On 13/03/2025 3:39 pm, Jan Beulich wrote:
> On 13.03.2025 16:35, Andrew Cooper wrote:
>> On 13/03/2025 1:52 pm, Jan Beulich wrote:
>>> ... before making changes to the involved logic.
>>>
>>> Signed-off-by: Jan Beulich <jbeul...@suse.com>
>>> ---
>>> With this FAST_SYMBOL_LOOKUP may make sense to permit enabling even
>>> when LIVEPATCH=n. Thoughts? (In this case "symbols: centralize and re-
>>> arrange $(all_symbols) calculation" would want pulling ahead.)
>>>
>>> --- a/xen/common/symbols.c
>>> +++ b/xen/common/symbols.c
>>> @@ -260,6 +260,41 @@ unsigned long symbols_lookup_by_name(con
>>> return 0;
>>> }
>>>
>>> +#ifdef CONFIG_SELF_TESTS
>>> +
>>> +static void __init test_lookup(unsigned long addr, const char *expected)
>>> +{
>>> + char buf[KSYM_NAME_LEN + 1];
>>> + const char *name, *symname;
>>> + unsigned long size, offs;
>>> +
>>> + name = symbols_lookup(addr, &size, &offs, buf);
>>> + if ( !name )
>>> + panic("%s: address not found\n", expected);
>>> + if ( offs )
>>> + panic("%s: non-zero offset (%#lx) unexpected\n", expected, offs);
>>> +
>>> + /* Cope with static symbols, where varying file names/paths may be
>>> used. */
>>> + symname = strchr(name, '#');
>>> + symname = symname ? symname + 1 : name;
>>> + if ( strcmp(symname, expected) )
>>> + panic("%s: unexpected symbol name: '%s'\n", expected, symname);
>>> +
>>> + offs = symbols_lookup_by_name(name);
>>> + if ( offs != addr )
>>> + panic("%s: address %#lx unexpected; wanted %#lx\n",
>>> + expected, offs, addr);
>>> +}
>>> +
>>> +static void __init __constructor test_symbols(void)
>>> +{
>>> + /* Be sure to only try this for cf_check functions. */
>> I'm very happy to see the take-up of SELF_TESTs. Although I probably
>> ought to tie it into a Kconfig option to make the errors non-fatal,
>> which I've been meaning to do for a bit.
>>
>> One question though. cf_check is an x86-ism, even if it leaks out into
>> common code.
>>
>> I think you mean "functions emitted into the final image"? If so, I
>> don't think this is relevant then, because ...
>>
>>> + test_lookup((unsigned long)dump_execstate, "dump_execstate");
>>> + test_lookup((unsigned long)test_symbols, __func__);
>> ... taking the function address here forces it to be emitted even if it
>> would otherwise have been inlined.
> No, I really mean cf_check. If we took the address of a non-cf_check
> function, the special gcc13 build's checking would trigger, aiui.
It's GCC-11 sadly. cf_check is part of the function type, and triggers
when a function type check would be relevant. Just casing to an integer
won't trigger it, I don't think.
~Andrew
