Syscall arguments are passed in registers x0..x7. If assembler code has to call C functions before passing control to syscall handler, it should restore original state of that registers after the call. Currently, syscall arguments restoring is opencoded in el0_svc_naked and __sys_trace. This patch introduces restore_syscall_args macro to use it there. Also, parameter 'syscall = 0' is removed from ct_user_exit to make el0_svc_naked call restore_syscall_args explicitly. This is needed because the following patch of the series adds another call to C function in el0_svc_naked, and restoring of syscall args becomes not only a matter of ct_user_exit. Signed-off-by: Yury Norov <ynorov@xxxxxxxxxxxxxxxxxx> --- arch/arm64/kernel/entry.S | 37 +++++++++++++++++++++---------------- 1 file changed, 21 insertions(+), 16 deletions(-) diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 9c06b4b80060..c8d9ec363ddd 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -37,22 +37,29 @@ #include <asm/unistd.h> /* - * Context tracking subsystem. Used to instrument transitions - * between user and kernel mode. + * Save/restore needed during syscalls. Restore syscall arguments from + * the values already saved on stack during kernel_entry. */ - .macro ct_user_exit, syscall = 0 -#ifdef CONFIG_CONTEXT_TRACKING - bl context_tracking_user_exit - .if \syscall == 1 - /* - * Save/restore needed during syscalls. Restore syscall arguments from - * the values already saved on stack during kernel_entry. - */ + .macro restore_syscall_args ldp x0, x1, [sp] ldp x2, x3, [sp, #S_X2] ldp x4, x5, [sp, #S_X4] ldp x6, x7, [sp, #S_X6] - .endif + .endm + + .macro el0_svc_restore_syscall_args +#if defined(CONFIG_CONTEXT_TRACKING) + restore_syscall_args +#endif + .endm + +/* + * Context tracking subsystem. Used to instrument transitions + * between user and kernel mode. + */ + .macro ct_user_exit +#ifdef CONFIG_CONTEXT_TRACKING + bl context_tracking_user_exit #endif .endm @@ -943,7 +950,8 @@ alternative_else_nop_endif el0_svc_naked: // compat entry point stp x0, xscno, [sp, #S_ORIG_X0] // save the original x0 and syscall number enable_daif - ct_user_exit 1 + ct_user_exit + el0_svc_restore_syscall_args tst x16, #_TIF_SYSCALL_WORK // check for syscall hooks b.ne __sys_trace @@ -976,10 +984,7 @@ __sys_trace: mov x1, sp // pointer to regs cmp wscno, wsc_nr // check upper syscall limit b.hs __ni_sys_trace - ldp x0, x1, [sp] // restore the syscall args - ldp x2, x3, [sp, #S_X2] - ldp x4, x5, [sp, #S_X4] - ldp x6, x7, [sp, #S_X6] + restore_syscall_args ldr x16, [stbl, xscno, lsl #3] // address in the syscall table blr x16 // call sys_* routine -- 2.14.1
