s390/bpf: Implement BPF_MEMSX

Implement the cpuv4 load with sign-extension, which is encoded as
BPF_MEMSX (and, for internal uses cases only, BPF_PROBE_MEMSX).

This is the same as BPF_MEM and BPF_PROBE_MEM, but with sign
extension instead of zero extension, and s390x has the necessary
instructions: lgb, lgh and lgf.

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Link: https://lore.kernel.org/r/20230919101336.2223655-6-iii@linux.ibm.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c
index 6fb24ebb36187ee63cd421ffaba71aca8304d357..957f5cbba4d8f8990d4539e611504c5e1e55815e 100644 (file)
--- a/arch/s390/net/bpf_jit_comp.c
+++ b/arch/s390/net/bpf_jit_comp.c
@@ -670,15 +670,18 @@ static void bpf_jit_epilogue(struct bpf_jit *jit, u32 stack_depth)
 static int get_probe_mem_regno(const u8 *insn)
 {
        /*
-        * insn must point to llgc, llgh, llgf or lg, which have destination
-        * register at the same position.
+        * insn must point to llgc, llgh, llgf, lg, lgb, lgh or lgf, which have
+        * destination register at the same position.
         */
-       if (insn[0] != 0xe3) /* common llgc, llgh, llgf and lg prefix */
+       if (insn[0] != 0xe3) /* common prefix */
                return -1;
        if (insn[5] != 0x90 && /* llgc */
            insn[5] != 0x91 && /* llgh */
            insn[5] != 0x16 && /* llgf */
-           insn[5] != 0x04) /* lg */
+           insn[5] != 0x04 && /* lg */
+           insn[5] != 0x77 && /* lgb */
+           insn[5] != 0x15 && /* lgh */
+           insn[5] != 0x14) /* lgf */
                return -1;
        return insn[1] >> 4;
 }
@@ -788,7 +791,8 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp,
        int err;
 
        if (BPF_CLASS(insn->code) == BPF_LDX &&
-           BPF_MODE(insn->code) == BPF_PROBE_MEM)
+           (BPF_MODE(insn->code) == BPF_PROBE_MEM ||
+            BPF_MODE(insn->code) == BPF_PROBE_MEMSX))
                probe_prg = jit->prg;
 
        switch (insn->code) {
@@ -1406,6 +1410,12 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp,
                if (insn_is_zext(&insn[1]))
                        insn_count = 2;
                break;
+       case BPF_LDX | BPF_MEMSX | BPF_B: /* dst = *(s8 *)(ul) (src + off) */
+       case BPF_LDX | BPF_PROBE_MEMSX | BPF_B:
+               /* lgb %dst,0(off,%src) */
+               EMIT6_DISP_LH(0xe3000000, 0x0077, dst_reg, src_reg, REG_0, off);
+               jit->seen |= SEEN_MEM;
+               break;
        case BPF_LDX | BPF_MEM | BPF_H: /* dst = *(u16 *)(ul) (src + off) */
        case BPF_LDX | BPF_PROBE_MEM | BPF_H:
                /* llgh %dst,0(off,%src) */
@@ -1414,6 +1424,12 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp,
                if (insn_is_zext(&insn[1]))
                        insn_count = 2;
                break;
+       case BPF_LDX | BPF_MEMSX | BPF_H: /* dst = *(s16 *)(ul) (src + off) */
+       case BPF_LDX | BPF_PROBE_MEMSX | BPF_H:
+               /* lgh %dst,0(off,%src) */
+               EMIT6_DISP_LH(0xe3000000, 0x0015, dst_reg, src_reg, REG_0, off);
+               jit->seen |= SEEN_MEM;
+               break;
        case BPF_LDX | BPF_MEM | BPF_W: /* dst = *(u32 *)(ul) (src + off) */
        case BPF_LDX | BPF_PROBE_MEM | BPF_W:
                /* llgf %dst,off(%src) */
@@ -1422,6 +1438,12 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp,
                if (insn_is_zext(&insn[1]))
                        insn_count = 2;
                break;
+       case BPF_LDX | BPF_MEMSX | BPF_W: /* dst = *(s32 *)(ul) (src + off) */
+       case BPF_LDX | BPF_PROBE_MEMSX | BPF_W:
+               /* lgf %dst,off(%src) */
+               jit->seen |= SEEN_MEM;
+               EMIT6_DISP_LH(0xe3000000, 0x0014, dst_reg, src_reg, REG_0, off);
+               break;
        case BPF_LDX | BPF_MEM | BPF_DW: /* dst = *(u64 *)(ul) (src + off) */
        case BPF_LDX | BPF_PROBE_MEM | BPF_DW:
                /* lg %dst,0(off,%src) */