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Date: Tue, 27 Jul 2021 00:10:45 +0800
From: Guo Ren <guoren@...nel.org>
To: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Al Viro <viro@...iv.linux.org.uk>,
Linus Torvalds <torvalds@...ux-foundation.org>,
linux-csky@...r.kernel.org
Subject: Re: [RFC PATCH 2/2] Revert "csky: Add support for restartable sequence"
Hi Mathieu,
Sorry for forgetting to CC you in the last patch, and that patch has
been merged into master which has the problem of syscall restart.
I still want to keep rseq feature for csky, and implement the
RSEQ_SKIP_FASTPATH for self-test, it that okay?
diff --git a/tools/testing/selftests/rseq/param_test.c
b/tools/testing/selftests/rseq/param_test.c
index 699ad5f93c34..1e67b212ad98 100644
--- a/tools/testing/selftests/rseq/param_test.c
+++ b/tools/testing/selftests/rseq/param_test.c
@@ -208,6 +208,8 @@ unsigned int yield_mod_cnt, nr_abort;
"bnez " INJECT_ASM_REG ", 222b\n\t" \
"333:\n\t"
+#elif defined(__csky__)
+#define RSEQ_SKIP_FASTPATH
#else
#error unsupported target
#endif
diff --git a/tools/testing/selftests/rseq/rseq.h
b/tools/testing/selftests/rseq/rseq.h
index 3f63eb362b92..c3dce298b36c 100644
--- a/tools/testing/selftests/rseq/rseq.h
+++ b/tools/testing/selftests/rseq/rseq.h
@@ -79,6 +79,8 @@ extern int __rseq_handled;
#include <rseq-mips.h>
#elif defined(__s390__)
#include <rseq-s390.h>
+#elif defined(__csky__)
+#include <rseq-csky.h>
#else
#error unsupported target
#endif
diff --git a/tools/testing/selftests/rseq/rseq-csky.h
b/tools/testing/selftests/rseq/rseq-csky.h
new file mode 100644
index 000000000000..ecad40e9aeda
--- /dev/null
+++ b/tools/testing/selftests/rseq/rseq-csky.h
@@ -0,0 +1,71 @@
+/* SPDX-License-Identifier: LGPL-2.1 OR MIT */
+
+#if __ORDER_LITTLE_ENDIAN__ == 1234
+#define RSEQ_SIG 0xc1e6643f /* mtcr r6, cr<31, 15> */
+#else
+#error "Currently, RSEQ only supports Little-Endian version"
+#endif
+
+/*
+ * bar.brwarws: ordering barrier for all load/store instructions
+ * before/after
+ *
+ * |31|30 26|25 21|20 16|15 10|9 5|4 0|
+ * 1 10000 00000 00000 100001 00001 0 bw br aw ar
+ *
+ * b: before
+ * a: after
+ * r: read
+ * w: write
+ *
+ * Here are all combinations:
+ *
+ * bar.brw
+ * bar.br
+ * bar.bw
+ * bar.arw
+ * bar.ar
+ * bar.aw
+ * bar.brwarw
+ * bar.brarw
+ * bar.bwarw
+ * bar.brwar
+ * bar.brwaw
+ * bar.brar
+ * bar.bwaw
+ */
+#define __bar_brw() asm volatile (".long 0x842cc000\n":::"memory")
+#define __bar_br() asm volatile (".long 0x8424c000\n":::"memory")
+#define __bar_bw() asm volatile (".long 0x8428c000\n":::"memory")
+#define __bar_arw() asm volatile (".long 0x8423c000\n":::"memory")
+#define __bar_ar() asm volatile (".long 0x8421c000\n":::"memory")
+#define __bar_aw() asm volatile (".long 0x8422c000\n":::"memory")
+#define __bar_brwarw() asm volatile (".long 0x842fc000\n":::"memory")
+#define __bar_brarw() asm volatile (".long 0x8427c000\n":::"memory")
+#define __bar_bwarw() asm volatile (".long 0x842bc000\n":::"memory")
+#define __bar_brwar() asm volatile (".long 0x842dc000\n":::"memory")
+#define __bar_brwaw() asm volatile (".long 0x842ec000\n":::"memory")
+#define __bar_brar() asm volatile (".long 0x8425c000\n":::"memory")
+#define __bar_brar() asm volatile (".long 0x8425c000\n":::"memory")
+#define __bar_bwaw() asm volatile (".long 0x842ac000\n":::"memory")
+
+#define rseq_smp_mb() __bar_brwarw()
+#define rseq_smp_rmb() __bar_brar()
+#define rseq_smp_wmb() __bar_bwaw()
+
+#define rseq_smp_load_acquire(p) \
+__extension__ ({ \
+ __typeof(*p) ____p1 = RSEQ_READ_ONCE(*p); \
+ __bar_brarw(); \
+ ____p1; \
+})
+
+#define rseq_smp_acquire__after_ctrl_dep() rseq_smp_rmb()
+
+#define rseq_smp_store_release(p, v) \
+do { \
+ __bar_brwaw(); \
+ RSEQ_WRITE_ONCE(*p, v); \
+} while (0)
+
+#include "rseq-skip.h"
On Sat, Jul 24, 2021 at 12:16 AM Mathieu Desnoyers
<mathieu.desnoyers@...icios.com> wrote:
>
> This reverts commit 9866d141a0977ace974400bf1f793dfc163409ce.
>
> The csky rseq support has been merged without ever notifying the rseq
> maintainers, and without any of the required asssembler glue in the rseq
> selftests, which means it is entirely untested.
>
> It is also derived from a non-upstream riscv patch which has known bugs.
I noticed that in [1]:
As Al Viro pointed out on IRC, the rseq_signal_deliver() should go after syscall
restart handling, similarly to what is done on every other supported
architecture.
[1] https://lore.kernel.org/linux-riscv/1257037909.25426.1626705790861.JavaMail.zimbra@efficios.com/
I still want to fixup it, instead of revert it.
>
> The assembly part of this revert should be carefully reviewed by the
> architecture maintainer because it touches code which has changed since
> the merge of the reverted patch.
>
> The rseq selftests assembly glue should be introduced at the same time
> as the architecture rseq support. Without the presence of any test, I
> recommend reverting rseq support from csky for now.
>
> Link: https://lore.kernel.org/lkml/1257037909.25426.1626705790861.JavaMail.zimbra@efficios.com/
> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
> Cc: Guo Ren <guoren@...nel.org>
> Cc: Al Viro <viro@...iv.linux.org.uk>
> Cc: Linus Torvalds <torvalds@...ux-foundation.org>
> Cc: linux-csky@...r.kernel.org
> ---
> arch/csky/Kconfig | 1 -
> arch/csky/kernel/entry.S | 4 ----
> arch/csky/kernel/signal.c | 3 ---
> 3 files changed, 8 deletions(-)
>
> diff --git a/arch/csky/Kconfig b/arch/csky/Kconfig
> index 2716f6395ba7..c9655f09e591 100644
> --- a/arch/csky/Kconfig
> +++ b/arch/csky/Kconfig
> @@ -66,7 +66,6 @@ config CSKY
> select HAVE_PERF_USER_STACK_DUMP
> select HAVE_DMA_CONTIGUOUS
> select HAVE_REGS_AND_STACK_ACCESS_API
> - select HAVE_RSEQ
> select HAVE_STACKPROTECTOR
> select HAVE_SYSCALL_TRACEPOINTS
> select MAY_HAVE_SPARSE_IRQ
> diff --git a/arch/csky/kernel/entry.S b/arch/csky/kernel/entry.S
> index d89afe3b24cc..cc2a7e84c8e5 100644
> --- a/arch/csky/kernel/entry.S
> +++ b/arch/csky/kernel/entry.S
> @@ -50,10 +50,6 @@ ENTRY(csky_systemcall)
> SAVE_ALL TRAP0_SIZE
> zero_fp
> context_tracking
> -#ifdef CONFIG_RSEQ_DEBUG
> - mov a0, sp
> - jbsr rseq_syscall
> -#endif
> psrset ee, ie
>
> lrw r9, __NR_syscalls
> diff --git a/arch/csky/kernel/signal.c b/arch/csky/kernel/signal.c
> index 312f046d452d..3cf08732b142 100644
> --- a/arch/csky/kernel/signal.c
> +++ b/arch/csky/kernel/signal.c
> @@ -175,8 +175,6 @@ static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
> sigset_t *oldset = sigmask_to_save();
> int ret;
>
> - rseq_signal_deliver(ksig, regs);
> -
> /* Are we from a system call? */
> if (in_syscall(regs)) {
> /* Avoid additional syscall restarting via ret_from_exception */
> @@ -262,6 +260,5 @@ asmlinkage void do_notify_resume(struct pt_regs *regs,
>
> if (thread_info_flags & _TIF_NOTIFY_RESUME) {
> tracehook_notify_resume(regs);
> - rseq_handle_notify_resume(NULL, regs);
> }
> }
> --
> 2.20.1
>
--
Best Regards
Guo Ren
ML: https://lore.kernel.org/linux-csky/
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