[PATCH] serial: core: Fix a NULL pointer dereference in uart_parse_earlycon()

[PATCH] serial: core: Fix a NULL pointer dereference in uart_parse_earlycon()

[Xiaochun Li]

console=uart and console=pl011 can reach the preferred console matching
path without an options field when a comma is absent from the command
line. In that case uart_parse_earlycon() receives a NULL pointer and
immediately passes it to strncmp(), which triggers a NULL pointer
dereference during console matching.

Address this by returning -EINVAL when the options pointer is missing,
ensuring incomplete console arguments are cleanly rejected while
preserving the behavior of all valid earlycon-style command lines.

Fixes: 73abaf87f01b ("serial: earlycon: Refactor parse_options into serial core")
Signed-off-by: Xiaochun Li <lixiaochun@open-hieco.net>
---
 drivers/tty/serial/serial_core.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index a530ad372b43..02e770bf8bf6 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -2084,7 +2084,8 @@ EXPORT_SYMBOL_GPL(uart_console_write);
 
 /**
  * uart_parse_earlycon - Parse earlycon options
- * @p:	     ptr to 2nd field (ie., just beyond '<name>,')
+ * @p:	     ptr to 2nd field (ie., just beyond '<name>,'); %NULL if
+ *	     no console options were supplied
  * @iotype:  ptr for decoded iotype (out)
  * @addr:    ptr for decoded mapbase/iobase (out)
  * @options: ptr for <options> field; %NULL if not present (out)
@@ -2104,6 +2105,9 @@ EXPORT_SYMBOL_GPL(uart_console_write);
 int uart_parse_earlycon(char *p, enum uart_iotype *iotype,
 			resource_size_t *addr, char **options)
 {
+	if (!p)
+		return -EINVAL;
+
 	if (strncmp(p, "mmio,", 5) == 0) {
 		*iotype = UPIO_MEM;
 		p += 5;
-- 
2.52.0

Re: [PATCH] serial: core: Fix a NULL pointer dereference in uart_parse_earlycon()

[Greg KH]

On Thu, Aug 06, 2026 at 02:10:11PM +0800, Xiaochun Li wrote:
> console=uart and console=pl011 can reach the preferred console matching
> path without an options field when a comma is absent from the command
> line. In that case uart_parse_earlycon() receives a NULL pointer and
> immediately passes it to strncmp(), which triggers a NULL pointer
> dereference during console matching.
> 
> Address this by returning -EINVAL when the options pointer is missing,
> ensuring incomplete console arguments are cleanly rejected while
> preserving the behavior of all valid earlycon-style command lines.
> 
> Fixes: 73abaf87f01b ("serial: earlycon: Refactor parse_options into serial core")
> Signed-off-by: Xiaochun Li <lixiaochun@open-hieco.net>
> ---
>  drivers/tty/serial/serial_core.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
> index a530ad372b43..02e770bf8bf6 100644
> --- a/drivers/tty/serial/serial_core.c
> +++ b/drivers/tty/serial/serial_core.c
> @@ -2084,7 +2084,8 @@ EXPORT_SYMBOL_GPL(uart_console_write);
>  
>  /**
>   * uart_parse_earlycon - Parse earlycon options
> - * @p:	     ptr to 2nd field (ie., just beyond '<name>,')
> + * @p:	     ptr to 2nd field (ie., just beyond '<name>,'); %NULL if
> + *	     no console options were supplied
>   * @iotype:  ptr for decoded iotype (out)
>   * @addr:    ptr for decoded mapbase/iobase (out)
>   * @options: ptr for <options> field; %NULL if not present (out)
> @@ -2104,6 +2105,9 @@ EXPORT_SYMBOL_GPL(uart_console_write);
>  int uart_parse_earlycon(char *p, enum uart_iotype *iotype,
>  			resource_size_t *addr, char **options)
>  {
> +	if (!p)
> +		return -EINVAL;
> +
>  	if (strncmp(p, "mmio,", 5) == 0) {
>  		*iotype = UPIO_MEM;
>  		p += 5;
> -- 
> 2.52.0
> 
> 

How was this tested?

Re: [PATCH] serial: core: Fix a NULL pointer dereference in uart_parse_earlycon()

[Greg KH]

On Thu, Aug 06, 2026 at 02:10:11PM +0800, Xiaochun Li wrote:
> console=uart and console=pl011 can reach the preferred console matching
> path without an options field when a comma is absent from the command
> line. In that case uart_parse_earlycon() receives a NULL pointer and
> immediately passes it to strncmp(), which triggers a NULL pointer
> dereference during console matching.
> 
> Address this by returning -EINVAL when the options pointer is missing,
> ensuring incomplete console arguments are cleanly rejected while
> preserving the behavior of all valid earlycon-style command lines.
> 
> Fixes: 73abaf87f01b ("serial: earlycon: Refactor parse_options into serial core")
> Signed-off-by: Xiaochun Li <lixiaochun@open-hieco.net>
> ---
>  drivers/tty/serial/serial_core.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
> index a530ad372b43..02e770bf8bf6 100644
> --- a/drivers/tty/serial/serial_core.c
> +++ b/drivers/tty/serial/serial_core.c
> @@ -2084,7 +2084,8 @@ EXPORT_SYMBOL_GPL(uart_console_write);
>  
>  /**
>   * uart_parse_earlycon - Parse earlycon options
> - * @p:	     ptr to 2nd field (ie., just beyond '<name>,')
> + * @p:	     ptr to 2nd field (ie., just beyond '<name>,'); %NULL if
> + *	     no console options were supplied
>   * @iotype:  ptr for decoded iotype (out)
>   * @addr:    ptr for decoded mapbase/iobase (out)
>   * @options: ptr for <options> field; %NULL if not present (out)
> @@ -2104,6 +2105,9 @@ EXPORT_SYMBOL_GPL(uart_console_write);
>  int uart_parse_earlycon(char *p, enum uart_iotype *iotype,
>  			resource_size_t *addr, char **options)
>  {
> +	if (!p)
> +		return -EINVAL;
> +
>  	if (strncmp(p, "mmio,", 5) == 0) {
>  		*iotype = UPIO_MEM;
>  		p += 5;
> -- 
> 2.52.0
> 
> 

Hi,

This is the friendly patch-bot of Greg Kroah-Hartman.  You have sent him
a patch that has triggered this response.  He used to manually respond
to these common problems, but in order to save his sanity (he kept
writing the same thing over and over, yet to different people), I was
created.  Hopefully you will not take offence and will fix the problem
in your patch and resubmit it so that it can be accepted into the Linux
kernel tree.

You are receiving this message because of the following common error(s)
as indicated below:

- You have marked a patch with a "Fixes:" tag for a commit that is in an
  older released kernel, yet you do not have a cc: stable line in the
  signed-off-by area at all, which means that the patch will not be
  applied to any older kernel releases.  To properly fix this, please
  follow the documented rules in the
  Documentation/process/stable-kernel-rules.rst file for how to resolve
  this.

If you wish to discuss this problem further, or you have questions about
how to resolve this issue, please feel free to respond to this email and
Greg will reply once he has dug out from the pending patches received
from other developers.

thanks,

greg k-h's patch email bot

Re: [PATCH] serial: core: Fix a NULL pointer dereference in uart_parse_earlycon()

[Xiaochun Li]

On 8/6/2026 2:16 PM, Greg KH wrote:
> On Thu, Aug 06, 2026 at 02:10:11PM +0800, Xiaochun Li wrote:
>> console=uart and console=pl011 can reach the preferred console matching
>> path without an options field when a comma is absent from the command
>> line. In that case uart_parse_earlycon() receives a NULL pointer and
>> immediately passes it to strncmp(), which triggers a NULL pointer
>> dereference during console matching.
>>
>> Address this by returning -EINVAL when the options pointer is missing,
>> ensuring incomplete console arguments are cleanly rejected while
>> preserving the behavior of all valid earlycon-style command lines.
>>
>> Fixes: 73abaf87f01b ("serial: earlycon: Refactor parse_options into serial core")
>> Signed-off-by: Xiaochun Li <lixiaochun@open-hieco.net>
>> ---
>>   drivers/tty/serial/serial_core.c | 6 +++++-
>>   1 file changed, 5 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
>> index a530ad372b43..02e770bf8bf6 100644
>> --- a/drivers/tty/serial/serial_core.c
>> +++ b/drivers/tty/serial/serial_core.c
>> @@ -2084,7 +2084,8 @@ EXPORT_SYMBOL_GPL(uart_console_write);
>>   
>>   /**
>>    * uart_parse_earlycon - Parse earlycon options
>> - * @p:	     ptr to 2nd field (ie., just beyond '<name>,')
>> + * @p:	     ptr to 2nd field (ie., just beyond '<name>,'); %NULL if
>> + *	     no console options were supplied
>>    * @iotype:  ptr for decoded iotype (out)
>>    * @addr:    ptr for decoded mapbase/iobase (out)
>>    * @options: ptr for <options> field; %NULL if not present (out)
>> @@ -2104,6 +2105,9 @@ EXPORT_SYMBOL_GPL(uart_console_write);
>>   int uart_parse_earlycon(char *p, enum uart_iotype *iotype,
>>   			resource_size_t *addr, char **options)
>>   {
>> +	if (!p)
>> +		return -EINVAL;
>> +
>>   	if (strncmp(p, "mmio,", 5) == 0) {
>>   		*iotype = UPIO_MEM;
>>   		p += 5;
>> -- 
>> 2.52.0
>>
>>
> 
> How was this tested?

Hi Greg,

The issue can be reproduced with QEMU using the following kernel
command line:

   earlyprintk=ttyS0 console=uart

Steps:
   1. Build v7.2-rc6 with CONFIG_SERIAL_8250=y and
      CONFIG_SERIAL_8250_CONSOLE=y
   2. Boot with QEMU:
      qemu-system-x86_64 -kernel bzImage -append "earlyprintk=ttyS0 console=uart" -nographic
   3. Kernel panics immediately during console_init()

The "console=uart" argument has no comma, so console_setup() in
kernel/printk/printk.c sets options to NULL. When
univ8250_console_match() is called during register_console(), it
passes that NULL directly to uart_parse_earlycon(), which
dereferences it in strncmp().

Panic log below:

[    0.000000] BUG: kernel NULL pointer dereference, address: 0000000000000000
[    0.000000] #PF: supervisor read access in kernel mode
[    0.000000] #PF: error_code(0x0000) - not-present page
[    0.000000] PGD 0 P4D 0
[    0.000000] Oops: Oops: 0000 [#1] SMP NOPTI
[    0.000000] CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted 7.2.0-rc6 #5 PREEMPT(lazy)
[    0.000000] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.1-0-g3208b098f51a-prebuilt.q4
[    0.000000] RIP: 0010:strncmp+0x1a/0x40
[    0.000000] Code: 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 48 85 d2 74 24 31 c0 eb 0d 84 c9
[    0.000000] RSP: 0000:ffffffff82c03df0 EFLAGS: 00000246
[    0.000000] RAX: 0000000000000000 RBX: ffffffff82c03e20 RCX: ffffffff82c03e20
[    0.000000] RDX: 0000000000000005 RSI: ffffffff82acb7a1 RDI: 0000000000000000
[    0.000000] RBP: 0000000000000000 R08: 0000000000000040 R09: 0000000000000001
[    0.000000] R10: 00000000ffffffea R11: ffffffff82c5cb20 R12: ffffffff82c03e30
[    0.000000] R13: ffffffff82c03e2c R14: 0000000000000001 R15: 0000000000014770
[    0.000000] FS:  0000000000000000(0000) GS:ffff8882b4460000(0000) knlGS:0000000000000000
[    0.000000] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[    0.000000] CR2: 0000000000000000 CR3: 0000000002c30000 CR4: 00000000000000b0
[    0.000000] Call Trace:
[    0.000000]  <TASK>
[    0.000000]  uart_parse_earlycon+0x27/0x140
[    0.000000]  univ8250_console_match+0x5d/0x130
[    0.000000]  ? __do_once_done+0x36/0xa0
[    0.000000]  try_enable_preferred_console+0x62/0x140
[    0.000000]  register_console+0x11a/0x5d0
[    0.000000]  ? __pfx_univ8250_console_init+0x10/0x10
[    0.000000]  univ8250_console_init+0x1f/0x30
[    0.000000]  console_init+0x31/0x110
[    0.000000]  start_kernel+0x50d/0x8b0
[    0.000000]  x86_64_start_reservations+0x18/0x30
[    0.000000]  x86_64_start_kernel+0x10d/0x120
[    0.000000]  common_startup_64+0x13e/0x158
[    0.000000]  </TASK>
[    0.000000] Modules linked in:
[    0.000000] CR2: 0000000000000000
[    0.000000] ---[ end trace 0000000000000000 ]---
[    0.000000] RIP: 0010:strncmp+0x1a/0x40
[    0.000000] Code: 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 48 85 d2 74 24 31 c0 eb 0d 84 c9
[    0.000000] RSP: 0000:ffffffff82c03df0 EFLAGS: 00000246
[    0.000000] RAX: 0000000000000000 RBX: ffffffff82c03e20 RCX: ffffffff82c03e20
[    0.000000] RDX: 0000000000000005 RSI: ffffffff82acb7a1 RDI: 0000000000000000
[    0.000000] RBP: 0000000000000000 R08: 0000000000000040 R09: 0000000000000001
[    0.000000] R10: 00000000ffffffea R11: ffffffff82c5cb20 R12: ffffffff82c03e30
[    0.000000] R13: ffffffff82c03e2c R14: 0000000000000001 R15: 0000000000014770
[    0.000000] FS:  0000000000000000(0000) GS:ffff8882b4460000(0000) knlGS:0000000000000000
[    0.000000] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[    0.000000] CR2: 0000000000000000 CR3: 0000000002c30000 CR4: 00000000000000b0
[    0.000000] Kernel panic - not syncing: Attempted to kill the idle task!
[    0.000000] ---[ end Kernel panic - not syncing: Attempted to kill the idle task! ]---


-- 
Best regards,
Xiaochun Li

Re: [PATCH] serial: core: Fix a NULL pointer dereference in uart_parse_earlycon()

[Greg KH]

On Thu, Aug 06, 2026 at 03:10:26PM +0800, Xiaochun Li wrote:
> On 8/6/2026 2:16 PM, Greg KH wrote:
> > On Thu, Aug 06, 2026 at 02:10:11PM +0800, Xiaochun Li wrote:
> > > console=uart and console=pl011 can reach the preferred console matching
> > > path without an options field when a comma is absent from the command
> > > line. In that case uart_parse_earlycon() receives a NULL pointer and
> > > immediately passes it to strncmp(), which triggers a NULL pointer
> > > dereference during console matching.
> > > 
> > > Address this by returning -EINVAL when the options pointer is missing,
> > > ensuring incomplete console arguments are cleanly rejected while
> > > preserving the behavior of all valid earlycon-style command lines.
> > > 
> > > Fixes: 73abaf87f01b ("serial: earlycon: Refactor parse_options into serial core")
> > > Signed-off-by: Xiaochun Li <lixiaochun@open-hieco.net>
> > > ---
> > >   drivers/tty/serial/serial_core.c | 6 +++++-
> > >   1 file changed, 5 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
> > > index a530ad372b43..02e770bf8bf6 100644
> > > --- a/drivers/tty/serial/serial_core.c
> > > +++ b/drivers/tty/serial/serial_core.c
> > > @@ -2084,7 +2084,8 @@ EXPORT_SYMBOL_GPL(uart_console_write);
> > >   /**
> > >    * uart_parse_earlycon - Parse earlycon options
> > > - * @p:	     ptr to 2nd field (ie., just beyond '<name>,')
> > > + * @p:	     ptr to 2nd field (ie., just beyond '<name>,'); %NULL if
> > > + *	     no console options were supplied
> > >    * @iotype:  ptr for decoded iotype (out)
> > >    * @addr:    ptr for decoded mapbase/iobase (out)
> > >    * @options: ptr for <options> field; %NULL if not present (out)
> > > @@ -2104,6 +2105,9 @@ EXPORT_SYMBOL_GPL(uart_console_write);
> > >   int uart_parse_earlycon(char *p, enum uart_iotype *iotype,
> > >   			resource_size_t *addr, char **options)
> > >   {
> > > +	if (!p)
> > > +		return -EINVAL;
> > > +
> > >   	if (strncmp(p, "mmio,", 5) == 0) {
> > >   		*iotype = UPIO_MEM;
> > >   		p += 5;
> > > -- 
> > > 2.52.0
> > > 
> > > 
> > 
> > How was this tested?
> 
> Hi Greg,
> 
> The issue can be reproduced with QEMU using the following kernel
> command line:
> 
>   earlyprintk=ttyS0 console=uart
> 
> Steps:
>   1. Build v7.2-rc6 with CONFIG_SERIAL_8250=y and
>      CONFIG_SERIAL_8250_CONSOLE=y
>   2. Boot with QEMU:
>      qemu-system-x86_64 -kernel bzImage -append "earlyprintk=ttyS0 console=uart" -nographic
>   3. Kernel panics immediately during console_init()
> 
> The "console=uart" argument has no comma, so console_setup() in
> kernel/printk/printk.c sets options to NULL. When
> univ8250_console_match() is called during register_console(), it
> passes that NULL directly to uart_parse_earlycon(), which
> dereferences it in strncmp().
> 
> Panic log below:
> 
> [    0.000000] BUG: kernel NULL pointer dereference, address: 0000000000000000
> [    0.000000] #PF: supervisor read access in kernel mode
> [    0.000000] #PF: error_code(0x0000) - not-present page
> [    0.000000] PGD 0 P4D 0
> [    0.000000] Oops: Oops: 0000 [#1] SMP NOPTI
> [    0.000000] CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted 7.2.0-rc6 #5 PREEMPT(lazy)
> [    0.000000] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.1-0-g3208b098f51a-prebuilt.q4
> [    0.000000] RIP: 0010:strncmp+0x1a/0x40
> [    0.000000] Code: 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 48 85 d2 74 24 31 c0 eb 0d 84 c9
> [    0.000000] RSP: 0000:ffffffff82c03df0 EFLAGS: 00000246
> [    0.000000] RAX: 0000000000000000 RBX: ffffffff82c03e20 RCX: ffffffff82c03e20
> [    0.000000] RDX: 0000000000000005 RSI: ffffffff82acb7a1 RDI: 0000000000000000
> [    0.000000] RBP: 0000000000000000 R08: 0000000000000040 R09: 0000000000000001
> [    0.000000] R10: 00000000ffffffea R11: ffffffff82c5cb20 R12: ffffffff82c03e30
> [    0.000000] R13: ffffffff82c03e2c R14: 0000000000000001 R15: 0000000000014770
> [    0.000000] FS:  0000000000000000(0000) GS:ffff8882b4460000(0000) knlGS:0000000000000000
> [    0.000000] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [    0.000000] CR2: 0000000000000000 CR3: 0000000002c30000 CR4: 00000000000000b0
> [    0.000000] Call Trace:
> [    0.000000]  <TASK>
> [    0.000000]  uart_parse_earlycon+0x27/0x140
> [    0.000000]  univ8250_console_match+0x5d/0x130
> [    0.000000]  ? __do_once_done+0x36/0xa0
> [    0.000000]  try_enable_preferred_console+0x62/0x140
> [    0.000000]  register_console+0x11a/0x5d0
> [    0.000000]  ? __pfx_univ8250_console_init+0x10/0x10
> [    0.000000]  univ8250_console_init+0x1f/0x30
> [    0.000000]  console_init+0x31/0x110
> [    0.000000]  start_kernel+0x50d/0x8b0
> [    0.000000]  x86_64_start_reservations+0x18/0x30
> [    0.000000]  x86_64_start_kernel+0x10d/0x120
> [    0.000000]  common_startup_64+0x13e/0x158
> [    0.000000]  </TASK>
> [    0.000000] Modules linked in:
> [    0.000000] CR2: 0000000000000000
> [    0.000000] ---[ end trace 0000000000000000 ]---
> [    0.000000] RIP: 0010:strncmp+0x1a/0x40
> [    0.000000] Code: 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 48 85 d2 74 24 31 c0 eb 0d 84 c9
> [    0.000000] RSP: 0000:ffffffff82c03df0 EFLAGS: 00000246
> [    0.000000] RAX: 0000000000000000 RBX: ffffffff82c03e20 RCX: ffffffff82c03e20
> [    0.000000] RDX: 0000000000000005 RSI: ffffffff82acb7a1 RDI: 0000000000000000
> [    0.000000] RBP: 0000000000000000 R08: 0000000000000040 R09: 0000000000000001
> [    0.000000] R10: 00000000ffffffea R11: ffffffff82c5cb20 R12: ffffffff82c03e30
> [    0.000000] R13: ffffffff82c03e2c R14: 0000000000000001 R15: 0000000000014770
> [    0.000000] FS:  0000000000000000(0000) GS:ffff8882b4460000(0000) knlGS:0000000000000000
> [    0.000000] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [    0.000000] CR2: 0000000000000000 CR3: 0000000002c30000 CR4: 00000000000000b0
> [    0.000000] Kernel panic - not syncing: Attempted to kill the idle task!
> [    0.000000] ---[ end Kernel panic - not syncing: Attempted to kill the idle task! ]---

Odd that this hasn't come up in the decades since it has been present :)

thanks,

greg k-h

Re: [PATCH] serial: core: Fix a NULL pointer dereference in uart_parse_earlycon()

[Jiri Slaby]

On 06. 08. 26, 9:29, Greg KH wrote:
> On Thu, Aug 06, 2026 at 03:10:26PM +0800, Xiaochun Li wrote:
>> Panic log below:
>>
>> [    0.000000] BUG: kernel NULL pointer dereference, address: 0000000000000000
>> [    0.000000] #PF: supervisor read access in kernel mode
>> [    0.000000] #PF: error_code(0x0000) - not-present page
>> [    0.000000] PGD 0 P4D 0
>> [    0.000000] Oops: Oops: 0000 [#1] SMP NOPTI
>> [    0.000000] CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted 7.2.0-rc6 #5 PREEMPT(lazy)
>> [    0.000000] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.1-0-g3208b098f51a-prebuilt.q4
>> [    0.000000] RIP: 0010:strncmp+0x1a/0x40
>> [    0.000000] Code: 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 48 85 d2 74 24 31 c0 eb 0d 84 c9
>> [    0.000000] RSP: 0000:ffffffff82c03df0 EFLAGS: 00000246
>> [    0.000000] RAX: 0000000000000000 RBX: ffffffff82c03e20 RCX: ffffffff82c03e20
>> [    0.000000] RDX: 0000000000000005 RSI: ffffffff82acb7a1 RDI: 0000000000000000
>> [    0.000000] RBP: 0000000000000000 R08: 0000000000000040 R09: 0000000000000001
>> [    0.000000] R10: 00000000ffffffea R11: ffffffff82c5cb20 R12: ffffffff82c03e30
>> [    0.000000] R13: ffffffff82c03e2c R14: 0000000000000001 R15: 0000000000014770
>> [    0.000000] FS:  0000000000000000(0000) GS:ffff8882b4460000(0000) knlGS:0000000000000000
>> [    0.000000] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> [    0.000000] CR2: 0000000000000000 CR3: 0000000002c30000 CR4: 00000000000000b0
>> [    0.000000] Call Trace:
>> [    0.000000]  <TASK>
>> [    0.000000]  uart_parse_earlycon+0x27/0x140
...
> Odd that this hasn't come up in the decades since it has been present :)

Everyone follows the documentation :P.

-- 
js
suse labs