memory-segmentation

问题 Looking into the internals of Linux and memory management, I just stumbled upon the segmented paging model that Linux uses. Correct me if I am wrong, but Linux (protected mode) does use paging for mapping a linear virtual address space to the physical address space. This linear address space constituted of pages, is split into four segments for the process flat memory model, namely: The kernel code segment ( __KERNEL_CS ); The kernel data segment ( __KERNEL_DS ); The user code segment ( _

问题 I'm trying to understand the workings of the D flag in the code segment descriptor when used in the x86-64 code. It's set in the D/B bit 22 of the code segment descriptor as shown on this diagram: The Intel documentation (from section 3.4.5 Segment Descriptors) states the following: D/B (default operation size/default stack pointer size and/or upper bound) flag Performs different functions depending on whether the segment descriptor is an executable code segment, an expand-down data segment,

问题 In x86, when you want to access a memory address, you would specify an address that would be translated into a memory address through two stages: segmentation , and paging : But is segmentation also used in x64? (I think it is not used, but I am not sure if it is not used in all cases, or are there some cases where it is used). 回答1: For the purpose of the picture you posted, segmentation is only used when the addressing mode uses the registers fs or gs (because these were being actively

来源： https://stackoverflow.com/questions/31944041/jumping-to-a-far-address-in-real-mode

来源： https://stackoverflow.com/questions/63133724/what-does-the-d-stand-for-in-386s-d-bit

来源： https://stackoverflow.com/questions/63133724/what-does-the-d-stand-for-in-386s-d-bit

来源： https://stackoverflow.com/questions/63133724/what-does-the-d-stand-for-in-386s-d-bit

问题 I noticed that in Assembly segments are used in opcodes. Example: MOV DWORD PTR SS:[EBP-30],30 I think that "PTR SS:" is used to specify that EBP-30 comes from the stack? (SS: stack segment) Am I right or am I completely wrong? :) And, could you please tell me the difference between the example above and MOV DWORD PTR[EBP-30],30 And what about DS (data segment) used in opcodes? 回答1: MOV DWORD PTR SS:[EBP-30],30 There are two separate modifiers here, DWORD PTR and SS: . The first one tells us

问题 I noticed that in Assembly segments are used in opcodes. Example: MOV DWORD PTR SS:[EBP-30],30 I think that "PTR SS:" is used to specify that EBP-30 comes from the stack? (SS: stack segment) Am I right or am I completely wrong? :) And, could you please tell me the difference between the example above and MOV DWORD PTR[EBP-30],30 And what about DS (data segment) used in opcodes? 回答1: MOV DWORD PTR SS:[EBP-30],30 There are two separate modifiers here, DWORD PTR and SS: . The first one tells us

问题 The movsb (move string, bytes) instruction fetches the byte at address ds:si, stores it at address es:di, and then increments or decrements the si and di registers by one. I know esi,si and edi,di registers, but not ds:si and es:di , what do they mean? 回答1: ds:si and es:di mean the segment:offset referred to by the registers in question. This is primarily important when you're working in real mode (where offsets are a maximum of 64K apiece). In real mode, the segment are offset are combined