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sel4: enable core console

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This commit is contained in:
Norman Feske 2014-10-15 18:17:08 +02:00 committed by Christian Helmuth
parent 666c74345f
commit 6b9185ab34
4 changed files with 39 additions and 32 deletions
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47
repos/base-sel4/doc/notes.txt
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@ -762,20 +762,19 @@ The next problem is more tricky:
! include/sel4/arch/syscalls.h:481:6: error: impossible register constraint in ‘asm’
The error refers to the system-call binding for 'seL4_DebugPutChar'. After
twiddling with the asm constraints, it turns
out that the error is caused by the use of an enum value as input argument.
The C++ compiler is free to pick any integer type that it sees fit for
representing an enum value. Even though the seL4 developers use a helper
macro (SEL4_FORCE_LONG_ENUM) to force a certain minimum bit width for the
used type, the C++ compiler complains. By explicitly casting the input
argument to 'int', this ambiguity can be resolved and the compiler becomes
happy. Unfortunately, this means that I will have to patch the system-call
bindings to make them fit for the use with C++. But looking at the bindings,
I think that a patch won't be avoidable anyway because the bindings clobber
the EBX register. This means that we won't be able to use the headers for
compiling position-independent code (as is the case for Genode). For now,
we have are not compiling with '-fPIC' enabled but this issue is clear
in front of us.
twiddling with the asm constraints, it turns out that the error is caused by
the use of an enum value as input argument. The C++ compiler is free to pick
any integer type that it sees fit for representing an enum value. Even though
the seL4 developers use a helper macro (SEL4_FORCE_LONG_ENUM) to force a
certain minimum bit width for the used type, the C++ compiler complains. By
explicitly casting the input argument to 'int', this ambiguity can be resolved
and the compiler becomes happy. Unfortunately, this means that I will have to
patch the system-call bindings to make them fit for the use with C++. But
looking at the bindings, I think that a patch won't be avoidable anyway
because the bindings clobber the EBX register. This means that we won't be
able to use the headers for compiling position-independent code (as is the
case for Genode). For now, we have are not compiling with '-fPIC' enabled but
this issue is clear in front of us.
Patches for the seL4 code will be reside at _base-sel4/src/kernel/_. E.g.,
we just added the current modification of the _syscalls.h_ header by
@ -802,10 +801,20 @@ built. Executing the run script produces the result that we longed for:
The first line is produced by our test program. Knowing how to print
characters using the kernel's debug interface, filling out the empty
stub function 'Genode::Core_console::_out_char' in _core_console.h_
is easy.
is easy. We can replace the main program with this version:
! #include <base/printf.h>
!
! int main()
! {
! PDBG("a message printed via Genode's PDBG");
!
! *(int *)0x1122 = 0;
! return 0;
! }
When running it via 'make run/test', it produces the expected result:
! int main(): a message printed via Genode's PDBG

10
repos/base-sel4/src/base/console/core_console.h
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@ -11,8 +11,12 @@
* under the terms of the GNU General Public License version 2.
*/
/* Genode includes */
#include <base/console.h>
/* seL4 includes */
#include <sel4/arch/functions.h>
#include <sel4/arch/syscalls.h>
namespace Genode
{
@ -20,8 +24,10 @@ namespace Genode
{
protected:
void _out_char(char c) { }
void _out_char(char c)
{
seL4_DebugPutChar(c);
}
};
}

10
repos/base-sel4/src/test/sel4/main.cc
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@ -12,17 +12,11 @@
*/
/* Genode includes */
#include <util/string.h>
/* seL4 includes */
#include <sel4/arch/functions.h>
#include <sel4/arch/syscalls.h>
#include <base/printf.h>
int main()
{
char const *string = "\nMessage printed via the kernel\n";
for (unsigned i = 0; i < Genode::strlen(string); i++)
seL4_DebugPutChar(string[i]);
PDBG("a message printed via Genode's PDBG");
*(int *)0x1122 = 0;
return 0;

4
repos/base-sel4/src/test/sel4/thread.cc
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@ -46,8 +46,6 @@ Thread_base::Thread_base(size_t, const char *name, size_t stack_size, Type type,
{
strncpy(_context->name, name, sizeof(_context->name));
_context->thread_base = this;
_init_platform_thread(type);
}
@ -55,4 +53,4 @@ Thread_base::Thread_base(size_t quota, const char *name, size_t stack_size, Type
: Thread_base(quota, name, stack_size, type, nullptr) { }
Thread_base::~Thread_base() { _deinit_platform_thread(); }
Thread_base::~Thread_base() { }