[libposix-development] [PATCH 2/2] x86_32: use 'int 0x80' for system calls to improve protability

[Kirill A. S. <ki...@sh...>]

Not every kernel provide __kernel_vsyscall. It's possible to add
configuration option later.

Signed-off-by: Kirill A. Shutemov <ki...@sh...>
---
 runtime/linux/x86_32/architecture_init.c |   22 +---------------------
 system/linux/x86_32/system_calls.S       |   17 ++---------------
 2 files changed, 3 insertions(+), 36 deletions(-)

diff --git a/runtime/linux/x86_32/architecture_init.c
b/runtime/linux/x86_32/architecture_init.c
index f080dc4..f3fb6e6 100644
--- a/runtime/linux/x86_32/architecture_init.c
+++ b/runtime/linux/x86_32/architecture_init.c
@@ -27,28 +27,8 @@ POSSIBILITY OF SUCH DAMAGE.
 #include <stddef.h>
 #include "runtime.h"

-void (*kernel_vsyscall)();
-
-/* AT_SYSINFO entry has the vsyscall address */
-#define AT_SYSINFO 32
-
-void set_kernel_vsyscall(const auxv_t *auxv)
-{
-	if (auxv != NULL) {
-		const auxv_t *auxv_walk;
-		for (auxv_walk = auxv; auxv_walk->a_type != 0; auxv_walk++) {
-			if (auxv_walk->a_type == AT_SYSINFO) {
-				kernel_vsyscall = auxv_walk->a_un.a_fcn;
-				return;
-				
-			}
-		}
-		// ERROR: AT_SYSINFO entry not found
-	}
-}
-
 void architecture_init(int argc, const char **argv, const char **envp,
                        const auxv_t *auxv)
 {
-	set_kernel_vsyscall(auxv);
+	/* Do nothing */
 }
diff --git a/system/linux/x86_32/system_calls.S
b/system/linux/x86_32/system_calls.S
index 8e1d6f9..f11f8ca 100644
--- a/system/linux/x86_32/system_calls.S
+++ b/system/linux/x86_32/system_calls.S
@@ -36,8 +36,6 @@ POSSIBILITY OF SUCH DAMAGE.
    Paramenter sequence is: %ebx, %ecx, %edx, %esi, %edi and %ebp
    See, for example:
    http://www.linuxjournal.com/article/4048
-
-   TODO: remove calculation for kernel_vsyscall (use a fixed address)
 */

 	
@@ -45,12 +43,9 @@ syscall1:
 	pushl %ebp
 	movl %esp, %ebp
 	pushl %ebx
-	call get_abs_address
-	addl $_GLOBAL_OFFSET_TABLE_, %ebx
-	movl kernel_vsyscall@GOT(%ebx), %ecx
 	movl 8(%ebp), %eax
 	movl 12(%ebp), %ebx
-	call *(%ecx)
+	int $0x80
 	popl %ebx
 	popl %ebp
 	ret
@@ -60,20 +55,12 @@ syscall3:
 	movl %esp, %ebp
 	pushl %edi
 	pushl %ebx
-	call get_abs_address
-	addl $_GLOBAL_OFFSET_TABLE_, %ebx
-	movl kernel_vsyscall@GOT(%ebx), %edi
 	movl 8(%ebp), %eax
 	movl 12(%ebp), %ebx
 	movl 16(%ebp), %ecx
 	movl 20(%ebp), %edx
-	call *(%edi)
+	int $0x80
 	popl %ebx
 	popl %edi
 	popl %ebp
 	ret
-
-get_abs_address:
-	mov (%esp), %ebx
-	ret
-
-- 
1.6.3.3