[PATCH 6.4 725/737] LoongArch: Ensure FP/SIMD registers in the core dump file is up to date

[Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>]

6.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Huacai Chen <chenhuacai@xxxxxxxxxxx>

[ Upstream commit 656f9aec07dba7c61d469727494a5d1b18d0bef4 ]

This is a port of commit 379eb01c21795edb4c ("riscv: Ensure the value
of FP registers in the core dump file is up to date").

The values of FP/SIMD registers in the core dump file come from the
thread.fpu. However, kernel saves the FP/SIMD registers only before
scheduling out the process. If no process switch happens during the
exception handling, kernel will not have a chance to save the latest
values of FP/SIMD registers. So it may cause their values in the core
dump file incorrect. To solve this problem, force fpr_get()/simd_get()
to save the FP/SIMD registers into the thread.fpu if the target task
equals the current task.

Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Huacai Chen <chenhuacai@xxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 arch/loongarch/include/asm/fpu.h | 22 ++++++++++++++++++----
 arch/loongarch/kernel/ptrace.c   |  2 ++
 2 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/arch/loongarch/include/asm/fpu.h b/arch/loongarch/include/asm/fpu.h
index 192f8e35d9126..b1dc4200ae6a4 100644
--- a/arch/loongarch/include/asm/fpu.h
+++ b/arch/loongarch/include/asm/fpu.h
@@ -117,16 +117,30 @@ static inline void restore_fp(struct task_struct *tsk)
 		_restore_fp(&tsk->thread.fpu);
 }
 
-static inline union fpureg *get_fpu_regs(struct task_struct *tsk)
+static inline void save_fpu_regs(struct task_struct *tsk)
 {
+	unsigned int euen;
+
 	if (tsk == current) {
 		preempt_disable();
-		if (is_fpu_owner())
+
+		euen = csr_read32(LOONGARCH_CSR_EUEN);
+
+#ifdef CONFIG_CPU_HAS_LASX
+		if (euen & CSR_EUEN_LASXEN)
+			_save_lasx(&current->thread.fpu);
+		else
+#endif
+#ifdef CONFIG_CPU_HAS_LSX
+		if (euen & CSR_EUEN_LSXEN)
+			_save_lsx(&current->thread.fpu);
+		else
+#endif
+		if (euen & CSR_EUEN_FPEN)
 			_save_fp(&current->thread.fpu);
+
 		preempt_enable();
 	}
-
-	return tsk->thread.fpu.fpr;
 }
 
 #endif /* _ASM_FPU_H */
diff --git a/arch/loongarch/kernel/ptrace.c b/arch/loongarch/kernel/ptrace.c
index 5fcffb4523676..286c0ca39eae0 100644
--- a/arch/loongarch/kernel/ptrace.c
+++ b/arch/loongarch/kernel/ptrace.c
@@ -147,6 +147,8 @@ static int fpr_get(struct task_struct *target,
 {
 	int r;
 
+	save_fpu_regs(target);
+
 	if (sizeof(target->thread.fpu.fpr[0]) == sizeof(elf_fpreg_t))
 		r = gfpr_get(target, &to);
 	else
-- 
2.40.1