linux: add RISC-V rseq signature
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Commit Message
From: Michael Jeanson <mjeanson@efficios.com>
The rseq syscall for the RISC-V architecture was added in Linux 5.18.
Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
---
sysdeps/unix/sysv/linux/riscv/bits/rseq.h | 43 +++++++++++++++++++++++
1 file changed, 43 insertions(+)
create mode 100644 sysdeps/unix/sysv/linux/riscv/bits/rseq.h
Comments
* Mathieu Desnoyers:
> From: Michael Jeanson <mjeanson@efficios.com>
>
> The rseq syscall for the RISC-V architecture was added in Linux 5.18.
>
> Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
I think the current guidance is that if you use Signed-off-by:, newly
added files shouldn't have FSF copyright. With FSF copyright, the year
on new files should start 2022, per FSF guidance.
> +#if __BYTE_ORDER == __LITTLE_ENDIAN
> +#define RSEQ_SIG 0xf1401073
> +#endif
“# define” per our style, I think. (I haven't verified that the number
is okay.)
Thanks,
Florian
----- On Jun 13, 2022, at 4:56 PM, Florian Weimer fweimer@redhat.com wrote:
> * Mathieu Desnoyers:
>
>> From: Michael Jeanson <mjeanson@efficios.com>
>>
>> The rseq syscall for the RISC-V architecture was added in Linux 5.18.
>>
>> Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
>> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
>
> I think the current guidance is that if you use Signed-off-by:, newly
> added files shouldn't have FSF copyright. With FSF copyright, the year
> on new files should start 2022, per FSF guidance.
Do you mean those files should have no copyright text at all, or
should they have a copyright text with the name of the author, or
should we use a SPDX license identifier ?
Thanks,
Mathieu
>
>> +#if __BYTE_ORDER == __LITTLE_ENDIAN
>> +#define RSEQ_SIG 0xf1401073
>> +#endif
>
> “# define” per our style, I think. (I haven't verified that the number
> is okay.)
>
> Thanks,
> Florian
* Mathieu Desnoyers via Libc-alpha:
> ----- On Jun 13, 2022, at 4:56 PM, Florian Weimer fweimer@redhat.com wrote:
>
>> * Mathieu Desnoyers:
>>
>>> From: Michael Jeanson <mjeanson@efficios.com>
>>>
>>> The rseq syscall for the RISC-V architecture was added in Linux 5.18.
>>>
>>> Signed-off-by: Michael Jeanson <mjeanson@efficios.com>
>>> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
>>
>> I think the current guidance is that if you use Signed-off-by:, newly
>> added files shouldn't have FSF copyright. With FSF copyright, the year
>> on new files should start 2022, per FSF guidance.
>
> Do you mean those files should have no copyright text at all, or
> should they have a copyright text with the name of the author, or
> should we use a SPDX license identifier ?
He current guidance is on the wiki:
<https://sourceware.org/glibc/wiki/Contribution%20checklist#Update_copyright_information>
It currently suggests
Copyright 2022 Free Software Foundation, Inc.
for the FSF case (no Signed-off-by: in the commit message), and
Copyright The GNU Toolchain Authors.
for Developer Certificate of Origin case.
new file mode 100644
@@ -0,0 +1,43 @@
+/* Restartable Sequences Linux RISC-V architecture header.
+ Copyright (C) 2021-2022 Free Software Foundation, Inc.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#ifndef _SYS_RSEQ_H
+# error "Never use <bits/rseq.h> directly; include <sys/rseq.h> instead."
+#endif
+
+#include <bits/endian.h>
+
+/*
+ RSEQ_SIG is a signature required before each abort handler code.
+
+ It is a 32-bit value that maps to actual architecture code compiled
+ into applications and libraries. It needs to be defined for each
+ architecture. When choosing this value, it needs to be taken into
+ account that generating invalid instructions may have ill effects on
+ tools like objdump, and may also have impact on the CPU speculative
+ execution efficiency in some cases.
+
+ Select the instruction "csrw mhartid, x0" as the RSEQ_SIG. Unlike
+ other architectures, the ebreak instruction has no immediate field for
+ distinguishing purposes. Hence, ebreak is not suitable as RSEQ_SIG.
+ "csrw mhartid, x0" can also satisfy the RSEQ requirement because it
+ is an uncommon instruction and will raise an illegal instruction
+ exception when executed in all modes. */
+
+#if __BYTE_ORDER == __LITTLE_ENDIAN
+#define RSEQ_SIG 0xf1401073
+#endif