Matthew Malcomson <matthew.malcom...@arm.com> writes:
> On 23/06/2020 16:48, Richard Sandiford wrote:
>> Matthew Malcomson <matthew.malcom...@arm.com> writes:
>>> @@ -14466,6 +14466,81 @@ aarch64_validate_mcpu (const char *str, const
>>> struct processor **res,
>>> return false;
>>> mfix-cortex-a53-835769
>>> Target Report Var(aarch64_fix_a53_err835769) Init(2) Save
>>> Workaround for ARM Cortex-A53 Erratum number 835769.
>>> diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
>>> index
>>> 35e8242af5fa4c52744fd2c3e2cfee0a617e22bb..8a3fab2964c9bb06c820766d284768751d63ac9a
>>> 100644
>>> --- a/gcc/doc/invoke.texi
>>> +++ b/gcc/doc/invoke.texi
>>> @@ -696,6 +696,7 @@ Objective-C and Objective-C++ Dialects}.
>>> -msign-return-address=@var{scope} @gol
>>> -mbranch-protection=@var{none}|@var{standard}|@var{pac-ret}[+@var{leaf}
>>> +@var{b-key}]|@var{bti} @gol
>>> +-mharden-sls=@var{none}|@var{all}|@var{retbr}|@var{blr} @gol
>>> -march=@var{name} -mcpu=@var{name} -mtune=@var{name} @gol
>>> -moverride=@var{string} -mverbose-cost-dump @gol
>>> -mstack-protector-guard=@var{guard}
>>> -mstack-protector-guard-reg=@var{sysreg} @gol
>>> @@ -17045,6 +17046,15 @@ functions. The optional argument @samp{b-key} can
>>> be used to sign the functions
>>> with the B-key instead of the A-key.
>>> @samp{bti} turns on branch target identification mechanism.
>>>
>>> +@item -mharden-sls=@var{none}|@var{all}|@var{retbr}|@var{blr}
>>> +@opindex mharden-sls
>>> +Enable compiler hardening against straight line speculation (SLS).
>>> +There are two options for hardening against straight line speculation.
>>> +@samp{retbr} allows inserting speculation barriers after every
>>> +@samp{br} and @samp{ret} instruction. While @samp{blr} enables replacing
>>> +@samp{blr} instructions with a @samp{bl} to a function stub.
>>> +@samp{all} enables all SLS hardening, while @samp{none} does not enable
>>> any.
>>
>> OK, so this is even more picky, sorry, but the syntax and description
>> imply to me that you can choose only one of the four options. I think
>> it would be more accurate to say something like:
>>
>> @item -mharden-sls=@var{opts}
>> @opindex mharden-sls
>> Enable compiler hardening against straight line speculation (SLS).
>> @var{opts} is a comma-separated list of the following options:
>> @table @samp
>> @item retbr
>> …
>> @item blr
>> …
>> @end table
>> In addition, @samp{-mharden-sls=all} enables all SLS hardening
>> while @samp{-mharden-sls=none} disables all SLS hardening.
>>
>> (assuming the above behaviour change for “none”)
>>
>> Thanks,
>> Richard
>>
>
> Another "just to check": the same change should be made in the short
> form right? (i.e. the hunk above is now `-mharden-sls=@var{opts}`)
Yeah.
