On 02.09.2025 00:27, [email protected] wrote: > On Mon, Sep 01, 2025 at 10:14:04AM +0200, Jan Beulich wrote: >> On 29.08.2025 21:27, Stefano Stabellini wrote: >>> On Thu, 28 Aug 2025, [email protected] wrote: >>>> --- /dev/null >>>> +++ b/xen/common/emul/vuart/vuart.c >>>> @@ -0,0 +1,156 @@ >>>> +/* SPDX-License-Identifier: GPL-2.0-only */ >>>> +/* >>>> + * UART emulator framework. >>>> + * >>>> + * Copyright 2025 Ford Motor Company >>>> + */ >>>> + >>>> +#include <xen/err.h> >>>> +#include <xen/sched.h> >>>> +#include <xen/vuart.h> >>>> +#include <xen/xvmalloc.h> >>>> + >>>> +#define for_each_emulator(e) \ >>>> + for ( e = vuart_array_start; e < vuart_array_end; e++ ) >>>> + >>>> +extern const struct vuart_emulator vuart_array_start[]; >>>> +extern const struct vuart_emulator vuart_array_end[]; >>>> + >>>> +static const struct vuart_emulator * >>>> +vuart_match_by_compatible(struct domain *d, const char *compat) >>>> +{ >>>> + const struct vuart_emulator *emulator; >>>> + >>>> + if ( d->console.vuart ) >>>> + return NULL; >>>> + >>>> + for_each_emulator(emulator) >>>> + if ( emulator->compatible && >>>> + !strncmp(emulator->compatible, compat, >>>> + strlen(emulator->compatible)) ) >>> >>> strncmp will continue until the given count even if compat is shorter >> >> Not really, one string having a nul char and the other not having one is a >> difference, at which point comparison will stop. There would be a problem >> if "compat" didn't point to a nul-terminated string, though (and I didn't >> check that aspect, not the least because then "shorter" doesn't really >> make much sense without a length passed in). > > re: NUL-termination: current assumption is that both compat and > emulator->compatible are NUL-terminated. > > Current `compat` comes from the hardcoded NUL-terminated string (vuart_info). > > In case of `compat` is not NUL-terminated (I plan to populate the field from > xl in the future), strncmp() will stop after strlen(emulator->compatible) > bytes.
Which might be too late; if not nul-terminated, "compat" may extend past a page boundary, with the latter page not mapped. Jan
