libc/string: prevent libc in the kernel/userspace optionally

Add the `LIBC_PREVENT_STRING_KERNEL` and `LIBC_PREVENT_STRING_USER`
that are meant to be selected by the chip if no libc implementation
is going to be built. If selected, neither NuttX's software version
of the libc nor any architecture-specific implementation will be
built in the kernel or in the userspace, respectively. In this
case, the linker may provide a ROM-defined version of the libc
functions instead.

libs/libc/Makefile

@@ -82,6 +82,7 @@ else
 endif
 
 CFLAGS += ${INCDIR_PREFIX}$(TOPDIR)$(DELIM)libs$(DELIM)libc
+AFLAGS += ${INCDIR_PREFIX}$(TOPDIR)$(DELIM)libs$(DELIM)libc
 
 # Rule for the symbol table generation
 

libs/libc/libc.h

@@ -27,15 +27,17 @@
 
 #include <nuttx/config.h>
 
-#include <sys/types.h>
-#include <stdbool.h>
-#include <stdio.h>
-#include <stdlib.h>
-#include <limits.h>
-#include <semaphore.h>
+#ifndef __ASSEMBLY__
+#  include <sys/types.h>
+#  include <stdbool.h>
+#  include <stdio.h>
+#  include <stdlib.h>
+#  include <limits.h>
+#  include <semaphore.h>
 
-#include <nuttx/lib/lib.h>
-#include <nuttx/streams.h>
+#  include <nuttx/lib/lib.h>
+#  include <nuttx/streams.h>
+#endif
 
 /****************************************************************************
  * Pre-processor Definitions
@@ -53,6 +55,12 @@
 
 #define LIB_BUFLEN_UNKNOWN INT_MAX
 
+#if defined(CONFIG_BUILD_FLAT) || \
+    ((!defined(CONFIG_LIBC_PREVENT_STRING_USER) && !defined(__KERNEL__))  || \
+     (!defined(CONFIG_LIBC_PREVENT_STRING_KERNEL) && defined(__KERNEL__)))
+#  define LIBC_BUILD_STRING
+#endif
+
 /****************************************************************************
  * Public Types
  ****************************************************************************/
@@ -61,6 +69,8 @@
  * Public Data
  ****************************************************************************/
 
+#ifndef __ASSEMBLY__
+
 #undef EXTERN
 #if defined(__cplusplus)
 #define EXTERN extern "C"
@@ -157,4 +167,6 @@ void lib_cxx_initialize(void);
 }
 #endif
 
+#endif /* __ASSEMBLY__ */
+
 #endif /* __LIBS_LIBC_LIBC_H */

libs/libc/machine/Kconfig

@@ -137,6 +137,30 @@ config LIBC_ARCH_ELF_64BIT
 	default n
 	depends on LIBC_ARCH_ELF
 
+config LIBC_PREVENT_STRING_KERNEL
+	bool
+	default n
+	---help---
+		Prevent any implementation of the libc from being built and linked
+		in the kernel, including NuttX's software-defined version of the libc
+		or any other architecture-specific version of it. The ROM-defined
+		version should be linked instead. This option is particularly useful
+		when it's required that the ROM-defined libc to be used by the kernel
+		(for accessing some driver resource, for instance) but the userspace
+		is forbidden to use the same ROM-defined versions. In this case,
+		NuttX's software-defined version of the libc or arch-specific
+		assembly version is built instead.
+
+config LIBC_PREVENT_STRING_USER
+	bool
+	default n
+	---help---
+		Prevent any implementation of the libc from being built and linked
+		in the userspace, including NuttX's software-defined version of the
+		libc or any other architecture-specific version of it. A ROM-defined
+		version of the libc may be linked to the userspace by the linker.
+
+
 # One or more the of above may be selected by architecture specific logic
 
 if ARCH_ARM

libs/libc/machine/arm/armv7-a/gnu/arch_memchr.S

@@ -66,6 +66,10 @@
  *
  ****************************************************************************/
 
+#include "libc.h"
+
+#ifdef LIBC_BUILD_STRING
+
 @ 2011-02-07 david.gilbert@linaro.org
 @    Extracted from local git a5b438d861
 @ 2011-07-14 david.gilbert@linaro.org
@@ -389,3 +393,5 @@ memchr:
 #else
   /* Defined in memchr-stub.c.  */
 #endif
+
+#endif

libs/libc/machine/arm/armv7-a/gnu/arch_memcpy.S

@@ -33,6 +33,10 @@
  *
  ****************************************************************************/
 
+#include "libc.h"
+
+#ifdef LIBC_BUILD_STRING
+
 /*
  * This memcpy routine is optimised for Cortex-A15 cores and takes advantage
  * of VFP or NEON when built with the appropriate flags.
@@ -624,3 +628,5 @@ def_fn memcpy p2align=6
 	bx	lr
 
 	.size	memcpy, . - memcpy
+
+#endif

libs/libc/machine/arm/armv7-a/gnu/arch_memmove.S

@@ -29,6 +29,10 @@
  *
  ****************************************************************************/
 
+#include "libc.h"
+
+#ifdef LIBC_BUILD_STRING
+
 	.thumb
 	.syntax unified
 	.global memmove
@@ -64,3 +68,5 @@ memmove:
 	pop	{r4}
 	bx	lr
 	.size memmove, . - memmove
+
+#endif

libs/libc/machine/arm/armv7-a/gnu/arch_memset.S

@@ -29,6 +29,10 @@
  *
  ****************************************************************************/
 
+#include "libc.h"
+
+#ifdef LIBC_BUILD_STRING
+
 	.arm
 	.syntax unified
 	.global memset
@@ -144,3 +148,5 @@ memset:
 	strbcs      r1, [r3], #1
 	bx          lr
 	.size memset, . - memset
+
+#endif

libs/libc/machine/arm/armv7-a/gnu/arch_strcmp.S

@@ -30,6 +30,10 @@
  *
  ****************************************************************************/
 
+#include "libc.h"
+
+#ifdef LIBC_BUILD_STRING
+
 #ifdef __ARMEB__
 #define SHFT2LSB lsl
 #define SHFT2LSBEQ lsleq
@@ -301,3 +305,5 @@ strcmp:
 	ldr	r5, [sp], #4
 	bx	lr
 	.size strcmp, . - strcmp
+
+#endif

libs/libc/machine/arm/armv7-a/gnu/arch_strlen.S

@@ -62,6 +62,10 @@
  *
  ****************************************************************************/
 
+#include "libc.h"
+
+#ifdef LIBC_BUILD_STRING
+
 #include "acle-compat.h"
 
 	.macro def_fn f p2align=0
@@ -182,3 +186,5 @@ def_fn	strlen p2align=6
 	mov	const_0, #0
 	b	.Lstart_realigned
 	.size	strlen, . - strlen
+
+#endif

libs/libc/machine/arm/armv7-m/gnu/arch_memchr.S

@@ -66,6 +66,10 @@
  *
  ****************************************************************************/
 
+#include "libc.h"
+
+#ifdef LIBC_BUILD_STRING
+
 @ 2011-02-07 david.gilbert@linaro.org
 @    Extracted from local git a5b438d861
 @ 2011-07-14 david.gilbert@linaro.org
@@ -427,3 +431,5 @@ memchr:
 #else
   /* Defined in memchr-stub.c.  */
 #endif
+
+#endif

libs/libc/machine/arm/armv7-m/gnu/arch_memcpy.S

@@ -29,6 +29,10 @@
  *
  ****************************************************************************/
 
+#include "libc.h"
+
+#ifdef LIBC_BUILD_STRING
+
 /* This memcpy routine is optimised for Cortex-M3/M4 cores with/without
    unaligned access.
 
@@ -345,3 +349,5 @@ memcpy:
 	.cantunwind
 	.fnend
 	.size	memcpy, .-memcpy
+
+#endif

libs/libc/machine/arm/armv7-m/gnu/arch_memmove.S

@@ -29,6 +29,10 @@
  *
  ****************************************************************************/
 
+#include "libc.h"
+
+#ifdef LIBC_BUILD_STRING
+
 #include "arm_asm.h"
 
 	.thumb
@@ -71,3 +75,5 @@ memmove:
 	.cantunwind
 	.fnend
 	.size memmove, . - memmove
+
+#endif

libs/libc/machine/arm/armv7-m/gnu/arch_memset.S

@@ -29,6 +29,10 @@
  *
  ****************************************************************************/
 
+#include "libc.h"
+
+#ifdef LIBC_BUILD_STRING
+
 #include "arm_asm.h"
 
 	.thumb
@@ -114,3 +118,5 @@ memset:
 	.cantunwind
 	.fnend
 	.size memset, . - memset
+
+#endif

libs/libc/machine/arm/armv7-m/gnu/arch_strcmp.S

@@ -29,6 +29,10 @@
  *
  ****************************************************************************/
 
+#include "libc.h"
+
+#ifdef LIBC_BUILD_STRING
+
 /* Very similar to the generic code, but uses Thumb2 as implemented
    in ARMv7-M.  */
 
@@ -419,3 +423,5 @@ def_fn strcmp
 	.cantunwind
 	.fnend
 	.size strcmp, . - strcmp
+
+#endif

libs/libc/machine/arm/armv7-m/gnu/arch_strcpy.S

@@ -18,6 +18,10 @@
  *
  ***************************************************************************/
 
+#include "libc.h"
+
+#ifdef LIBC_BUILD_STRING
+
 /* This strcpy borrowed some ideas from arch_strcmp.S(). */
 
 /* Parameters and result. */
@@ -306,3 +310,4 @@ offset_3:
     *dst++ = 0;
 #endif  /* Pseudo code end */
 
+#endif

libs/libc/machine/arm/armv7-m/gnu/arch_strlen.S

@@ -62,6 +62,10 @@
  *
  ****************************************************************************/
 
+#include "libc.h"
+
+#ifdef LIBC_BUILD_STRING
+
 #include "arm-acle-compat.h"
 #include "arm_asm.h"
 
@@ -193,3 +197,5 @@ def_fn	strlen p2align=6
 	.cantunwind
 	.fnend
 	.size	strlen, . - strlen
+
+#endif

libs/libc/machine/arm/armv7-r/gnu/arch_memchr.S

@@ -66,6 +66,10 @@
  *
  ****************************************************************************/
 
+#include "libc.h"
+
+#ifdef LIBC_BUILD_STRING
+
 @ 2011-02-07 david.gilbert@linaro.org
 @    Extracted from local git a5b438d861
 @ 2011-07-14 david.gilbert@linaro.org
@@ -389,3 +393,5 @@ memchr:
 #else
   /* Defined in memchr-stub.c.  */
 #endif
+
+#endif

libs/libc/machine/arm/armv7-r/gnu/arch_memcpy.S

@@ -33,6 +33,10 @@
  *
  ****************************************************************************/
 
+#include "libc.h"
+
+#ifdef LIBC_BUILD_STRING
+
 /*
  * This memcpy routine is optimised for Cortex-A15 cores and takes advantage
  * of VFP or NEON when built with the appropriate flags.
@@ -624,3 +628,5 @@ def_fn memcpy p2align=6
 	bx	lr
 
 	.size	memcpy, . - memcpy
+
+#endif

libs/libc/machine/arm/armv7-r/gnu/arch_memmove.S

@@ -29,6 +29,10 @@
  *
  ****************************************************************************/
 
+#include "libc.h"
+
+#ifdef LIBC_BUILD_STRING
+
 	.thumb
 	.syntax unified
 	.global memmove
@@ -64,3 +68,5 @@ memmove:
 	pop	{r4}
 	bx	lr
 	.size memmove, . - memmove
+
+#endif

libs/libc/machine/arm/armv7-r/gnu/arch_memset.S

@@ -29,6 +29,10 @@
  *
  ****************************************************************************/
 
+#include "libc.h"
+
+#ifdef LIBC_BUILD_STRING
+
 	.arm
 	.syntax unified
 	.global memset
@@ -144,3 +148,5 @@ memset:
 	strbcs      r1, [r3], #1
 	bx          lr
 	.size memset, . - memset
+
+#endif

libs/libc/machine/arm/armv7-r/gnu/arch_strcmp.S

@@ -30,6 +30,10 @@
  *
  ****************************************************************************/
 
+#include "libc.h"
+
+#ifdef LIBC_BUILD_STRING
+
 #ifdef __ARMEB__
 #define SHFT2LSB lsl
 #define SHFT2LSBEQ lsleq
@@ -301,3 +305,5 @@ strcmp:
 	ldr	r5, [sp], #4
 	bx	lr
 	.size strcmp, . - strcmp
+
+#endif

libs/libc/machine/arm/armv7-r/gnu/arch_strlen.S

@@ -62,6 +62,10 @@
  *
  ****************************************************************************/
 
+#include "libc.h"
+
+#ifdef LIBC_BUILD_STRING
+
 #include "acle-compat.h"
 
 	.macro def_fn f p2align=0
@@ -182,3 +186,5 @@ def_fn	strlen p2align=6
 	mov	const_0, #0
 	b	.Lstart_realigned
 	.size	strlen, . - strlen
+
+#endif

libs/libc/machine/arm/armv8-m/gnu/arch_memchr.S

@@ -66,6 +66,10 @@
  *
  ****************************************************************************/
 
+#include "libc.h"
+
+#ifdef LIBC_BUILD_STRING
+
 @ 2011-02-07 david.gilbert@linaro.org
 @    Extracted from local git a5b438d861
 @ 2011-07-14 david.gilbert@linaro.org
@@ -427,3 +431,5 @@ memchr:
 #else
   /* Defined in memchr-stub.c.  */
 #endif
+
+#endif

libs/libc/machine/arm/armv8-m/gnu/arch_memcpy.S

@@ -29,6 +29,10 @@
  *
  ****************************************************************************/
 
+#include "libc.h"
+
+#ifdef LIBC_BUILD_STRING
+
 /* This memcpy routine is optimised for Cortex-M3/M4 cores with/without
    unaligned access.
 
@@ -367,3 +371,5 @@ memcpy:
 	.cantunwind
 	.fnend
 	.size	memcpy, .-memcpy
+
+#endif

libs/libc/machine/arm/armv8-m/gnu/arch_memmove.S

@@ -29,6 +29,10 @@
  *
  ****************************************************************************/
 
+#include "libc.h"
+
+#ifdef LIBC_BUILD_STRING
+
 #include "arm_asm.h"
 
 	.thumb
@@ -71,3 +75,5 @@ memmove:
 	.cantunwind
 	.fnend
 	.size memmove, . - memmove
+
+#endif

libs/libc/machine/arm/armv8-m/gnu/arch_memset.S

@@ -29,6 +29,10 @@
  *
  ****************************************************************************/
 
+#include "libc.h"
+
+#ifdef LIBC_BUILD_STRING
+
 #include "arm_asm.h"
 
 	.thumb
@@ -129,3 +133,5 @@ memset:
 	.cantunwind
 	.fnend
 	.size memset, . - memset
+
+#endif

libs/libc/machine/arm/armv8-m/gnu/arch_strcmp.S

@@ -29,6 +29,10 @@
  *
  ****************************************************************************/
 
+#include "libc.h"
+
+#ifdef LIBC_BUILD_STRING
+
 /* Very similar to the generic code, but uses Thumb2 as implemented
    in ARMv7-M.  */
 
@@ -419,3 +423,5 @@ def_fn strcmp
 	.cantunwind
 	.fnend
 	.size strcmp, . - strcmp
+
+#endif

libs/libc/machine/arm/armv8-m/gnu/arch_strlen.S

@@ -62,6 +62,10 @@
  *
  ****************************************************************************/
 
+#include "libc.h"
+
+#ifdef LIBC_BUILD_STRING
+
 #include "arm-acle-compat.h"
 #include "arm_asm.h"
 
@@ -193,3 +197,5 @@ def_fn	strlen p2align=6
 	.cantunwind
 	.fnend
 	.size	strlen, . - strlen
+
+#endif

libs/libc/machine/arm64/gnu/arch_memchr.S

@@ -29,6 +29,10 @@
  *
  ****************************************************************************/
 
+#include "libc.h"
+
+#ifdef LIBC_BUILD_STRING
+
 /* Assumptions:
  *
  * ARMv8-a, AArch64
@@ -171,3 +175,5 @@ def_fn memchr
 	ret
 
 	.size	memchr, . - memchr
+
+#endif

libs/libc/machine/arm64/gnu/arch_memcmp.S

@@ -59,6 +59,10 @@
  *
  ****************************************************************************/
 
+#include "libc.h"
+
+#ifdef LIBC_BUILD_STRING
+
 /* Assumptions:
  *
  * ARMv8-a, AArch64, unaligned accesses.
@@ -194,3 +198,5 @@ L(byte_loop):
 	ret
 
 	.size	memcmp, . - memcmp
+
+#endif

libs/libc/machine/arm64/gnu/arch_memcpy.S

@@ -59,6 +59,10 @@
  *
  ****************************************************************************/
 
+#include "libc.h"
+
+#ifdef LIBC_BUILD_STRING
+
 /* Assumptions:
  *
  * ARMv8-a, AArch64, unaligned accesses.
@@ -230,3 +234,5 @@ L(copy_long):
 	ret
 
 	.size	memcpy, . - memcpy
+
+#endif

libs/libc/machine/arm64/gnu/arch_memmove.S

@@ -59,6 +59,10 @@
  *
  ****************************************************************************/
 
+#include "libc.h"
+
+#ifdef LIBC_BUILD_STRING
+
 /* Assumptions:
  *
  * ARMv8-a, AArch64, unaligned accesses
@@ -155,3 +159,5 @@ def_fn memmove, 6
 3:	ret
 
 	.size	memmove, . - memmove
+
+#endif

libs/libc/machine/arm64/gnu/arch_memset.S

@@ -59,6 +59,10 @@
  *
  ****************************************************************************/
 
+#include "libc.h"
+
+#ifdef LIBC_BUILD_STRING
+
 /* Assumptions:
  *
  * ARMv8-a, AArch64, unaligned accesses
@@ -240,3 +244,5 @@ L(zva_other):
 	b	L(tail64)
 
 	.size	memset, . - memset
+
+#endif

libs/libc/machine/arm64/gnu/arch_strchr.S

@@ -29,6 +29,10 @@
  *
  ****************************************************************************/
 
+#include "libc.h"
+
+#ifdef LIBC_BUILD_STRING
+
 /* Assumptions:
  *
  * ARMv8-a, AArch64
@@ -159,3 +163,5 @@ def_fn strchr
 	ret
 
 	.size	strchr, . - strchr
+
+#endif

libs/libc/machine/arm64/gnu/arch_strchrnul.S

@@ -29,6 +29,10 @@
  *
  ****************************************************************************/
 
+#include "libc.h"
+
+#ifdef LIBC_BUILD_STRING
+
 /* Assumptions:
  *
  * ARMv8-a, AArch64
@@ -144,3 +148,5 @@ def_fn strchrnul
 	ret
 
 	.size	strchrnul, . - strchrnul
+
+#endif

libs/libc/machine/arm64/gnu/arch_strcmp.S

@@ -33,6 +33,10 @@
  *
  ****************************************************************************/
 
+#include "libc.h"
+
+#ifdef LIBC_BUILD_STRING
+
 /* Assumptions:
  *
  * ARMv8-a, AArch64
@@ -203,3 +207,5 @@ L(done):
 	sub	result, data1, data2
 	ret
 	.size	strcmp, .-strcmp
+
+#endif

libs/libc/machine/arm64/gnu/arch_strcpy.S

@@ -29,6 +29,10 @@
  *
  ****************************************************************************/
 
+#include "libc.h"
+
+#ifdef LIBC_BUILD_STRING
+
 /* Assumptions:
  *
  * ARMv8-a, AArch64, unaligned accesses, min page size 4k.
@@ -336,3 +340,5 @@ def_fn STRCPY p2align=6
 	b	.Lfp_gt8
 
 	.size	STRCPY, . - STRCPY
+
+#endif

libs/libc/machine/arm64/gnu/arch_strlen.S

@@ -33,6 +33,10 @@
  *
  ****************************************************************************/
 
+#include "libc.h"
+
+#ifdef LIBC_BUILD_STRING
+
 /* Assumptions:
  *
  * ARMv8-a, AArch64, unaligned accesses, min page size 4k.
@@ -240,3 +244,5 @@ L(page_cross):
 	b	L(page_cross_entry)
 
 	.size	strlen, . - strlen
+
+#endif

libs/libc/machine/arm64/gnu/arch_strncmp.S

@@ -33,6 +33,10 @@
  *
  ****************************************************************************/
 
+#include "libc.h"
+
+#ifdef LIBC_BUILD_STRING
+
 /* Assumptions:
  *
  * ARMv8-a, AArch64
@@ -292,3 +296,5 @@ def_fn strncmp
 	mov	result, #0
 	ret
 	.size strncmp, . - strncmp
+
+#endif

libs/libc/machine/arm64/gnu/arch_strnlen.S

@@ -33,6 +33,10 @@
  *
  ****************************************************************************/
 
+#include "libc.h"
+
+#ifdef LIBC_BUILD_STRING
+
 /* Assumptions:
  *
  * ARMv8-a, AArch64
@@ -186,3 +190,5 @@ def_fn strnlen
 	csel	data2, data2, data2a, le
 	b	.Lrealigned
 	.size	strnlen, . - .Lstart	/* Include pre-padding in size.  */
+
+#endif

libs/libc/machine/arm64/gnu/arch_strrchr.S

@@ -29,6 +29,10 @@
  *
  ****************************************************************************/
 
+#include "libc.h"
+
+#ifdef LIBC_BUILD_STRING
+
 /* Assumptions:
  *
  * ARMv8-a, AArch64
@@ -177,3 +181,5 @@ def_fn strrchr
 	ret
 
 	.size	strrchr, . - strrchr
+
+#endif

libs/libc/machine/risc-v/gnu/arch_memcpy.S

@@ -18,6 +18,14 @@
  *
  ****************************************************************************/
 
+/************************************************************************************
+ * Included Files
+ ************************************************************************************/
+
+#include "libc.h"
+
+#ifdef LIBC_BUILD_STRING
+
 /************************************************************************************
  * Public Symbols
  ************************************************************************************/
@@ -128,3 +136,5 @@ memcpy:
 	bltu		a1, a3, 5b
 6:
 	ret
+
+#endif

libs/libc/machine/risc-v/gnu/arch_memset.S

@@ -13,6 +13,10 @@
  *
  ****************************************************************************/
 
+#include "libc.h"
+
+#ifdef LIBC_BUILD_STRING
+
 .text
 .global memset
 .type	memset, @function
@@ -104,3 +108,5 @@ memset:
 	bleu a2, t1, .Ltiny
 	j .Laligned
 	.size	memset, .-memset
+
+#endif

libs/libc/machine/risc-v/gnu/arch_strcmp.S

@@ -13,6 +13,10 @@
  *
  ****************************************************************************/
 
+#include "libc.h"
+
+#ifdef LIBC_BUILD_STRING
+
 #include "asm.h"
 
 .text
@@ -185,3 +189,5 @@ strcmp:
 mask:
 .dword 0x7f7f7f7f7f7f7f7f
 #endif
+
+#endif

libs/libc/machine/xtensa/arch_memcpy.S

@@ -27,6 +27,10 @@
 #include <arch/chip/core-isa.h>
 #include <arch/xtensa/xtensa_abi.h>
 
+#include "libc.h"
+
+#ifdef LIBC_BUILD_STRING
+
 /****************************************************************************
  * Pre-processor Macros
  ****************************************************************************/
@@ -276,3 +280,5 @@ __memcpy_aux:
   .end schedule
 
   .size memcpy, . - memcpy
+
+#endif

libs/libc/machine/xtensa/arch_memmove.S

@@ -27,6 +27,10 @@
 #include <arch/chip/core-isa.h>
 #include <arch/xtensa/xtensa_abi.h>
 
+#include "libc.h"
+
+#ifdef LIBC_BUILD_STRING
+
 /****************************************************************************
  * Pre-processor Macros
  ****************************************************************************/
@@ -479,3 +483,5 @@ memmove:
 
   .end schedule
   .size memmove, . - memmove
+
+#endif

libs/libc/machine/xtensa/arch_memset.S

@@ -27,6 +27,10 @@
 #include <arch/chip/core-isa.h>
 #include <arch/xtensa/xtensa_abi.h>
 
+#include "libc.h"
+
+#ifdef LIBC_BUILD_STRING
+
 /****************************************************************************
  * Public Functions
  ****************************************************************************/
@@ -175,3 +179,5 @@ __memset_aux:
 	.end schedule
 
 	.size	memset, . - memset
+
+#endif

libs/libc/machine/xtensa/arch_strcmp.S

@@ -27,6 +27,10 @@
 #include <arch/chip/core-isa.h>
 #include <arch/xtensa/xtensa_abi.h>
 
+#include "libc.h"
+
+#ifdef LIBC_BUILD_STRING
+
 /****************************************************************************
  * Pre-processor Macros
  ****************************************************************************/
@@ -760,3 +764,4 @@ strcmp:
   .end  schedule
   .size strcmp, . - strcmp
 
+#endif

libs/libc/machine/xtensa/arch_strcpy.S

@@ -27,6 +27,10 @@
 #include <arch/chip/core-isa.h>
 #include <arch/xtensa/xtensa_abi.h>
 
+#include "libc.h"
+
+#ifdef LIBC_BUILD_STRING
+
 /****************************************************************************
  * Public Functions
  ****************************************************************************/
@@ -240,3 +244,5 @@ strcpy:
   .end schedule
 
   .size strcpy, . - strcpy
+
+#endif

libs/libc/machine/xtensa/arch_strlen.S

@@ -27,6 +27,10 @@
 #include <arch/chip/core-isa.h>
 #include <arch/xtensa/xtensa_abi.h>
 
+#include "libc.h"
+
+#ifdef LIBC_BUILD_STRING
+
 /****************************************************************************
  * Public Functions
  ****************************************************************************/
@@ -120,3 +124,5 @@ strlen:
   .end schedule
 
   .size strlen, . - strlen
+
+#endif