diff options
Diffstat (limited to 'na/arch/riscv/trap/trap_md.cc')
| -rw-r--r-- | na/arch/riscv/trap/trap_md.cc | 38 |
1 files changed, 37 insertions, 1 deletions
diff --git a/na/arch/riscv/trap/trap_md.cc b/na/arch/riscv/trap/trap_md.cc index f910b26..e30aea6 100644 --- a/na/arch/riscv/trap/trap_md.cc +++ b/na/arch/riscv/trap/trap_md.cc @@ -120,16 +120,45 @@ static TrapInfo build_trap_info(arch::TrapFrame* tf, * * Reads RISC-V CSRs, translates to MI TrapCause, applies arch-specific * fixups, then calls MI trap_handle(). + * + * After trap_handle returns, we must return to user mode via userret(). + * The assembly jalr t3 that called us has NO return-to-user code after it, + * so trap_dispatch must never return normally. * ======================================================================== */ -extern "C" void trap_dispatch(arch::TrapFrame* tf) +extern "C" void userret(arch::TrapFrame* tf); + +extern "C" [[noreturn]] void trap_dispatch(arch::TrapFrame* tf) { + /* Switch stvec to kernelvec immediately so that any traps during + * kernel execution (timer IRQs, page faults from copy_from_user) + * go through the kernel trap entry, not the user trap entry. + * This matches Linux which sets stvec to handle_exception (kernel) + * at the top of the user trap path. */ + extern void kernelvec(); + arch::trap::set_vector(reinterpret_cast<uint64>(&kernelvec)); + + /* Enable SUM so S-mode can access user pages (PTE_U). + * Without this, any dereference of user-space pointers in syscall + * handlers (sys_write buf, sys_read buf, etc.) would page fault. */ + arch::trap::enable_sum(); + uint64 scause = arch::trap::get_cause(); uint64 stval = arch::trap::get_value(); TrapOrigin origin = origin_from_sstatus(tf->sstatus); TrapInfo info = build_trap_info(tf, scause, stval, origin); + /* Per-trap trace from user mode. Stored at KLOG_DEBUG / KLOG_SUBSYS_TRAP + * so it lives in the ring buffer for postmortem but stays off the console + * by default. No more in-band 20-trap window — flip console_level or + * dump the ring on demand instead. */ + if (origin == TrapOrigin::FromUser) { + pr_debug_s(KLOG_SUBSYS_TRAP, + "trap: cause=%u epc=%llx val=%llx\n", + static_cast<unsigned>(info.cause), info.epc, info.val); + } + /* Save trapframe in TCB for syscall handlers (like fork) */ TaskControlBlock* curr = current_task(); if (curr) { @@ -152,6 +181,13 @@ extern "C" void trap_dispatch(arch::TrapFrame* tf) /* Call MI-layer dispatcher (zero inline assembly from here on) */ trap_handle(tf, info); + + /* Return to user mode. + * Set stvec back to trap_vector for the next user-mode trap, + * then jump to userret which restores registers and does sret. */ + arch::trap::set_vector(reinterpret_cast<uint64>(&trap_vector)); + userret(tf); + __builtin_unreachable(); } /* ======================================================================== |