From: Richard Henderson <richard.henderson@linaro.org>
To: Vineet Gupta <vineetg@rivosinc.com>,
Vincent Chen <vincent.chen@sifive.com>
Cc: "Florian Weimer" <fweimer@redhat.com>,
"Rich Felker" <dalias@libc.org>,
"Andrew Waterman" <andrew@sifive.com>,
"Palmer Dabbelt" <palmer@rivosinc.com>,
"Kito Cheng" <kito.cheng@sifive.com>,
"Christoph Müllner" <christoph.muellner@vrull.eu>,
davidlt@rivosinc.com, "Arnd Bergmann" <arnd@arndb.de>,
"Björn Töpel" <bjorn@kernel.org>,
"Philipp Tomsich" <philipp.tomsich@vrull.eu>,
"Szabolcs Nagy" <szabolcs.nagy@arm.com>,
"Andy Chiu" <andy.chiu@sifive.com>,
"Greentime Hu" <greentime.hu@sifive.com>,
"Aaron Durbin" <adurbin@rivosinc.com>,
"Andrew de los Reyes" <adlr@rivosinc.com>,
linux-riscv <linux-riscv@lists.infradead.org>,
"GNU C Library" <libc-alpha@sourceware.org>
Subject: Re: Adding V-ext regs to signal context w/o expanding kernel struct sigcontext to avoid glibc ABI break
Date: Wed, 21 Dec 2022 21:32:51 -0800 [thread overview]
Message-ID: <b67238bf-4b5d-dd17-99ff-88b0270ce10a@linaro.org> (raw)
In-Reply-To: <7430f494-9b43-5e03-c1e9-6b83e2611a11@rivosinc.com>
On 12/21/22 11:52, Vineet Gupta wrote:
> This is not an issue, if we don't change sigcontext (in kernel and glibc) - it is
> essentially the case of existing binaries. kernel still saves regs on user stack, in
> rt_sigframe, its just that userspace is not able to access them in SA_SIGINFO signal
> handers. aarch64 have this implemented this approach and it is likely they can't do
> that either for SVE regs.
aarch64 can certainly access the SVE regs on the signal stack. It simply requires that
you parse the chain of extensions within __reserved to find it.
It's quite well designed, really.
What you can't do is "only" declare a sigcontext_t and be able to construct a new context,
nor copy the entire context via structure assignment.
There is room within the risc-v context for a similar scheme, via
sigcontext.sc_fpregs.q.reserved[3]
E.g.
reserved[0] -> magic
reserved[1] -> displacement to "extension area"
reserved[2] -> size of "extension area"
Thus the area can be located anywhere within 4GB and expand to 4GB.
Not that I'd hope any signal frame would require 4GB. :-)
r~
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next prev parent reply other threads:[~2022-12-22 5:33 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1631497278-29829-1-git-send-email-vincent.chen@sifive.com>
[not found] ` <1631497278-29829-3-git-send-email-vincent.chen@sifive.com>
[not found] ` <871r5sd1zq.fsf@oldenburg.str.redhat.com>
[not found] ` <20210913135247.GL13220@brightrain.aerifal.cx>
[not found] ` <CABvJ_xjGZ3S0oAkT08x4DToQFdcUH06omk2OTT1EHDZRJ-2wKg@mail.gmail.com>
[not found] ` <87sfy5ndid.fsf@oldenburg.str.redhat.com>
[not found] ` <CABvJ_xjSREsdemJkCJMGSx+09jrNoSbXCwuxF0zEQmZtHrWMvg@mail.gmail.com>
[not found] ` <d613968f-0fae-1994-3bee-fb10765167c3@rivosinc.com>
2022-12-20 20:05 ` Adding V-ext regs to signal context w/o expanding kernel struct sigcontext to avoid glibc ABI break Vineet Gupta
2022-12-21 15:53 ` Vincent Chen
2022-12-21 19:45 ` Vineet Gupta
2022-12-21 19:52 ` Vineet Gupta
2022-12-22 3:37 ` Vincent Chen
2022-12-22 19:25 ` Vineet Gupta
2022-12-23 2:27 ` Vincent Chen
2022-12-23 19:42 ` Vineet Gupta
2022-12-22 5:32 ` Richard Henderson [this message]
2022-12-22 18:33 ` Andy Chiu
2022-12-22 20:27 ` Vineet Gupta
2022-12-28 10:53 ` Andy Chiu
2023-01-03 19:17 ` Vineet Gupta
2023-01-04 16:34 ` Andy Chiu
2023-01-04 20:46 ` Vineet Gupta
2023-01-04 21:29 ` Philipp Tomsich
2023-01-04 21:37 ` Andrew Waterman
2023-01-04 22:43 ` Vineet Gupta
2023-01-09 13:33 ` Kito Cheng
2023-01-09 19:16 ` Vineet Gupta
2023-01-10 13:21 ` Kito Cheng
2023-01-10 18:07 ` Auto-enabling V unit and/or use of elf attributes (was Re: Adding V-ext regs to signal context w/o expanding kernel struct sigcontext to avoid glibc ABI break) Vineet Gupta
2023-01-11 1:22 ` Richard Henderson
2023-01-11 4:28 ` Jeff Law
2023-01-11 4:57 ` Richard Henderson
2023-01-11 5:07 ` Jeff Law
2023-01-11 6:00 ` Andy Chiu
2023-01-11 6:20 ` Jeff Law
2023-01-11 9:28 ` Andy Chiu
2023-01-11 12:13 ` Andy Chiu
2023-01-23 12:17 ` Conor Dooley
2023-01-23 13:29 ` Andy Chiu
2023-01-11 5:05 ` Anup Patel
2023-01-11 5:23 ` Richard Henderson
2022-12-22 22:33 ` Adding V-ext regs to signal context w/o expanding kernel struct sigcontext to avoid glibc ABI break Richard Henderson
2022-12-22 23:47 ` Conor Dooley
2022-12-22 23:58 ` Vineet Gupta
2022-12-22 20:30 ` Vineet Gupta
2022-12-22 21:38 ` Andrew Waterman
2022-12-22 1:50 ` Vincent Chen
2022-12-22 5:34 ` Richard Henderson
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