Drop prefix from own memcpy/memset/memcmp

C compiler might generate calls to memcpy, memset, memcmp, and memmove
as it seem fit (so far we haven't seen memmove being required). That
means we need to provide our own versions of it for code which is not
linked to a libc.

We already have a solution for that in commit bdf6051
("pie: provide memcpy/memcmp/memset for noglibc case")
but we faced another problem of compiler trying to optimize
our builtin_memset() by inserting calls to memset() which
is just an alias in our case and so it lead to infinite recursion.
This was workarounded in commit 8ea0ba7 ("string.h: fix memset
over-optimization with clang") but it's not clear that was a proper
fix.

This patch is considered to be the real solution. As we don't have
any other implementations of memset/memcpy/memcmp in non-libc case,
we can call ours without any prefixes and avoid using weak aliases.

Implementation notes:

1. mem*() functions code had to be moved from .h to .c for the functions
to be compatible with their prototypes declared in /usr/include/string.h
(i.e. "extern").

2. FORTIFY_SOURCE needed to be disabled for code not linked to libc,
because otherwise memcpy() may be replaced with a macro that expands
to __memcpy_chk() which of course can't be resolved during linking.

https://travis-ci.org/kolyshkin/criu/builds/198415449
Signed-off-by: Kir Kolyshkin <kir@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>

criu/arch/aarch64/include/asm/string.h

@@ -1,7 +0,0 @@
-#ifndef __CR_ASM_STRING_H__
-#define __CR_ASM_STRING_H__
-
-#include "common/compiler.h"
-#include "asm-generic/string.h"
-
-#endif /* __CR_ASM_STRING_H__ */

criu/arch/aarch64/include/features.h

@@ -0,0 +1,4 @@
+#ifndef __CRIU_ARCH_FEATURES_H
+#define __CRIU_ARCH_FEATURES_H
+
+#endif /* __CRIU_ARCH_FEATURES_H */

criu/arch/aarch64/restorer.c

@@ -2,7 +2,6 @@
 
 #include "restorer.h"
 #include "asm/restorer.h"
-#include "asm/string.h"
 
 #include "syscall.h"
 #include "log.h"

criu/arch/aarch64/vdso-pie.c

@@ -1,6 +1,5 @@
 #include <unistd.h>
 
-#include "asm/string.h"
 #include "asm/types.h"
 
 #include "syscall.h"

criu/arch/arm/include/asm/string.h

@@ -1,7 +0,0 @@
-#ifndef __CR_ASM_STRING_H__
-#define __CR_ASM_STRING_H__
-
-#include "common/compiler.h"
-#include "asm-generic/string.h"
-
-#endif /* __CR_ASM_STRING_H__ */

criu/arch/arm/include/features.h

@@ -0,0 +1,4 @@
+#ifndef __CRIU_ARCH_FEATURES_H
+#define __CRIU_ARCH_FEATURES_H
+
+#endif /* __CRIU_ARCH_FEATURES_H */

criu/arch/arm/restorer.c

@@ -2,7 +2,6 @@
 
 #include "restorer.h"
 #include "asm/restorer.h"
-#include "asm/string.h"
 
 #include "syscall.h"
 #include "log.h"

criu/arch/ppc64/include/asm/string.h

@@ -1,28 +0,0 @@
-#ifndef __CR_ASM_STRING_H__
-#define __CR_ASM_STRING_H__
-
-#include "common/compiler.h"
-
-#define HAS_BUILTIN_MEMCPY
-#define HAS_BUILTIN_MEMCMP
-
-#include "asm-generic/string.h"
-
-#ifdef CR_NOGLIBC
-extern void memcpy_power7(void *to, const void *from, unsigned long n);
-static inline void *builtin_memcpy(void *to, const void *from, unsigned long n)
-{
-	if (n)
-		memcpy_power7(to, from, n);
-	return to;
-}
-extern int builtin_memcmp(const void *cs, const void *ct, size_t count);
-#else
-/*
- * When building with the C library, call its services
- */
-#define builtin_memcpy memcpy
-#define builtin_memcmp memcmp
-#endif
-
-#endif /* __CR_ASM_STRING_H__ */

criu/arch/ppc64/include/features.h

@@ -0,0 +1,7 @@
+#ifndef __CRIU_ARCH_FEATURES_H
+#define __CRIU_ARCH_FEATURES_H
+
+#define ARCH_HAS_MEMCPY
+#define ARCH_HAS_MEMCMP
+
+#endif /* __CRIU_ARCH_FEATURES_H */

criu/arch/ppc64/memcmp_64.S

@@ -31,7 +31,7 @@
 #define LD	ldx
 #endif
 
-ENTRY(builtin_memcmp)
+ENTRY(memcmp)
 	cmpdi	cr1,r5,0
 
 	/* Use the short loop if both strings are not 8B aligned */

criu/arch/ppc64/memcpy_power7.S

@@ -28,7 +28,6 @@
  * service memcpy to initialise big local variable in the stack.
  */
 ENTRY(memcpy)
-ENTRY(memcpy_power7)
 	cmpldi	r5,16
 	std	r3,-STACKFRAMESIZE+STK_REG(R31)(r1)
 	blt	.Lshort_copy

criu/arch/ppc64/vdso-pie.c

@@ -1,6 +1,6 @@
 #include <unistd.h>
+#include <string.h>
 
-#include "asm/string.h"
 #include "asm/types.h"
 
 #include "syscall.h"
@@ -104,7 +104,7 @@ static unsigned long put_trampoline(unsigned long at, struct vdso_symtable *sym)
 
 			pr_debug("Putting vDSO trampoline in %s at %lx\n",
 				 sym->symbols[i].name, trampoline);
-			builtin_memcpy((void *)trampoline, &vdso_trampoline,
+			memcpy((void *)trampoline, &vdso_trampoline,
 				       size);
 			invalidate_caches(trampoline);
 		}

criu/arch/x86/include/asm/string.h

@@ -1,21 +0,0 @@
-#ifndef __CR_ASM_STRING_H__
-#define __CR_ASM_STRING_H__
-
-#define HAS_BUILTIN_MEMCPY
-
-#include "common/compiler.h"
-#include "asm-generic/string.h"
-
-#ifdef CR_NOGLIBC
-extern void *memcpy_x86(void *to, const void *from, size_t n);
-static inline void *builtin_memcpy(void *to, const void *from, size_t n)
-{
-	if (n)
-		memcpy_x86(to, from, n);
-	return to;
-}
-#else
-#define builtin_memcpy memcpy
-#endif /* CR_NOGLIBC */
-
-#endif /* __CR_ASM_STRING_H__ */

criu/arch/x86/include/features.h

@@ -0,0 +1,6 @@
+#ifndef __CRIU_ARCH_FEATURES_H
+#define __CRIU_ARCH_FEATURES_H
+
+#define ARCH_HAS_MEMCPY
+
+#endif /* __CRIU_ARCH_FEATURES_H */

criu/arch/x86/memcpy.S

@@ -16,7 +16,6 @@
  * Output:
  * rax original destination
  */
-ENTRY(memcpy_x86)
 ENTRY(memcpy)
 	movq %rdi, %rax
 	movq %rdx, %rcx
@@ -27,4 +26,3 @@ ENTRY(memcpy)
 	rep movsb
 	ret
 END(memcpy)
-END(memcpy_x86)

criu/arch/x86/vdso-pie.c

@@ -1,6 +1,6 @@
 #include <unistd.h>
 
-#include "asm/string.h"
+#include "string.h"
 #include "asm/types.h"
 
 #include "syscall.h"
@@ -41,7 +41,7 @@ int vdso_redirect_calls(unsigned long base_to, unsigned long base_from,
 			 base_to, to->symbols[i].offset, i);
 
 		jmp.imm64 = base_to + to->symbols[i].offset;
-		builtin_memcpy((void *)(base_from + from->symbols[i].offset), &jmp, sizeof(jmp));
+		memcpy((void *)(base_from + from->symbols[i].offset), &jmp, sizeof(jmp));
 	}
 
 	return 0;

criu/include/asm-generic/string.h

@@ -1,82 +0,0 @@
-#ifndef __CR_ASM_GENERIC_STRING_H__
-#define __CR_ASM_GENERIC_STRING_H__
-
-#include "common/compiler.h"
-
-/* C compiler may generate calls to memcmp, memset, memcpy and memmove,
- * so it relies on those to be available during linking.
- * In case we are not linking our code against glibc, we set CR_NOGLIBC
- * and have to provide our own implementations of mem*() functions.
- *
- * For now, not having memmove() seems OK for both gcc and clang.
- */
-
-#ifndef HAS_BUILTIN_MEMCPY
-static __maybe_unused void *builtin_memcpy(void *to, const void *from, size_t n)
-{
-	size_t i;
-	unsigned char *cto = to;
-	const unsigned char *cfrom = from;
-
-	for (i = 0; i < n; ++i, ++cto, ++cfrom) {
-		*cto = *cfrom;
-	}
-
-	return to;
-}
-#ifdef CR_NOGLIBC
-void *memcpy(void *to, const void *from, size_t n)	\
-	     __attribute__ ((weak, alias ("builtin_memcpy")));
-#endif
-#endif
-
-#ifndef HAS_BUILTIN_MEMCMP
-static __maybe_unused int builtin_memcmp(const void *cs, const void *ct, size_t count)
-{
-	const unsigned char *su1, *su2;
-	int res = 0;
-
-	for (su1 = cs, su2 = ct; 0 < count; ++su1, ++su2, count--)
-		if ((res = *su1 - *su2) != 0)
-			break;
-	return res;
-}
-#ifdef CR_NOGLIBC
-int memcmp(const void *cs, const void *ct, size_t count)	\
-	     __attribute__ ((weak, alias ("builtin_memcmp")));
-#endif
-#endif
-
-#ifndef HAS_BUILTIN_STRNCMP
-static always_inline int builtin_strncmp(const char *cs, const char *ct, size_t count)
-{
-	size_t i;
-
-	for (i = 0; i < count; i++) {
-		if (cs[i] != ct[i])
-			return cs[i] < ct[i] ? -1 : 1;
-		if (!cs[i])
-			break;
-	}
-	return 0;
-}
-#endif
-
-#ifndef HAS_BUILTIN_MEMSET
-static __maybe_unused void *builtin_memset(void *s, const int c, size_t count)
-{
-	volatile char *dest = s;
-	size_t i = 0;
-
-	while (i < count)
-		dest[i++] = (char) c;
-
-	return s;
-}
-#ifdef CR_NOGLIBC
-void *memset(void *s, const int c, size_t count)	\
-	     __attribute__ ((weak, alias ("builtin_memset")));
-#endif
-#endif
-
-#endif /* __CR_ASM_GENERIC_STRING_H__ */

criu/include/string.h

@@ -3,7 +3,6 @@
 
 #include <sys/types.h>
 #include <string.h>
-#include "asm/string.h"
 
 #ifdef CONFIG_HAS_LIBBSD
 # include <bsd/string.h>
@@ -19,4 +18,6 @@ extern size_t strlcpy(char *dest, const char *src, size_t size);
 extern size_t strlcat(char *dest, const char *src, size_t count);
 #endif
 
+extern int builtin_strncmp(const char *cs, const char *ct, size_t count);
+
 #endif /* __CR_STRING_H__ */

criu/pie/Makefile

@@ -21,6 +21,7 @@ CFLAGS			+= -iquote $(SRC_DIR)/criu/arch/$(ARCH)/include
 CFLAGS			+= -iquote $(SRC_DIR)/criu/include
 CFLAGS			+= -iquote $(SRC_DIR)/include
 CFLAGS			+= -iquote $(SRC_DIR)
+CFLAGS			+= -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=0
 
 
 ifneq ($(filter-out ia32,$(ARCH)),)

criu/pie/Makefile.library

@@ -1,6 +1,7 @@
 lib-y			+= log-simple.o
 lib-y			+= util-fd.o
 lib-y			+= util.o
+lib-y			+= string.o
 
 ifeq ($(VDSO),y)
         lib-y		+= util-vdso.o
@@ -47,3 +48,5 @@ ifneq ($(filter-out ia32,$(ARCH)),)
 else
         ccflags-y	+= -DCR_NOGLIBC -fno-pic -Wa,--noexecstack -fno-stack-protector
 endif
+
+ccflags-y		+= -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=0

criu/pie/restorer.c

@@ -672,7 +672,7 @@ static int restore_aio_ring(struct rst_aio_ring *raio)
 
 populate:
 	i = offsetof(struct aio_ring, io_events);
-	builtin_memcpy((void *)ctx + i, (void *)ring + i, raio->len - i);
+	memcpy((void *)ctx + i, (void *)ring + i, raio->len - i);
 
 	/*
 	 * If we failed to get the proper nr_req right and

criu/pie/string.c

@@ -0,0 +1,63 @@
+#include <string.h>
+#include "features.h"
+
+/* C compiler may generate calls to memcmp, memset, memcpy and memmove,
+ * so it relies on those to be available during linking.
+ * In case we are not linking our code against glibc, we set CR_NOGLIBC
+ * and have to provide our own implementations of mem*() functions.
+ *
+ * For now, not having memmove() seems OK for both gcc and clang.
+ */
+
+#ifndef ARCH_HAS_MEMCPY
+void *memcpy(void *to, const void *from, size_t n)
+{
+	size_t i;
+	unsigned char *cto = to;
+	const unsigned char *cfrom = from;
+
+	for (i = 0; i < n; ++i, ++cto, ++cfrom)
+		*cto = *cfrom;
+
+	return to;
+}
+#endif
+
+#ifndef ARCH_HAS_MEMCMP
+int memcmp(const void *cs, const void *ct, size_t count)
+{
+	const unsigned char *su1, *su2;
+	int res = 0;
+
+	for (su1 = cs, su2 = ct; 0 < count; ++su1, ++su2, count--)
+		if ((res = *su1 - *su2) != 0)
+			break;
+	return res;
+}
+#endif
+
+int builtin_strncmp(const char *cs, const char *ct, size_t count)
+{
+	size_t i;
+
+	for (i = 0; i < count; i++) {
+		if (cs[i] != ct[i])
+			return cs[i] < ct[i] ? -1 : 1;
+		if (!cs[i])
+			break;
+	}
+	return 0;
+}
+
+#ifndef ARCH_HAS_MEMSET
+void *memset(void *s, const int c, size_t count)
+{
+	char *dest = s;
+	size_t i = 0;
+
+	while (i < count)
+		dest[i++] = (char) c;
+
+	return s;
+}
+#endif

criu/pie/util-fd.c

@@ -19,8 +19,6 @@
 # define __sys_err(ret)	(-errno)
 #endif
 
-#define __memcpy builtin_memcpy
-
 #include "util-pie.h"
 #include "fcntl.h"
 

criu/pie/util-vdso.c

@@ -10,13 +10,20 @@
 #include <sys/stat.h>
 #include <sys/mman.h>
 
-#include "string.h"
 #include "image.h"
 #include "util-vdso.h"
 #include "vma.h"
 #include "log.h"
 #include "common/bug.h"
 
+#ifdef CR_NOGLIBC
+# include "string.h"
+#else
+# include <string.h>
+# define builtin_strncmp strncmp
+#endif
+
+
 #ifdef LOG_PREFIX
 # undef LOG_PREFIX
 #endif
@@ -81,7 +88,7 @@ static int has_elf_identity(Ehdr_t *ehdr)
 
 	BUILD_BUG_ON(sizeof(elf_ident) != sizeof(ehdr->e_ident));
 
-	if (builtin_memcmp(ehdr->e_ident, elf_ident, sizeof(elf_ident))) {
+	if (memcmp(ehdr->e_ident, elf_ident, sizeof(elf_ident))) {
 		pr_err("Elf header magic mismatch\n");
 		return false;
 	}
@@ -245,7 +252,7 @@ static void parse_elf_symbols(uintptr_t mem, size_t size, Phdr_t *load,
 			if (builtin_strncmp(name, symbol, vdso_symbol_length))
 				continue;
 
-			builtin_memcpy(t->symbols[i].name, name, vdso_symbol_length);
+			memcpy(t->symbols[i].name, name, vdso_symbol_length);
 			t->symbols[i].offset = (unsigned long)sym->st_value - load->p_vaddr;
 			break;
 		}

include/common/scm-code.c

@@ -2,10 +2,6 @@
 #error "The __sys macro is required"
 #endif
 
-#ifndef __memcpy
-#error "The __memcpy macro is required"
-#endif
-
 static void scm_fdset_init_chunk(struct scm_fdset *fdset, int nr_fds,
 		void *data, unsigned ch_size)
 {
@@ -62,7 +58,7 @@ int send_fds(int sock, struct sockaddr_un *saddr, int len,
 	for (i = 0; i < nr_fds; i += min_fd) {
 		min_fd = min(CR_SCM_MAX_FD, nr_fds - i);
 		scm_fdset_init_chunk(&fdset, min_fd, data, ch_size);
-		__memcpy(cmsg_data, &fds[i], sizeof(int) * min_fd);
+		memcpy(cmsg_data, &fds[i], sizeof(int) * min_fd);
 
 		ret = __sys(sendmsg)(sock, &fdset.hdr, 0);
 		if (ret <= 0)
@@ -113,7 +109,7 @@ int __recv_fds(int sock, int *fds, int nr_fds, void *data, unsigned ch_size, int
 		if (unlikely(min_fd <= 0))
 			return -EBADFD;
 
-		__memcpy(&fds[i], cmsg_data, sizeof(int) * min_fd);
+		memcpy(&fds[i], cmsg_data, sizeof(int) * min_fd);
 		if (data)
 			data += ch_size * min_fd;
 	}

scripts/build/Dockerfile.tmpl

@@ -22,8 +22,8 @@ COPY . /criu
 WORKDIR /criu
 
 RUN make mrproper
-RUN make -j $(nproc) CC=$CC criu/parasite-syscall.o
+RUN make -j $(nproc) CC=$CC V=1 criu/parasite-syscall.o
-RUN make -j $(nproc) CC=$CC
+RUN make -j $(nproc) CC=$CC V=1
 RUN make mrproper
 RUN bash -c 'CLEAN="$(git clean -ndx --exclude=scripts/build --exclude=.config)"; echo "${CLEAN}"; test -z "${CLEAN}"; exit $?'
 RUN make -j $(nproc) CC=$CC -C test/zdtm