On Mon, Jun 29, 2015 at 02:16:08PM -0400, William Cohen wrote: > On 06/29/2015 01:25 PM, Steve Capper wrote: > > On 15 June 2015 at 20:07, David Long <dave.l...@linaro.org> wrote: > >> diff --git a/arch/arm64/kernel/kprobes-arm64.h > >> b/arch/arm64/kernel/kprobes-arm64.h > >> index ff8a55f..bdcfa62 100644 > >> --- a/arch/arm64/kernel/kprobes-arm64.h > >> +++ b/arch/arm64/kernel/kprobes-arm64.h > >> @@ -27,4 +27,45 @@ extern kprobes_pstate_check_t * const > >> kprobe_condition_checks[16]; > >> enum kprobe_insn __kprobes > >> arm_kprobe_decode_insn(kprobe_opcode_t insn, struct arch_specific_insn > >> *asi); > >> > >> +#define SAVE_REGS_STRING\ > >> + " stp x0, x1, [sp, #16 * 0]\n" \ > >> + " stp x2, x3, [sp, #16 * 1]\n" \ > >> + " stp x4, x5, [sp, #16 * 2]\n" \ > >> + " stp x6, x7, [sp, #16 * 3]\n" \ > >> + " stp x8, x9, [sp, #16 * 4]\n" \ > >> + " stp x10, x11, [sp, #16 * 5]\n" \ > >> + " stp x12, x13, [sp, #16 * 6]\n" \ > >> + " stp x14, x15, [sp, #16 * 7]\n" \ > >> + " stp x16, x17, [sp, #16 * 8]\n" \ > >> + " stp x18, x19, [sp, #16 * 9]\n" \ > >> + " stp x20, x21, [sp, #16 * 10]\n" \ > >> + " stp x22, x23, [sp, #16 * 11]\n" \ > >> + " stp x24, x25, [sp, #16 * 12]\n" \ > >> + " stp x26, x27, [sp, #16 * 13]\n" \ > >> + " stp x28, x29, [sp, #16 * 14]\n" \ > >> + " str x30, [sp, #16 * 15]\n" \ > >> + " mrs x0, nzcv\n" \ > >> + " str x0, [sp, #8 * 33]\n" > >> + > >> + > >> +#define RESTORE_REGS_STRING\ > >> + " ldr x0, [sp, #8 * 33]\n" \ > >> + " msr nzcv, x0\n" \ > >> + " ldp x0, x1, [sp, #16 * 0]\n" \ > >> + " ldp x2, x3, [sp, #16 * 1]\n" \ > >> + " ldp x4, x5, [sp, #16 * 2]\n" \ > >> + " ldp x6, x7, [sp, #16 * 3]\n" \ > >> + " ldp x8, x9, [sp, #16 * 4]\n" \ > >> + " ldp x10, x11, [sp, #16 * 5]\n" \ > >> + " ldp x12, x13, [sp, #16 * 6]\n" \ > >> + " ldp x14, x15, [sp, #16 * 7]\n" \ > >> + " ldp x16, x17, [sp, #16 * 8]\n" \ > >> + " ldp x18, x19, [sp, #16 * 9]\n" \ > >> + " ldp x20, x21, [sp, #16 * 10]\n" \ > >> + " ldp x22, x23, [sp, #16 * 11]\n" \ > >> + " ldp x24, x25, [sp, #16 * 12]\n" \ > >> + " ldp x26, x27, [sp, #16 * 13]\n" \ > >> + " ldp x28, x29, [sp, #16 * 14]\n" \ > >> + " ldr x30, [sp, #16 * 15]\n" > > > > Do we need to restore x19..x28 as they are callee-saved? > > The goal was to make the trampoline not affect the values in any of > the registers, so if the calling conventions ever change the code will > still work. Figured it was safer and clearer just to save everything > rather than assuming that the compiler's code generated for > trampoline_probe_handler is going to save certain registers.
If the PCS ever changes, we have other issues like cpu_switch_to(). So it's safe to assume that x19..x29 are callee-saved. -- Catalin -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
