From: DJ Delorie <email@example.com>
To: "Madhavan T. Venkataraman" <firstname.lastname@example.org>
Subject: Re: [RFC PATCH v3 2/5] x86: Support for Static Trampolines
Date: Thu, 28 Jan 2021 17:17:55 -0500 [thread overview]
Message-ID: <email@example.com> (raw)
In-Reply-To: <firstname.lastname@example.org> (email@example.com)
"Madhavan T. Venkataraman" <firstname.lastname@example.org> writes:
>> Extern, but local to this port, yes?
> Yes. So, is this declaration acceptable?
>>> + /* Initialize the dynamic trampoline. */
>> Should these new APIs be inside #if FFI_EXEC_STATIC_TRAMP ?
> Strictly speaking, these should be inside that ifdef. I did it this
> way to avoid too many ifdefs in the code. If you prefer I put them
> inside the ifdefs, I will do it. I will try to minimize the number of
> ifdefs somehow.
No, it's ok, I was just worried that if ffi_tramp_is_present was in an
#ifdef any callers would be too - but as you noted in another email,
there's always a ffi_tramp_is_present even if it always returns false.
>> This hack to detect CET should be replaced by the logic in ffitarget.h,
>> or add a #define CET_ENABLED to ffitarget.h
> So, _CET_ENDBR for x64 is either defined as:
> If CET is present:
> #define _CET_ENDBR endbr64
> #define _CET_ENDBR
> So, it is always defined. So, I cannot do something like:
I was thinking of the conditionals in src/x86/ffitarget.h:
#if !defined(GENERATE_LIBFFI_MAP) && defined(__ASSEMBLER__) \
Obviously you'd omit the __ASSEMBLER__ one ;-)
If you duplicate the ffitarget.h logic you get the same results.
>> Copies first argument to %r10, discards return address and arg - closure
>> will return to whoever called it's caller. I'm not sure how this works,
>> which means *at least* a comment needs to be here ;-)
> The target code in this case is the alt entry point.
> This is what the alt code is doing:
> - load the data (closure) address in r10
> - discard the original value of r10 saved on the stack
> since we are using r10 we don't need its original value
> - restore the stack back to what it was when the static trampoline was
These kinds of short notes should be useful inline comments in the assembler:
movq 8(%rsp), %r10 /* load closure */
> I could add a small comment saying "see comment above trampoline_code_table".
> Is that acceptable?
That would be good too :-)
next prev parent reply other threads:[~2021-01-28 22:18 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1ef5c7e1c9a6ebb140a476ba555ec955681f4fba>
2021-01-15 18:46 ` [RFC PATCH v3 0/5] Libffi " madvenka
2021-01-15 18:46 ` [RFC PATCH v3 1/5] " madvenka
2021-01-27 3:31 ` DJ Delorie
2021-01-27 21:51 ` Madhavan T. Venkataraman
2021-01-27 22:15 ` DJ Delorie
2021-01-27 22:43 ` Madhavan T. Venkataraman
2021-01-15 18:46 ` [RFC PATCH v3 2/5] x86: Support for " madvenka
2021-01-27 3:31 ` DJ Delorie
2021-01-28 21:59 ` Madhavan T. Venkataraman
2021-01-28 22:17 ` DJ Delorie [this message]
2021-01-28 23:25 ` Madhavan T. Venkataraman
2021-01-29 2:09 ` DJ Delorie
2021-01-29 2:38 ` Madhavan T. Venkataraman
2021-01-29 2:48 ` DJ Delorie
2021-01-29 3:24 ` Madhavan T. Venkataraman
2021-01-29 6:07 ` DJ Delorie
2021-02-01 19:46 ` DJ Delorie
2021-01-15 18:46 ` [RFC PATCH v3 3/5] i386: " madvenka
2021-01-15 18:46 ` [RFC PATCH v3 4/5] arm64: " madvenka
2021-01-15 18:46 ` [RFC PATCH v3 5/5] arm: " madvenka
2021-01-26 23:41 ` [RFC PATCH v3 0/5] Libffi " Anthony Green
2021-01-27 17:20 ` Madhavan T. Venkataraman
2021-01-27 18:00 ` Anthony Green
2021-01-27 19:45 ` Madhavan T. Venkataraman
2021-01-28 14:21 ` Anthony Green
2021-01-28 17:01 ` Madhavan T. Venkataraman
2021-02-05 18:20 ` Madhavan T. Venkataraman
2021-02-05 18:46 ` Anthony Green
2021-02-05 19:38 ` Madhavan T. Venkataraman
2021-02-07 16:09 ` Madhavan T. Venkataraman
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