forked from cirosantilli/linux-kernel-module-cheat
/
arm.S
30 lines (25 loc) · 1.13 KB
/
arm.S
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
#include <lkmc.h>
.global lkmc_start
lkmc_start:
/* Prepare the stack for main, mandatory for C code. */
ldr sp, =stack_top
/* Enable floating point.
* Code copied from: http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.ddi0409h/CHDEGGFF.html
* Without this, SIMD operations such as vmov raise an exception.
*/
mrc p15, 0, r0, c1, c0, 2 /* Read CPACR into r0 */
orr r0, r0, 3 << 20 /* OR in User and Privileged access for CP10 */
orr r0, r0, 3 << 22 /* OR in User and Privileged access for CP11 */
bic r0, r0, 3 << 30 /* Clear ASEDIS/D32DIS if set */
mcr p15, 0, r0, c1, c0, 2 /* Store new access permissions into CPACR */
isb /* Ensure side-effect of CPACR is visible */
mov r0, 1 << 30 /* Create value with FPEXC (bit 30) set in r0 */
vmsr fpexc, r0 /* Enable VFP and SIMD extensions */
/* https://cirosantilli.com/linux-kernel-module-cheat#magic-failure-string */
ldr r0, =lkmc_baremetal_on_exit_callback
bl on_exit
/* Run main. */
mov r0, 0
bl main
/* If main returns, exit. */
bl exit