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[src/trunk]: src/sys/net Don't use saved EREG registers because sljit 0.91 ca...



details:   https://anonhg.NetBSD.org/src/rev/cb69ca6b02e1
branches:  trunk
changeset: 797747:cb69ca6b02e1
user:      alnsn <alnsn%NetBSD.org@localhost>
date:      Sat Jul 26 11:23:46 2014 +0000

description:
Don't use saved EREG registers because sljit 0.91 can generate
bogus code on amd64. The A and X registers are saved on the stack.

The most recent version of sljit fixes bogus code generation but
it's not backward compatible with sljit 0.91.

diffstat:

 sys/net/bpfjit.c |  131 ++++++++++++++++++++++++++++++++++++------------------
 1 files changed, 88 insertions(+), 43 deletions(-)

diffs (truncated from 301 to 300 lines):

diff -r d0c10016fc3d -r cb69ca6b02e1 sys/net/bpfjit.c
--- a/sys/net/bpfjit.c  Sat Jul 26 09:18:53 2014 +0000
+++ b/sys/net/bpfjit.c  Sat Jul 26 11:23:46 2014 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: bpfjit.c,v 1.31 2014/07/24 22:54:38 alnsn Exp $        */
+/*     $NetBSD: bpfjit.c,v 1.32 2014/07/26 11:23:46 alnsn Exp $        */
 
 /*-
  * Copyright (c) 2011-2014 Alexander Nasonov.
@@ -31,9 +31,9 @@
 
 #include <sys/cdefs.h>
 #ifdef _KERNEL
-__KERNEL_RCSID(0, "$NetBSD: bpfjit.c,v 1.31 2014/07/24 22:54:38 alnsn Exp $");
+__KERNEL_RCSID(0, "$NetBSD: bpfjit.c,v 1.32 2014/07/26 11:23:46 alnsn Exp $");
 #else
-__RCSID("$NetBSD: bpfjit.c,v 1.31 2014/07/24 22:54:38 alnsn Exp $");
+__RCSID("$NetBSD: bpfjit.c,v 1.32 2014/07/26 11:23:46 alnsn Exp $");
 #endif
 
 #include <sys/types.h>
@@ -89,12 +89,11 @@
 #define BJ_BUF         SLJIT_SAVED_REG1
 //#define BJ_ARGS      SLJIT_SAVED_REG2
 #define BJ_BUFLEN      SLJIT_SAVED_REG3
-#define BJ_XREG                SLJIT_SAVED_EREG1
-#define BJ_ASAVE       SLJIT_SAVED_EREG2
 #define BJ_AREG                SLJIT_SCRATCH_REG1
 #define BJ_TMP1REG     SLJIT_SCRATCH_REG2
 #define BJ_TMP2REG     SLJIT_SCRATCH_REG3
-#define BJ_TMP3REG     SLJIT_TEMPORARY_EREG1
+#define BJ_XREG                SLJIT_TEMPORARY_EREG1
+#define BJ_TMP3REG     SLJIT_TEMPORARY_EREG2
 
 #ifdef _KERNEL
 #define MAX_MEMWORDS BPF_MAX_MEMWORDS
@@ -136,6 +135,7 @@
 {
        bpf_ctx_t *ctx;
        uint32_t *extmem; /* pointer to external memory store */
+       uint32_t reg; /* saved A or X register */
 #ifdef _KERNEL
        int err; /* 3rd argument for m_xword/m_xhalf/m_xbyte function call */
 #endif
@@ -259,8 +259,16 @@
        if (hints & BJ_HINT_COP)
                rv = 3; /* calls copfunc with three arguments */
 
+       if (hints & BJ_HINT_XREG)
+               rv = 4; /* uses BJ_XREG */
+
+#ifdef _KERNEL
+       if (hints & BJ_HINT_LDX)
+               rv = 5; /* uses BJ_TMP3REG */
+#endif
+
        if (hints & BJ_HINT_COPX)
-               rv = 4; /* uses BJ_TMP3REG */
+               rv = 5; /* uses BJ_TMP3REG */
 
        return rv;
 }
@@ -274,14 +282,6 @@
 {
        sljit_si rv = 3;
 
-       if (hints & BJ_HINT_XREG)
-               rv = 4; /* uses BJ_XREG */
-
-#ifdef _KERNEL
-       if (hints & BJ_HINT_LDX)
-               rv = 5; /* uses BJ_ASAVE */
-#endif
-
        return rv;
 }
 
@@ -528,21 +528,30 @@
  *     BPF_LDX+BPF_B+BPF_MSH   X <- 4*(P[k:1]&0xf)
  */
 static int
-emit_xcall(struct sljit_compiler *compiler, const struct bpf_insn *pc,
-    int dst, struct sljit_jump ***ret0, size_t *ret0_size, size_t *ret0_maxsize,
+emit_xcall(struct sljit_compiler *compiler, bpfjit_hint_t hints,
+    const struct bpf_insn *pc, int dst, struct sljit_jump ***ret0,
+    size_t *ret0_size, size_t *ret0_maxsize,
     uint32_t (*fn)(const struct mbuf *, uint32_t, int *))
 {
+#if BJ_XREG == SLJIT_RETURN_REG   || \
+    BJ_XREG == SLJIT_SCRATCH_REG1 || \
+    BJ_XREG == SLJIT_SCRATCH_REG2 || \
+    BJ_XREG == SLJIT_SCRATCH_REG3
+#error "Not supported assignment of registers."
+#endif
        struct sljit_jump *jump;
+       sljit_si save_reg;
        int status;
 
-       BJ_ASSERT(dst != BJ_ASAVE);
+       save_reg = (BPF_CLASS(pc->code) == BPF_LDX) ? BJ_AREG : BJ_XREG;
 
-       if (BPF_CLASS(pc->code) == BPF_LDX) {
-               /* save A */
+       if (save_reg == BJ_AREG || (hints & BJ_HINT_XREG)) {
+               /* save A or X */
                status = sljit_emit_op1(compiler,
-                   SLJIT_MOV,
-                   BJ_ASAVE, 0,
-                   BJ_AREG, 0);
+                   SLJIT_MOV_UI, /* uint32_t destination */
+                   SLJIT_MEM1(SLJIT_LOCALS_REG),
+                   offsetof(struct bpfjit_stack, reg),
+                   save_reg, 0);
                if (status != SLJIT_SUCCESS)
                        return status;
        }
@@ -634,12 +643,13 @@
        if (!append_jump(jump, ret0, ret0_size, ret0_maxsize))
                return SLJIT_ERR_ALLOC_FAILED;
 
-       if (BPF_CLASS(pc->code) == BPF_LDX) {
-               /* restore A */
+       if (save_reg == BJ_AREG || (hints & BJ_HINT_XREG)) {
+               /* restore A or X */
                status = sljit_emit_op1(compiler,
-                   SLJIT_MOV,
-                   BJ_AREG, 0,
-                   BJ_ASAVE, 0);
+                   SLJIT_MOV_UI, /* uint32_t source */
+                   save_reg, 0,
+                   SLJIT_MEM1(SLJIT_LOCALS_REG),
+                   offsetof(struct bpfjit_stack, reg));
                if (status != SLJIT_SUCCESS)
                        return status;
        }
@@ -652,11 +662,15 @@
  * Emit code for BPF_COP and BPF_COPX instructions.
  */
 static int
-emit_cop(struct sljit_compiler *compiler,
+emit_cop(struct sljit_compiler *compiler, bpfjit_hint_t hints,
     const bpf_ctx_t *bc, const struct bpf_insn *pc,
     struct sljit_jump ***ret0, size_t *ret0_size, size_t *ret0_maxsize)
 {
-#if BJ_TMP3REG == SLJIT_SCRATCH_REG1 || \
+#if BJ_XREG    == SLJIT_RETURN_REG   || \
+    BJ_XREG    == SLJIT_SCRATCH_REG1 || \
+    BJ_XREG    == SLJIT_SCRATCH_REG2 || \
+    BJ_XREG    == SLJIT_SCRATCH_REG3 || \
+    BJ_TMP3REG == SLJIT_SCRATCH_REG1 || \
     BJ_TMP3REG == SLJIT_SCRATCH_REG2 || \
     BJ_TMP3REG == SLJIT_SCRATCH_REG3
 #error "Not supported assignment of registers."
@@ -669,6 +683,17 @@
 
        BJ_ASSERT(bc != NULL && bc->copfuncs != NULL);
 
+       if (hints & BJ_HINT_LDX) {
+               /* save X */
+               status = sljit_emit_op1(compiler,
+                   SLJIT_MOV_UI, /* uint32_t destination */
+                   SLJIT_MEM1(SLJIT_LOCALS_REG),
+                   offsetof(struct bpfjit_stack, reg),
+                   BJ_XREG, 0);
+               if (status != SLJIT_SUCCESS)
+                       return status;
+       }
+
        if (BPF_MISCOP(pc->code) == BPF_COP) {
                call_reg = SLJIT_IMM;
                call_off = SLJIT_FUNC_OFFSET(bc->copfuncs[pc->k]);
@@ -762,6 +787,17 @@
                return status;
 #endif
 
+       if (hints & BJ_HINT_LDX) {
+               /* restore X */
+               status = sljit_emit_op1(compiler,
+                   SLJIT_MOV_UI, /* uint32_t source */
+                   BJ_XREG, 0,
+                   SLJIT_MEM1(SLJIT_LOCALS_REG),
+                   offsetof(struct bpfjit_stack, reg));
+               if (status != SLJIT_SUCCESS)
+                       return status;
+       }
+
        return SLJIT_SUCCESS;
 }
 
@@ -775,7 +811,7 @@
  * BPF_LD+BPF_B+BPF_IND    A <- P[X+k:1]
  */
 static int
-emit_pkt_read(struct sljit_compiler *compiler,
+emit_pkt_read(struct sljit_compiler *compiler, bpfjit_hint_t hints,
     const struct bpf_insn *pc, struct sljit_jump *to_mchain_jump,
     struct sljit_jump ***ret0, size_t *ret0_size, size_t *ret0_maxsize)
 {
@@ -875,15 +911,15 @@
 
        switch (width) {
        case 4:
-               status = emit_xcall(compiler, pc, BJ_AREG,
+               status = emit_xcall(compiler, hints, pc, BJ_AREG,
                    ret0, ret0_size, ret0_maxsize, &m_xword);
                break;
        case 2:
-               status = emit_xcall(compiler, pc, BJ_AREG,
+               status = emit_xcall(compiler, hints, pc, BJ_AREG,
                    ret0, ret0_size, ret0_maxsize, &m_xhalf);
                break;
        case 1:
-               status = emit_xcall(compiler, pc, BJ_AREG,
+               status = emit_xcall(compiler, hints, pc, BJ_AREG,
                    ret0, ret0_size, ret0_maxsize, &m_xbyte);
                break;
        }
@@ -960,7 +996,7 @@
  * Emit code for BPF_LDX+BPF_B+BPF_MSH    X <- 4*(P[k:1]&0xf).
  */
 static int
-emit_msh(struct sljit_compiler *compiler,
+emit_msh(struct sljit_compiler *compiler, bpfjit_hint_t hints,
     const struct bpf_insn *pc, struct sljit_jump *to_mchain_jump,
     struct sljit_jump ***ret0, size_t *ret0_size, size_t *ret0_maxsize)
 {
@@ -1014,7 +1050,7 @@
                        return SLJIT_ERR_ALLOC_FAILED;
        }
 
-       status = emit_xcall(compiler, pc, BJ_TMP1REG,
+       status = emit_xcall(compiler, hints, pc, BJ_TMP1REG,
            ret0, ret0_size, ret0_maxsize, &m_xbyte);
        if (status != SLJIT_SUCCESS)
                return status;
@@ -1088,6 +1124,13 @@
 {
        int status;
 
+#if BJ_XREG == SLJIT_RETURN_REG   || \
+    BJ_XREG == SLJIT_SCRATCH_REG1 || \
+    BJ_XREG == SLJIT_SCRATCH_REG2 || \
+    BJ_AREG == SLJIT_SCRATCH_REG2
+#error "Not supported assignment of registers."
+#endif
+
 #if BJ_AREG != SLJIT_SCRATCH_REG1
        status = sljit_emit_op1(compiler,
            SLJIT_MOV,
@@ -1588,9 +1631,9 @@
 }
 
 static bool
-generate_insn_code(struct sljit_compiler *compiler, const bpf_ctx_t *bc,
-    const struct bpf_insn *insns, struct bpfjit_insn_data *insn_dat,
-    size_t insn_count)
+generate_insn_code(struct sljit_compiler *compiler, bpfjit_hint_t hints,
+    const bpf_ctx_t *bc, const struct bpf_insn *insns,
+    struct bpfjit_insn_data *insn_dat, size_t insn_count)
 {
        /* a list of jumps to out-of-bound return from a generated function */
        struct sljit_jump **ret0;
@@ -1736,7 +1779,7 @@
                        if (unconditional_ret)
                                continue;
 
-                       status = emit_pkt_read(compiler, pc,
+                       status = emit_pkt_read(compiler, hints, pc,
                            to_mchain_jump, &ret0, &ret0_size, &ret0_maxsize);
                        if (status != SLJIT_SUCCESS)
                                goto fail;
@@ -1796,7 +1839,7 @@
                        if (unconditional_ret)
                                continue;
 
-                       status = emit_msh(compiler, pc,
+                       status = emit_msh(compiler, hints, pc,
                            to_mchain_jump, &ret0, &ret0_size, &ret0_maxsize);
                        if (status != SLJIT_SUCCESS)
                                goto fail;
@@ -2004,7 +2047,7 @@
                                        goto fail;
                                }
 
-                               status = emit_cop(compiler, bc, pc,
+                               status = emit_cop(compiler, hints, bc, pc,
                                    &ret0, &ret0_size, &ret0_maxsize);
                                if (status != SLJIT_SUCCESS)
                                        goto fail;
@@ -2177,8 +2220,10 @@
        if (status != SLJIT_SUCCESS)
                goto fail;
 
-       if (!generate_insn_code(compiler, bc, insns, insn_dat, insn_count))
+       if (!generate_insn_code(compiler, hints,
+           bc, insns, insn_dat, insn_count)) {
                goto fail;
+       }
 
        rv = sljit_generate_code(compiler);



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