2015-04-07 14:29:38

by Daniel J Blueman

Subject: [PATCH] x86: Fix earlyprintk ttyS2/3

Quite a few platforms use ttyS2 for their serial-over-LAN, so fix early
printk support for ttyS2 and 3, avoiding the need to hard-code the IO port.

Signed-off-by: Daniel J Blueman <[email protected]>
---
arch/x86/boot/early_serial_console.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/arch/x86/boot/early_serial_console.c b/arch/x86/boot/early_serial_console.c
index 5df2869..4f4c2e6 100644
--- a/arch/x86/boot/early_serial_console.c
+++ b/arch/x86/boot/early_serial_console.c
@@ -71,15 +71,16 @@ static void parse_earlyprintk(void)
else
pos = e - arg;
} else if (!strncmp(arg + pos, "ttyS", 4)) {
- static const int bases[] = { 0x3f8, 0x2f8 };
- int idx = 0;
+ static const int bases[] = {0x3f8, 0x2f8, 0x3e8, 0x2e8};
+ unsigned idx = 0;

if (!strncmp(arg + pos, "ttyS", 4))
pos += 4;

- if (arg[pos++] == '1')
- idx = 1;
+ if ((arg[pos] - '0') < (sizeof(bases) / sizeof(bases[0])))
+ idx = arg[pos] - '0';

+ pos++;
port = bases[idx];
}

--
2.1.0

2015-04-07 14:39:18

by Joe Perches

Subject: Re: [PATCH] x86: Fix earlyprintk ttyS2/3

On Tue, 2015-04-07 at 22:29 +0800, Daniel J Blueman wrote:
> Quite a few platforms use ttyS2 for their serial-over-LAN, so fix early
> printk support for ttyS2 and 3, avoiding the need to hard-code the IO port.
[]
> diff --git a/arch/x86/boot/early_serial_console.c b/arch/x86/boot/early_serial_console.c
[]
> @@ -71,15 +71,16 @@ static void parse_earlyprintk(void)
> else
> pos = e - arg;
> } else if (!strncmp(arg + pos, "ttyS", 4)) {
> - static const int bases[] = { 0x3f8, 0x2f8 };
> - int idx = 0;
> + static const int bases[] = {0x3f8, 0x2f8, 0x3e8, 0x2e8};
> + unsigned idx = 0;
>
> if (!strncmp(arg + pos, "ttyS", 4))
> pos += 4;
>
> - if (arg[pos++] == '1')
> - idx = 1;
> + if ((arg[pos] - '0') < (sizeof(bases) / sizeof(bases[0])))
> + idx = arg[pos] - '0';

This doesn't prevent negative indexing in case someone
does something like shift key typo "ttyS!" for "ttyS1".

I've done that.

2015-04-07 14:45:59

by Ingo Molnar

Subject: Re: [PATCH] x86: Fix earlyprintk ttyS2/3

* Daniel J Blueman <[email protected]> wrote:

> Quite a few platforms use ttyS2 for their serial-over-LAN, so fix early
> printk support for ttyS2 and 3, avoiding the need to hard-code the IO port.

Nice.

>
> Signed-off-by: Daniel J Blueman <[email protected]>
> ---
> arch/x86/boot/early_serial_console.c | 9 +++++----
> 1 file changed, 5 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/boot/early_serial_console.c b/arch/x86/boot/early_serial_console.c
> index 5df2869..4f4c2e6 100644
> --- a/arch/x86/boot/early_serial_console.c
> +++ b/arch/x86/boot/early_serial_console.c
> @@ -71,15 +71,16 @@ static void parse_earlyprintk(void)
> else
> pos = e - arg;
> } else if (!strncmp(arg + pos, "ttyS", 4)) {
> - static const int bases[] = { 0x3f8, 0x2f8 };
> - int idx = 0;
> + static const int bases[] = {0x3f8, 0x2f8, 0x3e8, 0x2e8};
> + unsigned idx = 0;
>
> if (!strncmp(arg + pos, "ttyS", 4))
> pos += 4;

Btw., that's a weird pattern: why do the strncmp() twice? We already
know that we matched, in this branch. Could be written as:

pos += 4;

?

>
> - if (arg[pos++] == '1')
> - idx = 1;
> + if ((arg[pos] - '0') < (sizeof(bases) / sizeof(bases[0])))
> + idx = arg[pos] - '0';

Nit: use ARRAY_SIZE()?

Not so nit: with your change, a typo in boot parameters like "ttyS-"
would underflow the index and dereference randomly around bases[] with
a negative index:

Also, higher indices like "ttyS4" will overflow beyond the end of the
array.

Please add proper bounds checking and warning messages.

>
> + pos++;
> port = bases[idx];
> }

Thanks,

Ingo

2015-04-07 15:00:57

by Daniel J Blueman

Subject: Re: [PATCH] x86: Fix earlyprintk ttyS2/3

On Tue, Apr 7, 2015 at 10:39 PM, Joe Perches <[email protected]> wrote:
> On Tue, 2015-04-07 at 22:29 +0800, Daniel J Blueman wrote:
>> Quite a few platforms use ttyS2 for their serial-over-LAN, so fix
>> early
>> printk support for ttyS2 and 3, avoiding the need to hard-code the
>> IO port.
> []
>> diff --git a/arch/x86/boot/early_serial_console.c
>> b/arch/x86/boot/early_serial_console.c
> []
>> @@ -71,15 +71,16 @@ static void parse_earlyprintk(void)
>> else
>> pos = e - arg;
>> } else if (!strncmp(arg + pos, "ttyS", 4)) {
>> - static const int bases[] = { 0x3f8, 0x2f8 };
>> - int idx = 0;
>> + static const int bases[] = {0x3f8, 0x2f8, 0x3e8, 0x2e8};
>> + unsigned idx = 0;
>>
>> if (!strncmp(arg + pos, "ttyS", 4))
>> pos += 4;
>>
>> - if (arg[pos++] == '1')
>> - idx = 1;
>> + if ((arg[pos] - '0') < (sizeof(bases) / sizeof(bases[0])))
>> + idx = arg[pos] - '0';
>
> This doesn't prevent negative indexing in case someone
> does something like shift key typo "ttyS!" for "ttyS1".
>
> I've done that.

Gah; late night coding syndrome. Adding the missing cast in the first
case only:

Subject: [PATCH v2] x86: Fix earlyprintk ttyS2/3

Quite a few platforms use ttyS2 for their serial-over-LAN, so fix early
printk support for ttyS2 and 3, avoiding the need to hard-code the IO
port.

v2: Add missing unsigned cast to correct range check

Signed-off-by: Daniel J Blueman <[email protected]>
---
arch/x86/boot/early_serial_console.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/arch/x86/boot/early_serial_console.c
b/arch/x86/boot/early_serial_console.c
index 5df2869..3d7f112 100644
--- a/arch/x86/boot/early_serial_console.c
+++ b/arch/x86/boot/early_serial_console.c
@@ -71,15 +71,16 @@ static void parse_earlyprintk(void)
else
pos = e - arg;
} else if (!strncmp(arg + pos, "ttyS", 4)) {
- static const int bases[] = { 0x3f8, 0x2f8 };
+ static const int bases[] = {0x3f8, 0x2f8, 0x3e8, 0x2e8};
int idx = 0;

if (!strncmp(arg + pos, "ttyS", 4))
pos += 4;

- if (arg[pos++] == '1')
- idx = 1;
+ if ((unsigned)(arg[pos] - '0') < (sizeof(bases) / sizeof(bases[0])))
+ idx = arg[pos] - '0';

+ pos++;
port = bases[idx];
}

--