fix: code in non-executable ELF sections

Jonathan M. Wilbur committed 2 years ago

Commit e4d874d1 parent c85efac4 files · +45 −0Browse files

Unified · Split

4 files

 	    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:
         {

@@ -8303,6 +8303,7 @@ static void gen_function(Sym *sym) · 8302 unmodified lines
8303	cur_scope = root_scope = &f;	8303	cur_scope = root_scope = &f;
8304	nocode_wanted = 0;	8304	nocode_wanted = 0;
8305		8305
		8306	cur_text_section->sh_flags \|= SHF_EXECINSTR;
8306	ind = cur_text_section->data_offset;	8307	ind = cur_text_section->data_offset;
8307	if (sym->a.aligned) {	8308	if (sym->a.aligned) {
8308	size_t newoff = section_add(cur_text_section, 0,	8309	size_t newoff = section_add(cur_text_section, 0,

@@ -0,0 +1,28 @@
	1	/* Previously in TinyCC, ELF sections defined in assembly would always have the
	2	execute bit not set, so you would get segmentation faults when code in these
	3	sections was exectuted. This file is a minimal example of a file that will put
	4	the resulting code in a non-executable section (and invoke it) prior to the fix.
	5	*/
	6	#include <stdio.h>
	7
	8	void memset(void dst, int c, int len);
	9
	10	__asm__ (
	11	".section .text.nolibc_memset\n"
	12	".weak memset\n"
	13	"memset:\n"
	14	"xchgl %eax, %esi\n\t"
	15	"movq %rdx, %rcx\n\t"
	16	"pushq %rdi\n\t"
	17	"rep stosb\n\t"
	18	"popq %rax\n\t"
	19	"retq\n"
	20	);
	21
	22	int main () {
	23	char buf[10];
	24	memset(&buf[0], 'A', 9);
	25	buf[9] = 0;
	26	puts(buf);
	27	return 0;
	28	}

@@ -0,0 +1,13 @@
	1	/* Previously in TinyCC, ELF sections defined in attributes would always have
	2	the execute bit not set, so you would get segmentation faults when code in these
	3	sections was exectuted. This file is a minimal example of a file that will put
	4	the resulting code in a non-executable section (and invoke it) prior to the fix.
	5	*/
	6	__attribute__((section(".text.wumbo")))
	7	int wumbo (int arg) {
	8	return arg * 2;
	9	}
	10
	11	int main () {
	12	return wumbo(2);
	13	}

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