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![Weilin’s Most Evil Test
curl "http://rust-class.org/pages/ps2.html" | sed "s/[^a-zA-Z ]/ /g" | tr "A-Z " "a-zn"| grep "[a-z]" | sort -u
curl "http://rust-class.org/pages/ps2.html"
| sed "s/[^a-zA-Z ]/ /g" | tr "A-Z " "a-zn"
| grep "[a-z]" | sort -u
Rust Sticker* if you can handle this one!
*: while supplies last!
9](https://image.slidesharecdn.com/class6-inked-140204145541-phpapp02/75/Making-a-Process-Virtualizing-Memory-10-2048.jpg)
![#include <stdio.h>
#include <stdlib.h>
What will this program do?
int main(int argc, char **argv) {
char *s = (char *) malloc (1);
int i = 0;
while (1) {
printf("%d: %xn", i, s[i]);
i += 4;
}
}
63](https://image.slidesharecdn.com/class6-inked-140204145541-phpapp02/75/Making-a-Process-Virtualizing-Memory-64-2048.jpg)
![#include <stdio.h>
#include <stdlib.h>
What will this program do?
int main(int argc, char > ./a.out {
**argv)
char *s = (char *) malloc (1);
0: 0
int i = 0;
4: 0
while (1) {
8: 0
printf("%d: %xn", i, s[i]);
12: 0
i += 4;
…
}
}
1033876: 0
1033880: 0
1033884: 0
Segmentation fault: 11
64](https://image.slidesharecdn.com/class6-inked-140204145541-phpapp02/75/Making-a-Process-Virtualizing-Memory-65-2048.jpg)
Uploaded byDavid Evans
Making a Process (Virtualizing Memory)
The document outlines an agenda for an upcoming class and includes information on assignment deadlines, class policies, and details on operating system concepts such as process management and memory isolation. It highlights the history of operating systems development with a focus on virtual memory and the importance of managing resources securely and efficiently. Additionally, it emphasizes the significance of learning programming through customization and warns against academic dishonesty related to previous semester solutions.
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Making a Process (Virtualizing Memory)
- 2. Plan for Today Anti-GnashingGashing Tips How the Kernel Makes a Process: Virtual Memory PS2 is Due Sunday Exam 1 is out after class Tuesday (Feb 11) due 11:59pm Thursday (Feb 13) – open resources, most questions will be taken from notes 1
- 3. Today’s OS News Hestarted his career as a member of the technology staff at Sun Microsystems. In 1992, he joined Microsoft. He was on his way to get a master’s degree in business when the Microsoft job offer came. The company was building an operating system that ultimately would be known as Windows NT, and needed team members who understood UNIX and 32-bit operating systems, he says. Nadella wanted to complete his master’s degree and take the Microsoft job. He did both. 2
- 4.
- 5. Today’s Experiment! What shouldwe do to make things better? “Please excuse the paradox, but stop listening to young white males like me. Other people deserve a voice.” 4
- 6. Honor Policy Remember thehonor policy: don’t abuse solutions from last semester They are easy to find, but viewing them at all is abuse. 5
- 7. Foreground Processes main gashthread run_command(p) main gash thread 6
- 8. Background Processes main gashthread new task spawn(…) run_command(p) main gash thread 7
- 9. Parsing Commands Not ourmain focus The main tests will be fairly simple, but you should definitely be able to handle ifconfig | grep "flags" | tail command := program command := command & command := command < file command := command > file command := command | command program := valid program name file := valid pathname 8
- 10. Weilin’s Most EvilTest curl "http://rust-class.org/pages/ps2.html" | sed "s/[^a-zA-Z ]/ /g" | tr "A-Z " "a-zn"| grep "[a-z]" | sort -u curl "http://rust-class.org/pages/ps2.html" | sed "s/[^a-zA-Z ]/ /g" | tr "A-Z " "a-zn" | grep "[a-z]" | sort -u Rust Sticker* if you can handle this one! *: while supplies last! 9
- 11. Handling Signals main gashthread run_command(p) Process P 10
- 12. Handling Signals gash Process ChildProcess main gash thread run_command(p) Process P Ctrl-C 11
- 13. main gash thread run_command(p) ProcessP Ctrl-C Kernel 12
- 14. main gash thread run_command(p) ProcessP signal handler Ctrl-C Kernel SIGINT 13
- 15. main gash thread run_command(p) ProcessP signal handler Ctrl-C Kernel SIGINT 14
- 16. Handling Signals Jumping aroundcode like this is inherently unsafe: you will need to use libc functions and unsafe use std::io::signal::{Listener, Interrupt}; use std::libc::funcs::posix88::signal; … unsafe { signal::kill(fgpid, libc::SIGINT); } 15
- 17. How the KernelMakes a Process 16
- 18. From Class 3: Program BatchProcessing Computer Center Your Program Runs Output: Invalid Operation Charge: $174.32 17
- 19. Process Abstraction Provide eachprogram with the illusion that it owns the whole machine. The best example of this way to do things is Linux, which is an operating system, which is a program that keeps track of other programs in a computer and gives each its due in space and time. Guy Steele, “How to Grow a Language” 18
- 20. Memory Isolation Physical memory Process1 should only be able to access Memory Space 1 Process 2 should only be able to access Memory Space 2 Memory Space 1 Memory Space 2 Do we need special hardware support do provide memory isolation? 19
- 21. Software-Based Memory Isolation OriginalCode … movq %rax, -8(%rbp) … “Sandboxed” Code Safe Loader … movq -8(%rbp),%rdx andq %rdx,%rgx movq %rax, %rdx … Assumes %rdx is reserved and %rgx is protected and holds a mask for the memory segment 20
- 22.
- 23.
- 24. Hardware-Based Memory Isolation OriginalCode Running Code … movq %rax, -8(%rbp) … … movq %rax, -8(%rbp) … Loader Memory Space 1 Memory Space 2 23
- 25. Virtual Memory address inProcess P Virtual Memory Mapping physical address owned by Process P User-level processes cannot access physical memory directly: all memory addresses created by process P are virtual addresses, mapped into physical addresses owned by process P 24
- 26. Virtual Memory address inProcess P Virtual Memory Mapping physical address owned by Process P Who controls the virtual memory mapping? 25
- 27. Getting Into theDetails… 26
- 28. SOSP 1967 Procedure BaseRegister: segment number of executing procedure Argument Pointer Base Pointer Linkage Pointer Stack Pointer Descriptor Base Register 27
- 29. Generating an Address 18bits 18 bits 218 = 262144 28
- 30. Addressing Mode selects: ArgumentPointer Base Pointer Linkage Pointer Stack Pointer 29
- 31. Addressing Mode selects: ArgumentPointer Base Pointer Linkage Pointer Stack Pointer 30
- 32. What does the MULTICS kerneldo to switch processes? 31
- 33.
- 34. 1982 “It used tobe that programs were easy to copy and change. But manufacturers began to lose money as many people made copies of software and gave them to their friends. Now, many manufacturers have figured out how to 'copy-protect' discs. To our mind this is a disaster: Most people learn programming by changing programs to fit their own needs. This capability of customization is what makes computers so attractive. New ways of copy protection will probably be found soon. Until then, a computer owner may have to put up with being 'locked out' of his (sic) own machine.” Popular Mechanics, January 1982 33
- 35. Intel 80186 Intel 80286 Firstx86 Processor with Virtual Memory Support “Protected Mode” 34
- 36.
- 37. Five x86-64 ProcessorModes Real Mode: pretend to be an 8086 20-bit direct-access address space Protected Mode: “native state” System Management Mode: platform-specific power management and security (separate address space) Compatibility Mode: pretend to be x86-32 IA-32e/64-bit Mode: run applications in 64-bit address space “For brevity, the 64-bit sub- mode is referred to as 64-bit mode in IA-32 architecture.” 36
- 38. Protected State (can onlybe modified by the kernel): RFLAGS (includes EFLAGS) Includes I/O Privilege Level Control Registers CR0 bit 0: controls if processor is in protected mode CR3: page directory base register 37
- 39. Address Translation Memory Physical Address LinearAddress Paging Unit Logical Address Segmentation Unit 38
- 40. Accessing Memory 16 bitsto select segment, 16- 32- or 64- bits to select offset Actual addressable space for user-level process in Unix: 247 bytes = 128TiB 39
- 41. Memory Paging Unit Physical Address Linear Address LogicalAddress Segmentatio n Unit Computing the Linear Address Segment selection is inferred from instruction type Logical (“General”, “Virtual”) Address Segment Selector Offset 40
- 42. Fetching an Instruction EIP CS InstructionPointer (Offset) Code Segment 32 bits 16 bits 13 bits 1 Table Index Ring Global or Local Table Only Kernel can write to Segment Registers 2 41
- 43. Segmentation Tables Global DescriptorTable (GDT) limit base address linear address space 0-264 - 1 Segments can overlap! 13 bits – up to 8192 entries 42
- 44. Segmentation Tables Global DescriptorTable (GDT) Local Descriptor Table (per process) 13 bits – up to 8192 entries How does the processor find the GDT/LDT? 43
- 45. The GDT andLDT are just data structures in memory! Special registers store their locations 44
- 46.
- 47. Logical Address Linear Address Segmentation Unit ` Memory PhysicalAddress Paging Unit 46
- 48. Linear Address Logical Address 64 2 Segmentation Unit Paging linear addresses Whatwould it cost to have 264 bytes of RAM? 47
- 49. $10 per 1GB= 230 bytes $172B 264 bytes = $10 * 234 Apple’s 2013 revenue US federal spending for 18 days 48
- 50. Paging Memory Paging Unit Physical Address Linear Address LogicalAddress Segmentation Unit We don’t need to store the whole address space in memory! Most of it is unused: store rarely-used parts on the disk. 49
- 51. Memory Physical Address Linear Address 50 Imagefrom Wikipedia Paging Unit
- 52. Overview (Intel 386) CR3 32-bitlinear address Offset Dir Page 10 bits (1K tables) Page Directory 10 bits 12 bits (1K entries) (4K pages) Page Entry Page Table Physical Memory Page + Offset CR3+Dir 51
- 53. Page Table Entries CR3 PageEntry Page Table Page Directory 20 bits: physical address 12 bits: flags user/kernel page write permission present Physical Memory Page + Offset 52
- 54. 386 Checkup 32-bitlinear address CR3 Page Directory Physical Memory Offset Dir Page 10 bits 12 bits 10 bits (1K tables) (1K entries) (4K pages) 20 bits addr / 12 bits flags Page Table Page + Offset How many pages do we need to store the page table? 53
- 55. How slow isthis???! Memory GDTR Page Paging Unit Physical Address Dir Linear Address Logical Address Segmentation Unit Offset CR3 Physical Memory Global Descriptor Table Page Directory 20 bits addr / 12 bits flags Page Table Page + Offset 54
- 56. Translation Lookaside Buffer(Cache) Memory GDTR Page Paging Unit Physical Address Dir Linear Address Logical Address Segmentation Unit Offset CR3 Physical Memory Global Descriptor Table Page Directory 20 bits addr / 12 bits flags Page Table Page + Offset 55
- 57. My Favorite Statementin the Linux Kernel Code! 56
- 58.
- 59. Translation Lookaside Buffer(Cache) Offset Memory GDTR Page Paging Unit Physical Address Dir Linear Address Logical Address Segmentation Unit flush cache! CR3 Physical Memory Global Descriptor Table Page Directory 20 bits addr / 12 bits flags Page Table Page + Offset 58
- 60. Page Fault CR3 Page Entry PageTable Page Directory 20 bits: physical address 12 bits: flags user/kernel page write permission present Physical Memory 59
- 61. How expensive isa page fault? 60
- 62. How common arepage faults? 61
- 63. top -o mem-stats pid,command,cpu,mem,mregion,vsize,faults 62
- 64. #include <stdio.h> #include <stdlib.h> Whatwill this program do? int main(int argc, char **argv) { char *s = (char *) malloc (1); int i = 0; while (1) { printf("%d: %xn", i, s[i]); i += 4; } } 63
- 65. #include <stdio.h> #include <stdlib.h> Whatwill this program do? int main(int argc, char > ./a.out { **argv) char *s = (char *) malloc (1); 0: 0 int i = 0; 4: 0 while (1) { 8: 0 printf("%d: %xn", i, s[i]); 12: 0 i += 4; … } } 1033876: 0 1033880: 0 1033884: 0 Segmentation fault: 11 64
- 66. Charge Examine the memoryuse of processes running on your computer Problem Set 2 is due Sunday, 9 February Sign-up for your PS2 demo now/soon! 65