intro / what is an OS / processes and system calls 1 Changelog 14 - - PowerPoint PPT Presentation
intro / what is an OS / processes and system calls 1 Changelog 14 January 2020: reorganize slides to move process defjnition earlier 14 January 2020: use 64 instead of 0x40 in write() fmow chart to be more consistent with code
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via National Library of Medicine; computer operators operating an Honeywell 800
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return via trap()
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return via trap()
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... lidt(idt, sizeof(idt)); ... SETGATE(idt[T_SYSCALL], 1, SEG_KCODE<<3, vectors[T_SYSCALL], DPL_USER); ...
// Set up a normal interrupt/trap gate descriptor. // - istrap: 1 for a trap gate, 0 for an interrupt gate. // interrupt gate clears FL_IF, trap gate leaves FL_IF alone // - sel: Code segment selector for interrupt/trap handler // - off: Offset in code segment for interrupt/trap handler // - dpl: Descriptor Privilege Level - // the privilege level required for software to invoke // this interrupt/trap gate explicitly using an int instruction. #define SETGATE(gate, istrap, sel, off, d) \
vector64: pushl $0 pushl $64 jmp alltraps ...
alltraps: ... call trap ... iret
void trap(struct trapframe *tf) { ...
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... lidt(idt, sizeof(idt)); ... SETGATE(idt[T_SYSCALL], 1, SEG_KCODE<<3, vectors[T_SYSCALL], DPL_USER); ...
// Set up a normal interrupt/trap gate descriptor. // - istrap: 1 for a trap gate, 0 for an interrupt gate. // interrupt gate clears FL_IF, trap gate leaves FL_IF alone // - sel: Code segment selector for interrupt/trap handler // - off: Offset in code segment for interrupt/trap handler // - dpl: Descriptor Privilege Level - // the privilege level required for software to invoke // this interrupt/trap gate explicitly using an int instruction. #define SETGATE(gate, istrap, sel, off, d) \
vector64: pushl $0 pushl $64 jmp alltraps ...
alltraps: ... call trap ... iret
void trap(struct trapframe *tf) { ...
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... lidt(idt, sizeof(idt)); ... SETGATE(idt[T_SYSCALL], 1, SEG_KCODE<<3, vectors[T_SYSCALL], DPL_USER); ...
// Set up a normal interrupt/trap gate descriptor. // - istrap: 1 for a trap gate, 0 for an interrupt gate. // interrupt gate clears FL_IF, trap gate leaves FL_IF alone // - sel: Code segment selector for interrupt/trap handler // - off: Offset in code segment for interrupt/trap handler // - dpl: Descriptor Privilege Level - // the privilege level required for software to invoke // this interrupt/trap gate explicitly using an int instruction. #define SETGATE(gate, istrap, sel, off, d) \
vector64: pushl $0 pushl $64 jmp alltraps ...
alltraps: ... call trap ... iret
void trap(struct trapframe *tf) { ...
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... lidt(idt, sizeof(idt)); ... SETGATE(idt[T_SYSCALL], 1, SEG_KCODE<<3, vectors[T_SYSCALL], DPL_USER); ...
// Set up a normal interrupt/trap gate descriptor. // - istrap: 1 for a trap gate, 0 for an interrupt gate. // interrupt gate clears FL_IF, trap gate leaves FL_IF alone // - sel: Code segment selector for interrupt/trap handler // - off: Offset in code segment for interrupt/trap handler // - dpl: Descriptor Privilege Level - // the privilege level required for software to invoke // this interrupt/trap gate explicitly using an int instruction. #define SETGATE(gate, istrap, sel, off, d) \
vector64: pushl $0 pushl $64 jmp alltraps ...
alltraps: ... call trap ... iret
void trap(struct trapframe *tf) { ...
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... lidt(idt, sizeof(idt)); ... SETGATE(idt[T_SYSCALL], 1, SEG_KCODE<<3, vectors[T_SYSCALL], DPL_USER); ...
// Set up a normal interrupt/trap gate descriptor. // - istrap: 1 for a trap gate, 0 for an interrupt gate. // interrupt gate clears FL_IF, trap gate leaves FL_IF alone // - sel: Code segment selector for interrupt/trap handler // - off: Offset in code segment for interrupt/trap handler // - dpl: Descriptor Privilege Level - // the privilege level required for software to invoke // this interrupt/trap gate explicitly using an int instruction. #define SETGATE(gate, istrap, sel, off, d) \
vector64: pushl $0 pushl $64 jmp alltraps ...
alltraps: ... call trap ... iret
void trap(struct trapframe *tf) { ...
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... lidt(idt, sizeof(idt)); ... SETGATE(idt[T_SYSCALL], 1, SEG_KCODE<<3, vectors[T_SYSCALL], DPL_USER); ...
// Set up a normal interrupt/trap gate descriptor. // - istrap: 1 for a trap gate, 0 for an interrupt gate. // interrupt gate clears FL_IF, trap gate leaves FL_IF alone // - sel: Code segment selector for interrupt/trap handler // - off: Offset in code segment for interrupt/trap handler // - dpl: Descriptor Privilege Level - // the privilege level required for software to invoke // this interrupt/trap gate explicitly using an int instruction. #define SETGATE(gate, istrap, sel, off, d) \
vector64: pushl $0 pushl $64 jmp alltraps ...
alltraps: ... call trap ... iret
void trap(struct trapframe *tf) { ...
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... lidt(idt, sizeof(idt)); ... SETGATE(idt[T_SYSCALL], 1, SEG_KCODE<<3, vectors[T_SYSCALL], DPL_USER); ...
// Set up a normal interrupt/trap gate descriptor. // - istrap: 1 for a trap gate, 0 for an interrupt gate. // interrupt gate clears FL_IF, trap gate leaves FL_IF alone // - sel: Code segment selector for interrupt/trap handler // - off: Offset in code segment for interrupt/trap handler // - dpl: Descriptor Privilege Level - // the privilege level required for software to invoke // this interrupt/trap gate explicitly using an int instruction. #define SETGATE(gate, istrap, sel, off, d) \
vector64: pushl $0 pushl $64 jmp alltraps ...
alltraps: ... call trap ... iret
void trap(struct trapframe *tf) { ...
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... lidt(idt, sizeof(idt)); ... SETGATE(idt[T_SYSCALL], 1, SEG_KCODE<<3, vectors[T_SYSCALL], DPL_USER); ...
// Set up a normal interrupt/trap gate descriptor. // - istrap: 1 for a trap gate, 0 for an interrupt gate. // interrupt gate clears FL_IF, trap gate leaves FL_IF alone // - sel: Code segment selector for interrupt/trap handler // - off: Offset in code segment for interrupt/trap handler // - dpl: Descriptor Privilege Level - // the privilege level required for software to invoke // this interrupt/trap gate explicitly using an int instruction. #define SETGATE(gate, istrap, sel, off, d) \
vector64: pushl $0 pushl $64 jmp alltraps ...
alltraps: ... call trap ... iret
void trap(struct trapframe *tf) { ...
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... lidt(idt, sizeof(idt)); ... SETGATE(idt[T_SYSCALL], 1, SEG_KCODE<<3, vectors[T_SYSCALL], DPL_USER); ...
// Set up a normal interrupt/trap gate descriptor. // - istrap: 1 for a trap gate, 0 for an interrupt gate. // interrupt gate clears FL_IF, trap gate leaves FL_IF alone // - sel: Code segment selector for interrupt/trap handler // - off: Offset in code segment for interrupt/trap handler // - dpl: Descriptor Privilege Level - // the privilege level required for software to invoke // this interrupt/trap gate explicitly using an int instruction. #define SETGATE(gate, istrap, sel, off, d) \
vector64: pushl $0 pushl $64 jmp alltraps ...
alltraps: ... call trap ... iret
void trap(struct trapframe *tf) { ...
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void trap(struct trapframe *tf) { if(tf−>trapno == T_SYSCALL){ if(myproc()−>killed) exit(); myproc()−>tf = tf; syscall(); if(myproc()−>killed) exit(); return; } ... }
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void trap(struct trapframe *tf) { if(tf−>trapno == T_SYSCALL){ if(myproc()−>killed) exit(); myproc()−>tf = tf; syscall(); if(myproc()−>killed) exit(); return; } ... }
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void trap(struct trapframe *tf) { if(tf−>trapno == T_SYSCALL){ if(myproc()−>killed) exit(); myproc()−>tf = tf; syscall(); if(myproc()−>killed) exit(); return; } ... }
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void trap(struct trapframe *tf) { if(tf−>trapno == T_SYSCALL){ if(myproc()−>killed) exit(); myproc()−>tf = tf; syscall(); if(myproc()−>killed) exit(); return; } ... }
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static int (*syscalls[])(void) = { ... [SYS_write] sys_write, ... }; ... void syscall(void) { ... num = curproc−>tf−>eax; if(num > 0 && num < NELEM(syscalls) && syscalls[num]) { curproc−>tf−>eax = syscalls[num](); } else { ...
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static int (*syscalls[])(void) = { ... [SYS_write] sys_write, ... }; ... void syscall(void) { ... num = curproc−>tf−>eax; if(num > 0 && num < NELEM(syscalls) && syscalls[num]) { curproc−>tf−>eax = syscalls[num](); } else { ...
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static int (*syscalls[])(void) = { ... [SYS_write] sys_write, ... }; ... void syscall(void) { ... num = curproc−>tf−>eax; if(num > 0 && num < NELEM(syscalls) && syscalls[num]) { curproc−>tf−>eax = syscalls[num](); } else { ...
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static int (*syscalls[])(void) = { ... [SYS_write] sys_write, ... }; ... void syscall(void) { ... num = curproc−>tf−>eax; if(num > 0 && num < NELEM(syscalls) && syscalls[num]) { curproc−>tf−>eax = syscalls[num](); } else { ...
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int sys_write(void) { struct file *f; int n; char *p; if(argfd(0, 0, &f) < 0 || argint(2, &n) < 0 || argptr(1, &p, n) < 0) return −1; return filewrite(f, p, n); }
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int sys_write(void) { struct file *f; int n; char *p; if(argfd(0, 0, &f) < 0 || argint(2, &n) < 0 || argptr(1, &p, n) < 0) return −1; return filewrite(f, p, n); }
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int sys_write(void) { struct file *f; int n; char *p; if(argfd(0, 0, &f) < 0 || argint(2, &n) < 0 || argptr(1, &p, n) < 0) return −1; return filewrite(f, p, n); }
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... lidt(idt, sizeof(idt)); ... SETGATE(idt[T_SYSCALL], 1, SEG_KCODE<<3, vectors[T_SYSCALL], DPL_USER); ...
// Set up a normal interrupt/trap gate descriptor. // - istrap: 1 for a trap gate, 0 for an interrupt gate. // interrupt gate clears FL_IF, trap gate leaves FL_IF alone // - sel: Code segment selector for interrupt/trap handler // - off: Offset in code segment for interrupt/trap handler // - dpl: Descriptor Privilege Level - // the privilege level required for software to invoke // this interrupt/trap gate explicitly using an int instruction. #define SETGATE(gate, istrap, sel, off, d) \
vector64: pushl $0 pushl $64 jmp alltraps ...
alltraps: ... call trap ... iret
void trap(struct trapframe *tf) { ...
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return via trap()
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return via trap()
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loop.exe ssh.exe firefox.exe loop.exe ssh.exe
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loop.exe ssh.exe firefox.exe loop.exe ssh.exe
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