selftests/bpf: add verifier sign extension bound computation tests.

This commit adds 3 tests to verify a common compiler generated
pattern for sign extension (r1 <<= 32; r1 s>>= 32).
The tests make sure the register bounds are correctly computed both for
positive and negative register values.

Signed-off-by: Cupertino Miranda  <cupertino.miranda@oracle.com>
Signed-off-by: Andrew Pinski  <andrew.pinski@oss.qualcomm.com>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Cc: David Faust  <david.faust@oracle.com>
Cc: Jose Marchesi  <jose.marchesi@oracle.com>
Cc: Elena Zannoni  <elena.zannoni@oracle.com>
Link: https://lore.kernel.org/r/20251202180220.11128-3-cupertino.miranda@oracle.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/tools/testing/selftests/bpf/progs/verifier_subreg.c b/tools/testing/selftests/bpf/progs/verifier_subreg.c
index 8613ea160dcdf79c3d7cba22f17a198167d98630..b3e1c3eef9ae4470b5144e883d321c9587ec0874 100644 (file)
--- a/tools/testing/selftests/bpf/progs/verifier_subreg.c
+++ b/tools/testing/selftests/bpf/progs/verifier_subreg.c
@@ -531,6 +531,74 @@ __naked void arsh32_imm_zero_extend_check(void)
        : __clobber_all);
 }
 
+SEC("socket")
+__description("arsh32 imm sign positive extend check")
+__success __retval(0)
+__log_level(2)
+__msg("2: (57) r6 &= 4095                    ; R6=scalar(smin=smin32=0,smax=umax=smax32=umax32=4095,var_off=(0x0; 0xfff))")
+__msg("3: (67) r6 <<= 32                     ; R6=scalar(smin=smin32=0,smax=umax=0xfff00000000,smax32=umax32=0,var_off=(0x0; 0xfff00000000))")
+__msg("4: (c7) r6 s>>= 32                    ; R6=scalar(smin=smin32=0,smax=umax=smax32=umax32=4095,var_off=(0x0; 0xfff))")
+__naked void arsh32_imm_sign_extend_positive_check(void)
+{
+       asm volatile ("                                 \
+       call %[bpf_get_prandom_u32];                    \
+       r6 = r0;                                        \
+       r6 &= 4095;                                     \
+       r6 <<= 32;                                      \
+       r6 s>>= 32;                                     \
+       r0 = 0;                                         \
+       exit;                                           \
+"      :
+       : __imm(bpf_get_prandom_u32)
+       : __clobber_all);
+}
+
+SEC("socket")
+__description("arsh32 imm sign negative extend check")
+__success __retval(0)
+__log_level(2)
+__msg("3: (17) r6 -= 4095                    ; R6=scalar(smin=smin32=-4095,smax=smax32=0)")
+__msg("4: (67) r6 <<= 32                     ; R6=scalar(smin=0xfffff00100000000,smax=smax32=umax32=0,umax=0xffffffff00000000,smin32=0,var_off=(0x0; 0xffffffff00000000))")
+__msg("5: (c7) r6 s>>= 32                    ; R6=scalar(smin=smin32=-4095,smax=smax32=0)")
+__naked void arsh32_imm_sign_extend_negative_check(void)
+{
+       asm volatile ("                                 \
+       call %[bpf_get_prandom_u32];                    \
+       r6 = r0;                                        \
+       r6 &= 4095;                                     \
+       r6 -= 4095;                                     \
+       r6 <<= 32;                                      \
+       r6 s>>= 32;                                     \
+       r0 = 0;                                         \
+       exit;                                           \
+"      :
+       : __imm(bpf_get_prandom_u32)
+       : __clobber_all);
+}
+
+SEC("socket")
+__description("arsh32 imm sign extend check")
+__success __retval(0)
+__log_level(2)
+__msg("3: (17) r6 -= 2047                    ; R6=scalar(smin=smin32=-2047,smax=smax32=2048)")
+__msg("4: (67) r6 <<= 32                     ; R6=scalar(smin=0xfffff80100000000,smax=0x80000000000,umax=0xffffffff00000000,smin32=0,smax32=umax32=0,var_off=(0x0; 0xffffffff00000000))")
+__msg("5: (c7) r6 s>>= 32                    ; R6=scalar(smin=smin32=-2047,smax=smax32=2048)")
+__naked void arsh32_imm_sign_extend_check(void)
+{
+       asm volatile ("                                 \
+       call %[bpf_get_prandom_u32];                    \
+       r6 = r0;                                        \
+       r6 &= 4095;                                     \
+       r6 -= 2047;                                     \
+       r6 <<= 32;                                      \
+       r6 s>>= 32;                                     \
+       r0 = 0;                                         \
+       exit;                                           \
+"      :
+       : __imm(bpf_get_prandom_u32)
+       : __clobber_all);
+}
+
 SEC("socket")
 __description("end16 (to_le) reg zero extend check")
 __success __success_unpriv __retval(0)