auto import from //depot/cupcake/@135843

1 files changed, 34 insertions, 0 deletions

diff --git a/libc/arch-x86/bionic/_exit_with_stack_teardown.S b/libc/arch-x86/bionic/_exit_with_stack_teardown.S
new file mode 100644
index 0000000..83a504d
--- /dev/null
+++ b/libc/arch-x86/bionic/_exit_with_stack_teardown.S
@@ -0,0 +1,34 @@
+#include <sys/linux-syscalls.h>
+
+.text
+.type _exit_with_stack_teardown, @function
+.globl _exit_with_stack_teardown
+.align 4
+
+/*
+ * void _exit_with_stack_teardown(void *stackBase, int stackSize, int *retCode) 
+ */
+
+_exit_with_stack_teardown:
+    /* we can trash %ebx here since this call should never return. */
+    /* We can also take advantage of the fact that the linux syscall trap
+     * handler saves all the registers, so we don't need a stack to keep
+     * the retCode argument for exit while doing the munmap */
+
+    /* TODO(dmtriyz): No one expects this code to return, so even if
+     * munmap fails, we have to exit. This should probably be fixed, but
+     * since ARM side does the same thing, leave it as is.
+     */
+    mov     4(%esp), %ebx             /* stackBase */
+    mov     8(%esp), %ecx             /* stackSize */
+    mov     12(%esp), %edx           /* retCode, not used for munmap */
+    mov     $__NR_munmap, %eax
+    int     $0x80
+    mov     %edx, %ebx                /* retrieve the retCode */
+    movl    $__NR_exit, %eax
+    int     $0x80
+    /* exit does not return */
+    /* can't have a ret here since we no longer have a usable stack. Seems
+     * that presently, 'hlt' will cause the program to segfault.. but this
+     * should never happen :) */
+    hlt