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What is trapframe
// per-process data for the trap handling code in trampoline.S.
// sits in a page by itself just under the trampoline page in the
// user page table. not specially mapped in the kernel page table.
// the sscratch register points here.
// uservec in trampoline.S saves user registers in the trapframe,
// then initializes registers from the trapframe's
// kernel_sp, kernel_hartid, kernel_satp, and jumps to kernel_trap.
// usertrapret() and userret in trampoline.S set up
// the trapframe's kernel_*, restore user registers from the
// trapframe, switch to the user page table, and enter user space.
// the trapframe includes callee-saved user registers like s0-s11 because the
// return-to-user path via usertrapret() doesn't return through
// the entire kernel call stack.
struct trapframe {
/* 0 */ uint64 kernel_satp; // kernel page table
/* 8 */ uint64 kernel_sp; // top of process’s kernel stack
/* 16 */ uint64 kernel_trap; // usertrap()
/* 24 */ uint64 epc; // saved user program counter
/* 32 */ uint64 kernel_hartid; // saved kernel tp
/* 40 */ uint64 ra;
/* 48 */ uint64 sp;
/* 56 */ uint64 gp;
/* 64 */ uint64 tp;
/* 72 */ uint64 t0;
/* 80 */ uint64 t1;
/* 88 */ uint64 t2;
/* 96 */ uint64 s0;
/* 104 */ uint64 s1;
/* 112 */ uint64 a0;
/* 120 */ uint64 a1;
/* 128 */ uint64 a2;
/* 136 */ uint64 a3;
/* 144 */ uint64 a4;
/* 152 */ uint64 a5;
/* 160 */ uint64 a6;
/* 168 */ uint64 a7;
/* 176 */ uint64 s2;
/* 184 */ uint64 s3;
/* 192 */ uint64 s4;
/* 200 */ uint64 s5;
/* 208 */ uint64 s6;
/* 216 */ uint64 s7;
/* 224 */ uint64 s8;
/* 232 */ uint64 s9;
/* 240 */ uint64 s10;
/* 248 */ uint64 s11;
/* 256 */ uint64 t3;
/* 264 */ uint64 t4;
/* 272 */ uint64 t5;
/* 280 */ uint64 t6;
};
usertrap() handles an interrupt, exception, or system call from user space. Called from
trampoline.SLast modified 3yr ago