From e4d874d88a2ef874a9c2fd7c47d3d3a35ae986e2 Mon Sep 17 00:00:00 2001
From: "Jonathan M. Wilbur" <jonathan@wilbur.space>
Date: Tue, 30 Jul 2024 10:33:44 -0400
Subject: [PATCH] fix: code in non-executable ELF sections

---
 tccasm.c                    |  3 +++
 tccgen.c                    |  1 +
 tests/exec_section_in_asm.c | 28 ++++++++++++++++++++++++++++
 tests/exec_section_in_c.c   | 13 +++++++++++++
 4 files changed, 45 insertions(+)
 create mode 100644 tests/exec_section_in_asm.c
 create mode 100644 tests/exec_section_in_c.c

diff --git a/tccasm.c b/tccasm.c
index d056c7031..a75661e44 100644
--- a/tccasm.c
+++ b/tccasm.c
@@ -893,6 +893,9 @@ static void asm_parse_directive(TCCState *s1, int global)
 	    if (old_nb_section != s1->nb_sections)
 	        cur_text_section->sh_addralign = 1;
         }
+        /* The section directive supports flags, but they are unsupported.
+        For now, just assume any section contains code. */
+        cur_text_section->sh_flags |= SHF_EXECINSTR;
         break;
     case TOK_ASMDIR_previous:
         { 
diff --git a/tccgen.c b/tccgen.c
index a1c7db473..57bc493f2 100644
--- a/tccgen.c
+++ b/tccgen.c
@@ -8303,6 +8303,7 @@ static void gen_function(Sym *sym)
     cur_scope = root_scope = &f;
     nocode_wanted = 0;
 
+    cur_text_section->sh_flags |= SHF_EXECINSTR;
     ind = cur_text_section->data_offset;
     if (sym->a.aligned) {
 	size_t newoff = section_add(cur_text_section, 0,
diff --git a/tests/exec_section_in_asm.c b/tests/exec_section_in_asm.c
new file mode 100644
index 000000000..8f13a418c
--- /dev/null
+++ b/tests/exec_section_in_asm.c
@@ -0,0 +1,28 @@
+/* Previously in TinyCC, ELF sections defined in assembly would always have the
+execute bit not set, so you would get segmentation faults when code in these
+sections was exectuted. This file is a minimal example of a file that will put
+the resulting code in a non-executable section (and invoke it) prior to the fix.
+*/
+#include <stdio.h>
+
+void *memset(void *dst, int c, int len);
+
+__asm__ (
+".section .text.nolibc_memset\n"
+".weak memset\n"
+"memset:\n"
+	"xchgl %eax, %esi\n\t"
+	"movq  %rdx, %rcx\n\t"
+	"pushq %rdi\n\t"
+	"rep stosb\n\t"
+	"popq  %rax\n\t"
+	"retq\n"
+);
+
+int main () {
+    char buf[10];
+    memset(&buf[0], 'A', 9);
+    buf[9] = 0;
+    puts(buf);
+    return 0;
+}
diff --git a/tests/exec_section_in_c.c b/tests/exec_section_in_c.c
new file mode 100644
index 000000000..8a6fbac39
--- /dev/null
+++ b/tests/exec_section_in_c.c
@@ -0,0 +1,13 @@
+/* Previously in TinyCC, ELF sections defined in attributes would always have
+the execute bit not set, so you would get segmentation faults when code in these
+sections was exectuted. This file is a minimal example of a file that will put
+the resulting code in a non-executable section (and invoke it) prior to the fix.
+*/
+__attribute__((section(".text.wumbo")))
+int wumbo (int arg) {
+    return arg * 2;
+}
+
+int main () {
+    return wumbo(2);
+}