指令STMFD和LDMFD分析；
根據(jù)ATPCS規(guī)則,我們一般使用FD（Full Descending）類型的數(shù)據(jù)棧!所以經(jīng)常使用的指令就有STMFD和LDMFD,
通過ARM對于棧操作和批量Load/Store指令尋址方式,可以知道指令STMFD和LDMFD的地址計算方法：
STMFD指令的尋址方式為事前遞減方式(DB)
而DB尋址方式實際內(nèi)存地址為：
start_address = Rn - (Number_Of_Set_Bits_In(register_list)*4)
end_address = Rn - 4
STM指令操作的偽代碼：
if ConditionPassed(cond) then
address = start_address
for i = 0 to 15
if register_list[i] == 1
Memory[address] = Ri
address = address + 4
有上面兩個偽代碼可以得出 STMFD SP!,{R0-R7,LR} 的偽代碼如下：
SP ＝ SP － 9×4；
address = SP;
for i = 0 to 7
Memory[address] = Ri;
address = address + 4;
Memory[address] = LR;
LDMFD指令的尋址方式為事后遞增方式(IA)
IA內(nèi)存的實際地址的偽代碼
start_address = Rn
end_address = Rn + (Number_of_set_bits_in(register_list)*4) - 4
LDM指令操作的偽代碼(未考慮PC寄存器)：
if ConditionPassed(cond) then
address = start_address
for i = 0 to 15
if register_list[i] == 1
Ri ＝ Memory[address,4]
address = address + 4
所以LDMFD SP!,{R0-R7,PC}^ （；恢復(fù)現(xiàn)場,異常處理返回）偽代碼是:
address = SP;
for i = 0 to 7
Ri = Memory[address ,4]
address = address + 4;
SP = address;