This is a s390 port of x86 commit 3dec541b2e63 ("bpf: Add support for BTF
pointers to x86 JIT").
Signed-off-by: Ilya Leoshkevich <iii@xxxxxxxxxxxxx>
Reviewed-by: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
---
arch/s390/net/bpf_jit_comp.c | 138 ++++++++++++++++++++++++++++++++++-
1 file changed, 137 insertions(+), 1 deletion(-)
diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c
index f4242b894cf2..af210ea64b69 100644
--- a/arch/s390/net/bpf_jit_comp.c
+++ b/arch/s390/net/bpf_jit_comp.c
@@ -49,6 +49,7 @@ struct bpf_jit {
int r1_thunk_ip; /* Address of expoline thunk for 'br %r1' */
int r14_thunk_ip; /* Address of expoline thunk for 'br %r14' */
int tail_call_start; /* Tail call start offset */
+ int excnt; /* Number of exception table entries */
int labels[1]; /* Labels for local jumps */
};
@@ -588,6 +589,84 @@ 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.
+ */
+ if (insn[0] != 0xe3) /* common llgc, llgh, llgf and lg prefix */
+ return -1;
+ if (insn[5] != 0x90 && /* llgc */
+ insn[5] != 0x91 && /* llgh */
+ insn[5] != 0x16 && /* llgf */
+ insn[5] != 0x04) /* lg */
+ return -1;
+ return insn[1] >> 4;
+}
+
+static bool ex_handler_bpf(const struct exception_table_entry *x,
+ struct pt_regs *regs)
+{
+ int regno;
+ u8 *insn;
+
+ regs->psw.addr = extable_fixup(x);
+ insn = (u8 *)__rewind_psw(regs->psw, regs->int_code >> 16);
+ regno = get_probe_mem_regno(insn);
+ if (WARN_ON_ONCE(regno < 0))
+ /* JIT bug - unexpected instruction. */
+ return false;
+ regs->gprs[regno] = 0;
+ return true;
+}
+
+static int bpf_jit_probe_mem(struct bpf_jit *jit, struct bpf_prog *fp,
+ int probe_prg, int nop_prg)
+{
+ struct exception_table_entry *ex;
+ s64 delta;
+ u8 *insn;
+ int prg;
+ int i;
+
+ if (!fp->aux->extable)
+ /* Do nothing during early JIT passes. */
+ return 0;
+ insn = jit->prg_buf + probe_prg;
+ if (WARN_ON_ONCE(get_probe_mem_regno(insn) < 0))
+ /* JIT bug - unexpected probe instruction. */
+ return -1;
+ if (WARN_ON_ONCE(probe_prg + insn_length(*insn) != nop_prg))
+ /* JIT bug - gap between probe and nop instructions. */
+ return -1;
+ for (i = 0; i < 2; i++) {
+ if (WARN_ON_ONCE(jit->excnt >= fp->aux->num_exentries))
+ /* Verifier bug - not enough entries. */
+ return -1;
+ ex = &fp->aux->extable[jit->excnt];
+ /* Add extable entries for probe and nop instructions. */
+ prg = i == 0 ? probe_prg : nop_prg;
+ delta = jit->prg_buf + prg - (u8 *)&ex->insn;
+ if (WARN_ON_ONCE(delta < INT_MIN || delta > INT_MAX))
+ /* JIT bug - code and extable must be close. */
+ return -1;
+ ex->insn = delta;
+ /*
+ * Always land on the nop. Note that extable infrastructure
+ * ignores fixup field, it is handled by ex_handler_bpf().
+ */
+ delta = jit->prg_buf + nop_prg - (u8 *)&ex->fixup;
+ if (WARN_ON_ONCE(delta < INT_MIN || delta > INT_MAX))
+ /* JIT bug - landing pad and extable must be close. */
+ return -1;
+ ex->fixup = delta;
+ ex->handler = (u8 *)ex_handler_bpf - (u8 *)&ex->handler;
+ jit->excnt++;
+ }
+ return 0;
+}
+
/*
* Compile one eBPF instruction into s390x code
*
@@ -604,7 +683,14 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp,
u32 *addrs = jit->addrs;
s32 imm = insn->imm;
s16 off = insn->off;
+ int probe_prg = -1;
unsigned int mask;
+ int nop_prg;
+ int err;
+
+ if (BPF_CLASS(insn->code) == BPF_LDX &&
+ BPF_MODE(insn->code) == BPF_PROBE_MEM)
+ probe_prg = jit->prg;
switch (insn->code) {
/*
@@ -1119,6 +1205,7 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp,
* BPF_LDX
*/
case BPF_LDX | BPF_MEM | BPF_B: /* dst = *(u8 *)(ul) (src + off) */
+ case BPF_LDX | BPF_PROBE_MEM | BPF_B:
/* llgc %dst,0(off,%src) */
EMIT6_DISP_LH(0xe3000000, 0x0090, dst_reg, src_reg, REG_0, off);
jit->seen |= SEEN_MEM;
@@ -1126,6 +1213,7 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp,
insn_count = 2;
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) */
EMIT6_DISP_LH(0xe3000000, 0x0091, dst_reg, src_reg, REG_0, off);
jit->seen |= SEEN_MEM;
@@ -1133,6 +1221,7 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp,
insn_count = 2;
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) */
jit->seen |= SEEN_MEM;
EMIT6_DISP_LH(0xe3000000, 0x0016, dst_reg, src_reg, REG_0, off);
@@ -1140,6 +1229,7 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp,
insn_count = 2;
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) */
jit->seen |= SEEN_MEM;
EMIT6_DISP_LH(0xe3000000, 0x0004, dst_reg, src_reg, REG_0, off);
@@ -1485,6 +1575,23 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp,
pr_err("Unknown opcode %02x\n", insn->code);
return -1;
}
+
+ if (probe_prg != -1) {
+ /*
+ * Handlers of certain exceptions leave psw.addr pointing to
+ * the instruction directly after the failing one. Therefore,
+ * create two exception table entries and also add a nop in
+ * case two probing instructions come directly after each
+ * other.
+ */
+ nop_prg = jit->prg;
+ /* bcr 0,%0 */
+ _EMIT2(0x0700);
+ err = bpf_jit_probe_mem(jit, fp, probe_prg, nop_prg);
+ if (err < 0)
+ return err;
+ }
+
return insn_count;
}
@@ -1551,6 +1658,12 @@ static int bpf_jit_prog(struct bpf_jit *jit, struct bpf_prog *fp,
jit->lit64_start = ALIGN(jit->lit64_start, 8);
jit->size = jit->lit64_start + lit64_size;
jit->size_prg = jit->prg;
+
+ if (WARN_ON_ONCE(fp->aux->extable &&
+ jit->excnt != fp->aux->num_exentries))
+ /* Verifier bug - too many entries. */
+ return -1;
+
return 0;
}
@@ -1565,6 +1678,29 @@ struct s390_jit_data {
int pass;
};
+static struct bpf_binary_header *bpf_jit_alloc(struct bpf_jit *jit,
+ struct bpf_prog *fp)
+{
+ struct bpf_binary_header *header;
+ u32 extable_size;
+ u32 code_size;
+
+ /* We need two entries per insn. */
+ fp->aux->num_exentries *= 2;
+
+ code_size = roundup(jit->size,
+ __alignof__(struct exception_table_entry));
+ extable_size = fp->aux->num_exentries *
+ sizeof(struct exception_table_entry);
+ header = bpf_jit_binary_alloc(code_size + extable_size, &jit->prg_buf,
+ 8, jit_fill_hole);
+ if (!header)
+ return NULL;
+ fp->aux->extable = (struct exception_table_entry *)
+ (jit->prg_buf + code_size);
+ return header;
+}
+
/*
* Compile eBPF program "fp"
*/
@@ -1631,7 +1767,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp)
/*
* Final pass: Allocate and generate program
*/
- header = bpf_jit_binary_alloc(jit.size, &jit.prg_buf, 8, jit_fill_hole);
+ header = bpf_jit_alloc(&jit, fp);
if (!header) {
fp = orig_fp;
goto free_addrs;
--
2.25.4
