jmp cycles

"0" written in front0.1) The purpose of this code:The purpose of this text is to explain the function of the local descriptor, its definition, initialization and jump, etc.0.2)The personal summary at the end of the article is dry, the preceding code is for reference only, and source code from Orange's implemention of a OS.0.3)Since the code in this article and the "Steps of the real mode and protected mode switching" source code has a similarity of 90%, see http://blog.csdn.net/pacosonswjtu/arti

1. Mastering machine codes for NOP, JNE, JE, JMP, CMP assembly instructionsNOP : The NOP instruction is the "null instruction". When executing to the NOP instruction, the CPU does nothing, just as an instruction to execute the past and continue executing a command behind NOP. (Machine code: 90)JNE : Conditional transfer directives, if not equal, jumps. (Machine code: 75)JE : The conditional transfer instruction, if equal, jumps. (Machine code: 74)

80483cf:ff FC pushl-0x4 (%ECX) 80483d2:55 Push%ebp 80483d3:89 e5 mov%esp,%ebp 80483d5:51 Push%ecx 80483d6:83 EC $0x4,%esp Hello_world (); 80483d9:e8 d6 FF FF FF call 80483B4 return 0; 80483de:b8 xx xx $0x0,%eax}When calling Hello_world, the assembly code corresponds to the call 80483b4 When calling printf, the assembly code corresponds to the call 80482f0 080482f0 Now let's analyze it with a debugger:GDB test(GDB) B main breakpoint 1 at 0x80483d9:file test.c, line 12. (GDB

system method; occupancy: 2w,1e. Thread number 0, highest priority.Main (); Executes user-written code, user code entry.Wret; Pseudo-return instruction, actually jump, JMP thread_wait (); and return.}Thread_wait () {///when the front-thread waits for a message to block the method. Occupation: 4W; Time: 4nsA0. PROCESS_XMUB.TBLOCKED.PRR.L = 0;Masks the current thread. System methodCompiled into: R1 = A0; R1 = + process_xmub.blocked; R1. PRR. L = 0;The

UltraISO (startup disk maker) is that because we have written the FAT32 file system information, the system can recognize that the device is a USB stick, So we can open the USB flash drive can also store other files inside without affecting the boot. Note: There may be a large list of messages that cannot be started when restarting: The system found unauthorized changes on the Fimware, operating system, or UEFI drivers ..... Enter the BIOS setup, the tab "boot" There is a column "Safe boot" opt

instruction description0000 FA CLI; shielded interrupt0001 33c0 XOR Ax,ax0003 8ed0 MOV ss,ax;(SS) =0000h0005 bc007c MOV sp,7c00;(SP) =7c00h0008 8bf4 MOV si,sp;(SI) =7c00h000A PUSH AX000B POP es;(es) =0000h000C PUSH AX000D 1F POP DS;(D s) =0000h000E FB STI000F FC CLD0010 BF0006 MOV di,06000013 B90001 MOV cx,0100; Total 512 bytes0016 F2 REPNZ0017 A5 movsw; the master bootloader moved itself from the 0000:7C00 to theAt 0000:0600, the boot program for the DOS partition is free; Out of space0018 ea1

) with a byte (or word) in an additional segment specified by (DI) and does not save the result, but sets the condition code according to the result. The other characteristics of the instruction are the same as those of the Movs. V. CONTROL and TRANSFER instructions1. Unconditional Transfer Instruction. JMP (JMP) Jump instruction1) Direct short transfer within paragraphFormat:

:and Ax,001eh; 24 Valid double values15:push BX; Reserved after use16:push DX; Ditto17:mov Si,ax; AX cannot be indirectly addressable18:and cl,07h; Valid values19:call Ccodtb[si]; Suppose Cs=ds20:pop DX21:pop BX22:JMP Ccodin; The main process of the program23:CCOD00:; Code for Yards24:add sp,6; This program is a subroutine25:ret; Code is 0 execution complete26:CCOD06:; 06 for E,f27:SHL cl,1; E,f Weight Value Double28:CLFT02:; Left-pointing Horizontal2

F8 0040e8f0 01DB Add ebx,ebx 0040e8f2 jnz Short UPX.0040E8FB we ran all the way down and found the following code two upward jumps, the following is the NOP statement, my treatment is under the NOP next line of code F4, because NOP is empty, no data. The same way we continue to F8 one-step operation. of course, there are many similar upward jumps in the program, I do not describe each, when the F8 step to run for a period of time, you may encounter such a situation Highlights: 0040e9f4 f2:ae

char code[9]; * ((DWORD *) code[0]) = 0x042444FF; /* inc dword ptr [esp+4] */ 　　　　　 　　code[4]　= 0xe9;　　　 /* JMP */ * ((DWORD *) code[5]) = (DWORD) foo - (DWORD) code[0] - 9; /* 跳转偏移量 */ void (*pf)(int/* a*/) = (void (*)(int)) code[0]; pf (6); This is a typical thunk code, and its execution result is "in Foo, a = 7". As you can see, it defines an array of code[9], and then assigns the machine code of each assembly instruction that is checked in adva

), that is, the reciprocal of the operating frequency of the CPU crystal oscillator is the most basic and minimum time unit in the computer. It is usually a cycle pulse or a T cycle. For the single-chip microcomputer clock cycle, the clock cycle is the basic time unit of the single-chip microcomputer, two oscillation cycles (always cycle) constitute a state cycle. Oscillation cycle(Oscillating period) In the attenuation oscillation, the time between

In the previous article, I. Test Platform1. CPU: Cortex-A8 1 GHz2. OS: wince6r33. complier: 1. vs2005 2. wec7 2. Test code Link1. http://gruntthepeon.free.fr/ssemath/neon_mathfun.html2. http://blog.csdn.net/zht9961020/article/details/7232924 Iii. Test Results sin .. -> 0.0 millions of vector evaluations/second -> 9900 cycles/valuecos .. -> 0.0 millions of vector evaluations/second -> 10750 cycles/val

of several S-cycles (state cycles).A machine cycle of 8051 series MCU is composed of 6 s cycles (state cycle). As mentioned earlier, a clock cycle is defined as a beat (expressed in P), two beats are defined as a state cycle (in s), and the 8051 SCM Machine Cycle consists of 6 state cycles, i.e. one machine cycle = 6

divided into several stages, each of which completes a work. For example, taking instructions, memory reads, Memory writes, and so on, each of these tasks is called a basic operation. The time required to complete a basic operation is called the machine cycle. Typically, a machine cycle consists of several S-cycles (state cycles) . A machine cycle of the 8051 series microcontroller consists of 6 s

"Reprint" http://bbs.pediy.com/showthread.php?t=199036Although the skills are relatively old, but common sense is to understand1._declspec (Naked) tells the compiler not to optimize the codeFor JMP type hooks, if your own process does not use _DECLSPEC (naked), then the system will automatically add some extra code to control the stack balance, but these additional code will break the stack of the hook function.For call type hooks, be careful to resto

SIGFPE can report arithmetic anomalies. including overflow, except 0 and so on.C standard library says: the exception types that are reported by various implementations are also very different, but almost no implementation reports an integer overflow. Are you sure? I tested it and found that on GCC, integer, floating-point overflow would not be reported, except that 0 would be reported. After using the -O3 compile option, even if 0 is not reported, continue execution directly.It see

4.1 Program hack20135206 at Jia Xin?Basic directives:The NOP:NOP instruction is the "null instruction". When executing to the NOP instruction, the CPU does nothing, just as an instruction to execute the past and continue executing a command behind NOP. (Machine code: 90)JNE: Conditional transfer directives, if not equal, jumps. (Machine code: 75)JE: Conditional transfer instruction, if equal, jumps. (Machine code: 74)JMP: Unconditional transfer instru

following dialog box is displayed:You can set both of them to a breakpoint. This program only needs to set a breakpoint in the first command. Okay. Now, the first method we mentioned above is to set a breakpoint for each reference. In this way, the two Commands will set a breakpoint. After the breakpoint is set, we go to the program we are debugging. Now we click the "check it" button on the program we are debugging and it is broken by ollydbg:00401323 |. E8 4c010000 call 00401328 |. E8 a500000

PUSH; Gptr00404120 FFD0 call EAX; Request 800 bytes00404122 8905 CA404000 MOV DWORD PTR ds:[4040ca],eax00404128 89c7 MOV Edi,eax0040412A be 00104000 MOV esi,ahpack.004010000040412F Pushad; start Aplib00404130 FC CLD00404131 B2 MOV dl,8000404133 31DB XOR ebx,ebx00404135 A4 MOVS BYTE ptr es:[edi],byte ptr Ds:[esi]00404136 B3 MOV bl,200404138 E8 6d000000 call AHPACK.004041AA0040413D ^ F6 JNB short ahpack.004041350040413F 31c9 XOR ecx,ecx00404141 E8 64000000 call AHPACK.004041AA00404146 1C JNB shor

instructions1. Unconditional Transfer Instruction. JMP (JMP) jump command1) Direct Short transfer within a segmentFormat: JMP short OPROperation: (IP) 2) Direct near transfer within the segmentFormat: JMP near PTR OPROperation: (IP) 3) indirect transfer within the segmentFormat: J