errno: implement _get_errno() in common code

We really should have more faith in the compiler, it generates
code to implement this exactly like the arch-specific assembly
versions, and on ARM is actually 4 bytes shorter.

FUNC_NO_FP used to disable the usual C preamble to update the
frame/stack pointers, which is how the sizes are still the same
or less. It's debatable how useful the occasional use of
FUNC_NO_FP is in practice since it hinders debugging and in a
production build frame pointers should be globally disabled, but
we can address that later.

Change-Id: I6c4b64ab3e3a9b6f91d52fa8c92e6e79a986fc77
Signed-off-by: Andrew Boie <andrew.p.boie@intel.com>

arch/arc/core/Makefile

@@ -13,7 +13,6 @@ obj-y += prep_c.o \
          vector_table.o
 
 obj-$(CONFIG_IRQ_OFFLOAD) += irq_offload.o
-obj-$(CONFIG_ERRNO) += errno.o
 
 ifneq ($(CONFIG_ATOMIC_OPERATIONS_C),y)
 obj-y += atomic.o

arch/arc/core/errno.S

@@ -1,39 +0,0 @@
-/*
- * Copyright (c) 2015 Wind River Systems, Inc.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-/** @file
- *
- * @brief Per-thread errno accessor function
- *
- * Allow accessing the errno for the current thread without involving the
- * context switching.
- */
-
-#define _ASMLANGUAGE
-
-#include <nano_private.h>
-#include <offsets.h>
-
-GTEXT(_nanokernel)
-GTEXT(_get_errno)
-
-SECTION_FUNC(TEXT, _get_errno)
-
-	mov_s r0, _nanokernel
-	ld_s r0, [r0, __tNANO_current_OFFSET]
-	add_s r0, r0, __tTCS_errno_var_OFFSET
-	j_s.nd [blink]
-	nop_s

arch/arm/core/cortex_m/Makefile

@@ -7,6 +7,5 @@ obj-y = vector_table.o reset.o \
 	nmi_on_reset.o prep_c.o scs.o scb.o nmi.o \
 	exc_manage.o exc_wrapper.o
 
-obj-$(CONFIG_ERRNO) += errno.o
 obj-$(CONFIG_IRQ_VECTOR_TABLE_SOC) += irq_vector_table.o
 obj-$(CONFIG_SW_ISR_TABLE) += sw_isr_table.o

arch/arm/core/cortex_m/errno.S

@@ -1,40 +0,0 @@
-/*
- * Copyright (c) 2015 Wind River Systems, Inc.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-/** @file
- *
- * @brief Per-thread errno accessor function
- *
- * Allow accessing the errno for the current thread without involving the
- * context switching.
- */
-
-#define _ASMLANGUAGE
-
-#include <nano_private.h>
-#include <offsets.h>	/* nanokernel structure offset definitions */
-
-_ASM_FILE_PROLOGUE
-
-GTEXT(_nanokernel)
-GTEXT(_get_errno)
-
-SECTION_FUNC(TEXT, _get_errno)
-
-	ldr r0, =_nanokernel
-	ldr r0, [r0, #__tNANO_current_OFFSET]
-	adds.n r0, #__tTCS_errno_var_OFFSET
-	bx lr

arch/x86/core/Makefile

@@ -25,7 +25,6 @@ obj-y += fatal.o cpuhalt.o \
 obj-$(CONFIG_IRQ_OFFLOAD) += irq_offload.o
 obj-$(CONFIG_FP_SHARING) += float.o
 obj-$(CONFIG_MICROKERNEL) += strtask.o
-obj-$(CONFIG_ERRNO) += errno.o
 obj-$(CONFIG_GDT_DYNAMIC) += gdt.o
 obj-$(CONFIG_REBOOT_RST_CNT) += reboot_rst_cnt.o
 

kernel/nanokernel/Makefile

@@ -18,3 +18,4 @@ obj-$(CONFIG_KERNEL_EVENT_LOGGER) += event_logger.o
 obj-$(CONFIG_KERNEL_EVENT_LOGGER) += kernel_event_logger.o
 obj-$(CONFIG_RING_BUFFER) += ring_buffer.o
 obj-$(CONFIG_ATOMIC_OPERATIONS_C) += atomic_c.o
+obj-$(CONFIG_ERRNO) += errno.o

kernel/nanokernel/errno.c

@@ -22,17 +22,9 @@
  * context switching.
  */
 
-#define _ASMLANGUAGE
-
 #include <nano_private.h>
-#include <arch/x86/asm.h>
-#include <offsets.h>
 
-GTEXT(_nanokernel)
-GTEXT(_get_errno)
-
-SECTION_FUNC(TEXT, _get_errno)
-
-	movl _nanokernel + __tNANO_current_OFFSET, %eax
-	addl $__tTCS_errno_var_OFFSET, %eax
-	ret
+FUNC_NO_FP int *_get_errno(void)
+{
+	return &_nanokernel.current->errno_var;
+}

kernel/nanokernel/include/nano_offsets.h

@@ -57,10 +57,6 @@ GEN_OFFSET_SYM(tTCS, preempReg); /* start of prempt register set */
 GEN_OFFSET_SYM(tTCS, next_thread);
 #endif
 
-#ifdef CONFIG_ERRNO
-GEN_OFFSET_SYM(tTCS, errno_var);
-#endif
-
 /* size of the entire struct tcs structure */
 
 GEN_ABSOLUTE_SYM(__tTCS_SIZEOF, sizeof(tTCS));