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Subject[PATCH V2] MIPS: Add get_thread_area syscall
Date
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 syscall get_thread_area, criu restore will fail on MIPS
platform.because a variable with GCC __thread is 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");

With this patch, 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 | 10 ++++++++++
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, 16 insertions(+)

diff --git a/arch/mips/kernel/syscall.c b/arch/mips/kernel/syscall.c
index c333e57..20bf4c5 100644
--- a/arch/mips/kernel/syscall.c
+++ b/arch/mips/kernel/syscall.c
@@ -94,6 +94,16 @@ 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 (copy_to_user(u_info, &(ti->tp_value), sizeof(ti->tp_value)))
+ return -EFAULT;
+
+ return 0;
+}
+
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
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