console: make awesome

README.adoc

@@ -1832,34 +1832,68 @@ It is useless with QEMU since we already have full system visibility with `-gdb`
 
 Cheaper than JTAG (free) and easier to setup (all you need is serial), but with less visibility as it depends on the kernel working, so e.g.: dies on panic, does not see boot sequence.
 
-Usage:
+First run the kernel with:
 
 ....
 ./run --kgdb
-./run-gdb --kgdb
 ....
 
-In GDB:
+this passes the following options on the kernel CLI:
 
 ....
-c
+kgdbwait kgdboc=ttyS1,115200
 ....
 
-In QEMU:
+`kgdbwait` tells the kernel to wait for KGDB to connect.
+
+So the kernel sets things up enough for KGDB to start working, and then boot pauses waiting for connection:
+
+....
+<6>[    4.866050] Serial: 8250/16550 driver, 4 ports, IRQ sharing disabled
+<6>[    4.893205] 00:05: ttyS0 at I/O 0x3f8 (irq = 4, base_baud = 115200) is a 16550A
+<6>[    4.916271] 00:06: ttyS1 at I/O 0x2f8 (irq = 3, base_baud = 115200) is a 16550A
+<6>[    4.987771] KGDB: Registered I/O driver kgdboc
+<2>[    4.996053] KGDB: Waiting for connection from remote gdb...
+
+Entering kdb (current=0x(____ptrval____), pid 1) on processor 0 due to Keyboard Entry
+[0]kdb>
+....
+
+KGDB expects the connection at `ttyS1`, our second serial port after `ttyS0` which contains the terminal.
+
+So now we can connect to the serial port with GDB:
+
+....
+./run-gdb --kgdb --no-continue
+....
+
+Once GDB connects, it is left inside the function `kgdb_breakpoint`.
+
+So now we can set breakpoints and continue as usual.
+
+For example, in GDB:
+
+....
+continue
+....
+
+Then in QEMU:
 
 ....
 /count.sh &
 /kgdb.sh
 ....
 
-In GDB:
+link:rootfs_overlay:kgdb.sh[] pauses the kernel for KGDB, and gives control back to GDB.
+
+And now in GDB we do the usual:
 
 ....
-b __x64_sys_write
+break __x64_sys_write
-c
+continue
-c
+continue
-c
+continue
-c
+continue
 ....
 
 And now you can count from GDB!
@@ -1873,9 +1907,11 @@ See also:
 
 === KGDB ARM
 
-GDB not connecting to KGDB in ARM. Possibly linked to `-serial stdio`. See also: https://stackoverflow.com/questions/14155577/how-to-use-kgdb-on-arm
+GDB not connecting to KGDB in `arm` and `aarch64`.
 
-Main shell just falls on:
+Main question: https://stackoverflow.com/questions/14155577/how-to-use-kgdb-on-arm
+
+The main console just hangs on:
 
 ....
 Entering kdb (current=0xf8ce07d3, pid 1) due to Keyboard Entry
@@ -1893,6 +1929,8 @@ Ignoring packet error, continuing...
 Remote replied unexpectedly to 'vMustReplyEmpty': timeout
 ....
 
+I wanted to try to and run run KGDB on a second serial to see if it makes a difference, but QEMU `-M virt` does not seem to support it: https://stackoverflow.com/questions/53080745/can-qemu-m-virt-on-arm-aarch64-have-multiple-serial-ttys-like-such-as-pl011-t
+
 === KGDB kernel modules
 
 In QEMU:

common.py

@@ -670,6 +670,7 @@ def setup(parser):
         args.gem5_build_id = args.gem5_worktree
     this_module.machine = args.machine
     this_module.setup_dry_run_arguments(args)
+    this_module.is_arm = False
     if args.arch == 'arm':
         this_module.armv = 7
         this_module.gem5_arch = 'ARM'
@@ -683,6 +684,7 @@ def setup(parser):
         else:
             if this_module.machine is None:
                 this_module.machine = 'virt'
+        this_module.is_arm = True
     elif args.arch == 'aarch64':
         this_module.armv = 8
         this_module.gem5_arch = 'ARM'
@@ -696,6 +698,7 @@ def setup(parser):
         else:
             if this_module.machine is None:
                 this_module.machine = 'virt'
+        this_module.is_arm = True
     elif args.arch == 'x86_64':
         this_module.crosstool_ng_toolchain_prefix = 'x86_64-unknown-elf'
         this_module.gem5_arch = 'X86'

download-dependencies

@@ -117,6 +117,7 @@ scons \
   if "$baremetal"; then
     pkgs="${pkgs} \
 docbook2x \
+libtool-bin \
 "
   fi
   command -v apt-get >/dev/null 2>&1 || {

run

@@ -81,11 +81,22 @@ def main(args, extra_args=None):
         kernel_cli += ' {}=/eval_base64.sh'.format(initarg)
         kernel_cli_after_dash += ' lkmc_eval="{}"'.format(common.base64_encode(args.eval))
     if not args.graphic:
-        if args.arch == 'x86_64':
-            kernel_cli += ' console=ttyS0'
-        else:
-            kernel_cli += ' console=ttyAMA0'
         extra_qemu_args.append('-nographic')
+    console = None
+    console_type = None
+    console_count = 0
+    if args.arch == 'x86_64':
+        console_type = 'ttyS'
+    elif common.is_arm:
+        console_type = 'ttyAMA'
+    console = '{}{}'.format(console_type, console_count)
+    if not (args.arch == 'x86_64' and args.graphic):
+        console_count += 1
+        kernel_cli += ' console={}'.format(console)
+    extra_console = '{}{}'.format(console_type, console_count)
+    console_count += 1
+    if args.kgdb:
+        kernel_cli += ' kgdboc={},115200'.format(console)
     if kernel_cli_after_dash:
         kernel_cli += " -{}".format(kernel_cli_after_dash)
     extra_env = {}
@@ -161,12 +172,12 @@ def main(args, extra_args=None):
                 if args.arch == 'x86_64':
                     if args.kvm:
                         cmd.extend(['--cpu-type', 'X86KvmCPU'])
-                    cmd.extend(['--command-line', 'earlyprintk=ttyS0 lpj=7999923 root=/dev/sda {}'.format(kernel_cli)])
+                    cmd.extend(['--command-line', 'earlyprintk={} lpj=7999923 root=/dev/sda {}'.format(console, kernel_cli)])
-                elif args.arch == 'arm' or args.arch == 'aarch64':
+                elif common.is_arm:
                     # TODO why is it mandatory to pass mem= here? Not true for QEMU.
                     # Anything smaller than physical blows up as expected, but why can't it auto-detect the right value?
                     cmd.extend([
-                        '--command-line', 'earlyprintk=pl011,0x1c090000 console=ttyAMA0 lpj=19988480 rw loglevel=8 mem={} root=/dev/sda {}'.format(memory, kernel_cli),
+                        '--command-line', 'earlyprintk=pl011,0x1c090000 lpj=19988480 rw loglevel=8 mem={} root=/dev/sda {}'.format(memory, kernel_cli),
                         '--dtb-filename', os.path.join(common.gem5_system_dir, 'arm', 'dt', 'armv{}_gem5_v1_{}cpu.dtb'.format(common.armv, args.cpus)),
                         '--machine-type', common.machine,
                         '--param', 'system.panic_on_panic = True',
@@ -295,17 +306,13 @@ def main(args, extra_args=None):
             else:
                 virtio_gpu_pci = ['-device', 'virtio-gpu-pci']
             if args.arch == 'x86_64':
-                if args.kgdb:
-                    kernel_cli += ' kgdboc=ttyS1,115200'
                 append = ['-append', '{} nopat {}'.format(root, kernel_cli)]
                 cmd.extend([
                     '-M', common.machine,
                     '-device', 'edu',
                 ])
-            elif args.arch == 'arm' or args.arch == 'aarch64':
+            elif common.is_arm:
                 extra_emulator_args.append('-semihosting')
-                if args.kgdb:
-                    kernel_cli += ' kgdboc=ttyAMA0,115200'
                 if args.arch == 'arm':
                     cpu = 'cortex-a15'
                 else: