s390/bpf: Get rid of get_probe_mem_regno()

Commit 7fc8c362e782 ("s390/bpf: encode register within extable entry")
introduced explicit passing of the number of the register to be cleared
to ex_handler_bpf(), which replaced deducing it from the respective
native load instruction using get_probe_mem_regno().

Replace the second and last usage in the same manner, and remove this
function.

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20240701234304.14336-4-iii@linux.ibm.com

diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c
index 260e7009784b8e07e44202f273500ee7a825a87c..d9d79aa2be1ba14e3516555ef6fd16c44c28fc23 100644 (file)
--- a/arch/s390/net/bpf_jit_comp.c
+++ b/arch/s390/net/bpf_jit_comp.c
@@ -667,25 +667,6 @@ static void bpf_jit_epilogue(struct bpf_jit *jit, u32 stack_depth)
        jit->prg += sizeof(struct bpf_plt);
 }
 
-static int get_probe_mem_regno(const u8 *insn)
-{
-       /*
-        * 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 prefix */
-               return -1;
-       if (insn[5] != 0x90 && /* llgc */
-           insn[5] != 0x91 && /* llgh */
-           insn[5] != 0x16 && /* llgf */
-           insn[5] != 0x04 && /* lg */
-           insn[5] != 0x77 && /* lgb */
-           insn[5] != 0x15 && /* lgh */
-           insn[5] != 0x14) /* lgf */
-               return -1;
-       return insn[1] >> 4;
-}
-
 bool ex_handler_bpf(const struct exception_table_entry *x, struct pt_regs *regs)
 {
        regs->psw.addr = extable_fixup(x);
@@ -699,12 +680,14 @@ bool ex_handler_bpf(const struct exception_table_entry *x, struct pt_regs *regs)
 struct bpf_jit_probe {
        int prg;        /* JITed instruction offset */
        int nop_prg;    /* JITed nop offset */
+       int reg;        /* Register to clear on exception */
 };
 
 static void bpf_jit_probe_init(struct bpf_jit_probe *probe)
 {
        probe->prg = -1;
        probe->nop_prg = -1;
+       probe->reg = -1;
 }
 
 /*
@@ -725,7 +708,7 @@ static int bpf_jit_probe_mem(struct bpf_jit *jit, struct bpf_prog *fp,
                             struct bpf_jit_probe *probe)
 {
        struct exception_table_entry *ex;
-       int i, prg, reg;
+       int i, prg;
        s64 delta;
        u8 *insn;
 
@@ -734,10 +717,6 @@ static int bpf_jit_probe_mem(struct bpf_jit *jit, struct bpf_prog *fp,
                /* Do nothing during early JIT passes. */
                return 0;
        insn = jit->prg_buf + probe->prg;
-       reg = get_probe_mem_regno(insn);
-       if (WARN_ON_ONCE(reg < 0))
-               /* JIT bug - unexpected probe instruction. */
-               return -1;
        if (WARN_ON_ONCE(probe->prg + insn_length(*insn) != probe->nop_prg))
                /* JIT bug - gap between probe and nop instructions. */
                return -1;
@@ -763,7 +742,7 @@ static int bpf_jit_probe_mem(struct bpf_jit *jit, struct bpf_prog *fp,
                        return -1;
                ex->fixup = delta;
                ex->type = EX_TYPE_BPF;
-               ex->data = reg;
+               ex->data = probe->reg;
                jit->excnt++;
        }
        return 0;
@@ -821,8 +800,10 @@ static noinline int bpf_jit_insn(struct bpf_jit *jit, struct bpf_prog *fp,
        bpf_jit_probe_init(&probe);
        if (BPF_CLASS(insn->code) == BPF_LDX &&
            (BPF_MODE(insn->code) == BPF_PROBE_MEM ||
-            BPF_MODE(insn->code) == BPF_PROBE_MEMSX))
+            BPF_MODE(insn->code) == BPF_PROBE_MEMSX)) {
                probe.prg = jit->prg;
+               probe.reg = reg2hex[dst_reg];
+       }
 
        switch (insn->code) {
        /*