Mu - linux/bootstrap/029syscalls.cc

From 3350c34a74844e21ea69077e01efff3bae64bdcd Mon Sep 17 00:00:00 2001 From: Kartik Agaram Date: Tue, 23 Mar 2021 17:31:08 -0700 Subject: . --- html/linux/bootstrap/029syscalls.cc.html | 189 +++++++++++++++++++++++++++++++ 1 file changed, 189 insertions(+) create mode 100644 html/linux/bootstrap/029syscalls.cc.html (limited to 'html/linux/bootstrap/029syscalls.cc.html') diff --git a/html/linux/bootstrap/029syscalls.cc.html b/html/linux/bootstrap/029syscalls.cc.html new file mode 100644 index 00000000..75df3e81 --- /dev/null +++ b/html/linux/bootstrap/029syscalls.cc.html @@ -0,0 +1,189 @@ + + + + +Mu - linux/bootstrap/029syscalls.cc + + + + + + + + + + +https://github.com/akkartik/mu/blob/main/linux/bootstrap/029syscalls.cc +

+  1 :(before "End Initialize Op Names")
+  2 put_new(Name, "cd", "software interrupt (int)");
+  3 
+  4 :(before "End Single-Byte Opcodes")
+  5 case 0xcd: {  // int imm8 (software interrupt)
+  6   trace(Callstack_depth+1, "run") << "syscall" << end();
+  7   uint8_t code = next();
+  8   if (code != 0x80) {
+  9     raise << "Unimplemented interrupt code " << HEXBYTE << code << '\n' << end();
+ 10     raise << "  Only `int 80h` supported for now.\n" << end();
+ 11     break;
+ 12   }
+ 13   process_int80();
+ 14   break;
+ 15 }
+ 16 
+ 17 :(code)
+ 18 void process_int80() {
+ 19   switch (Reg[EAX].u) {
+ 20   case 1:
+ 21     exit(/*exit code*/Reg[EBX].u);
+ 22     break;
+ 23   case 3:
+ 24     trace(Callstack_depth+1, "run") << "read: " << Reg[EBX].u << ' ' << Reg[ECX].u << ' ' << Reg[EDX].u << end();
+ 25     Reg[EAX].i = read(/*file descriptor*/Reg[EBX].u, /*memory buffer*/mem_addr_u8(Reg[ECX].u), /*size*/Reg[EDX].u);
+ 26     trace(Callstack_depth+1, "run") << "result: " << Reg[EAX].i << end();
+ 27     if (Reg[EAX].i == -1) raise << "read: " << strerror(errno) << '\n' << end();
+ 28     break;
+ 29   case 4:
+ 30     trace(Callstack_depth+1, "run") << "write: " << Reg[EBX].u << ' ' << Reg[ECX].u << ' ' << Reg[EDX].u << end();
+ 31     trace(Callstack_depth+1, "run") << Reg[ECX].u << " => " << mem_addr_string(Reg[ECX].u, Reg[EDX].u) << end();
+ 32     Reg[EAX].i = write(/*file descriptor*/Reg[EBX].u, /*memory buffer*/mem_addr_u8(Reg[ECX].u), /*size*/Reg[EDX].u);
+ 33     trace(Callstack_depth+1, "run") << "result: " << Reg[EAX].i << end();
+ 34     if (Reg[EAX].i == -1) raise << "write: " << strerror(errno) << '\n' << end();
+ 35     break;
+ 36   case 5: {
+ 37     check_flags(ECX);
+ 38     check_mode(EDX);
+ 39     trace(Callstack_depth+1, "run") << "open: " << Reg[EBX].u << ' ' << Reg[ECX].u << end();
+ 40     trace(Callstack_depth+1, "run") << Reg[EBX].u << " => " << mem_addr_kernel_string(Reg[EBX].u) << end();
+ 41     Reg[EAX].i = open(/*filename*/mem_addr_kernel_string(Reg[EBX].u), /*flags*/Reg[ECX].u, /*mode*/0640);
+ 42     trace(Callstack_depth+1, "run") << "result: " << Reg[EAX].i << end();
+ 43     if (Reg[EAX].i == -1) raise << "open: " << strerror(errno) << '\n' << end();
+ 44     break;
+ 45   }
+ 46   case 6:
+ 47     trace(Callstack_depth+1, "run") << "close: " << Reg[EBX].u << end();
+ 48     Reg[EAX].i = close(/*file descriptor*/Reg[EBX].u);
+ 49     trace(Callstack_depth+1, "run") << "result: " << Reg[EAX].i << end();
+ 50     if (Reg[EAX].i == -1) raise << "close: " << strerror(errno) << '\n' << end();
+ 51     break;
+ 52   case 8:
+ 53     check_mode(ECX);
+ 54     trace(Callstack_depth+1, "run") << "creat: " << Reg[EBX].u << end();
+ 55     trace(Callstack_depth+1, "run") << Reg[EBX].u << " => " << mem_addr_kernel_string(Reg[EBX].u) << end();
+ 56     Reg[EAX].i = creat(/*filename*/mem_addr_kernel_string(Reg[EBX].u), /*mode*/0640);
+ 57     trace(Callstack_depth+1, "run") << "result: " << Reg[EAX].i << end();
+ 58     if (Reg[EAX].i == -1) raise << "creat: " << strerror(errno) << '\n' << end();
+ 59     break;
+ 60   case 10:
+ 61     trace(Callstack_depth+1, "run") << "unlink: " << Reg[EBX].u << end();
+ 62     trace(Callstack_depth+1, "run") << Reg[EBX].u << " => " << mem_addr_kernel_string(Reg[EBX].u) << end();
+ 63     Reg[EAX].i = unlink(/*filename*/mem_addr_kernel_string(Reg[EBX].u));
+ 64     trace(Callstack_depth+1, "run") << "result: " << Reg[EAX].i << end();
+ 65     if (Reg[EAX].i == -1) raise << "unlink: " << strerror(errno) << '\n' << end();
+ 66     break;
+ 67   case 38:
+ 68     trace(Callstack_depth+1, "run") << "rename: " << Reg[EBX].u << " -> " << Reg[ECX].u << end();
+ 69     trace(Callstack_depth+1, "run") << Reg[EBX].u << " => " << mem_addr_kernel_string(Reg[EBX].u) << end();
+ 70     trace(Callstack_depth+1, "run") << Reg[ECX].u << " => " << mem_addr_kernel_string(Reg[ECX].u) << end();
+ 71     Reg[EAX].i = rename(/*old filename*/mem_addr_kernel_string(Reg[EBX].u), /*new filename*/mem_addr_kernel_string(Reg[ECX].u));
+ 72     trace(Callstack_depth+1, "run") << "result: " << Reg[EAX].i << end();
+ 73     if (Reg[EAX].i == -1) raise << "rename: " << strerror(errno) << '\n' << end();
+ 74     break;
+ 75   case 90:  // mmap: allocate memory outside existing segment allocations
+ 76     trace(Callstack_depth+1, "run") << "mmap: allocate new segment" << end();
+ 77     // Ignore most arguments for now: address hint, protection flags, sharing flags, fd, offset.
+ 78     // We only support anonymous maps.
+ 79     Reg[EAX].u = new_segment(/*length*/read_mem_u32(Reg[EBX].u+0x4));
+ 80     trace(Callstack_depth+1, "run") << "result: " << Reg[EAX].u << end();
+ 81     break;
+ 82   case 0xa2:  // nanosleep
+ 83     cerr << "not sleeping\n";
+ 84     break;
+ 85   default:
+ 86     raise << HEXWORD << EIP << ": unimplemented syscall " << Reg[EAX].u << '\n' << end();
+ 87   }
+ 88 }
+ 89 
+ 90 // SubX is oblivious to file permissions, directories, symbolic links, terminals, and much else besides.
+ 91 // Also ignoring any concurrency considerations for now.
+ 92 void check_flags(int reg) {
+ 93   uint32_t flags = Reg[reg].u;
+ 94   if (flags != ((flags & O_RDONLY) | (flags & O_WRONLY))) {
+ 95     cerr << HEXWORD << EIP << ": most POSIX flags to the open() syscall are not supported. Just O_RDONLY and O_WRONLY for now. Zero concurrent access support.\n";
+ 96     exit(1);
+ 97   }
+ 98   if ((flags & O_RDONLY) && (flags & O_WRONLY)) {
+ 99     cerr << HEXWORD << EIP << ": can't open a file for both reading and writing at once. See http://man7.org/linux/man-pages/man2/open.2.html.\n";
+100     exit(1);
+101   }
+102 }
+103 
+104 void check_mode(int reg) {
+105   if (Reg[reg].u != 0600) {
+106     cerr << HEXWORD << EIP << ": SubX is oblivious to file permissions; register " << reg << " must be 0x180.\n";
+107     exit(1);
+108   }
+109 }
+110 
+111 :(before "End Globals")
+112 // Very primitive/fixed/insecure mmap segments for now.
+113 uint32_t Segments_allocated_above = END_HEAP;
+114 :(code)
+115 // always allocate multiples of the segment size
+116 uint32_t new_segment(uint32_t length) {
+117   assert(length > 0);
+118   uint32_t result = (Segments_allocated_above - length) & 0xff000000;  // same number of zeroes as SEGMENT_ALIGNMENT
+119   if (result <= START_HEAP) {
+120     raise << "Allocated too many segments; the VM ran out of memory. "
+121           << "Maybe SEGMENT_ALIGNMENT can be smaller?\n" << die();
+122   }
+123   Mem.push_back(vma(result, result+length));
+124   Segments_allocated_above = result;
+125   return result;
+126 }
+

+ + + -- cgit 1.4.1-2-gfad0