[PATCH v4 0/3] um: allow static linking for non-glibc libc implementations

[PATCH v4 0/3] um: allow static linking for non-glibc libc implementations

[Ignat Korchagin]

Changes from v3:
  * restored FORBID_STATIC_LINK and renamed it to MAY_HAVE_RUNTIME_DEPS, so we
    don't have to maintain a static list of options, which may produce runtime
    dependencies

This is a continuation of [1]. Since I was able to produce a working UML binary
with UML_NET_VECTOR linked with musl with the changes included in the patches
here. I was compiling on Arch Linux, so hopefully all the latest versions of
the compiler, libraries and binutils.

I also tested allyesconfig with both musl and glibc. The compilation succeeds
with both, however both binaries (glibc one being dynamically linked) segfault
on start. This is probably of some incompatible config option/module being
included and not related to musl/glibc.

[1]: https://patchwork.ozlabs.org/project/linux-um/patch/20200624212319.403689-1-ignat@cloudflare.com/

Ignat Korchagin (3):
  um/kconfig: introduce CC_CAN_LINK_STATIC_NO_RUNTIME_DEPS
  um: some fixes to build UML with musl
  um: allow static linking for non-glibc implementations

 arch/um/Kconfig               |  6 +++---
 arch/um/drivers/Kconfig       |  6 +++---
 arch/um/drivers/daemon_user.c |  1 +
 arch/um/drivers/pcap_user.c   | 12 ++++++------
 arch/um/drivers/slip_user.c   |  2 +-
 arch/um/drivers/vector_user.c |  4 +---
 arch/um/os-Linux/util.c       |  2 +-
 arch/x86/um/user-offsets.c    |  2 +-
 init/Kconfig                  |  6 ++++++
 scripts/cc-can-link.sh        |  5 +++--
 10 files changed, 26 insertions(+), 20 deletions(-)

-- 
2.20.1

[PATCH v4 0/3] um: allow static linking for non-glibc libc implementations

[Ignat Korchagin]

Changes from v3:
  * restored FORBID_STATIC_LINK and renamed it to MAY_HAVE_RUNTIME_DEPS, so we
    don't have to maintain a static list of options, which may produce runtime
    dependencies

This is a continuation of [1]. Since I was able to produce a working UML binary
with UML_NET_VECTOR linked with musl with the changes included in the patches
here. I was compiling on Arch Linux, so hopefully all the latest versions of
the compiler, libraries and binutils.

I also tested allyesconfig with both musl and glibc. The compilation succeeds
with both, however both binaries (glibc one being dynamically linked) segfault
on start. This is probably of some incompatible config option/module being
included and not related to musl/glibc.

[1]: https://patchwork.ozlabs.org/project/linux-um/patch/20200624212319.403689-1-ignat@cloudflare.com/

Ignat Korchagin (3):
  um/kconfig: introduce CC_CAN_LINK_STATIC_NO_RUNTIME_DEPS
  um: some fixes to build UML with musl
  um: allow static linking for non-glibc implementations

 arch/um/Kconfig               |  6 +++---
 arch/um/drivers/Kconfig       |  6 +++---
 arch/um/drivers/daemon_user.c |  1 +
 arch/um/drivers/pcap_user.c   | 12 ++++++------
 arch/um/drivers/slip_user.c   |  2 +-
 arch/um/drivers/vector_user.c |  4 +---
 arch/um/os-Linux/util.c       |  2 +-
 arch/x86/um/user-offsets.c    |  2 +-
 init/Kconfig                  |  6 ++++++
 scripts/cc-can-link.sh        |  5 +++--
 10 files changed, 26 insertions(+), 20 deletions(-)

-- 
2.20.1


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[PATCH v4 1/3] um/kconfig: introduce CC_CAN_LINK_STATIC_NO_RUNTIME_DEPS

[Ignat Korchagin]

For statically linked UML build it is important to take into account the
standard C-library implementation. Some implementations, notably glibc have
caveats: even when linked statically, the final program might require some
runtime dependencies, if certain functions are used within the code.

Consider the following program:
int main(void)
{
	getpwent();
	return 0;
}

Compiling this program and linking statically with glibc produces the following
warning from the linker:
/usr/sbin/ld: /tmp/ccuthw1o.o: in function `main':
test.c:(.text+0x5): warning: Using 'getpwent' in statically linked
applications requires at runtime the shared libraries from the glibc version
used for linking

We will use the flag to detect such C-library implementation build time and
possibly disable static linking for UML to avoid producing a binary with
unexpected behaviour and dependencies.

Signed-off-by: Ignat Korchagin <ignat@cloudflare.com>
Reviewed-by: Brendan Higgins <brendanhiggins@google.com>
Tested-by: Brendan Higgins <brendanhiggins@google.com>
---
 init/Kconfig           | 6 ++++++
 scripts/cc-can-link.sh | 5 +++--
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/init/Kconfig b/init/Kconfig
index 0498af567f70..0a1ec56c9f33 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -57,6 +57,12 @@ config CC_CAN_LINK_STATIC
 	default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m64-flag) -static) if 64BIT
 	default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m32-flag) -static)
 
+config CC_CAN_LINK_STATIC_NO_RUNTIME_DEPS
+	bool
+	depends on UML && CC_CAN_LINK_STATIC
+	default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m64-flag) -static -Xlinker --fatal-warnings) if 64BIT
+	default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m32-flag) -static -Xlinker --fatal-warnings)
+
 config CC_HAS_ASM_GOTO
 	def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC))
 
diff --git a/scripts/cc-can-link.sh b/scripts/cc-can-link.sh
index 6efcead31989..e5011a46103e 100755
--- a/scripts/cc-can-link.sh
+++ b/scripts/cc-can-link.sh
@@ -2,10 +2,11 @@
 # SPDX-License-Identifier: GPL-2.0
 
 cat << "END" | $@ -x c - -o /dev/null >/dev/null 2>&1
-#include <stdio.h>
+#include <sys/types.h>
+#include <pwd.h>
 int main(void)
 {
-	printf("");
+	getpwent();
 	return 0;
 }
 END
-- 
2.20.1

[PATCH v4 1/3] um/kconfig: introduce CC_CAN_LINK_STATIC_NO_RUNTIME_DEPS

[Ignat Korchagin]

For statically linked UML build it is important to take into account the
standard C-library implementation. Some implementations, notably glibc have
caveats: even when linked statically, the final program might require some
runtime dependencies, if certain functions are used within the code.

Consider the following program:
int main(void)
{
	getpwent();
	return 0;
}

Compiling this program and linking statically with glibc produces the following
warning from the linker:
/usr/sbin/ld: /tmp/ccuthw1o.o: in function `main':
test.c:(.text+0x5): warning: Using 'getpwent' in statically linked
applications requires at runtime the shared libraries from the glibc version
used for linking

We will use the flag to detect such C-library implementation build time and
possibly disable static linking for UML to avoid producing a binary with
unexpected behaviour and dependencies.

Signed-off-by: Ignat Korchagin <ignat@cloudflare.com>
Reviewed-by: Brendan Higgins <brendanhiggins@google.com>
Tested-by: Brendan Higgins <brendanhiggins@google.com>
---
 init/Kconfig           | 6 ++++++
 scripts/cc-can-link.sh | 5 +++--
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/init/Kconfig b/init/Kconfig
index 0498af567f70..0a1ec56c9f33 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -57,6 +57,12 @@ config CC_CAN_LINK_STATIC
 	default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m64-flag) -static) if 64BIT
 	default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m32-flag) -static)
 
+config CC_CAN_LINK_STATIC_NO_RUNTIME_DEPS
+	bool
+	depends on UML && CC_CAN_LINK_STATIC
+	default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m64-flag) -static -Xlinker --fatal-warnings) if 64BIT
+	default $(success,$(srctree)/scripts/cc-can-link.sh $(CC) $(CLANG_FLAGS) $(m32-flag) -static -Xlinker --fatal-warnings)
+
 config CC_HAS_ASM_GOTO
 	def_bool $(success,$(srctree)/scripts/gcc-goto.sh $(CC))
 
diff --git a/scripts/cc-can-link.sh b/scripts/cc-can-link.sh
index 6efcead31989..e5011a46103e 100755
--- a/scripts/cc-can-link.sh
+++ b/scripts/cc-can-link.sh
@@ -2,10 +2,11 @@
 # SPDX-License-Identifier: GPL-2.0
 
 cat << "END" | $@ -x c - -o /dev/null >/dev/null 2>&1
-#include <stdio.h>
+#include <sys/types.h>
+#include <pwd.h>
 int main(void)
 {
-	printf("");
+	getpwent();
 	return 0;
 }
 END
-- 
2.20.1


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[PATCH v4 2/3] um: some fixes to build UML with musl

[Ignat Korchagin]

musl toolchain and headers are a bit more strict. These fixes enable building
UML with musl as well as seem not to break on glibc.

Signed-off-by: Ignat Korchagin <ignat@cloudflare.com>
Tested-by: Brendan Higgins <brendanhiggins@google.com>
---
 arch/um/drivers/daemon_user.c |  1 +
 arch/um/drivers/pcap_user.c   | 12 ++++++------
 arch/um/drivers/slip_user.c   |  2 +-
 arch/um/drivers/vector_user.c |  4 +---
 arch/um/os-Linux/util.c       |  2 +-
 arch/x86/um/user-offsets.c    |  2 +-
 6 files changed, 11 insertions(+), 12 deletions(-)

diff --git a/arch/um/drivers/daemon_user.c b/arch/um/drivers/daemon_user.c
index 3695821d06a2..785baedc3555 100644
--- a/arch/um/drivers/daemon_user.c
+++ b/arch/um/drivers/daemon_user.c
@@ -7,6 +7,7 @@
  */
 
 #include <stdint.h>
+#include <string.h>
 #include <unistd.h>
 #include <errno.h>
 #include <sys/types.h>
diff --git a/arch/um/drivers/pcap_user.c b/arch/um/drivers/pcap_user.c
index bbd20638788a..52ddda3e3b10 100644
--- a/arch/um/drivers/pcap_user.c
+++ b/arch/um/drivers/pcap_user.c
@@ -32,7 +32,7 @@ static int pcap_user_init(void *data, void *dev)
 	return 0;
 }
 
-static int pcap_open(void *data)
+static int pcap_user_open(void *data)
 {
 	struct pcap_data *pri = data;
 	__u32 netmask;
@@ -44,14 +44,14 @@ static int pcap_open(void *data)
 	if (pri->filter != NULL) {
 		err = dev_netmask(pri->dev, &netmask);
 		if (err < 0) {
-			printk(UM_KERN_ERR "pcap_open : dev_netmask failed\n");
+			printk(UM_KERN_ERR "pcap_user_open : dev_netmask failed\n");
 			return -EIO;
 		}
 
 		pri->compiled = uml_kmalloc(sizeof(struct bpf_program),
 					UM_GFP_KERNEL);
 		if (pri->compiled == NULL) {
-			printk(UM_KERN_ERR "pcap_open : kmalloc failed\n");
+			printk(UM_KERN_ERR "pcap_user_open : kmalloc failed\n");
 			return -ENOMEM;
 		}
 
@@ -59,14 +59,14 @@ static int pcap_open(void *data)
 				   (struct bpf_program *) pri->compiled,
 				   pri->filter, pri->optimize, netmask);
 		if (err < 0) {
-			printk(UM_KERN_ERR "pcap_open : pcap_compile failed - "
+			printk(UM_KERN_ERR "pcap_user_open : pcap_compile failed - "
 			       "'%s'\n", pcap_geterr(pri->pcap));
 			goto out;
 		}
 
 		err = pcap_setfilter(pri->pcap, pri->compiled);
 		if (err < 0) {
-			printk(UM_KERN_ERR "pcap_open : pcap_setfilter "
+			printk(UM_KERN_ERR "pcap_user_open : pcap_setfilter "
 			       "failed - '%s'\n", pcap_geterr(pri->pcap));
 			goto out;
 		}
@@ -127,7 +127,7 @@ int pcap_user_read(int fd, void *buffer, int len, struct pcap_data *pri)
 
 const struct net_user_info pcap_user_info = {
 	.init		= pcap_user_init,
-	.open		= pcap_open,
+	.open		= pcap_user_open,
 	.close	 	= NULL,
 	.remove	 	= pcap_remove,
 	.add_address	= NULL,
diff --git a/arch/um/drivers/slip_user.c b/arch/um/drivers/slip_user.c
index 8016d32b6809..482a19c5105c 100644
--- a/arch/um/drivers/slip_user.c
+++ b/arch/um/drivers/slip_user.c
@@ -9,7 +9,7 @@
 #include <errno.h>
 #include <fcntl.h>
 #include <string.h>
-#include <sys/termios.h>
+#include <termios.h>
 #include <sys/wait.h>
 #include <net_user.h>
 #include <os.h>
diff --git a/arch/um/drivers/vector_user.c b/arch/um/drivers/vector_user.c
index c4a0f26b2824..45d4164ad355 100644
--- a/arch/um/drivers/vector_user.c
+++ b/arch/um/drivers/vector_user.c
@@ -18,9 +18,7 @@
 #include <fcntl.h>
 #include <sys/socket.h>
 #include <sys/un.h>
-#include <net/ethernet.h>
 #include <netinet/ip.h>
-#include <netinet/ether.h>
 #include <linux/if_ether.h>
 #include <linux/if_packet.h>
 #include <sys/wait.h>
@@ -332,7 +330,7 @@ static struct vector_fds *user_init_unix_fds(struct arglist *ifspec, int id)
 	}
 	switch (id) {
 	case ID_BESS:
-		if (connect(fd, remote_addr, sizeof(struct sockaddr_un)) < 0) {
+		if (connect(fd, (const struct sockaddr *) remote_addr, sizeof(struct sockaddr_un)) < 0) {
 			printk(UM_KERN_ERR "bess open:cannot connect to %s %i", remote_addr->sun_path, -errno);
 			goto unix_cleanup;
 		}
diff --git a/arch/um/os-Linux/util.c b/arch/um/os-Linux/util.c
index ecf2f390fad2..07327425d06e 100644
--- a/arch/um/os-Linux/util.c
+++ b/arch/um/os-Linux/util.c
@@ -10,7 +10,7 @@
 #include <signal.h>
 #include <string.h>
 #include <termios.h>
-#include <wait.h>
+#include <sys/wait.h>
 #include <sys/mman.h>
 #include <sys/utsname.h>
 #include <init.h>
diff --git a/arch/x86/um/user-offsets.c b/arch/x86/um/user-offsets.c
index c51dd8363d25..bae61554abcc 100644
--- a/arch/x86/um/user-offsets.c
+++ b/arch/x86/um/user-offsets.c
@@ -2,7 +2,7 @@
 #include <stdio.h>
 #include <stddef.h>
 #include <signal.h>
-#include <sys/poll.h>
+#include <poll.h>
 #include <sys/mman.h>
 #include <sys/user.h>
 #define __FRAME_OFFSETS
-- 
2.20.1

[PATCH v4 2/3] um: some fixes to build UML with musl

[Ignat Korchagin]

musl toolchain and headers are a bit more strict. These fixes enable building
UML with musl as well as seem not to break on glibc.

Signed-off-by: Ignat Korchagin <ignat@cloudflare.com>
Tested-by: Brendan Higgins <brendanhiggins@google.com>
---
 arch/um/drivers/daemon_user.c |  1 +
 arch/um/drivers/pcap_user.c   | 12 ++++++------
 arch/um/drivers/slip_user.c   |  2 +-
 arch/um/drivers/vector_user.c |  4 +---
 arch/um/os-Linux/util.c       |  2 +-
 arch/x86/um/user-offsets.c    |  2 +-
 6 files changed, 11 insertions(+), 12 deletions(-)

diff --git a/arch/um/drivers/daemon_user.c b/arch/um/drivers/daemon_user.c
index 3695821d06a2..785baedc3555 100644
--- a/arch/um/drivers/daemon_user.c
+++ b/arch/um/drivers/daemon_user.c
@@ -7,6 +7,7 @@
  */
 
 #include <stdint.h>
+#include <string.h>
 #include <unistd.h>
 #include <errno.h>
 #include <sys/types.h>
diff --git a/arch/um/drivers/pcap_user.c b/arch/um/drivers/pcap_user.c
index bbd20638788a..52ddda3e3b10 100644
--- a/arch/um/drivers/pcap_user.c
+++ b/arch/um/drivers/pcap_user.c
@@ -32,7 +32,7 @@ static int pcap_user_init(void *data, void *dev)
 	return 0;
 }
 
-static int pcap_open(void *data)
+static int pcap_user_open(void *data)
 {
 	struct pcap_data *pri = data;
 	__u32 netmask;
@@ -44,14 +44,14 @@ static int pcap_open(void *data)
 	if (pri->filter != NULL) {
 		err = dev_netmask(pri->dev, &netmask);
 		if (err < 0) {
-			printk(UM_KERN_ERR "pcap_open : dev_netmask failed\n");
+			printk(UM_KERN_ERR "pcap_user_open : dev_netmask failed\n");
 			return -EIO;
 		}
 
 		pri->compiled = uml_kmalloc(sizeof(struct bpf_program),
 					UM_GFP_KERNEL);
 		if (pri->compiled == NULL) {
-			printk(UM_KERN_ERR "pcap_open : kmalloc failed\n");
+			printk(UM_KERN_ERR "pcap_user_open : kmalloc failed\n");
 			return -ENOMEM;
 		}
 
@@ -59,14 +59,14 @@ static int pcap_open(void *data)
 				   (struct bpf_program *) pri->compiled,
 				   pri->filter, pri->optimize, netmask);
 		if (err < 0) {
-			printk(UM_KERN_ERR "pcap_open : pcap_compile failed - "
+			printk(UM_KERN_ERR "pcap_user_open : pcap_compile failed - "
 			       "'%s'\n", pcap_geterr(pri->pcap));
 			goto out;
 		}
 
 		err = pcap_setfilter(pri->pcap, pri->compiled);
 		if (err < 0) {
-			printk(UM_KERN_ERR "pcap_open : pcap_setfilter "
+			printk(UM_KERN_ERR "pcap_user_open : pcap_setfilter "
 			       "failed - '%s'\n", pcap_geterr(pri->pcap));
 			goto out;
 		}
@@ -127,7 +127,7 @@ int pcap_user_read(int fd, void *buffer, int len, struct pcap_data *pri)
 
 const struct net_user_info pcap_user_info = {
 	.init		= pcap_user_init,
-	.open		= pcap_open,
+	.open		= pcap_user_open,
 	.close	 	= NULL,
 	.remove	 	= pcap_remove,
 	.add_address	= NULL,
diff --git a/arch/um/drivers/slip_user.c b/arch/um/drivers/slip_user.c
index 8016d32b6809..482a19c5105c 100644
--- a/arch/um/drivers/slip_user.c
+++ b/arch/um/drivers/slip_user.c
@@ -9,7 +9,7 @@
 #include <errno.h>
 #include <fcntl.h>
 #include <string.h>
-#include <sys/termios.h>
+#include <termios.h>
 #include <sys/wait.h>
 #include <net_user.h>
 #include <os.h>
diff --git a/arch/um/drivers/vector_user.c b/arch/um/drivers/vector_user.c
index c4a0f26b2824..45d4164ad355 100644
--- a/arch/um/drivers/vector_user.c
+++ b/arch/um/drivers/vector_user.c
@@ -18,9 +18,7 @@
 #include <fcntl.h>
 #include <sys/socket.h>
 #include <sys/un.h>
-#include <net/ethernet.h>
 #include <netinet/ip.h>
-#include <netinet/ether.h>
 #include <linux/if_ether.h>
 #include <linux/if_packet.h>
 #include <sys/wait.h>
@@ -332,7 +330,7 @@ static struct vector_fds *user_init_unix_fds(struct arglist *ifspec, int id)
 	}
 	switch (id) {
 	case ID_BESS:
-		if (connect(fd, remote_addr, sizeof(struct sockaddr_un)) < 0) {
+		if (connect(fd, (const struct sockaddr *) remote_addr, sizeof(struct sockaddr_un)) < 0) {
 			printk(UM_KERN_ERR "bess open:cannot connect to %s %i", remote_addr->sun_path, -errno);
 			goto unix_cleanup;
 		}
diff --git a/arch/um/os-Linux/util.c b/arch/um/os-Linux/util.c
index ecf2f390fad2..07327425d06e 100644
--- a/arch/um/os-Linux/util.c
+++ b/arch/um/os-Linux/util.c
@@ -10,7 +10,7 @@
 #include <signal.h>
 #include <string.h>
 #include <termios.h>
-#include <wait.h>
+#include <sys/wait.h>
 #include <sys/mman.h>
 #include <sys/utsname.h>
 #include <init.h>
diff --git a/arch/x86/um/user-offsets.c b/arch/x86/um/user-offsets.c
index c51dd8363d25..bae61554abcc 100644
--- a/arch/x86/um/user-offsets.c
+++ b/arch/x86/um/user-offsets.c
@@ -2,7 +2,7 @@
 #include <stdio.h>
 #include <stddef.h>
 #include <signal.h>
-#include <sys/poll.h>
+#include <poll.h>
 #include <sys/mman.h>
 #include <sys/user.h>
 #define __FRAME_OFFSETS
-- 
2.20.1


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http://lists.infradead.org/mailman/listinfo/linux-um

[PATCH v4 3/3] um: allow static linking for non-glibc implementations

[Ignat Korchagin]

It is possible to produce a statically linked UML binary with UML_NET_VECTOR,
UML_NET_VDE and UML_NET_PCAP options enabled using alternative libc
implementations, which do not rely on NSS, such as musl.

Allow static linking in this case.

Signed-off-by: Ignat Korchagin <ignat@cloudflare.com>
Reviewed-by: Brendan Higgins <brendanhiggins@google.com>
Tested-by: Brendan Higgins <brendanhiggins@google.com>
---
 arch/um/Kconfig         | 6 +++---
 arch/um/drivers/Kconfig | 6 +++---
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/arch/um/Kconfig b/arch/um/Kconfig
index 9318dc6d1a0c..d888b859c167 100644
--- a/arch/um/Kconfig
+++ b/arch/um/Kconfig
@@ -62,12 +62,12 @@ config NR_CPUS
 
 source "arch/$(HEADER_ARCH)/um/Kconfig"
 
-config FORBID_STATIC_LINK
-	bool
+config MAY_HAVE_RUNTIME_DEPS
+        bool
 
 config STATIC_LINK
 	bool "Force a static link"
-	depends on !FORBID_STATIC_LINK
+	depends on CC_CAN_LINK_STATIC_NO_RUNTIME_DEPS || !MAY_HAVE_RUNTIME_DEPS
 	help
 	  This option gives you the ability to force a static link of UML.
 	  Normally, UML is linked as a shared binary.  This is inconvenient for
diff --git a/arch/um/drivers/Kconfig b/arch/um/drivers/Kconfig
index 9160ead56e33..2e7b8e0e7194 100644
--- a/arch/um/drivers/Kconfig
+++ b/arch/um/drivers/Kconfig
@@ -234,7 +234,7 @@ config UML_NET_DAEMON
 config UML_NET_VECTOR
 	bool "Vector I/O high performance network devices"
 	depends on UML_NET
-	select FORBID_STATIC_LINK
+	select MAY_HAVE_RUNTIME_DEPS
 	help
 	This User-Mode Linux network driver uses multi-message send
 	and receive functions. The host running the UML guest must have
@@ -246,7 +246,7 @@ config UML_NET_VECTOR
 config UML_NET_VDE
 	bool "VDE transport (obsolete)"
 	depends on UML_NET
-	select FORBID_STATIC_LINK
+	select MAY_HAVE_RUNTIME_DEPS
 	help
 	This User-Mode Linux network transport allows one or more running
 	UMLs on a single host to communicate with each other and also
@@ -294,7 +294,7 @@ config UML_NET_MCAST
 config UML_NET_PCAP
 	bool "pcap transport (obsolete)"
 	depends on UML_NET
-	select FORBID_STATIC_LINK
+	select MAY_HAVE_RUNTIME_DEPS
 	help
 	The pcap transport makes a pcap packet stream on the host look
 	like an ethernet device inside UML.  This is useful for making
-- 
2.20.1

[PATCH v4 3/3] um: allow static linking for non-glibc implementations

[Ignat Korchagin]

It is possible to produce a statically linked UML binary with UML_NET_VECTOR,
UML_NET_VDE and UML_NET_PCAP options enabled using alternative libc
implementations, which do not rely on NSS, such as musl.

Allow static linking in this case.

Signed-off-by: Ignat Korchagin <ignat@cloudflare.com>
Reviewed-by: Brendan Higgins <brendanhiggins@google.com>
Tested-by: Brendan Higgins <brendanhiggins@google.com>
---
 arch/um/Kconfig         | 6 +++---
 arch/um/drivers/Kconfig | 6 +++---
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/arch/um/Kconfig b/arch/um/Kconfig
index 9318dc6d1a0c..d888b859c167 100644
--- a/arch/um/Kconfig
+++ b/arch/um/Kconfig
@@ -62,12 +62,12 @@ config NR_CPUS
 
 source "arch/$(HEADER_ARCH)/um/Kconfig"
 
-config FORBID_STATIC_LINK
-	bool
+config MAY_HAVE_RUNTIME_DEPS
+        bool
 
 config STATIC_LINK
 	bool "Force a static link"
-	depends on !FORBID_STATIC_LINK
+	depends on CC_CAN_LINK_STATIC_NO_RUNTIME_DEPS || !MAY_HAVE_RUNTIME_DEPS
 	help
 	  This option gives you the ability to force a static link of UML.
 	  Normally, UML is linked as a shared binary.  This is inconvenient for
diff --git a/arch/um/drivers/Kconfig b/arch/um/drivers/Kconfig
index 9160ead56e33..2e7b8e0e7194 100644
--- a/arch/um/drivers/Kconfig
+++ b/arch/um/drivers/Kconfig
@@ -234,7 +234,7 @@ config UML_NET_DAEMON
 config UML_NET_VECTOR
 	bool "Vector I/O high performance network devices"
 	depends on UML_NET
-	select FORBID_STATIC_LINK
+	select MAY_HAVE_RUNTIME_DEPS
 	help
 	This User-Mode Linux network driver uses multi-message send
 	and receive functions. The host running the UML guest must have
@@ -246,7 +246,7 @@ config UML_NET_VECTOR
 config UML_NET_VDE
 	bool "VDE transport (obsolete)"
 	depends on UML_NET
-	select FORBID_STATIC_LINK
+	select MAY_HAVE_RUNTIME_DEPS
 	help
 	This User-Mode Linux network transport allows one or more running
 	UMLs on a single host to communicate with each other and also
@@ -294,7 +294,7 @@ config UML_NET_MCAST
 config UML_NET_PCAP
 	bool "pcap transport (obsolete)"
 	depends on UML_NET
-	select FORBID_STATIC_LINK
+	select MAY_HAVE_RUNTIME_DEPS
 	help
 	The pcap transport makes a pcap packet stream on the host look
 	like an ethernet device inside UML.  This is useful for making
-- 
2.20.1


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