* [PATCH V3] MIPS: Add get_thread_area syscall
@ 2019-12-16 2:17 Guoyun Sun
2019-12-16 19:33 ` Paul Burton
0 siblings, 1 reply; 3+ messages in thread
From: Guoyun Sun @ 2019-12-16 2:17 UTC (permalink / raw)
To: Ralf Baechle, Paul Burton, James Hogan, Peter Zijlstra,
Christian Brauner, Arnd Bergmann, Heiko Carstens, David Howells,
Geert Uytterhoeven, Catalin Marinas, linux-mips, linux-kernel
Cc: Tiezhu Yang, Xuefeng Li, Guoyun Sun
CRIU(https://criu.org/) tools will dump TLS(Thread Local Storage) by
get_thread_area during checkpoint and restore TLS by set_thread_area during
restore. without this syscall, criu restore will fail on MIPS platform
because a variable with GCC __thread will be invalid.
The following function will be called when criu restore
static inline void restore_tls(tls_t *ptls) {
asm volatile(
"move $4, %0 \n"
"li $2, "__stringify(__NR_set_thread_area)" \n"
"syscall \n"
:
: "r"(*ptls)
: "$4","$2","memory");
the *ptls can be obtained by get_thread_area on MIPS platform when criu
checkpoint. just like this:
static inline void arch_get_tls(tls_t *ptls)
{
asm volatile(
"move $4, %0 \n"
"li $2, "__stringify(__NR_get_thread_area)" \n"
"syscall \n"
:
: "r"(ptls)
: "$4","$2","memory");
}
Signed-off-by: Guoyun Sun <sunguoyun@loongson.cn>
---
arch/mips/kernel/syscall.c | 11 +++++++++++
arch/mips/kernel/syscalls/syscall_n32.tbl | 2 ++
arch/mips/kernel/syscalls/syscall_n64.tbl | 2 ++
arch/mips/kernel/syscalls/syscall_o32.tbl | 2 ++
4 files changed, 17 insertions(+)
diff --git a/arch/mips/kernel/syscall.c b/arch/mips/kernel/syscall.c
index c333e57..7ac78bf 100644
--- a/arch/mips/kernel/syscall.c
+++ b/arch/mips/kernel/syscall.c
@@ -27,6 +27,7 @@
#include <linux/slab.h>
#include <linux/elf.h>
#include <linux/sched/task_stack.h>
+#include <linux/compat.h>
#include <asm/asm.h>
#include <asm/asm-eva.h>
@@ -94,6 +95,16 @@ SYSCALL_DEFINE1(set_thread_area, unsigned long, addr)
return 0;
}
+SYSCALL_DEFINE1(get_thread_area, unsigned long __user *, u_info)
+{
+ struct thread_info *ti = task_thread_info(current);
+
+ if (in_compat_syscall())
+ return put_user(ti->tp_value, (__u32 *)u_info);
+
+ return put_user(ti->tp_value, u_info);
+}
+
static inline int mips_atomic_set(unsigned long addr, unsigned long new)
{
unsigned long old, tmp;
diff --git a/arch/mips/kernel/syscalls/syscall_n32.tbl b/arch/mips/kernel/syscalls/syscall_n32.tbl
index e7c5ab3..3aa4858 100644
--- a/arch/mips/kernel/syscalls/syscall_n32.tbl
+++ b/arch/mips/kernel/syscalls/syscall_n32.tbl
@@ -341,6 +341,8 @@
330 n32 statx sys_statx
331 n32 rseq sys_rseq
332 n32 io_pgetevents compat_sys_io_pgetevents
+333 n32 get_thread_area sys_get_thread_area
+
# 333 through 402 are unassigned to sync up with generic numbers
403 n32 clock_gettime64 sys_clock_gettime
404 n32 clock_settime64 sys_clock_settime
diff --git a/arch/mips/kernel/syscalls/syscall_n64.tbl b/arch/mips/kernel/syscalls/syscall_n64.tbl
index 13cd665..14b6796 100644
--- a/arch/mips/kernel/syscalls/syscall_n64.tbl
+++ b/arch/mips/kernel/syscalls/syscall_n64.tbl
@@ -337,6 +337,8 @@
326 n64 statx sys_statx
327 n64 rseq sys_rseq
328 n64 io_pgetevents sys_io_pgetevents
+329 n64 get_thread_area sys_get_thread_area
+
# 329 through 423 are reserved to sync up with other architectures
424 n64 pidfd_send_signal sys_pidfd_send_signal
425 n64 io_uring_setup sys_io_uring_setup
diff --git a/arch/mips/kernel/syscalls/syscall_o32.tbl b/arch/mips/kernel/syscalls/syscall_o32.tbl
index 353539e..bb4e050 100644
--- a/arch/mips/kernel/syscalls/syscall_o32.tbl
+++ b/arch/mips/kernel/syscalls/syscall_o32.tbl
@@ -380,6 +380,8 @@
366 o32 statx sys_statx
367 o32 rseq sys_rseq
368 o32 io_pgetevents sys_io_pgetevents_time32 compat_sys_io_pgetevents
+369 o32 get_thread_area sys_get_thread_area
+
# room for arch specific calls
393 o32 semget sys_semget
394 o32 semctl sys_semctl compat_sys_semctl
--
2.1.0
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH V3] MIPS: Add get_thread_area syscall
2019-12-16 2:17 [PATCH V3] MIPS: Add get_thread_area syscall Guoyun Sun
@ 2019-12-16 19:33 ` Paul Burton
2019-12-17 1:47 ` 孙国云
0 siblings, 1 reply; 3+ messages in thread
From: Paul Burton @ 2019-12-16 19:33 UTC (permalink / raw)
To: Guoyun Sun
Cc: Ralf Baechle, James Hogan, Peter Zijlstra, Christian Brauner,
Arnd Bergmann, Heiko Carstens, David Howells, Geert Uytterhoeven,
Catalin Marinas, linux-mips, linux-kernel, Tiezhu Yang,
Xuefeng Li
Hi Guoyun,
On Mon, Dec 16, 2019 at 10:17:51AM +0800, Guoyun Sun wrote:
> CRIU(https://criu.org/) tools will dump TLS(Thread Local Storage) by
> get_thread_area during checkpoint and restore TLS by set_thread_area during
> restore. without this syscall, criu restore will fail on MIPS platform
> because a variable with GCC __thread will be invalid.
>
> The following function will be called when criu restore
>
> static inline void restore_tls(tls_t *ptls) {
> asm volatile(
> "move $4, %0 \n"
> "li $2, "__stringify(__NR_set_thread_area)" \n"
> "syscall \n"
> :
> : "r"(*ptls)
> : "$4","$2","memory");
>
> the *ptls can be obtained by get_thread_area on MIPS platform when criu
> checkpoint. just like this:
>
> static inline void arch_get_tls(tls_t *ptls)
> {
> asm volatile(
> "move $4, %0 \n"
> "li $2, "__stringify(__NR_get_thread_area)" \n"
> "syscall \n"
> :
> : "r"(ptls)
> : "$4","$2","memory");
>
> }
Why would you need a syscall for this?
Why not retrieve the value using the rdhwr instruction just like every
other bit of code using thread-local storage does?
ie. something like:
static inline void arch_get_tls(tls_t *ptls)
{
asm("rdhwr %0, $29" : "=r"(*ptls));
}
Thanks,
Paul
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: Re: [PATCH V3] MIPS: Add get_thread_area syscall
2019-12-16 19:33 ` Paul Burton
@ 2019-12-17 1:47 ` 孙国云
0 siblings, 0 replies; 3+ messages in thread
From: 孙国云 @ 2019-12-17 1:47 UTC (permalink / raw)
To: Paul Burton
Cc: Ralf Baechle, James Hogan, Peter Zijlstra, Christian Brauner,
Arnd Bergmann, Heiko Carstens, David Howells, Geert Uytterhoeven,
Catalin Marinas, linux-mips, linux-kernel, Tiezhu Yang,
Xuefeng Li
Dear Paul,
Thank you very much.
I didn`t know this way asm("rdhwr %0, $29" : "=r"(*ptls)) before.Now I have a test for it and it realy can work normally.
I just find get_thread_area syscall at path arch/x86.so I have a implement on MIPS platform. And I think set_thread_area and get_thread_area is matched in pairs.
Now it seems that the get_thread_area syscall is not necessary for criu.
Thanks,
Guoyun Sun
> -----原始邮件-----
> 发件人: "Paul Burton" <paulburton@kernel.org>
> 发送时间: 2019-12-17 03:33:33 (星期二)
> 收件人: "Guoyun Sun" <sunguoyun@loongson.cn>
> 抄送: "Ralf Baechle" <ralf@linux-mips.org>, "James Hogan" <jhogan@kernel.org>, "Peter Zijlstra" <peterz@infradead.org>, "Christian Brauner" <christian.brauner@ubuntu.com>, "Arnd Bergmann" <arnd@arndb.de>, "Heiko Carstens" <heiko.carstens@de.ibm.com>, "David Howells" <dhowells@redhat.com>, "Geert Uytterhoeven" <geert@linux-m68k.org>, "Catalin Marinas" <catalin.marinas@arm.com>, linux-mips@vger.kernel.org, linux-kernel@vger.kernel.org, "Tiezhu Yang" <yangtiezhu@loongson.cn>, "Xuefeng Li" <lixuefeng@loongson.cn>
> 主题: Re: [PATCH V3] MIPS: Add get_thread_area syscall
>
> Hi Guoyun,
>
> On Mon, Dec 16, 2019 at 10:17:51AM +0800, Guoyun Sun wrote:
> > CRIU(https://criu.org/) tools will dump TLS(Thread Local Storage) by
> > get_thread_area during checkpoint and restore TLS by set_thread_area during
> > restore. without this syscall, criu restore will fail on MIPS platform
> > because a variable with GCC __thread will be invalid.
> >
> > The following function will be called when criu restore
> >
> > static inline void restore_tls(tls_t *ptls) {
> > asm volatile(
> > "move $4, %0 \n"
> > "li $2, "__stringify(__NR_set_thread_area)" \n"
> > "syscall \n"
> > :
> > : "r"(*ptls)
> > : "$4","$2","memory");
> >
> > the *ptls can be obtained by get_thread_area on MIPS platform when criu
> > checkpoint. just like this:
> >
> > static inline void arch_get_tls(tls_t *ptls)
> > {
> > asm volatile(
> > "move $4, %0 \n"
> > "li $2, "__stringify(__NR_get_thread_area)" \n"
> > "syscall \n"
> > :
> > : "r"(ptls)
> > : "$4","$2","memory");
> >
> > }
>
> Why would you need a syscall for this?
>
> Why not retrieve the value using the rdhwr instruction just like every
> other bit of code using thread-local storage does?
>
> ie. something like:
>
> static inline void arch_get_tls(tls_t *ptls)
> {
> asm("rdhwr %0, $29" : "=r"(*ptls));
> }
>
> Thanks,
> Paul
</lixuefeng@loongson.cn></yangtiezhu@loongson.cn></catalin.marinas@arm.com></geert@linux-m68k.org></dhowells@redhat.com></heiko.carstens@de.ibm.com></arnd@arndb.de></christian.brauner@ubuntu.com></peterz@infradead.org></jhogan@kernel.org></ralf@linux-mips.org></sunguoyun@loongson.cn></paulburton@kernel.org>
^ permalink raw reply [flat|nested] 3+ messages in thread
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2019-12-16 19:33 ` Paul Burton
2019-12-17 1:47 ` 孙国云
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