diff mbox series

[kvm-unit-tests,v3,1/4] lib: s390x: add support for SCLP console read

Message ID 20220420134557.1307305-2-nrb@linux.ibm.com (mailing list archive)
State Superseded, archived
Headers show
Series s390x: add migration test support | expand

Commit Message

Nico Boehr April 20, 2022, 1:45 p.m. UTC 
Add a basic implementation for reading from the SCLP ASCII console. The goal of
this is to support migration tests on s390x. To know when the migration has been
finished, we need to listen for a newline on our console.

Hence, this implementation is focused on the SCLP ASCII console of QEMU and
currently won't work under e.g. LPAR.

Signed-off-by: Nico Boehr <nrb@linux.ibm.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
---
 lib/s390x/sclp-console.c | 79 +++++++++++++++++++++++++++++++++++++---
 lib/s390x/sclp.h         |  8 ++++
 s390x/Makefile           |  1 +
 3 files changed, 82 insertions(+), 6 deletions(-)

Comments

Claudio Imbrenda April 20, 2022, 2:16 p.m. UTC | #1 
On Wed, 20 Apr 2022 15:45:54 +0200
Nico Boehr <nrb@linux.ibm.com> wrote:

> Add a basic implementation for reading from the SCLP ASCII console. The goal of
> this is to support migration tests on s390x. To know when the migration has been
> finished, we need to listen for a newline on our console.
> 
> Hence, this implementation is focused on the SCLP ASCII console of QEMU and
> currently won't work under e.g. LPAR.
> 
> Signed-off-by: Nico Boehr <nrb@linux.ibm.com>
> Reviewed-by: Thomas Huth <thuth@redhat.com>

Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>

> ---
>  lib/s390x/sclp-console.c | 79 +++++++++++++++++++++++++++++++++++++---
>  lib/s390x/sclp.h         |  8 ++++
>  s390x/Makefile           |  1 +
>  3 files changed, 82 insertions(+), 6 deletions(-)
> 
> diff --git a/lib/s390x/sclp-console.c b/lib/s390x/sclp-console.c
> index fa36a6a42381..8c4bf68cbbab 100644
> --- a/lib/s390x/sclp-console.c
> +++ b/lib/s390x/sclp-console.c
> @@ -89,6 +89,10 @@ static char lm_buff[120];
>  static unsigned char lm_buff_off;
>  static struct spinlock lm_buff_lock;
>  
> +static char read_buf[4096];
> +static int read_index = sizeof(read_buf) - 1;
> +static int read_buf_end = 0;
> +
>  static void sclp_print_ascii(const char *str)
>  {
>  	int len = strlen(str);
> @@ -185,7 +189,7 @@ static void sclp_print_lm(const char *str)
>   * indicating which messages the control program (we) want(s) to
>   * send/receive.
>   */
> -static void sclp_set_write_mask(void)
> +static void sclp_write_event_mask(int receive_mask, int send_mask)
>  {
>  	WriteEventMask *sccb = (void *)_sccb;
>  
> @@ -195,18 +199,27 @@ static void sclp_set_write_mask(void)
>  	sccb->h.function_code = SCLP_FC_NORMAL_WRITE;
>  	sccb->mask_length = sizeof(sccb_mask_t);
>  
> -	/* For now we don't process sclp input. */
> -	sccb->cp_receive_mask = 0;
> -	/* We send ASCII and line mode. */
> -	sccb->cp_send_mask = SCLP_EVENT_MASK_MSG_ASCII | SCLP_EVENT_MASK_MSG;
> +	sccb->cp_receive_mask = receive_mask;
> +	sccb->cp_send_mask = send_mask;
>  
>  	sclp_service_call(SCLP_CMD_WRITE_EVENT_MASK, sccb);
>  	assert(sccb->h.response_code == SCLP_RC_NORMAL_COMPLETION);
>  }
>  
> +static void sclp_console_enable_read(void)
> +{
> +	sclp_write_event_mask(SCLP_EVENT_MASK_MSG_ASCII, SCLP_EVENT_MASK_MSG_ASCII | SCLP_EVENT_MASK_MSG);
> +}
> +
> +static void sclp_console_disable_read(void)
> +{
> +	sclp_write_event_mask(0, SCLP_EVENT_MASK_MSG_ASCII | SCLP_EVENT_MASK_MSG);
> +}
> +
>  void sclp_console_setup(void)
>  {
> -	sclp_set_write_mask();
> +	/* We send ASCII and line mode. */
> +	sclp_write_event_mask(0, SCLP_EVENT_MASK_MSG_ASCII | SCLP_EVENT_MASK_MSG);
>  }
>  
>  void sclp_print(const char *str)
> @@ -227,3 +240,57 @@ void sclp_print(const char *str)
>  	sclp_print_ascii(str);
>  	sclp_print_lm(str);
>  }
> +
> +static int console_refill_read_buffer(void)
> +{
> +	const int max_event_buffer_len = SCCB_SIZE - offsetof(ReadEventDataAsciiConsole, ebh);
> +	ReadEventDataAsciiConsole *sccb = (void *)_sccb;
> +	const int event_buffer_ascii_recv_header_len = sizeof(sccb->ebh) + sizeof(sccb->type);
> +	int ret = -1;
> +
> +	sclp_console_enable_read();
> +
> +	sclp_mark_busy();
> +	memset(sccb, 0, SCCB_SIZE);
> +	sccb->h.length = PAGE_SIZE;
> +	sccb->h.function_code = SCLP_UNCONDITIONAL_READ;
> +	sccb->h.control_mask[2] = SCLP_CM2_VARIABLE_LENGTH_RESPONSE;
> +
> +	sclp_service_call(SCLP_CMD_READ_EVENT_DATA, sccb);
> +
> +	if (sccb->h.response_code == SCLP_RC_NO_EVENT_BUFFERS_STORED ||
> +	    sccb->ebh.type != SCLP_EVENT_ASCII_CONSOLE_DATA ||
> +	    sccb->type != SCLP_EVENT_ASCII_TYPE_DATA_STREAM_FOLLOWS) {
> +		ret = -1;
> +		goto out;
> +	}
> +
> +	assert(sccb->ebh.length <= max_event_buffer_len);
> +	assert(sccb->ebh.length > event_buffer_ascii_recv_header_len);
> +
> +	read_buf_end = sccb->ebh.length - event_buffer_ascii_recv_header_len;
> +
> +	assert(read_buf_end <= sizeof(read_buf));
> +	memcpy(read_buf, sccb->data, read_buf_end);
> +
> +	read_index = 0;
> +	ret = 0;
> +
> +out:
> +	sclp_console_disable_read();
> +
> +	return ret;
> +}
> +
> +int __getchar(void)
> +{
> +	int ret;
> +
> +	if (read_index >= read_buf_end) {
> +		ret = console_refill_read_buffer();
> +		if (ret < 0)
> +			return ret;
> +	}
> +
> +	return read_buf[read_index++];
> +}
> diff --git a/lib/s390x/sclp.h b/lib/s390x/sclp.h
> index fead007a6037..e48a5a3df20b 100644
> --- a/lib/s390x/sclp.h
> +++ b/lib/s390x/sclp.h
> @@ -313,6 +313,14 @@ typedef struct ReadEventData {
>  	uint32_t mask;
>  } __attribute__((packed)) ReadEventData;
>  
> +#define SCLP_EVENT_ASCII_TYPE_DATA_STREAM_FOLLOWS 0
> +typedef struct ReadEventDataAsciiConsole {
> +	SCCBHeader h;
> +	EventBufferHeader ebh;
> +	uint8_t type;
> +	char data[];
> +} __attribute__((packed)) ReadEventDataAsciiConsole;
> +
>  extern char _sccb[];
>  void sclp_setup_int(void);
>  void sclp_handle_ext(void);
> diff --git a/s390x/Makefile b/s390x/Makefile
> index c11f6efbd767..f38f442b9cb1 100644
> --- a/s390x/Makefile
> +++ b/s390x/Makefile
> @@ -75,6 +75,7 @@ cflatobjs += lib/alloc_phys.o
>  cflatobjs += lib/alloc_page.o
>  cflatobjs += lib/vmalloc.o
>  cflatobjs += lib/alloc_phys.o
> +cflatobjs += lib/getchar.o
>  cflatobjs += lib/s390x/io.o
>  cflatobjs += lib/s390x/stack.o
>  cflatobjs += lib/s390x/sclp.o
Janosch Frank April 21, 2022, 2:29 p.m. UTC | #2 
On 4/20/22 15:45, Nico Boehr wrote:
> Add a basic implementation for reading from the SCLP ASCII console. The goal of
> this is to support migration tests on s390x. To know when the migration has been
> finished, we need to listen for a newline on our console.
> 
> Hence, this implementation is focused on the SCLP ASCII console of QEMU and
> currently won't work under e.g. LPAR.
> 
> Signed-off-by: Nico Boehr <nrb@linux.ibm.com>
> Reviewed-by: Thomas Huth <thuth@redhat.com>
> ---
>   lib/s390x/sclp-console.c | 79 +++++++++++++++++++++++++++++++++++++---
>   lib/s390x/sclp.h         |  8 ++++
>   s390x/Makefile           |  1 +
>   3 files changed, 82 insertions(+), 6 deletions(-)
> 
> diff --git a/lib/s390x/sclp-console.c b/lib/s390x/sclp-console.c
> index fa36a6a42381..8c4bf68cbbab 100644
> --- a/lib/s390x/sclp-console.c
> +++ b/lib/s390x/sclp-console.c
> @@ -89,6 +89,10 @@ static char lm_buff[120];
>   static unsigned char lm_buff_off;
>   static struct spinlock lm_buff_lock;
>   
> +static char read_buf[4096];
> +static int read_index = sizeof(read_buf) - 1;
> +static int read_buf_end = 0;
> +
>   static void sclp_print_ascii(const char *str)
>   {
>   	int len = strlen(str);
> @@ -185,7 +189,7 @@ static void sclp_print_lm(const char *str)
>    * indicating which messages the control program (we) want(s) to
>    * send/receive.
>    */
> -static void sclp_set_write_mask(void)
> +static void sclp_write_event_mask(int receive_mask, int send_mask)
>   {
>   	WriteEventMask *sccb = (void *)_sccb;
>   
> @@ -195,18 +199,27 @@ static void sclp_set_write_mask(void)
>   	sccb->h.function_code = SCLP_FC_NORMAL_WRITE;
>   	sccb->mask_length = sizeof(sccb_mask_t);
>   
> -	/* For now we don't process sclp input. */
> -	sccb->cp_receive_mask = 0;
> -	/* We send ASCII and line mode. */
> -	sccb->cp_send_mask = SCLP_EVENT_MASK_MSG_ASCII | SCLP_EVENT_MASK_MSG;
> +	sccb->cp_receive_mask = receive_mask;
> +	sccb->cp_send_mask = send_mask;
>   
>   	sclp_service_call(SCLP_CMD_WRITE_EVENT_MASK, sccb);
>   	assert(sccb->h.response_code == SCLP_RC_NORMAL_COMPLETION);
>   }
>   
> +static void sclp_console_enable_read(void)
> +{
> +	sclp_write_event_mask(SCLP_EVENT_MASK_MSG_ASCII, SCLP_EVENT_MASK_MSG_ASCII | SCLP_EVENT_MASK_MSG);
> +}
> +
> +static void sclp_console_disable_read(void)
> +{
> +	sclp_write_event_mask(0, SCLP_EVENT_MASK_MSG_ASCII | SCLP_EVENT_MASK_MSG);
> +}
> +
>   void sclp_console_setup(void)
>   {
> -	sclp_set_write_mask();
> +	/* We send ASCII and line mode. */
> +	sclp_write_event_mask(0, SCLP_EVENT_MASK_MSG_ASCII | SCLP_EVENT_MASK_MSG);
>   }
>   
>   void sclp_print(const char *str)
> @@ -227,3 +240,57 @@ void sclp_print(const char *str)
>   	sclp_print_ascii(str);
>   	sclp_print_lm(str);
>   }
> +
> +static int console_refill_read_buffer(void)
> +{
> +	const int max_event_buffer_len = SCCB_SIZE - offsetof(ReadEventDataAsciiConsole, ebh);
> +	ReadEventDataAsciiConsole *sccb = (void *)_sccb;
> +	const int event_buffer_ascii_recv_header_len = sizeof(sccb->ebh) + sizeof(sccb->type);
> +	int ret = -1;
> +
> +	sclp_console_enable_read();
> +
> +	sclp_mark_busy();
> +	memset(sccb, 0, SCCB_SIZE);
> +	sccb->h.length = PAGE_SIZE;
> +	sccb->h.function_code = SCLP_UNCONDITIONAL_READ;
> +	sccb->h.control_mask[2] = SCLP_CM2_VARIABLE_LENGTH_RESPONSE;
> +
> +	sclp_service_call(SCLP_CMD_READ_EVENT_DATA, sccb);
> +
> +	if (sccb->h.response_code == SCLP_RC_NO_EVENT_BUFFERS_STORED ||
> +	    sccb->ebh.type != SCLP_EVENT_ASCII_CONSOLE_DATA ||
> +	    sccb->type != SCLP_EVENT_ASCII_TYPE_DATA_STREAM_FOLLOWS) {
> +		ret = -1;
> +		goto out;
> +	}
> +
> +	assert(sccb->ebh.length <= max_event_buffer_len);
> +	assert(sccb->ebh.length > event_buffer_ascii_recv_header_len);
> +
> +	read_buf_end = sccb->ebh.length - event_buffer_ascii_recv_header_len;

Isn't this more like a length of the current read buffer contents?

> +
> +	assert(read_buf_end <= sizeof(read_buf));
> +	memcpy(read_buf, sccb->data, read_buf_end);
> +
> +	read_index = 0;
> +	ret = 0;
> +
> +out:
> +	sclp_console_disable_read();
> +
> +	return ret;
> +}
> +
> +int __getchar(void)
> +{
> +	int ret;
> +
> +	if (read_index >= read_buf_end) {
> +		ret = console_refill_read_buffer();
> +		if (ret < 0)
> +			return ret;
> +	}
> +
> +	return read_buf[read_index++];
> +}
> diff --git a/lib/s390x/sclp.h b/lib/s390x/sclp.h
> index fead007a6037..e48a5a3df20b 100644
> --- a/lib/s390x/sclp.h
> +++ b/lib/s390x/sclp.h
> @@ -313,6 +313,14 @@ typedef struct ReadEventData {
>   	uint32_t mask;
>   } __attribute__((packed)) ReadEventData;
>   
> +#define SCLP_EVENT_ASCII_TYPE_DATA_STREAM_FOLLOWS 0

Hrm, I'm not completely happy with the naming here since I confused it 
to the ebh->type when looking up the constants. But now I understand why 
you chose it.

> +typedef struct ReadEventDataAsciiConsole {
> +	SCCBHeader h;
> +	EventBufferHeader ebh;
> +	uint8_t type;
> +	char data[];
> +} __attribute__((packed)) ReadEventDataAsciiConsole;
> +
>   extern char _sccb[];
>   void sclp_setup_int(void);
>   void sclp_handle_ext(void);
> diff --git a/s390x/Makefile b/s390x/Makefile
> index c11f6efbd767..f38f442b9cb1 100644
> --- a/s390x/Makefile
> +++ b/s390x/Makefile
> @@ -75,6 +75,7 @@ cflatobjs += lib/alloc_phys.o
>   cflatobjs += lib/alloc_page.o
>   cflatobjs += lib/vmalloc.o
>   cflatobjs += lib/alloc_phys.o
> +cflatobjs += lib/getchar.o
>   cflatobjs += lib/s390x/io.o
>   cflatobjs += lib/s390x/stack.o
>   cflatobjs += lib/s390x/sclp.o
Nico Boehr April 22, 2022, 7:50 a.m. UTC | #3 
On Thu, 2022-04-21 at 16:29 +0200, Janosch Frank wrote:
> 
[...]
> > diff --git a/lib/s390x/sclp-console.c b/lib/s390x/sclp-console.c
> > index fa36a6a42381..8c4bf68cbbab 100644
> > --- a/lib/s390x/sclp-console.c
> > +++ b/lib/s390x/sclp-console.c
[...]
> > +       read_buf_end = sccb->ebh.length -
> > event_buffer_ascii_recv_header_len;
> 
> Isn't this more like a length of the current read buffer contents?

Right, thanks, length is a much better name. 

[...]
> > diff --git a/lib/s390x/sclp.h b/lib/s390x/sclp.h
> > index fead007a6037..e48a5a3df20b 100644
> > --- a/lib/s390x/sclp.h
> > +++ b/lib/s390x/sclp.h
> > @@ -313,6 +313,14 @@ typedef struct ReadEventData {
> >         uint32_t mask;
> >   } __attribute__((packed)) ReadEventData;
> >   
> > +#define SCLP_EVENT_ASCII_TYPE_DATA_STREAM_FOLLOWS 0
> 
> Hrm, I'm not completely happy with the naming here since I confused
> it 
> to the ebh->type when looking up the constants. But now I understand
> why 
> you chose it.

Yeah, it sure is confusing.

Maybe it is better if we leave out the "type" entirely, but this might
make it harder to understand where it's coming from:
SCLP_ASCII_RECEIVE_DATA_STREAM_FOLLOWS

Another alternative I thought about is using enums, it won't fix the
naming, but at least it might be clearer to which type it belongs.

Let me know what you think.
Janosch Frank April 22, 2022, 8:01 a.m. UTC | #4 
On 4/22/22 09:50, Nico Boehr wrote:
> On Thu, 2022-04-21 at 16:29 +0200, Janosch Frank wrote:
>>
> [...]
>>> diff --git a/lib/s390x/sclp-console.c b/lib/s390x/sclp-console.c
>>> index fa36a6a42381..8c4bf68cbbab 100644
>>> --- a/lib/s390x/sclp-console.c
>>> +++ b/lib/s390x/sclp-console.c
> [...]
>>> +       read_buf_end = sccb->ebh.length -
>>> event_buffer_ascii_recv_header_len;
>>
>> Isn't this more like a length of the current read buffer contents?
> 
> Right, thanks, length is a much better name.
> 
> [...]
>>> diff --git a/lib/s390x/sclp.h b/lib/s390x/sclp.h
>>> index fead007a6037..e48a5a3df20b 100644
>>> --- a/lib/s390x/sclp.h
>>> +++ b/lib/s390x/sclp.h
>>> @@ -313,6 +313,14 @@ typedef struct ReadEventData {
>>>          uint32_t mask;
>>>    } __attribute__((packed)) ReadEventData;
>>>    
>>> +#define SCLP_EVENT_ASCII_TYPE_DATA_STREAM_FOLLOWS 0
>>
>> Hrm, I'm not completely happy with the naming here since I confused
>> it
>> to the ebh->type when looking up the constants. But now I understand
>> why
>> you chose it.
> 
> Yeah, it sure is confusing.
> 
> Maybe it is better if we leave out the "type" entirely, but this might
> make it harder to understand where it's coming from:
> SCLP_ASCII_RECEIVE_DATA_STREAM_FOLLOWS
> 
> Another alternative I thought about is using enums, it won't fix the
> naming, but at least it might be clearer to which type it belongs.
> 
> Let me know what you think.

It should be fine as is. I don't expect that we have to touch this file 
very often.
diff mbox series

Patch

diff --git a/lib/s390x/sclp-console.c b/lib/s390x/sclp-console.c
index fa36a6a42381..8c4bf68cbbab 100644
--- a/lib/s390x/sclp-console.c
+++ b/lib/s390x/sclp-console.c
@@ -89,6 +89,10 @@  static char lm_buff[120];
 static unsigned char lm_buff_off;
 static struct spinlock lm_buff_lock;
 
+static char read_buf[4096];
+static int read_index = sizeof(read_buf) - 1;
+static int read_buf_end = 0;
+
 static void sclp_print_ascii(const char *str)
 {
 	int len = strlen(str);
@@ -185,7 +189,7 @@  static void sclp_print_lm(const char *str)
  * indicating which messages the control program (we) want(s) to
  * send/receive.
  */
-static void sclp_set_write_mask(void)
+static void sclp_write_event_mask(int receive_mask, int send_mask)
 {
 	WriteEventMask *sccb = (void *)_sccb;
 
@@ -195,18 +199,27 @@  static void sclp_set_write_mask(void)
 	sccb->h.function_code = SCLP_FC_NORMAL_WRITE;
 	sccb->mask_length = sizeof(sccb_mask_t);
 
-	/* For now we don't process sclp input. */
-	sccb->cp_receive_mask = 0;
-	/* We send ASCII and line mode. */
-	sccb->cp_send_mask = SCLP_EVENT_MASK_MSG_ASCII | SCLP_EVENT_MASK_MSG;
+	sccb->cp_receive_mask = receive_mask;
+	sccb->cp_send_mask = send_mask;
 
 	sclp_service_call(SCLP_CMD_WRITE_EVENT_MASK, sccb);
 	assert(sccb->h.response_code == SCLP_RC_NORMAL_COMPLETION);
 }
 
+static void sclp_console_enable_read(void)
+{
+	sclp_write_event_mask(SCLP_EVENT_MASK_MSG_ASCII, SCLP_EVENT_MASK_MSG_ASCII | SCLP_EVENT_MASK_MSG);
+}
+
+static void sclp_console_disable_read(void)
+{
+	sclp_write_event_mask(0, SCLP_EVENT_MASK_MSG_ASCII | SCLP_EVENT_MASK_MSG);
+}
+
 void sclp_console_setup(void)
 {
-	sclp_set_write_mask();
+	/* We send ASCII and line mode. */
+	sclp_write_event_mask(0, SCLP_EVENT_MASK_MSG_ASCII | SCLP_EVENT_MASK_MSG);
 }
 
 void sclp_print(const char *str)
@@ -227,3 +240,57 @@  void sclp_print(const char *str)
 	sclp_print_ascii(str);
 	sclp_print_lm(str);
 }
+
+static int console_refill_read_buffer(void)
+{
+	const int max_event_buffer_len = SCCB_SIZE - offsetof(ReadEventDataAsciiConsole, ebh);
+	ReadEventDataAsciiConsole *sccb = (void *)_sccb;
+	const int event_buffer_ascii_recv_header_len = sizeof(sccb->ebh) + sizeof(sccb->type);
+	int ret = -1;
+
+	sclp_console_enable_read();
+
+	sclp_mark_busy();
+	memset(sccb, 0, SCCB_SIZE);
+	sccb->h.length = PAGE_SIZE;
+	sccb->h.function_code = SCLP_UNCONDITIONAL_READ;
+	sccb->h.control_mask[2] = SCLP_CM2_VARIABLE_LENGTH_RESPONSE;
+
+	sclp_service_call(SCLP_CMD_READ_EVENT_DATA, sccb);
+
+	if (sccb->h.response_code == SCLP_RC_NO_EVENT_BUFFERS_STORED ||
+	    sccb->ebh.type != SCLP_EVENT_ASCII_CONSOLE_DATA ||
+	    sccb->type != SCLP_EVENT_ASCII_TYPE_DATA_STREAM_FOLLOWS) {
+		ret = -1;
+		goto out;
+	}
+
+	assert(sccb->ebh.length <= max_event_buffer_len);
+	assert(sccb->ebh.length > event_buffer_ascii_recv_header_len);
+
+	read_buf_end = sccb->ebh.length - event_buffer_ascii_recv_header_len;
+
+	assert(read_buf_end <= sizeof(read_buf));
+	memcpy(read_buf, sccb->data, read_buf_end);
+
+	read_index = 0;
+	ret = 0;
+
+out:
+	sclp_console_disable_read();
+
+	return ret;
+}
+
+int __getchar(void)
+{
+	int ret;
+
+	if (read_index >= read_buf_end) {
+		ret = console_refill_read_buffer();
+		if (ret < 0)
+			return ret;
+	}
+
+	return read_buf[read_index++];
+}
diff --git a/lib/s390x/sclp.h b/lib/s390x/sclp.h
index fead007a6037..e48a5a3df20b 100644
--- a/lib/s390x/sclp.h
+++ b/lib/s390x/sclp.h
@@ -313,6 +313,14 @@  typedef struct ReadEventData {
 	uint32_t mask;
 } __attribute__((packed)) ReadEventData;
 
+#define SCLP_EVENT_ASCII_TYPE_DATA_STREAM_FOLLOWS 0
+typedef struct ReadEventDataAsciiConsole {
+	SCCBHeader h;
+	EventBufferHeader ebh;
+	uint8_t type;
+	char data[];
+} __attribute__((packed)) ReadEventDataAsciiConsole;
+
 extern char _sccb[];
 void sclp_setup_int(void);
 void sclp_handle_ext(void);
diff --git a/s390x/Makefile b/s390x/Makefile
index c11f6efbd767..f38f442b9cb1 100644
--- a/s390x/Makefile
+++ b/s390x/Makefile
@@ -75,6 +75,7 @@  cflatobjs += lib/alloc_phys.o
 cflatobjs += lib/alloc_page.o
 cflatobjs += lib/vmalloc.o
 cflatobjs += lib/alloc_phys.o
+cflatobjs += lib/getchar.o
 cflatobjs += lib/s390x/io.o
 cflatobjs += lib/s390x/stack.o
 cflatobjs += lib/s390x/sclp.o