Add support for uninstrumented .text.trusted section

zyedidia · Dec 12, 2024 · 3873bd2 · 3873bd2
1 parent d1f147a
commit 3873bd2
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Showing 5 changed files with 46 additions and 2 deletions.
diff --git a/lfi-leg/amd64/amd64.c b/lfi-leg/amd64/amd64.c
@@ -99,9 +99,17 @@ amd64_rewrite(FILE* input, struct output* output)
         if (passes[i].disabled)
             continue;
         struct op* op = ops;
+        bool trusted = false;
         while (op) {
             struct op* next = op->next;
-            passes[i].fn(op);
+            if (op->truststart)
+                trusted = true;
+            if (op->notruststart)
+                trusted = false;
+
+            if (!trusted)
+                passes[i].fn(op);
+
             op = next;
         }
     }

diff --git a/lfi-leg/amd64/parse.leg b/lfi-leg/amd64/parse.leg
@@ -16,6 +16,8 @@ Top = Insn* !.
 
 Insn = - Label? (
       BundleDirective
+    | TrustedDirective
+    | UntrustedDirective
     | Directive Comment?
     | Comment
     | AnyPrefix
@@ -46,6 +48,17 @@ FnDirective = < '.type' - ([^,])* ',' - [@%] 'function' - > {
     mkdirective(bundle_align());
 }
 
+TrustedDirective = '.section' - '.text.trusted' rest:REMAINDER {
+    struct op* op = mkdirective(xasprintf(".section .text.trusted%s", rest.val));
+    op->truststart = true;
+    rfree(rest);
+}
+
+UntrustedDirective = < ('.text' | '.section') (!EOL .)* > {
+    struct op* op = mkdirective(strndup(yytext, yyleng));
+    op->notruststart = true;
+}
+
 PREFIX = < ('lock' | 'rep' | 'rex64' | 'rex') > [ \t\r\n;]+ {
     $$ = (Result) { .val = strndup(yytext, yyleng) }
 }

diff --git a/lfi-leg/arm64/arm64.c b/lfi-leg/arm64/arm64.c
@@ -99,9 +99,17 @@ arm64_rewrite(FILE* input, struct output* output)
         if (passes[i].disabled)
             continue;
         struct op* op = ops;
+        bool trusted = false;
         while (op) {
             struct op* next = op->next;
-            passes[i].fn(op);
+            if (op->truststart)
+                trusted = true;
+            if (op->notruststart)
+                trusted = false;
+
+            if (!trusted)
+                passes[i].fn(op);
+
             op = next;
         }
     }

diff --git a/lfi-leg/arm64/parse.leg b/lfi-leg/arm64/parse.leg
@@ -17,6 +17,8 @@ Top = Insn* !.
 Insn = - Label? (
       FnDirective Comment?
     | BundleDirective Comment?
+    | TrustedDirective
+    | UntrustedDirective
     | Directive Comment?
     | Comment
     | Any
@@ -44,6 +46,17 @@ FnDirective = < '.type' - ([^,])* ',' - [@%] 'function' - > {
     // mkdirective(bundle_align());
 }
 
+TrustedDirective = '.section' - '.text.trusted' rest:REMAINDER {
+    struct op* op = mkdirective(xasprintf(".section .text.trusted%s", rest.val));
+    op->truststart = true;
+    rfree(rest);
+}
+
+UntrustedDirective = < ('.text' | '.section') (!EOL .)* > {
+    struct op* op = mkdirective(strndup(yytext, yyleng));
+    op->notruststart = true;
+}
+
 Directive = < '.' (!EOL .)* > - {
     mkdirective(strndup(yytext, yyleng));
 }

diff --git a/lfi-leg/op.h b/lfi-leg/op.h
@@ -14,6 +14,8 @@ struct op {
     char* replace;
     char* target;
     bool rmforward;
+    bool truststart;
+    bool notruststart;
 
     struct op* next;
     struct op* prev;