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-rw-r--r--glibc.mdwn5
-rw-r--r--glibc/debugging.mdwn11
-rw-r--r--glibc/debugging/ld_so_console.mdwn17
-rw-r--r--glibc/debugging/ld_so_console/dl-sysdep.c.patch63
4 files changed, 96 insertions, 0 deletions
diff --git a/glibc.mdwn b/glibc.mdwn
index c7313c1c..936bf0c2 100644
--- a/glibc.mdwn
+++ b/glibc.mdwn
@@ -65,6 +65,11 @@ Some of these are well-known as [[UNIX]] [[system call]]s.
* [[poll]]
+# Debugging
+
+Some hints for [[debugging]].
+
+
# Open Issues
[[!inline pages=tag/open_issue_glibc raw=yes feeds=no]]
diff --git a/glibc/debugging.mdwn b/glibc/debugging.mdwn
new file mode 100644
index 00000000..6b035c12
--- /dev/null
+++ b/glibc/debugging.mdwn
@@ -0,0 +1,11 @@
+[[!meta copyright="Copyright © 2011 Free Software Foundation, Inc."]]
+
+[[!meta license="""[[!toggle id="license" text="GFDL 1.2+"]][[!toggleable
+id="license" text="Permission is granted to copy, distribute and/or modify this
+document under the terms of the GNU Free Documentation License, Version 1.2 or
+any later version published by the Free Software Foundation; with no Invariant
+Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license
+is included in the section entitled [[GNU Free Documentation
+License|/fdl]]."]]"""]]
+
+ * [[ld_so_console]]
diff --git a/glibc/debugging/ld_so_console.mdwn b/glibc/debugging/ld_so_console.mdwn
new file mode 100644
index 00000000..d36317b6
--- /dev/null
+++ b/glibc/debugging/ld_so_console.mdwn
@@ -0,0 +1,17 @@
+[[!meta copyright="Copyright © 2011 Free Software Foundation, Inc."]]
+
+[[!meta license="""[[!toggle id="license" text="GFDL 1.2+"]][[!toggleable
+id="license" text="Permission is granted to copy, distribute and/or modify this
+document under the terms of the GNU Free Documentation License, Version 1.2 or
+any later version published by the Free Software Foundation; with no Invariant
+Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license
+is included in the section entitled [[GNU Free Documentation
+License|/fdl]]."]]"""]]
+
+If you need to debug something in the early `ld.so` startup, and can't refrain
+from good old `printf` debugging, there is a caveat: the available API in
+`ld.so` is rather limited. See the few functions is `dl-sysdep.c`. For
+example, there's a private `__libc_write`, which you should be able to use for
+writing to FD stderr -- but, at early `ld.so` startup, this isn't usable as
+`_hurd_init_dtable` is still all zeros, etc. To get you started, here is a
+simple [[dl-sysdep.c.patch]] to get access to the Mach console.
diff --git a/glibc/debugging/ld_so_console/dl-sysdep.c.patch b/glibc/debugging/ld_so_console/dl-sysdep.c.patch
new file mode 100644
index 00000000..eec8d7c6
--- /dev/null
+++ b/glibc/debugging/ld_so_console/dl-sysdep.c.patch
@@ -0,0 +1,63 @@
+diff --git a/sysdeps/mach/hurd/dl-sysdep.c b/sysdeps/mach/hurd/dl-sysdep.c
+index ff37add..7e6d352 100644
+--- a/sysdeps/mach/hurd/dl-sysdep.c
++++ b/sysdeps/mach/hurd/dl-sysdep.c
+@@ -44,6 +44,8 @@
+ #include <dl-machine.h>
+ #include <dl-procinfo.h>
+
++#include <device/device.h>
++
+ extern void __mach_init (void);
+
+ extern int _dl_argc;
+@@ -116,6 +118,29 @@ static void fmh(void) {
+ /* XXX loser kludge for vm_map kernel bug */
+ #endif
+
++/* Return a port to the Mach console. */
++static mach_port_t
++get_console (void)
++{
++ mach_port_t device_master, console;
++ /* We cannot use __get_privileged_ports (from hurd/privports.c), as this
++ drags in too much other libc stuff. */
++#if 0
++ error_t err = __get_privileged_ports (0, &device_master);
++
++ if (err)
++ return MACH_PORT_NULL;
++#else
++ error_t err = 0;
++ device_master = 2;
++#endif
++
++ err = __device_open (device_master, D_WRITE | D_READ, "console", &console);
++ if (err)
++ return MACH_PORT_NULL;
++
++ return console;
++}
+
+ ElfW(Addr)
+ _dl_sysdep_start (void **start_argptr,
+@@ -256,6 +279,20 @@ unfmh(); /* XXX */
+ /* Set up so we can do RPCs. */
+ __mach_init ();
+
++ /* Open the Mach console so that any message can actually be seen. This is
++ particularly useful at boot time, when started by the bootstrap file
++ system. */
++ mach_port_t console = get_console ();
++ if (console != MACH_PORT_NULL)
++ {
++ /* stdout = mach_open_devstream (console, "w"); */
++ /* stderr = stdout; */
++ /* if (stdout != NULL) */
++ /* printf ("Hello, world!\n"); */
++ int written;
++ __device_write_inband (console, 0, 0, "hello, world!\n", 14, &written);
++ }
++
+ /* Initialize frequently used global variable. */
+ GLRO(dl_pagesize) = __getpagesize (); \ No newline at end of file