On Fri, Jul 08, 2016 at 12:35:52PM -0400, David Long wrote: > --- /dev/null > +++ b/arch/arm64/kernel/probes/kprobes_trampoline.S > @@ -0,0 +1,85 @@ > +/* > + * trampoline entry and return code for kretprobes. > + */ > + > +#include <linux/linkage.h> > +#include <asm/asm-offsets.h> > +#include <asm/assembler.h> > + > + .text > + > +.macro save_all_base_regs > + stp x0, x1, [sp, #S_X0] > + stp x2, x3, [sp, #S_X2] > + stp x4, x5, [sp, #S_X4] > + stp x6, x7, [sp, #S_X6] > + stp x8, x9, [sp, #S_X8] > + stp x10, x11, [sp, #S_X10] > + stp x12, x13, [sp, #S_X12] > + stp x14, x15, [sp, #S_X14] > + stp x16, x17, [sp, #S_X16] > + stp x18, x19, [sp, #S_X18] > + stp x20, x21, [sp, #S_X20] > + stp x22, x23, [sp, #S_X22] > + stp x24, x25, [sp, #S_X24] > + stp x26, x27, [sp, #S_X26] > + stp x28, x29, [sp, #S_X28] > + add x0, sp, #S_FRAME_SIZE > + stp lr, x0, [sp, #S_LR] > +/* > + * Construct a useful saved PSTATE > + */ > + mrs x0, nzcv > + and x0, x0, #(PSR_N_BIT | PSR_Z_BIT | PSR_C_BIT | PSR_V_BIT) > + mrs x1, daif > + and x1, x1, #(PSR_D_BIT | PSR_A_BIT | PSR_I_BIT | PSR_F_BIT)
I don't think you need the masking here, the mrs should return the corresponding 4 bits. > + orr x0, x0, x1 > + mrs x1, CurrentEL > + and x1, x1, #(3 << 2) > + orr x0, x1, x0 > + mrs x1, SPSel > + and x1, x1, #1 Same here. > + orr x0, x1, x0 > + str x0, [sp, #S_PSTATE] > +.endm How is this pstate used, other than the restoring of the condition flag in the restore_all_base_regs macro? Does a kretprobes handler need access to them? Anyway, it's worth doing an stp xzr, x0, [sp, S_PC] so that we initialise the pc in pt_regs. > + > +.macro restore_all_base_regs > + ldr x0, [sp, #S_PSTATE] > + and x0, x0, #(PSR_N_BIT | PSR_Z_BIT | PSR_C_BIT | PSR_V_BIT) > + msr nzcv, x0 > + ldp x0, x1, [sp, #S_X0] > + ldp x2, x3, [sp, #S_X2] > + ldp x4, x5, [sp, #S_X4] > + ldp x6, x7, [sp, #S_X6] > + ldp x8, x9, [sp, #S_X8] > + ldp x10, x11, [sp, #S_X10] > + ldp x12, x13, [sp, #S_X12] > + ldp x14, x15, [sp, #S_X14] > + ldp x16, x17, [sp, #S_X16] > + ldp x18, x19, [sp, #S_X18] > + ldp x20, x21, [sp, #S_X20] > + ldp x22, x23, [sp, #S_X22] > + ldp x24, x25, [sp, #S_X24] > + ldp x26, x27, [sp, #S_X26] > + ldp x28, x29, [sp, #S_X28] > +.endm > + > +ENTRY(kretprobe_trampoline) > + > + sub sp, sp, #S_FRAME_SIZE > + > + save_all_base_regs > + > + mov x0, sp > + bl trampoline_probe_handler > + /* Replace trampoline address in lr with actual > + orig_ret_addr return address. */ > + mov lr, x0 > + > + restore_all_base_regs > + > + add sp, sp, #S_FRAME_SIZE > + > + ret > + > +ENDPROC(kretprobe_trampoline) -- Catalin
