lib9p: idl.gen: Enforce a max WELEM for 9P2000.e

1 files changed, 68 insertions, 12 deletions

diff --git a/lib9p/idl.gen b/lib9p/idl.gen
index ead9bc5..bf0935c 100755
--- a/lib9p/idl.gen
+++ b/lib9p/idl.gen
@@ -224,7 +224,9 @@ class BufferSize:
     exp_size: int  # "expected" or max-reasonable size
     max_size: int  # really just here to sanity-check against typ.max_size(version)
     max_copy: int
+    max_copy_extra: str
     max_iov: int
+    max_iov_extra: str
     _starts_with_copy: bool
     _ends_with_copy: bool
 
@@ -233,7 +235,9 @@ class BufferSize:
         self.exp_size = 0
         self.max_size = 0
         self.max_copy = 0
+        self.max_copy_extra = ""
         self.max_iov = 0
+        self.max_iov_extra = ""
         self._starts_with_copy = False
         self._ends_with_copy = False
 
@@ -271,17 +275,36 @@ def get_buffer_size(typ: idl.Type, version: str) -> BufferSize:
                 sub = get_buffer_size(child.typ, version)
                 ret.exp_size += sub.exp_size * 16  # HEURISTIC: MAXWELEM
                 ret.max_size += sub.max_size * child.max_cnt
-                ret.max_copy += sub.max_copy * child.max_cnt
-                if sub.max_iov == 1 and sub._starts_with_copy:  # is purely copy
-                    ret.max_iov += 1
-                else:  # contains zero-copy segments
-                    ret.max_iov += sub.max_iov * child.max_cnt
-                if ret._ends_with_copy and sub._starts_with_copy:
-                    # we can merge this one
+                if child.name == "wname" and path.root.name in (
+                    "Tsread",
+                    "Tswrite",
+                ):  # SPECIAL (9P2000.e)
+                    assert ret._ends_with_copy
+                    assert sub._starts_with_copy
+                    assert not sub._ends_with_copy
+                    ret.max_copy_extra = (
+                        f" + (CONFIG_9P_MAX_9P2000_e_WELEM * {sub.max_copy})"
+                    )
+                    ret.max_iov_extra = (
+                        f" + (CONFIG_9P_MAX_9P2000_e_WELEM * {sub.max_iov})"
+                    )
                     ret.max_iov -= 1
-                if sub._ends_with_copy and sub._starts_with_copy and sub.max_iov > 1:
-                    # we can merge these
-                    ret.max_iov -= child.max_cnt - 1
+                else:
+                    ret.max_copy += sub.max_copy * child.max_cnt
+                    if sub.max_iov == 1 and sub._starts_with_copy:  # is purely copy
+                        ret.max_iov += 1
+                    else:  # contains zero-copy segments
+                        ret.max_iov += sub.max_iov * child.max_cnt
+                    if ret._ends_with_copy and sub._starts_with_copy:
+                        # we can merge this one
+                        ret.max_iov -= 1
+                    if (
+                        sub._ends_with_copy
+                        and sub._starts_with_copy
+                        and sub.max_iov > 1
+                    ):
+                        # we can merge these
+                        ret.max_iov -= child.max_cnt - 1
                 ret._ends_with_copy = sub._ends_with_copy
                 return WalkCmd.DONT_RECURSE
             elif not isinstance(child.typ, idl.Struct):
@@ -332,6 +355,14 @@ def gen_h(versions: set[str], typs: list[idl.Type]) -> str:
         ret += "\n"
         ret += f"#ifndef {c_ver_ifdef({ver})}\n"
         ret += f"\t#error config.h must define {c_ver_ifdef({ver})}\n"
+        if ver == "9P2000.e":  # SPECIAL (9P2000.e)
+            ret += "#else\n"
+            ret += f"\t#if {c_ver_ifdef({ver})}\n"
+            ret += "\t\t#ifndef(CONFIG_9P_MAX_9P2000_e_WELEM)\n"
+            ret += f"\t\t\t#error if {c_ver_ifdef({ver})} then config.h must define CONFIG_9P_MAX_9P2000_e_WELEM\n"
+            ret += "\t\t#endif\n"
+            ret += "\t\tstatic_assert(CONFIG_9P_MAX_9P2000_e_WELEM > 0);\n"
+            ret += "\t#endif\n"
         ret += "#endif\n"
 
     ret += f"""
@@ -404,7 +435,7 @@ enum {idprefix}version {{
                 ret += f"min_size = {sz.min_size:,} ; exp_size = {sz.exp_size:,} ; max_size = {sz.max_size:,}"
             if sz.max_size > u32max:
                 ret += " (warning: >UINT32_MAX)"
-            ret += f" ; max_iov = {sz.max_iov:,} ; max_copy = {sz.max_copy:,}"
+            ret += f" ; max_iov = {sz.max_iov:,}{sz.max_iov_extra} ; max_copy = {sz.max_copy:,}{sz.max_copy_extra}"
             return ret
 
         ret += per_version_comment(typ, sum_size)
@@ -478,6 +509,9 @@ enum {idprefix}version {{
     ret += """
 /* sizes **********************************************************************/
 """
+    ret += "\n"
+    ret += f"#define _{idprefix.upper()}MAX(a, b) ((a) > (b)) ? (a) : (b)\n"
+
     tmsg_max_iov: dict[str, int] = {}
     tmsg_max_copy: dict[str, int] = {}
     rmsg_max_iov: dict[str, int] = {}
@@ -485,6 +519,8 @@ enum {idprefix}version {{
     for typ in typs:
         if not isinstance(typ, idl.Message):
             continue
+        if typ.name in ("Tsread", "Tswrite"):  # SPECIAL (9P2000.e)
+            continue
         max_iov = tmsg_max_iov if typ.msgid % 2 == 0 else rmsg_max_iov
         max_copy = tmsg_max_copy if typ.msgid % 2 == 0 else rmsg_max_copy
         for version in typ.in_versions:
@@ -511,9 +547,29 @@ enum {idprefix}version {{
 
         ret += "\n"
         directive = "if"
+        seen_e = False  # SPECIAL (9P2000.e)
         for maxval in sorted(inv, reverse=True):
             ret += f"#{directive} {c_ver_ifdef(inv[maxval])}\n"
-            ret += f"\t#define {idprefix.upper()}{name.upper()} {maxval}\n"
+            indent = 1
+            if name.startswith("tmsg") and not seen_e:  # SPECIAL (9P2000.e)
+                typ = next(typ for typ in typs if typ.name == "Tswrite")
+                sz = get_buffer_size(typ, "9P2000.e")
+                match name:
+                    case "tmsg_max_iov":
+                        maxexpr = f"{sz.max_iov}{sz.max_iov_extra}"
+                    case "tmsg_max_copy":
+                        maxexpr = f"{sz.max_copy}{sz.max_copy_extra}"
+                    case _:
+                        assert False
+                ret += f"\t#if {c_ver_ifdef({"9P2000.e"})}\n"
+                ret += f"\t\t#define {idprefix.upper()}{name.upper()} _{idprefix.upper()}MAX({maxval}, {maxexpr})\n"
+                ret += f"\t#else\n"
+                indent += 1
+            ret += f"{'\t'*indent}#define {idprefix.upper()}{name.upper()} {maxval}\n"
+            if name.startswith("tmsg") and not seen_e:  # SPECIAL (9P2000.e)
+                ret += "\t#endif\n"
+                if "9P2000.e" in inv[maxval]:
+                    seen_e = True
             directive = "elif"
         ret += "#endif\n"