Messages in this thread | | | Date | Tue, 7 Apr 2015 16:45:21 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH] x86: Fix earlyprintk ttyS2/3 |
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* Daniel J Blueman <daniel@numascale.com> 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 <daniel@numascale.com> > --- > 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
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