diff mbox series

[bpf-next,v2,09/15] selftests/bpf: Test assigning ID to scalars on spill

Message ID 20240108205209.838365-10-maxtram95@gmail.com (mailing list archive)
State Accepted
Commit 3893f0b6a0698aeeb3d27cb22baef7c4ca1a07f1
Headers show
Series Improvements for tracking scalars in the BPF verifier | expand

Commit Message

Maxim Mikityanskiy Jan. 8, 2024, 8:52 p.m. UTC 
From: Maxim Mikityanskiy <maxim@isovalent.com>

The previous commit implemented assigning IDs to registers holding
scalars before spill. Add the test cases to check the new functionality.

Signed-off-by: Maxim Mikityanskiy <maxim@isovalent.com>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
---
 .../selftests/bpf/progs/verifier_spill_fill.c | 133 ++++++++++++++++++
 1 file changed, 133 insertions(+)

Comments

Andrii Nakryiko Jan. 9, 2024, 11:34 p.m. UTC | #1 
On Mon, Jan 8, 2024 at 12:53 PM Maxim Mikityanskiy <maxtram95@gmail.com> wrote:
>
> From: Maxim Mikityanskiy <maxim@isovalent.com>
>
> The previous commit implemented assigning IDs to registers holding
> scalars before spill. Add the test cases to check the new functionality.
>
> Signed-off-by: Maxim Mikityanskiy <maxim@isovalent.com>
> Acked-by: Eduard Zingerman <eddyz87@gmail.com>
> ---
>  .../selftests/bpf/progs/verifier_spill_fill.c | 133 ++++++++++++++++++
>  1 file changed, 133 insertions(+)
>
> diff --git a/tools/testing/selftests/bpf/progs/verifier_spill_fill.c b/tools/testing/selftests/bpf/progs/verifier_spill_fill.c
> index f303ac19cf41..b05aab925ee5 100644
> --- a/tools/testing/selftests/bpf/progs/verifier_spill_fill.c
> +++ b/tools/testing/selftests/bpf/progs/verifier_spill_fill.c
> @@ -766,4 +766,137 @@ l0_%=:    r0 = 0;                                         \
>         : __clobber_all);
>  }
>

[...]

> +
> +SEC("xdp")
> +__description("8-bit spill of 8-bit reg should assign ID")
> +__success __retval(0)
> +__naked void spill_8bit_of_8bit_ok(void)
> +{
> +       asm volatile ("                                 \
> +       /* Roll one bit to make the register inexact. */\
> +       call %[bpf_get_prandom_u32];                    \
> +       r0 &= 0x80;                                     \
> +       /* 8-bit spill r0 to stack - should assign an ID. */\
> +       *(u8*)(r10 - 8) = r0;                           \
> +       /* 8-bit fill r1 from stack - should preserve the ID. */\
> +       r1 = *(u8*)(r10 - 8);                           \
> +       /* Compare r1 with another register to trigger find_equal_scalars.\
> +        * Having one random bit is important here, otherwise the verifier cuts\
> +        * the corners.                                 \
> +        */                                             \
> +       r2 = 0;                                         \
> +       if r1 != r2 goto l0_%=;                         \
> +       /* The result of this comparison is predefined. */\
> +       if r0 == r2 goto l0_%=;                         \
> +       /* Dead branch: the verifier should prune it. Do an invalid memory\
> +        * access if the verifier follows it.           \
> +        */                                             \
> +       r0 = *(u64*)(r9 + 0);                           \
> +       exit;                                           \
> +l0_%=: r0 = 0;                                         \
> +       exit;                                           \
> +"      :
> +       : __imm(bpf_get_prandom_u32)
> +       : __clobber_all);
> +}
> +

Can you add a test where we spill register of one size and fill a
different size? And what should the behavior be? Should we or should
we not preserve linked IDs in such situation?

>  char _license[] SEC("license") = "GPL";
> --
> 2.43.0
>
diff mbox series

Patch

diff --git a/tools/testing/selftests/bpf/progs/verifier_spill_fill.c b/tools/testing/selftests/bpf/progs/verifier_spill_fill.c
index f303ac19cf41..b05aab925ee5 100644
--- a/tools/testing/selftests/bpf/progs/verifier_spill_fill.c
+++ b/tools/testing/selftests/bpf/progs/verifier_spill_fill.c
@@ -766,4 +766,137 @@  l0_%=:	r0 = 0;						\
 	: __clobber_all);
 }
 
+SEC("xdp")
+__description("64-bit spill of 64-bit reg should assign ID")
+__success __retval(0)
+__naked void spill_64bit_of_64bit_ok(void)
+{
+	asm volatile ("					\
+	/* Roll one bit to make the register inexact. */\
+	call %[bpf_get_prandom_u32];			\
+	r0 &= 0x80000000;				\
+	r0 <<= 32;					\
+	/* 64-bit spill r0 to stack - should assign an ID. */\
+	*(u64*)(r10 - 8) = r0;				\
+	/* 64-bit fill r1 from stack - should preserve the ID. */\
+	r1 = *(u64*)(r10 - 8);				\
+	/* Compare r1 with another register to trigger find_equal_scalars.\
+	 * Having one random bit is important here, otherwise the verifier cuts\
+	 * the corners.					\
+	 */						\
+	r2 = 0;						\
+	if r1 != r2 goto l0_%=;				\
+	/* The result of this comparison is predefined. */\
+	if r0 == r2 goto l0_%=;				\
+	/* Dead branch: the verifier should prune it. Do an invalid memory\
+	 * access if the verifier follows it.		\
+	 */						\
+	r0 = *(u64*)(r9 + 0);				\
+	exit;						\
+l0_%=:	r0 = 0;						\
+	exit;						\
+"	:
+	: __imm(bpf_get_prandom_u32)
+	: __clobber_all);
+}
+
+SEC("xdp")
+__description("32-bit spill of 32-bit reg should assign ID")
+__success __retval(0)
+__naked void spill_32bit_of_32bit_ok(void)
+{
+	asm volatile ("					\
+	/* Roll one bit to make the register inexact. */\
+	call %[bpf_get_prandom_u32];			\
+	w0 &= 0x80000000;				\
+	/* 32-bit spill r0 to stack - should assign an ID. */\
+	*(u32*)(r10 - 8) = r0;				\
+	/* 32-bit fill r1 from stack - should preserve the ID. */\
+	r1 = *(u32*)(r10 - 8);				\
+	/* Compare r1 with another register to trigger find_equal_scalars.\
+	 * Having one random bit is important here, otherwise the verifier cuts\
+	 * the corners.					\
+	 */						\
+	r2 = 0;						\
+	if r1 != r2 goto l0_%=;				\
+	/* The result of this comparison is predefined. */\
+	if r0 == r2 goto l0_%=;				\
+	/* Dead branch: the verifier should prune it. Do an invalid memory\
+	 * access if the verifier follows it.		\
+	 */						\
+	r0 = *(u64*)(r9 + 0);				\
+	exit;						\
+l0_%=:	r0 = 0;						\
+	exit;						\
+"	:
+	: __imm(bpf_get_prandom_u32)
+	: __clobber_all);
+}
+
+SEC("xdp")
+__description("16-bit spill of 16-bit reg should assign ID")
+__success __retval(0)
+__naked void spill_16bit_of_16bit_ok(void)
+{
+	asm volatile ("					\
+	/* Roll one bit to make the register inexact. */\
+	call %[bpf_get_prandom_u32];			\
+	r0 &= 0x8000;					\
+	/* 16-bit spill r0 to stack - should assign an ID. */\
+	*(u16*)(r10 - 8) = r0;				\
+	/* 16-bit fill r1 from stack - should preserve the ID. */\
+	r1 = *(u16*)(r10 - 8);				\
+	/* Compare r1 with another register to trigger find_equal_scalars.\
+	 * Having one random bit is important here, otherwise the verifier cuts\
+	 * the corners.					\
+	 */						\
+	r2 = 0;						\
+	if r1 != r2 goto l0_%=;				\
+	/* The result of this comparison is predefined. */\
+	if r0 == r2 goto l0_%=;				\
+	/* Dead branch: the verifier should prune it. Do an invalid memory\
+	 * access if the verifier follows it.		\
+	 */						\
+	r0 = *(u64*)(r9 + 0);				\
+	exit;						\
+l0_%=:	r0 = 0;						\
+	exit;						\
+"	:
+	: __imm(bpf_get_prandom_u32)
+	: __clobber_all);
+}
+
+SEC("xdp")
+__description("8-bit spill of 8-bit reg should assign ID")
+__success __retval(0)
+__naked void spill_8bit_of_8bit_ok(void)
+{
+	asm volatile ("					\
+	/* Roll one bit to make the register inexact. */\
+	call %[bpf_get_prandom_u32];			\
+	r0 &= 0x80;					\
+	/* 8-bit spill r0 to stack - should assign an ID. */\
+	*(u8*)(r10 - 8) = r0;				\
+	/* 8-bit fill r1 from stack - should preserve the ID. */\
+	r1 = *(u8*)(r10 - 8);				\
+	/* Compare r1 with another register to trigger find_equal_scalars.\
+	 * Having one random bit is important here, otherwise the verifier cuts\
+	 * the corners.					\
+	 */						\
+	r2 = 0;						\
+	if r1 != r2 goto l0_%=;				\
+	/* The result of this comparison is predefined. */\
+	if r0 == r2 goto l0_%=;				\
+	/* Dead branch: the verifier should prune it. Do an invalid memory\
+	 * access if the verifier follows it.		\
+	 */						\
+	r0 = *(u64*)(r9 + 0);				\
+	exit;						\
+l0_%=:	r0 = 0;						\
+	exit;						\
+"	:
+	: __imm(bpf_get_prandom_u32)
+	: __clobber_all);
+}
+
 char _license[] SEC("license") = "GPL";