Patch "LoongArch: Ensure FP/SIMD registers in the core dump file is up to date" has been added to the 6.4-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    LoongArch: Ensure FP/SIMD registers in the core dump file is up to date

to the 6.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     loongarch-ensure-fp-simd-registers-in-the-core-dump-.patch
and it can be found in the queue-6.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 91912d42a93b089d96febe08717606fe7604bbe1
Author: Huacai Chen <chenhuacai@xxxxxxxxxx>
Date:   Sat Aug 26 22:21:57 2023 +0800

    LoongArch: Ensure FP/SIMD registers in the core dump file is up to date
    
    [ 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>

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