/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
 * Userland implementation of getrandom() for processes
 * for use in the vDSO
 *
 * Copyright (C) 2024 Christophe Leroy <christophe.leroy@csgroup.eu>, CS GROUP France
 */
#include <asm/processor.h>
#include <asm/ppc_asm.h>
#include <asm/vdso.h>
#include <asm/vdso_datapage.h>
#include <asm/asm-offsets.h>
#include <asm/unistd.h>

/*
 * The macro sets two stack frames, one for the caller and one for the callee
 * because there are no requirement for the caller to set a stack frame when
 * calling VDSO so it may have omitted to set one, especially on PPC64
 */

.macro cvdso_call funct
  .cfi_startproc
        PPC_STLU        r1, -PPC_MIN_STKFRM(r1)
  .cfi_adjust_cfa_offset PPC_MIN_STKFRM
        mflr            r0
        PPC_STLU        r1, -PPC_MIN_STKFRM(r1)
  .cfi_adjust_cfa_offset PPC_MIN_STKFRM
        PPC_STL         r0, PPC_MIN_STKFRM + PPC_LR_STKOFF(r1)
  .cfi_rel_offset lr, PPC_MIN_STKFRM + PPC_LR_STKOFF
#ifdef __powerpc64__
        PPC_STL         r2, PPC_MIN_STKFRM + STK_GOT(r1)
  .cfi_rel_offset r2, PPC_MIN_STKFRM + STK_GOT
#endif
        bl              CFUNC(DOTSYM(\funct))
        PPC_LL          r0, PPC_MIN_STKFRM + PPC_LR_STKOFF(r1)
#ifdef __powerpc64__
        PPC_LL          r2, PPC_MIN_STKFRM + STK_GOT(r1)
  .cfi_restore r2
#endif
        cmpwi           r3, 0
        mtlr            r0
        addi            r1, r1, 2 * PPC_MIN_STKFRM
  .cfi_restore lr
  .cfi_def_cfa_offset 0
        crclr           so
        bgelr+
        crset           so
        neg             r3, r3
        blr
  .cfi_endproc
.endm

        .text
V_FUNCTION_BEGIN(__kernel_getrandom)
        cvdso_call __c_kernel_getrandom
V_FUNCTION_END(__kernel_getrandom)