Hello,
(Cc Andrew, Grant)
On (08/25/17 17:37), Rob Herring wrote:
> On Sat, Aug 26, 2017 at 02:36:47AM +0900, Sergey Senozhatsky wrote:
> > If add_preferred_console() returns error then we must free a
> > copy of `of_stdout_options' that we create right before the
> > console registration.
> >
> > Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx>
> > ---
> > drivers/of/base.c | 11 +++++++++--
> > 1 file changed, 9 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/of/base.c b/drivers/of/base.c
> > index 260d33c0f26c..9fcf7011d206 100644
> > --- a/drivers/of/base.c
> > +++ b/drivers/of/base.c
> > @@ -1779,10 +1779,17 @@ EXPORT_SYMBOL_GPL(of_alias_get_highest_id);
> > */
> > bool of_console_check(struct device_node *dn, char *name, int index)
> > {
> > + bool ret;
> > + char *options;
> > +
> > if (!dn || dn != of_stdout || console_set_on_cmdline)
> > return false;
> > - return !add_preferred_console(name, index,
> > - kstrdup(of_stdout_options, GFP_KERNEL));
> > +
> > + options = kstrdup(of_stdout_options, GFP_KERNEL);
>
> The real question is why are we doing the kstrdup in the first place.
I wouldn't know :) let's find that out
the patch used to pass `of_stdout_options' in v1 and v2
https://patches.linaro.org/patch/41559/
starting from v3 options are kstrdup-ed
https://patchwork.kernel.org/patch/5398761/
> AFAICT, the only reason is options within the console/printk code is a
> char * and not a const char *. I can't imagine that options need
> modifications?
as far as I can tell, ->match callback has side efects, sometimes.
for example,
register_console()
newcon->match(newcon, c->name, c->index, c->options)
for amba-pl011.c ends up in pl011_console_match(), which calls
uart_parse_earlycon(options, &iotype, &addr, &options)
and uart_parse_earlycon() does the following
int uart_parse_earlycon(char *p, unsigned char *iotype, resource_size_t *addr,
char **options)
{
if (strncmp(p, "mmio,", 5) == 0) {
*iotype = UPIO_MEM;
p += 5;
} else if (strncmp(p, "mmio16,", 7) == 0) {
*iotype = UPIO_MEM16;
p += 7;
} else if (strncmp(p, "mmio32,", 7) == 0) {
*iotype = UPIO_MEM32;
p += 7;
} else if (strncmp(p, "mmio32be,", 9) == 0) {
*iotype = UPIO_MEM32BE;
p += 9;
} else if (strncmp(p, "mmio32native,", 13) == 0) {
*iotype = IS_ENABLED(CONFIG_CPU_BIG_ENDIAN) ?
UPIO_MEM32BE : UPIO_MEM32;
p += 13;
} else if (strncmp(p, "io,", 3) == 0) {
*iotype = UPIO_PORT;
p += 3;
} else if (strncmp(p, "0x", 2) == 0) {
*iotype = UPIO_MEM;
} else {
return -EINVAL;
}
/*
* Before you replace it with kstrtoull(), think about options separator
* (',') it will not tolerate
*/
*addr = simple_strtoull(p, NULL, 0);
p = strchr(p, ',');
if (p)
p++;
*options = p;
return 0;
}
that's just one example I found after a very quick grepping. may be
there are other control paths that can change ->options.
wondering if something like this was the reason for kstrdup().
-ss
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