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#------------------------------------------------------------------------------
#
# Copyright (c) Microsoft Corporation.
# Copyright (c) 2026, Loongson Technology Corporation Limited. All rights reserved.<BR>
# SPDX-License-Identifier: BSD-2-Clause-Patent
#
# Module Name:
#
# DynamicCookieGcc.S
#
# Abstract:
#
# Generates random number through the RdTime instruction on a 64-bit LOONGARCH64 platform
# to store a random value in the GCC __stack_check_guard stack cookie.
# The first byte is 0'd to prevent string copy functions from clobbering
# the stack cookie.
#
# Notes:
#
# Use the RngLib library to get random numbers. LoongArch64 currently does not support like
# `RdRand` or `RNDR` instructions, it can use the `RdTime` and a xorshift64 algorithms to
# generate pseudo-random numbers.
#
#------------------------------------------------------------------------------
#include <Library/RngLib.h>
ASM_GLOBAL ASM_PFX (_ModuleEntryPoint)
#------------------------------------------------------------------------------
# VOID
# EFIAPI
# _ModuleEntryPoint (
# The parameters are saved to the stack when it calls other functions.
# )
#------------------------------------------------------------------------------
ASM_PFX(_ModuleEntryPoint):
addi.d $sp, $sp, -0x20
st.d $a0, $sp, 0x0
st.d $a1, $sp, 0x8
st.d $ra, $sp, 0x10
//
// Use the stack to pass parameters.
//
addi.d $a0, $sp, 0x18
bl GetRandomNumber64
//
// Load the random number from the stack.
//
ld.d $t0, $sp, 0x18
//
// Zero the first byte of the random value
//
bstrins.d $t0, $zero, 7, 0
la.local $t1, __stack_chk_guard
st.d $t0, $t1, 0
dbar 0
ld.d $a0, $sp, 0x0
ld.d $a1, $sp, 0x8
ld.d $ra, $sp, 0x10
addi.d $sp, $sp, 0x20
c_entry:
b _CModuleEntryPoint // Jump to the C module entry point
.end
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