_1, BPF_REG_7),
+	BPF_MOV64_IMM(BPF_REG_2, 0),
+	BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_ringbuf_submit),
+	BPF_MOV64_IMM(BPF_REG_0, 0),
+	BPF_EXIT_INSN(),
+	},
+	.fixup_map_ringbuf = { 1 },
+	.result = ACCEPT,
+	.result_unpriv = ACCEPT,
+},
 {
 	"check corrupted spill/fill",
 	.insns = {
-- 
2.27.0


^ permalink raw reply	[flat|nested] 7+ messages in thread

* Re: [PATCH 2/2] selftests/bpf: add verifier test for PTR_TO_MEM spill
  2021-01-12  9:15 [PATCH 2/2] selftests/bpf: add verifier test for PTR_TO_MEM spill Gilad Reti
@ 2021-01-12 14:55 ` KP Singh
  2021-01-12 15:35   ` Gilad Reti
  0 siblings, 1 reply; 7+ messages in thread
From: KP Singh @ 2021-01-12 14:55 UTC (permalink / raw)
  To: Gilad Reti
  Cc: bpf, Shuah Khan, Alexei Starovoitov, Daniel Borkmann,
	Andrii Nakryiko, Martin KaFai Lau, Song Liu, Yonghong Song,
	John Fastabend, linux-kselftest, Networking, open list

On Tue, Jan 12, 2021 at 10:16 AM Gilad Reti <gilad.reti@gmail.com> wrote:
>
> Add test to check that the verifier is able to recognize spilling of
> PTR_TO_MEM registers.
>

It would be nice to have some explanation of what the test does to
recognize the spilling of the PTR_TO_MEM registers in the commit
log as well.

Would it be possible to augment an existing test_progs
program like tools/testing/selftests/bpf/progs/test_ringbuf.c to test
this functionality?



> The patch was partially contibuted by CyberArk Software, Inc.
>
> Signed-off-by: Gilad Reti <gilad.reti@gmail.com>
> ---
>  tools/testing/selftests/bpf/test_verifier.c   | 12 +++++++-
>  .../selftests/bpf/verifier/spill_fill.c       | 30 +++++++++++++++++++
>  2 files changed, 41 insertions(+), 1 deletion(-)
>
> diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c
> index 777a81404fdb..f8569f04064b 100644
> --- a/tools/testing/selftests/bpf/test_verifier.c
> +++ b/tools/testing/selftests/bpf/test_verifier.c
> @@ -50,7 +50,7 @@
>  #define MAX_INSNS      BPF_MAXINSNS
>  #define MAX_TEST_INSNS 1000000
>  #define MAX_FIXUPS     8
> -#define MAX_NR_MAPS    20
> +#define MAX_NR_MAPS    21
>  #define MAX_TEST_RUNS  8
>  #define POINTER_VALUE  0xcafe4all
>  #define TEST_DATA_LEN  64
> @@ -87,6 +87,7 @@ struct bpf_test {
>         int fixup_sk_storage_map[MAX_FIXUPS];
>         int fixup_map_event_output[MAX_FIXUPS];
>         int fixup_map_reuseport_array[MAX_FIXUPS];
> +       int fixup_map_ringbuf[MAX_FIXUPS];
>         const char *errstr;
>         const char *errstr_unpriv;
>         uint32_t insn_processed;
> @@ -640,6 +641,7 @@ static void do_test_fixup(struct bpf_test *test, enum bpf_prog_type prog_type,
>         int *fixup_sk_storage_map = test->fixup_sk_storage_map;
>         int *fixup_map_event_output = test->fixup_map_event_output;
>         int *fixup_map_reuseport_array = test->fixup_map_reuseport_array;
> +       int *fixup_map_ringbuf = test->fixup_map_ringbuf;
>
>         if (test->fill_helper) {
>                 test->fill_insns = calloc(MAX_TEST_INSNS, sizeof(struct bpf_insn));
> @@ -817,6 +819,14 @@ static void do_test_fixup(struct bpf_test *test, enum bpf_prog_type prog_type,
>                         fixup_map_reuseport_array++;
>                 } while (*fixup_map_reuseport_array);
>         }
> +       if (*fixup_map_ringbuf) {
> +               map_fds[20] = create_map(BPF_MAP_TYPE_RINGBUF, 0,
> +                                          0, 4096);
> +               do {
> +                       prog[*fixup_map_ringbuf].imm = map_fds[20];
> +                       fixup_map_ringbuf++;
> +               } while (*fixup_map_ringbuf);
> +       }
>  }
>
>  struct libcap {
> diff --git a/tools/testing/selftests/bpf/verifier/spill_fill.c b/tools/testing/selftests/bpf/verifier/spill_fill.c
> index 45d43bf82f26..1833b6c730dd 100644
> --- a/tools/testing/selftests/bpf/verifier/spill_fill.c
> +++ b/tools/testing/selftests/bpf/verifier/spill_fill.c
> @@ -28,6 +28,36 @@
>         .result = ACCEPT,
>         .result_unpriv = ACCEPT,
>  },
> +{
> +       "check valid spill/fill, ptr to mem",
> +       .insns = {
> +       /* reserve 8 byte ringbuf memory */
> +       BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0),
> +       BPF_LD_MAP_FD(BPF_REG_1, 0),
> +       BPF_MOV64_IMM(BPF_REG_2, 8),
> +       BPF_MOV64_IMM(BPF_REG_3, 0),
> +       BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_ringbuf_reserve),
> +       /* store a pointer to the reserved memory in R6 */
> +       BPF_MOV64_REG(BPF_REG_6, BPF_REG_0),
> +       /* check whether the reservation was successful */
> +       BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 6),
> +       /* spill R6(mem) into the stack */
> +       BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_6, -8),
> +       /* fill it back in R7 */
> +       BPF_LDX_MEM(BPF_DW, BPF_REG_7, BPF_REG_10, -8),
> +       /* should be able to access *(R7) = 0 */
> +       BPF_ST_MEM(BPF_DW, BPF_REG_7, 0, 0),
> +       /* submit the reserved rungbuf memory */
> +       BPF_MOV64_REG(BPF_REG_1, BPF_REG_7),
> +       BPF_MOV64_IMM(BPF_REG_2, 0),
> +       BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_ringbuf_submit),
> +       BPF_MOV64_IMM(BPF_REG_0, 0),
> +       BPF_EXIT_INSN(),
> +       },
> +       .fixup_map_ringbuf = { 1 },
> +       .result = ACCEPT,
> +       .result_unpriv = ACCEPT,
> +},
>  {
>         "check corrupted spill/fill",
>         .insns = {
> --
> 2.27.0
>

^ permalink raw reply	[flat|nested] 7+ messages in thread

* Re: [PATCH 2/2] selftests/bpf: add verifier test for PTR_TO_MEM spill
  2021-01-12 14:55 ` KP Singh
@ 2021-01-12 15:35   ` Gilad Reti
  2021-01-12 15:43     ` Daniel Borkmann
  0 siblings, 1 reply; 7+ messages in thread
From: Gilad Reti @ 2021-01-12 15:35 UTC (permalink / raw)
  To: KP Singh
  Cc: bpf, Shuah Khan, Alexei Starovoitov, Daniel Borkmann,
	Andrii Nakryiko, Martin KaFai Lau, Song Liu, Yonghong Song,
	John Fastabend, linux-kselftest, Networking, open list

On Tue, Jan 12, 2021 at 4:56 PM KP Singh <kpsingh@kernel.org> wrote:
>
> On Tue, Jan 12, 2021 at 10:16 AM Gilad Reti <gilad.reti@gmail.com> wrote:
> >
> > Add test to check that the verifier is able to recognize spilling of
> > PTR_TO_MEM registers.
> >
>
> It would be nice to have some explanation of what the test does to
> recognize the spilling of the PTR_TO_MEM registers in the commit
> log as well.
>
> Would it be possible to augment an existing test_progs
> program like tools/testing/selftests/bpf/progs/test_ringbuf.c to test
> this functionality?
>

It may be possible, but from what I understood from Daniel's comment here

https://lore.kernel.org/bpf/17629073-4fab-a922-ecc3-25b019960f44@iogearbox.net/

the test should be a part of the verifier tests (which is reasonable
to me since it is
a verifier bugfix)

>
>
> > The patch was partially contibuted by CyberArk Software, Inc.
> >
> > Signed-off-by: Gilad Reti <gilad.reti@gmail.com>
> > ---
> >  tools/testing/selftests/bpf/test_verifier.c   | 12 +++++++-
> >  .../selftests/bpf/verifier/spill_fill.c       | 30 +++++++++++++++++++
> >  2 files changed, 41 insertions(+), 1 deletion(-)
> >
> > diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c
> > index 777a81404fdb..f8569f04064b 100644
> > --- a/tools/testing/selftests/bpf/test_verifier.c
> > +++ b/tools/testing/selftests/bpf/test_verifier.c
> > @@ -50,7 +50,7 @@
> >  #define MAX_INSNS      BPF_MAXINSNS
> >  #define MAX_TEST_INSNS 1000000
> >  #define MAX_FIXUPS     8
> > -#define MAX_NR_MAPS    20
> > +#define MAX_NR_MAPS    21
> >  #define MAX_TEST_RUNS  8
> >  #define POINTER_VALUE  0xcafe4all
> >  #define TEST_DATA_LEN  64
> > @@ -87,6 +87,7 @@ struct bpf_test {
> >         int fixup_sk_storage_map[MAX_FIXUPS];
> >         int fixup_map_event_output[MAX_FIXUPS];
> >         int fixup_map_reuseport_array[MAX_FIXUPS];
> > +       int fixup_map_ringbuf[MAX_FIXUPS];
> >         const char *errstr;
> >         const char *errstr_unpriv;
> >         uint32_t insn_processed;
> > @@ -640,6 +641,7 @@ static void do_test_fixup(struct bpf_test *test, enum bpf_prog_type prog_type,
> >         int *fixup_sk_storage_map = test->fixup_sk_storage_map;
> >         int *fixup_map_event_output = test->fixup_map_event_output;
> >         int *fixup_map_reuseport_array = test->fixup_map_reuseport_array;
> > +       int *fixup_map_ringbuf = test->fixup_map_ringbuf;
> >
> >         if (test->fill_helper) {
> >                 test->fill_insns = calloc(MAX_TEST_INSNS, sizeof(struct bpf_insn));
> > @@ -817,6 +819,14 @@ static void do_test_fixup(struct bpf_test *test, enum bpf_prog_type prog_type,
> >                         fixup_map_reuseport_array++;
> >                 } while (*fixup_map_reuseport_array);
> >         }
> > +       if (*fixup_map_ringbuf) {
> > +               map_fds[20] = create_map(BPF_MAP_TYPE_RINGBUF, 0,
> > +                                          0, 4096);
> > +               do {
> > +                       prog[*fixup_map_ringbuf].imm = map_fds[20];
> > +                       fixup_map_ringbuf++;
> > +               } while (*fixup_map_ringbuf);
> > +       }
> >  }
> >
> >  struct libcap {
> > diff --git a/tools/testing/selftests/bpf/verifier/spill_fill.c b/tools/testing/selftests/bpf/verifier/spill_fill.c
> > index 45d43bf82f26..1833b6c730dd 100644
> > --- a/tools/testing/selftests/bpf/verifier/spill_fill.c
> > +++ b/tools/testing/selftests/bpf/verifier/spill_fill.c
> > @@ -28,6 +28,36 @@
> >         .result = ACCEPT,
> >         .result_unpriv = ACCEPT,
> >  },
> > +{
> > +       "check valid spill/fill, ptr to mem",
> > +       .insns = {
> > +       /* reserve 8 byte ringbuf memory */
> > +       BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0),
> > +       BPF_LD_MAP_FD(BPF_REG_1, 0),
> > +       BPF_MOV64_IMM(BPF_REG_2, 8),
> > +       BPF_MOV64_IMM(BPF_REG_3, 0),
> > +       BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_ringbuf_reserve),
> > +       /* store a pointer to the reserved memory in R6 */
> > +       BPF_MOV64_REG(BPF_REG_6, BPF_REG_0),
> > +       /* check whether the reservation was successful */
> > +       BPF_JMP_IMM(BPF_JEQ, BPF_REG_0, 0, 6),
> > +       /* spill R6(mem) into the stack */
> > +       BPF_STX_MEM(BPF_DW, BPF_REG_10, BPF_REG_6, -8),
> > +       /* fill it back in R7 */
> > +       BPF_LDX_MEM(BPF_DW, BPF_REG_7, BPF_REG_10, -8),
> > +       /* should be able to access *(R7) = 0 */
> > +       BPF_ST_MEM(BPF_DW, BPF_REG_7, 0, 0),
> > +       /* submit the reserved rungbuf memory */
> > +       BPF_MOV64_REG(BPF_REG_1, BPF_REG_7),
> > +       BPF_MOV64_IMM(BPF_REG_2, 0),
> > +       BPF_RAW_INSN(BPF_JMP | BPF_CALL, 0, 0, 0, BPF_FUNC_ringbuf_submit),
> > +       BPF_MOV64_IMM(BPF_REG_0, 0),
> > +       BPF_EXIT_INSN(),
> > +       },
> > +       .fixup_map_ringbuf = { 1 },
> > +       .result = ACCEPT,
> > +       .result_unpriv = ACCEPT,
> > +},
> >  {
> >         "check corrupted spill/fill",
> >         .insns = {
> > --
> > 2.27.0
> >

^ permalink raw reply	[flat|nested] 7+ messages in thread

* Re: [PATCH 2/2] selftests/bpf: add verifier test for PTR_TO_MEM spill
  2021-01-12 15:35   ` Gilad Reti
@ 2021-01-12 15:43     ` Daniel Borkmann
  2021-01-12 16:17       ` KP Singh
  2021-01-12 16:59       ` Yonghong Song
  0 siblings, 2 replies; 7+ messages in thread
From: Daniel Borkmann @ 2021-01-12 15:43 UTC (permalink / raw)
  To: Gilad Reti, KP Singh
  Cc: bpf, Shuah Khan, Alexei Starovoitov, Andrii Nakryiko,
	Martin KaFai Lau, Song Liu, Yonghong Song, John Fastabend,
	linux-kselftest, Networking, open list

On 1/12/21 4:35 PM, Gilad Reti wrote:
> On Tue, Jan 12, 2021 at 4:56 PM KP Singh <kpsingh@kernel.org> wrote:
>> On Tue, Jan 12, 2021 at 10:16 AM Gilad Reti <gilad.reti@gmail.com> wrote:
>>>
>>> Add test to check that the verifier is able to recognize spilling of
>>> PTR_TO_MEM registers.
>>
>> It would be nice to have some explanation of what the test does to
>> recognize the spilling of the PTR_TO_MEM registers in the commit
>> log as well.
>>
>> Would it be possible to augment an existing test_progs
>> program like tools/testing/selftests/bpf/progs/test_ringbuf.c to test
>> this functionality?

How would you guarantee that LLVM generates the spill/fill, via inline asm?

> It may be possible, but from what I understood from Daniel's comment here
> 
> https://lore.kernel.org/bpf/17629073-4fab-a922-ecc3-25b019960f44@iogearbox.net/
> 
> the test should be a part of the verifier tests (which is reasonable
> to me since it is
> a verifier bugfix)

Yeah, the test_verifier case as you have is definitely the most straight
forward way to add coverage in this case.

^ permalink raw reply	[flat|nested] 7+ messages in thread

* Re: [PATCH 2/2] selftests/bpf: add verifier test for PTR_TO_MEM spill
  2021-01-12 15:43     ` Daniel Borkmann
@ 2021-01-12 16:17       ` KP Singh
  2021-01-12 16:24         ` Gilad Reti
  2021-01-12 16:59       ` Yonghong Song
  1 sibling, 1 reply; 7+ messages in thread
From: KP Singh @ 2021-01-12 16:17 UTC (permalink / raw)
  To: Daniel Borkmann
  Cc: Gilad Reti, bpf, Shuah Khan, Alexei Starovoitov, Andrii Nakryiko,
	Martin KaFai Lau, Song Liu, Yonghong Song, John Fastabend,
	linux-kselftest, Networking, open list

On Tue, Jan 12, 2021 at 4:43 PM Daniel Borkmann <daniel@iogearbox.net> wrote:
>
> On 1/12/21 4:35 PM, Gilad Reti wrote:
> > On Tue, Jan 12, 2021 at 4:56 PM KP Singh <kpsingh@kernel.org> wrote:
> >> On Tue, Jan 12, 2021 at 10:16 AM Gilad Reti <gilad.reti@gmail.com> wrote:
> >>>
> >>> Add test to check that the verifier is able to recognize spilling of
> >>> PTR_TO_MEM registers.
> >>
> >> It would be nice to have some explanation of what the test does to
> >> recognize the spilling of the PTR_TO_MEM registers in the commit
> >> log as well.
> >>
> >> Would it be possible to augment an existing test_progs
> >> program like tools/testing/selftests/bpf/progs/test_ringbuf.c to test
> >> this functionality?
>
> How would you guarantee that LLVM generates the spill/fill, via inline asm?

Yeah, I guess there is no sure-shot way to do it and, adding inline asm would
just be doing the same thing as this verifier test. You can ignore me
on this one :)

It would, however, be nice to have a better description about what the test is
actually doing./


>
> > It may be possible, but from what I understood from Daniel's comment here
> >
> > https://lore.kernel.org/bpf/17629073-4fab-a922-ecc3-25b019960f44@iogearbox.net/
> >
> > the test should be a part of the verifier tests (which is reasonable
> > to me since it is
> > a verifier bugfix)
>
> Yeah, the test_verifier case as you have is definitely the most straight
> forward way to add coverage in this case.

^ permalink raw reply	[flat|nested] 7+ messages in thread

* Re: [PATCH 2/2] selftests/bpf: add verifier test for PTR_TO_MEM spill
  2021-01-12 16:17       ` KP Singh
@ 2021-01-12 16:24         ` Gilad Reti
  0 siblings, 0 replies; 7+ messages in thread
From: Gilad Reti @ 2021-01-12 16:24 UTC (permalink / raw)
  To: KP Singh
  Cc: Daniel Borkmann, bpf, Shuah Khan, Alexei Starovoitov,
	Andrii Nakryiko, Martin KaFai Lau, Song Liu, Yonghong Song,
	John Fastabend, linux-kselftest, Networking, open list

On Tue, Jan 12, 2021 at 6:17 PM KP Singh <kpsingh@kernel.org> wrote:
>
> On Tue, Jan 12, 2021 at 4:43 PM Daniel Borkmann <daniel@iogearbox.net> wrote:
> >
> > On 1/12/21 4:35 PM, Gilad Reti wrote:
> > > On Tue, Jan 12, 2021 at 4:56 PM KP Singh <kpsingh@kernel.org> wrote:
> > >> On Tue, Jan 12, 2021 at 10:16 AM Gilad Reti <gilad.reti@gmail.com> wrote:
> > >>>
> > >>> Add test to check that the verifier is able to recognize spilling of
> > >>> PTR_TO_MEM registers.
> > >>
> > >> It would be nice to have some explanation of what the test does to
> > >> recognize the spilling of the PTR_TO_MEM registers in the commit
> > >> log as well.
> > >>
> > >> Would it be possible to augment an existing test_progs
> > >> program like tools/testing/selftests/bpf/progs/test_ringbuf.c to test
> > >> this functionality?
> >
> > How would you guarantee that LLVM generates the spill/fill, via inline asm?
>
> Yeah, I guess there is no sure-shot way to do it and, adding inline asm would
> just be doing the same thing as this verifier test. You can ignore me
> on this one :)
>
> It would, however, be nice to have a better description about what the test is
> actually doing./
>
>

I will re-submit the patch tomorrow. Thank you all for your patience.

> >
> > > It may be possible, but from what I understood from Daniel's comment here
> > >
> > > https://lore.kernel.org/bpf/17629073-4fab-a922-ecc3-25b019960f44@iogearbox.net/
> > >
> > > the test should be a part of the verifier tests (which is reasonable
> > > to me since it is
> > > a verifier bugfix)
> >
> > Yeah, the test_verifier case as you have is definitely the most straight
> > forward way to add coverage in this case.

^ permalink raw reply	[flat|nested] 7+ messages in thread

* Re: [PATCH 2/2] selftests/bpf: add verifier test for PTR_TO_MEM spill
  2021-01-12 15:43     ` Daniel Borkmann
  2021-01-12 16:17       ` KP Singh
@ 2021-01-12 16:59       ` Yonghong Song
  1 sibling, 0 replies; 7+ messages in thread
From: Yonghong Song @ 2021-01-12 16:59 UTC (permalink / raw)
  To: Daniel Borkmann, Gilad Reti, KP Singh
  Cc: bpf, Shuah Khan, Alexei Starovoitov, Andrii Nakryiko,
	Martin KaFai Lau, Song Liu, John Fastabend, linux-kselftest,
	Networking, open list



On 1/12/21 7:43 AM, Daniel Borkmann wrote:
> On 1/12/21 4:35 PM, Gilad Reti wrote:
>> On Tue, Jan 12, 2021 at 4:56 PM KP Singh <kpsingh@kernel.org> wrote:
>>> On Tue, Jan 12, 2021 at 10:16 AM Gilad Reti <gilad.reti@gmail.com> 
>>> wrote:
>>>>
>>>> Add test to check that the verifier is able to recognize spilling of
>>>> PTR_TO_MEM registers.
>>>
>>> It would be nice to have some explanation of what the test does to
>>> recognize the spilling of the PTR_TO_MEM registers in the commit
>>> log as well.
>>>
>>> Would it be possible to augment an existing test_progs
>>> program like tools/testing/selftests/bpf/progs/test_ringbuf.c to test
>>> this functionality?
> 
> How would you guarantee that LLVM generates the spill/fill, via inline asm?

You can make the following change to force the return value ("sample" 
here) of bpf_ringbuf_reserve() to spill on the stack.

diff --git a/tools/testing/selftests/bpf/progs/test_ringbuf.c 
b/tools/testing/selftests/bpf/progs/test_ringbuf.c
index 8ba9959b036b..011521170856 100644
--- a/tools/testing/selftests/bpf/progs/test_ringbuf.c
+++ b/tools/testing/selftests/bpf/progs/test_ringbuf.c
@@ -40,7 +40,7 @@ SEC("tp/syscalls/sys_enter_getpgid")
  int test_ringbuf(void *ctx)
  {
         int cur_pid = bpf_get_current_pid_tgid() >> 32;
-       struct sample *sample;
+       struct sample * volatile sample;
         int zero = 0;

         if (cur_pid != pid)

This change will cause verifier failure without Patch #1.

> 
>> It may be possible, but from what I understood from Daniel's comment here
>>
>> https://lore.kernel.org/bpf/17629073-4fab-a922-ecc3-25b019960f44@iogearbox.net/ 
>>
>>
>> the test should be a part of the verifier tests (which is reasonable
>> to me since it is
>> a verifier bugfix)
> 
> Yeah, the test_verifier case as you have is definitely the most straight
> forward way to add coverage in this case.

^ permalink raw reply	[flat|nested] 7+ messages in thread

end of thread, back to index

Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-01-12  9:15 [PATCH 2/2] selftests/bpf: add verifier test for PTR_TO_MEM spill Gilad Reti
2021-01-12 14:55 ` KP Singh
2021-01-12 15:35   ` Gilad Reti
2021-01-12 15:43     ` Daniel Borkmann
2021-01-12 16:17       ` KP Singh
2021-01-12 16:24         ` Gilad Reti
2021-01-12 16:59       ` Yonghong Song

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