[PATCH] LoongArch: Add LBT extensions support

From: Qi Hu
Date: Mon Jul 10 2023 - 08:41:13 EST

Loongson Binary Translation (LBT) is used to accelerate binary translation,
which contains 4 scratch registers (scr0 to scr3), x86/ARM eflags (eflags)
and x87 fpu stack pointer (ftop).

This patch support kernel to save/restore these registers, handle the LBT
exception and maintain sigcontext.

Signed-off-by: Qi Hu <huqi@xxxxxxxxxxx>
---
arch/loongarch/Kconfig | 13 ++
arch/loongarch/include/asm/asm-prototypes.h | 1 +
arch/loongarch/include/asm/asmmacro.h | 85 +++++++-
arch/loongarch/include/asm/lbt.h | 115 +++++++++++
arch/loongarch/include/asm/loongarch.h | 4 +
arch/loongarch/include/asm/processor.h | 6 +-
arch/loongarch/include/asm/switch_to.h | 2 +
arch/loongarch/include/asm/thread_info.h | 4 +
arch/loongarch/include/uapi/asm/ptrace.h | 6 +
arch/loongarch/include/uapi/asm/sigcontext.h | 10 +
arch/loongarch/kernel/Makefile | 2 +
arch/loongarch/kernel/asm-offsets.c | 1 +
arch/loongarch/kernel/cpu-probe.c | 14 ++
arch/loongarch/kernel/fpu.S | 9 +-
arch/loongarch/kernel/lbt.S | 166 ++++++++++++++++
arch/loongarch/kernel/process.c | 5 +
arch/loongarch/kernel/ptrace.c | 54 ++++++
arch/loongarch/kernel/signal.c | 193 +++++++++++++++++++
arch/loongarch/kernel/traps.c | 44 ++++-
19 files changed, 722 insertions(+), 12 deletions(-)
create mode 100644 arch/loongarch/include/asm/lbt.h
create mode 100644 arch/loongarch/kernel/lbt.S

diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index 6ae21f4f7dd3..fa7b8a68e69b 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -255,6 +255,9 @@ config AS_HAS_LSX_EXTENSION
config AS_HAS_LASX_EXTENSION
def_bool $(as-instr,xvld \$xr0$(comma)\$a0$(comma)0)

+config AS_HAS_LBT_EXTENSION
+ def_bool $(as-instr,movscr2gr \$a0$(comma)\$scr0)
+
menu "Kernel type and options"

source "kernel/Kconfig.hz"
@@ -535,6 +538,16 @@ config CPU_HAS_LASX

If unsure, say Y.

+config CPU_HAS_LBT
+ bool "Support for Loongson Binary Translation"
+ depends on AS_HAS_LBT_EXTENSION
+ help
+ Loongson Binary Translation (LBT) introduces 4 sketch registers (SCR0 to SCR3),
+ x86/ARM eflags (eflags) and x87 fpu stack pointer (ftop).
+ When this option is enabled, the kernel will support allocation and switching
+ LBT related registers.
+ If you want to use this feature or Loongson Architecture Translator (LAT), say Y.
+
config CPU_HAS_PREFETCH
bool
default y
diff --git a/arch/loongarch/include/asm/asm-prototypes.h b/arch/loongarch/include/asm/asm-prototypes.h
index ed06d3997420..cf8e1a4e7c19 100644
--- a/arch/loongarch/include/asm/asm-prototypes.h
+++ b/arch/loongarch/include/asm/asm-prototypes.h
@@ -1,6 +1,7 @@
/* SPDX-License-Identifier: GPL-2.0 */
#include <linux/uaccess.h>
#include <asm/fpu.h>
+#include <asm/lbt.h>
#include <asm/mmu_context.h>
#include <asm/page.h>
#include <asm/ftrace.h>
diff --git a/arch/loongarch/include/asm/asmmacro.h b/arch/loongarch/include/asm/asmmacro.h
index 79e1d53fea89..203491c0d0fc 100644
--- a/arch/loongarch/include/asm/asmmacro.h
+++ b/arch/loongarch/include/asm/asmmacro.h
@@ -148,12 +148,53 @@

.macro fpu_save_csr thread tmp
movfcsr2gr \tmp, fcsr0
- stptr.w \tmp, \thread, THREAD_FCSR
+ stptr.w \tmp, \thread, THREAD_FCSR
+#ifdef CONFIG_CPU_HAS_LBT
+ andi \tmp, \tmp, FPU_CSR_TM
+ beqz \tmp, 1f
+ /* save ftop */
+ x86mftop \tmp
+ st.b \tmp, \thread, THREAD_FTOP
+ /* Since LSX/LASX is not controlled by TM, we need
+ * to turn off TM before each context switch to ensure
+ * that the order of FPR in memory is independent of TM.
+ */
+ x86clrtm
+ 1 :
+#endif
.endm

- .macro fpu_restore_csr thread tmp
- ldptr.w \tmp, \thread, THREAD_FCSR
- movgr2fcsr fcsr0, \tmp
+ .macro fpu_restore_csr thread tmp0 tmp1
+ ldptr.w \tmp0, \thread, THREAD_FCSR
+ movgr2fcsr fcsr0, \tmp0
+#ifdef CONFIG_CPU_HAS_LBT
+ /* TM bit is always 0 if LBT not supported */
+ andi \tmp0, \tmp0, FPU_CSR_TM
+ beqz \tmp0, 1f
+ /* restore ftop */
+ ld.b \tmp0, \thread, THREAD_FTOP
+ andi \tmp0, \tmp0, 0x7
+ la.pcrel \tmp1, 2f
+ alsl.d \tmp1, \tmp0, \tmp1, 3
+ jr \tmp1
+ 2 :
+ x86mttop 0
+ b 1f
+ x86mttop 1
+ b 1f
+ x86mttop 2
+ b 1f
+ x86mttop 3
+ b 1f
+ x86mttop 4
+ b 1f
+ x86mttop 5
+ b 1f
+ x86mttop 6
+ b 1f
+ x86mttop 7
+ 1 :
+#endif
.endm

.macro fpu_save_cc thread tmp0 tmp1
@@ -353,7 +394,7 @@
.macro lsx_restore_all thread tmp0 tmp1
lsx_restore_data \thread, \tmp0
fpu_restore_cc \thread, \tmp0, \tmp1
- fpu_restore_csr \thread, \tmp0
+ fpu_restore_csr \thread, \tmp0, \tmp1
.endm

.macro lsx_save_upper vd base tmp off
@@ -563,7 +604,7 @@
.macro lasx_restore_all thread tmp0 tmp1
lasx_restore_data \thread, \tmp0
fpu_restore_cc \thread, \tmp0, \tmp1
- fpu_restore_csr \thread, \tmp0
+ fpu_restore_csr \thread, \tmp0, \tmp1
.endm

.macro lasx_save_upper xd base tmp off
@@ -663,6 +704,38 @@
lasx_init_upper $xr31 \tmp
.endm

+ .macro lbt_save_scr thread tmp
+ movscr2gr \tmp, $scr0
+ stptr.d \tmp, \thread, THREAD_SCR0
+ movscr2gr \tmp, $scr1
+ stptr.d \tmp, \thread, THREAD_SCR1
+ movscr2gr \tmp, $scr2
+ stptr.d \tmp, \thread, THREAD_SCR2
+ movscr2gr \tmp, $scr3
+ stptr.d \tmp, \thread, THREAD_SCR3
+ .endm
+
+ .macro lbt_restore_scr thread tmp
+ ldptr.d \tmp, \thread, THREAD_SCR0
+ movgr2scr $scr0, \tmp
+ ldptr.d \tmp, \thread, THREAD_SCR1
+ movgr2scr $scr1, \tmp
+ ldptr.d \tmp, \thread, THREAD_SCR2
+ movgr2scr $scr2, \tmp
+ ldptr.d \tmp, \thread, THREAD_SCR3
+ movgr2scr $scr3, \tmp
+ .endm
+
+ .macro lbt_save_eflag thread tmp
+ x86mfflag \tmp, 0x3f
+ stptr.d \tmp, \thread, THREAD_EFLAGS
+ .endm
+
+ .macro lbt_restore_eflag thread tmp
+ ldptr.d \tmp, \thread, THREAD_EFLAGS
+ x86mtflag \tmp, 0x3f
+ .endm
+
.macro not dst src
nor \dst, \src, zero
.endm
diff --git a/arch/loongarch/include/asm/lbt.h b/arch/loongarch/include/asm/lbt.h
new file mode 100644
index 000000000000..ef1242d10356
--- /dev/null
+++ b/arch/loongarch/include/asm/lbt.h
@@ -0,0 +1,115 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Author: Qi Hu <huqi@xxxxxxxxxxx>
+ * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
+ */
+#ifndef _ASM_LBT_H
+#define _ASM_LBT_H
+
+#include <linux/sched.h>
+#include <linux/sched/task_stack.h>
+#include <linux/ptrace.h>
+#include <linux/thread_info.h>
+#include <linux/bitops.h>
+
+#include <asm/cpu.h>
+#include <asm/cpu-features.h>
+#include <asm/current.h>
+#include <asm/loongarch.h>
+#include <asm/processor.h>
+#include <asm/ptrace.h>
+
+extern void _save_lbt(struct task_struct *);
+extern void _restore_lbt(struct task_struct *);
+
+static inline int is_lbt_enabled(void)
+{
+ if (!cpu_has_lbt)
+ return 0;
+ return (csr_read32(LOONGARCH_CSR_EUEN) & CSR_EUEN_LBTEN) != 0;
+}
+
+static inline int is_lbt_owner(void)
+{
+ return test_thread_flag(TIF_USEDLBT);
+}
+
+#ifdef CONFIG_CPU_HAS_LBT
+
+static inline void enable_lbt(void)
+{
+ if (cpu_has_lbt)
+ csr_xchg32(CSR_EUEN_LBTEN, CSR_EUEN_LBTEN, LOONGARCH_CSR_EUEN);
+}
+
+static inline void disable_lbt(void)
+{
+ if (cpu_has_lbt)
+ csr_xchg32(0, CSR_EUEN_LBTEN, LOONGARCH_CSR_EUEN);
+}
+
+
+static inline void __own_lbt(void)
+{
+ enable_lbt();
+ set_thread_flag(TIF_USEDLBT);
+ KSTK_EUEN(current) |= CSR_EUEN_LBTEN;
+}
+
+static inline void own_lbt_inatomic(int restore)
+{
+ if (cpu_has_lbt && !is_lbt_owner()) {
+ __own_lbt();
+ if (restore)
+ _restore_lbt(current);
+ }
+}
+
+static inline void own_lbt(int restore)
+{
+ preempt_disable();
+ own_lbt_inatomic(restore);
+ preempt_enable();
+}
+
+static inline void lose_lbt_inatomic(int save, struct task_struct *tsk)
+{
+ if (cpu_has_lbt && is_lbt_owner()) {
+ if (save)
+ _save_lbt(tsk);
+
+ disable_lbt();
+ clear_tsk_thread_flag(tsk, TIF_USEDLBT);
+ }
+ KSTK_EUEN(tsk) &= ~(CSR_EUEN_LBTEN);
+}
+
+static inline void lose_lbt(int save)
+{
+ preempt_disable();
+ lose_lbt_inatomic(save, current);
+ preempt_enable();
+}
+
+static inline void init_lbt(void)
+{
+ __own_lbt();
+ set_thread_flag(TIF_LBT_CTX_LIVE);
+}
+#else
+static inline void enable_lbt(void) {}
+static inline void disable_lbt(void) {}
+static inline void own_lbt_inatomic(int restore) {}
+static inline void lose_lbt_inatomic(int save, struct task_struct *tsk) {}
+static inline void own_lbt(int restore) {}
+static inline void lose_lbt(int save) {}
+#endif
+
+static inline int thread_lbt_context_live(void)
+{
+ if (!cpu_has_lbt)
+ return 0;
+ return test_thread_flag(TIF_LBT_CTX_LIVE);
+}
+
+#endif /* _ASM_LBT_H */
diff --git a/arch/loongarch/include/asm/loongarch.h b/arch/loongarch/include/asm/loongarch.h
index 10748a20a2ab..d1324e8accfe 100644
--- a/arch/loongarch/include/asm/loongarch.h
+++ b/arch/loongarch/include/asm/loongarch.h
@@ -1453,6 +1453,10 @@ __BUILD_CSR_OP(tlbidx)
#define FPU_CSR_RU 0x200 /* towards +Infinity */
#define FPU_CSR_RD 0x300 /* towards -Infinity */

+/* Bit 6 of FPU Status Register specify the LBT TOP simulation mode */
+#define FPU_CSR_TM_SHIFT 0x6
+#define FPU_CSR_TM (_ULCAST_(1) << FPU_CSR_TM_SHIFT)
+
#define read_fcsr(source) \
({ \
unsigned int __res; \
diff --git a/arch/loongarch/include/asm/processor.h b/arch/loongarch/include/asm/processor.h
index 636e1c66398c..1c8e2aab3538 100644
--- a/arch/loongarch/include/asm/processor.h
+++ b/arch/loongarch/include/asm/processor.h
@@ -80,8 +80,9 @@ BUILD_FPR_ACCESS(32)
BUILD_FPR_ACCESS(64)

struct loongarch_fpu {
- unsigned int fcsr;
uint64_t fcc; /* 8x8 */
+ uint32_t fcsr;
+ uint32_t ftop;
union fpureg fpr[NUM_FPU_REGS];
};

@@ -174,8 +175,9 @@ struct thread_struct {
* FPU & vector registers \
*/ \
.fpu = { \
- .fcsr = 0, \
.fcc = 0, \
+ .fcsr = 0, \
+ .ftop = 0, \
.fpr = {{{0,},},}, \
}, \
.hbp_break = {0}, \
diff --git a/arch/loongarch/include/asm/switch_to.h b/arch/loongarch/include/asm/switch_to.h
index 24e3094bebab..5b225aff3ba2 100644
--- a/arch/loongarch/include/asm/switch_to.h
+++ b/arch/loongarch/include/asm/switch_to.h
@@ -7,6 +7,7 @@

#include <asm/cpu-features.h>
#include <asm/fpu.h>
+#include <asm/lbt.h>

struct task_struct;

@@ -34,6 +35,7 @@ extern asmlinkage struct task_struct *__switch_to(struct task_struct *prev,
#define switch_to(prev, next, last) \
do { \
lose_fpu_inatomic(1, prev); \
+ lose_lbt_inatomic(1, prev); \
hw_breakpoint_thread_switch(next); \
(last) = __switch_to(prev, next, task_thread_info(next), \
__builtin_return_address(0), __builtin_frame_address(0)); \
diff --git a/arch/loongarch/include/asm/thread_info.h b/arch/loongarch/include/asm/thread_info.h
index 1a3354ca056e..8cb653d49a54 100644
--- a/arch/loongarch/include/asm/thread_info.h
+++ b/arch/loongarch/include/asm/thread_info.h
@@ -84,6 +84,8 @@ register unsigned long current_stack_pointer __asm__("$sp");
#define TIF_SINGLESTEP 16 /* Single Step */
#define TIF_LSX_CTX_LIVE 17 /* LSX context must be preserved */
#define TIF_LASX_CTX_LIVE 18 /* LASX context must be preserved */
+#define TIF_USEDLBT 19 /* LBT was used by this task this quantum (SMP) */
+#define TIF_LBT_CTX_LIVE 20 /* LBT context must be preserved */

#define _TIF_SIGPENDING (1<<TIF_SIGPENDING)
#define _TIF_NEED_RESCHED (1<<TIF_NEED_RESCHED)
@@ -101,6 +103,8 @@ register unsigned long current_stack_pointer __asm__("$sp");
#define _TIF_SINGLESTEP (1<<TIF_SINGLESTEP)
#define _TIF_LSX_CTX_LIVE (1<<TIF_LSX_CTX_LIVE)
#define _TIF_LASX_CTX_LIVE (1<<TIF_LASX_CTX_LIVE)
+#define _TIF_USEDLBT (1<<TIF_USEDLBT)
+#define _TIF_LBT_CTX_LIVE (1<<TIF_LBT_CTX_LIVE)

#endif /* __KERNEL__ */
#endif /* _ASM_THREAD_INFO_H */
diff --git a/arch/loongarch/include/uapi/asm/ptrace.h b/arch/loongarch/include/uapi/asm/ptrace.h
index 06e3be52cb04..ac915f841650 100644
--- a/arch/loongarch/include/uapi/asm/ptrace.h
+++ b/arch/loongarch/include/uapi/asm/ptrace.h
@@ -56,6 +56,12 @@ struct user_lasx_state {
uint64_t vregs[32*4];
};

+struct user_lbt_state {
+ uint64_t scr[4];
+ uint32_t eflags;
+ uint32_t ftop;
+};
+
struct user_watch_state {
uint64_t dbg_info;
struct {
diff --git a/arch/loongarch/include/uapi/asm/sigcontext.h b/arch/loongarch/include/uapi/asm/sigcontext.h
index 4cd7d16f7037..6c22f616b8f1 100644
--- a/arch/loongarch/include/uapi/asm/sigcontext.h
+++ b/arch/loongarch/include/uapi/asm/sigcontext.h
@@ -59,4 +59,14 @@ struct lasx_context {
__u32 fcsr;
};

+/* LBT context */
+#define LBT_CTX_MAGIC 0x42540001
+#define LBT_CTX_ALIGN 8
+struct lbt_context {
+ __u64 regs[4];
+ __u32 eflags;
+ __u32 ftop;
+};
+
+
#endif /* _UAPI_ASM_SIGCONTEXT_H */
diff --git a/arch/loongarch/kernel/Makefile b/arch/loongarch/kernel/Makefile
index 9048ab4e5d40..6601b6d00738 100644
--- a/arch/loongarch/kernel/Makefile
+++ b/arch/loongarch/kernel/Makefile
@@ -15,6 +15,8 @@ obj-$(CONFIG_EFI) += efi.o

obj-$(CONFIG_CPU_HAS_FPU) += fpu.o kfpu.o

+obj-$(CONFIG_CPU_HAS_LBT) += lbt.o
+
obj-$(CONFIG_ARCH_STRICT_ALIGN) += unaligned.o

ifdef CONFIG_FUNCTION_TRACER
diff --git a/arch/loongarch/kernel/asm-offsets.c b/arch/loongarch/kernel/asm-offsets.c
index 505e4bf59603..2f79ba93e895 100644
--- a/arch/loongarch/kernel/asm-offsets.c
+++ b/arch/loongarch/kernel/asm-offsets.c
@@ -172,6 +172,7 @@ void output_thread_fpu_defines(void)

OFFSET(THREAD_FCSR, loongarch_fpu, fcsr);
OFFSET(THREAD_FCC, loongarch_fpu, fcc);
+ OFFSET(THREAD_FTOP, loongarch_fpu, ftop);
BLANK();
}

diff --git a/arch/loongarch/kernel/cpu-probe.c b/arch/loongarch/kernel/cpu-probe.c
index e925579c7a71..55320813ee08 100644
--- a/arch/loongarch/kernel/cpu-probe.c
+++ b/arch/loongarch/kernel/cpu-probe.c
@@ -144,6 +144,20 @@ static void cpu_probe_common(struct cpuinfo_loongarch *c)
c->options |= LOONGARCH_CPU_LVZ;
elf_hwcap |= HWCAP_LOONGARCH_LVZ;
}
+#ifdef CONFIG_CPU_HAS_LBT
+ if (config & CPUCFG2_X86BT) {
+ c->options |= LOONGARCH_CPU_LBT_X86;
+ elf_hwcap |= HWCAP_LOONGARCH_LBT_X86;
+ }
+ if (config & CPUCFG2_ARMBT) {
+ c->options |= LOONGARCH_CPU_LBT_ARM;
+ elf_hwcap |= HWCAP_LOONGARCH_LBT_ARM;
+ }
+ if (config & CPUCFG2_MIPSBT) {
+ c->options |= LOONGARCH_CPU_LBT_MIPS;
+ elf_hwcap |= HWCAP_LOONGARCH_LBT_MIPS;
+ }
+#endif

config = read_cpucfg(LOONGARCH_CPUCFG6);
if (config & CPUCFG6_PMP)
diff --git a/arch/loongarch/kernel/fpu.S b/arch/loongarch/kernel/fpu.S
index f3df5f0a4509..9526b15f1c83 100644
--- a/arch/loongarch/kernel/fpu.S
+++ b/arch/loongarch/kernel/fpu.S
@@ -138,6 +138,13 @@
.macro sc_save_fcsr base, tmp0
movfcsr2gr \tmp0, fcsr0
EX st.w \tmp0, \base, 0
+#if defined(CONFIG_CPU_HAS_LBT)
+ /* TM bit is always 0 if LBT not supported */
+ andi \tmp0, \tmp0, FPU_CSR_TM
+ beqz \tmp0, 1f
+ x86clrtm
+ 1:
+#endif
.endm

.macro sc_restore_fcsr base, tmp0
@@ -309,7 +316,7 @@ EXPORT_SYMBOL(_save_fp)
*/
SYM_FUNC_START(_restore_fp)
fpu_restore_double a0 t1 # clobbers t1
- fpu_restore_csr a0 t1
+ fpu_restore_csr a0 t1 t2
fpu_restore_cc a0 t1 t2 # clobbers t1, t2
jr ra
SYM_FUNC_END(_restore_fp)
diff --git a/arch/loongarch/kernel/lbt.S b/arch/loongarch/kernel/lbt.S
new file mode 100644
index 000000000000..40cfeec2018c
--- /dev/null
+++ b/arch/loongarch/kernel/lbt.S
@@ -0,0 +1,166 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Author: Lu Zeng <zenglu@xxxxxxxxxxx>
+ * Pei Huang <huangpei@xxxxxxxxxxx>
+ * Huacai Chen <chenhuacai@xxxxxxxxxxx>
+ *
+ * Copyright (C) 2020-2022 Loongson Technology Corporation Limited
+ */
+#include <asm/asm.h>
+#include <asm/asmmacro.h>
+#include <asm/asm-extable.h>
+#include <asm/asm-offsets.h>
+#include <asm/errno.h>
+#include <asm/export.h>
+#include <asm/fpregdef.h>
+#include <asm/loongarch.h>
+#include <asm/regdef.h>
+
+#if defined(CONFIG_CPU_HAS_LBT)
+
+#define SCR_REG_WIDTH 8
+
+ .macro EX insn, reg, src, offs
+.ex\@: \insn \reg, \src, \offs
+ _asm_extable .ex\@, lbt_fault
+ .endm
+
+ .macro sc_save_scr base, tmp0
+ movscr2gr \tmp0, $scr0
+ EX st.d \tmp0, \base, (0 * SCR_REG_WIDTH)
+ movscr2gr \tmp0, $scr1
+ EX st.d \tmp0, \base, (1 * SCR_REG_WIDTH)
+ movscr2gr \tmp0, $scr2
+ EX st.d \tmp0, \base, (2 * SCR_REG_WIDTH)
+ movscr2gr \tmp0, $scr3
+ EX st.d \tmp0, \base, (3 * SCR_REG_WIDTH)
+ .endm
+
+ .macro sc_restore_scr base, tmp0
+ EX ld.d \tmp0, \base, (0 * SCR_REG_WIDTH)
+ movgr2scr $scr0, \tmp0
+ EX ld.d \tmp0, \base, (1 * SCR_REG_WIDTH)
+ movgr2scr $scr1, \tmp0
+ EX ld.d \tmp0, \base, (2 * SCR_REG_WIDTH)
+ movgr2scr $scr2, \tmp0
+ EX ld.d \tmp0, \base, (3 * SCR_REG_WIDTH)
+ movgr2scr $scr3, \tmp0
+ .endm
+
+ .macro sc_save_eflag base, tmp0
+ x86mfflag \tmp0, 0x3f
+ EX st.w \tmp0, \base, 0
+ .endm
+
+ .macro sc_restore_eflag base, tmp0
+ EX ld.w \tmp0, \base, 0
+ x86mtflag \tmp0, 0x3f
+ .endm
+
+/*
+ * Save a thread's lbt context.
+ */
+SYM_FUNC_START(_save_lbt)
+ lbt_save_scr a0 t1 # clobbers t1
+ lbt_save_eflag a0 t1 # clobbers t1
+ jr ra
+SYM_FUNC_END(_save_lbt)
+EXPORT_SYMBOL(_save_lbt)
+
+/*
+ * Restore a thread's lbt context.
+ */
+SYM_FUNC_START(_restore_lbt)
+ lbt_restore_eflag a0 t1 # clobbers t1
+ lbt_restore_scr a0 t1 # clobbers t1
+ jr ra
+SYM_FUNC_END(_restore_lbt)
+EXPORT_SYMBOL(_restore_lbt)
+
+/*
+ * a0: scr
+ * a1: eflag
+ */
+SYM_FUNC_START(_save_lbt_context)
+ sc_save_scr a0 t1
+ sc_save_eflag a1 t1
+ li.w a0, 0 # success
+ jr ra
+SYM_FUNC_END(_save_lbt_context)
+
+/*
+ * a0: scr
+ * a1: eflag
+ */
+SYM_FUNC_START(_restore_lbt_context)
+ sc_restore_scr a0 t1
+ sc_restore_eflag a1 t1
+ li.w a0, 0 # success
+ jr ra
+SYM_FUNC_END(_restore_lbt_context)
+
+/*
+ * a0: ftop
+ */
+SYM_FUNC_START(_save_ftop_context)
+ x86mftop t1
+ st.b t1, a0, 0
+ li.w a0, 0 # success
+ jr ra
+SYM_FUNC_END(_save_ftop_context)
+
+/*
+ * a0: ftop
+ */
+SYM_FUNC_START(_restore_ftop_context)
+ ld.b t1, a0, 0
+ andi t1, t1, 0x7
+ la.pcrel a0, 2f
+ alsl.d a0, t1, a0, 3
+ jr a0
+ 2 :
+ x86mttop 0
+ b 1f
+ x86mttop 1
+ b 1f
+ x86mttop 2
+ b 1f
+ x86mttop 3
+ b 1f
+ x86mttop 4
+ b 1f
+ x86mttop 5
+ b 1f
+ x86mttop 6
+ b 1f
+ x86mttop 7
+ 1 :
+ li.w a0, 0 # success
+ jr ra
+SYM_FUNC_END(_restore_ftop_context)
+
+
+SYM_FUNC_START(lbt_fault)
+ li.w a0, -EFAULT # failure
+ jr ra
+SYM_FUNC_END(lbt_fault)
+
+#else
+
+/*
+ * Save a thread's lbt context.
+ */
+SYM_FUNC_START(_save_lbt)
+ jr ra
+SYM_FUNC_END(_save_lbt)
+EXPORT_SYMBOL(_save_lbt)
+
+/*
+ * Restore a thread's lbt context.
+ */
+SYM_FUNC_START(_restore_lbt)
+ jr ra
+SYM_FUNC_END(_restore_lbt)
+EXPORT_SYMBOL(_restore_lbt)
+
+#endif
diff --git a/arch/loongarch/kernel/process.c b/arch/loongarch/kernel/process.c
index 2e04eb07abb6..7e11ef2c8fd2 100644
--- a/arch/loongarch/kernel/process.c
+++ b/arch/loongarch/kernel/process.c
@@ -38,6 +38,7 @@
#include <asm/cpu.h>
#include <asm/elf.h>
#include <asm/fpu.h>
+#include <asm/lbt.h>
#include <asm/io.h>
#include <asm/irq.h>
#include <asm/irq_regs.h>
@@ -89,9 +90,11 @@ void start_thread(struct pt_regs *regs, unsigned long pc, unsigned long sp)
euen = regs->csr_euen & ~(CSR_EUEN_FPEN);
regs->csr_euen = euen;
lose_fpu(0);
+ lose_lbt(0);

clear_thread_flag(TIF_LSX_CTX_LIVE);
clear_thread_flag(TIF_LASX_CTX_LIVE);
+ clear_thread_flag(TIF_LBT_CTX_LIVE);
clear_used_math();
regs->csr_era = pc;
regs->regs[3] = sp;
@@ -196,8 +199,10 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args)
ptrace_hw_copy_thread(p);
clear_tsk_thread_flag(p, TIF_USEDFPU);
clear_tsk_thread_flag(p, TIF_USEDSIMD);
+ clear_tsk_thread_flag(p, TIF_USEDLBT);
clear_tsk_thread_flag(p, TIF_LSX_CTX_LIVE);
clear_tsk_thread_flag(p, TIF_LASX_CTX_LIVE);
+ clear_tsk_thread_flag(p, TIF_LBT_CTX_LIVE);

return 0;
}
diff --git a/arch/loongarch/kernel/ptrace.c b/arch/loongarch/kernel/ptrace.c
index a0767c3a0f0a..4192e20c6277 100644
--- a/arch/loongarch/kernel/ptrace.c
+++ b/arch/loongarch/kernel/ptrace.c
@@ -38,6 +38,7 @@
#include <asm/cpu.h>
#include <asm/cpu-info.h>
#include <asm/fpu.h>
+#include <asm/lbt.h>
#include <asm/loongarch.h>
#include <asm/page.h>
#include <asm/pgtable.h>
@@ -334,6 +335,46 @@ static int simd_set(struct task_struct *target,

#endif /* CONFIG_CPU_HAS_LSX */

+#ifdef CONFIG_CPU_HAS_LBT
+static int lbt_get(struct task_struct *target,
+ const struct user_regset *regset,
+ struct membuf to)
+{
+ int r;
+
+ r = membuf_write(&to, &target->thread.scr0, sizeof(target->thread.scr0));
+ r = membuf_write(&to, &target->thread.scr1, sizeof(target->thread.scr1));
+ r = membuf_write(&to, &target->thread.scr2, sizeof(target->thread.scr2));
+ r = membuf_write(&to, &target->thread.scr3, sizeof(target->thread.scr3));
+
+ r = membuf_write(&to, &target->thread.eflags, sizeof(u32));
+ r = membuf_write(&to, &target->thread.fpu.ftop, sizeof(u32));
+
+ return r;
+}
+
+static int lbt_set(struct task_struct *target,
+ const struct user_regset *regset,
+ unsigned int pos, unsigned int count,
+ const void *kbuf, const void __user *ubuf)
+{
+ const int eflags_start = 4 * sizeof(target->thread.scr0);
+ const int ftop_start = eflags_start + sizeof(u32);
+ int err = 0;
+
+ err |= user_regset_copyin(&pos, &count, &kbuf, &ubuf,
+ &target->thread.scr0,
+ 0, 4 * sizeof(target->thread.scr0));
+ err |= user_regset_copyin(&pos, &count, &kbuf, &ubuf,
+ &target->thread.eflags,
+ eflags_start, ftop_start);
+ err |= user_regset_copyin(&pos, &count, &kbuf, &ubuf,
+ &target->thread.fpu.ftop, ftop_start,
+ ftop_start + sizeof(u32));
+ return err;
+}
+#endif /* CONFIG_CPU_HAS_LBT */
+
#ifdef CONFIG_HAVE_HW_BREAKPOINT

/*
@@ -798,6 +839,9 @@ enum loongarch_regset {
#ifdef CONFIG_CPU_HAS_LASX
REGSET_LASX,
#endif
+#ifdef CONFIG_CPU_HAS_LBT
+ REGSET_LBT,
+#endif
#ifdef CONFIG_HAVE_HW_BREAKPOINT
REGSET_HW_BREAK,
REGSET_HW_WATCH,
@@ -849,6 +893,16 @@ static const struct user_regset loongarch64_regsets[] = {
.set = simd_set,
},
#endif
+#ifdef CONFIG_CPU_HAS_LBT
+ [REGSET_LBT] = {
+ .core_note_type = NT_LOONGARCH_LBT,
+ .n = 5,
+ .size = sizeof(u64),
+ .align = sizeof(u64),
+ .regset_get = lbt_get,
+ .set = lbt_set,
+ },
+#endif
#ifdef CONFIG_HAVE_HW_BREAKPOINT
[REGSET_HW_BREAK] = {
.core_note_type = NT_LOONGARCH_HW_BREAK,
diff --git a/arch/loongarch/kernel/signal.c b/arch/loongarch/kernel/signal.c
index ceb899366c0a..7ebfa49e7456 100644
--- a/arch/loongarch/kernel/signal.c
+++ b/arch/loongarch/kernel/signal.c
@@ -32,6 +32,7 @@
#include <asm/cacheflush.h>
#include <asm/cpu-features.h>
#include <asm/fpu.h>
+#include <asm/lbt.h>
#include <asm/ucontext.h>
#include <asm/vdso.h>

@@ -44,6 +45,9 @@
/* Make sure we will not lose FPU ownership */
#define lock_fpu_owner() ({ preempt_disable(); pagefault_disable(); })
#define unlock_fpu_owner() ({ pagefault_enable(); preempt_enable(); })
+/* Make sure we will not lose LBT ownership */
+#define lock_lbt_owner() lock_fpu_owner()
+#define unlock_lbt_owner() unlock_fpu_owner()

/* Assembly functions to move context to/from the FPU */
extern asmlinkage int
@@ -58,6 +62,12 @@ extern asmlinkage int
_save_lasx_context(void __user *fpregs, void __user *fcc, void __user *fcsr);
extern asmlinkage int
_restore_lasx_context(void __user *fpregs, void __user *fcc, void __user *fcsr);
+#ifdef CONFIG_CPU_HAS_LBT
+extern asmlinkage int _save_lbt_context(void __user *regs, void __user *eflags);
+extern asmlinkage int _restore_lbt_context(void __user *regs, void __user *eflags);
+extern asmlinkage int _save_ftop_context(void __user *ftop);
+extern asmlinkage int _restore_ftop_context(void __user *ftop);
+#endif

struct rt_sigframe {
struct siginfo rs_info;
@@ -75,6 +85,7 @@ struct extctx_layout {
struct _ctx_layout fpu;
struct _ctx_layout lsx;
struct _ctx_layout lasx;
+ struct _ctx_layout lbt;
struct _ctx_layout end;
};

@@ -125,6 +136,54 @@ static int copy_fpu_from_sigcontext(struct fpu_context __user *ctx)
return err;
}

+#ifdef CONFIG_CPU_HAS_LBT
+static int copy_lbt_to_sigcontext(struct lbt_context __user *ctx)
+{
+ int err = 0;
+ uint64_t __user *regs = (uint64_t *)&ctx->regs;
+ uint32_t __user *eflags = &ctx->eflags;
+
+ err |= __put_user(current->thread.scr0, &regs[0]);
+ err |= __put_user(current->thread.scr1, &regs[1]);
+ err |= __put_user(current->thread.scr2, &regs[2]);
+ err |= __put_user(current->thread.scr3, &regs[3]);
+
+ err |= __put_user(current->thread.eflags, eflags);
+
+ return err;
+}
+
+static int copy_lbt_from_sigcontext(struct lbt_context __user *ctx)
+{
+ int err = 0;
+ uint64_t __user *regs = (uint64_t *)&ctx->regs;
+ uint32_t __user *eflags = &ctx->eflags;
+
+ err |= __get_user(current->thread.scr0, &regs[0]);
+ err |= __get_user(current->thread.scr1, &regs[1]);
+ err |= __get_user(current->thread.scr2, &regs[2]);
+ err |= __get_user(current->thread.scr3, &regs[3]);
+
+ err |= __get_user(current->thread.eflags, eflags);
+
+ return err;
+}
+
+static int copy_ftop_to_sigcontext(struct lbt_context __user *ctx)
+{
+ uint32_t __user *ftop = &ctx->ftop;
+
+ return __put_user(current->thread.fpu.ftop, ftop);
+}
+
+static int copy_ftop_from_sigcontext(struct lbt_context __user *ctx)
+{
+ uint32_t __user *ftop = &ctx->ftop;
+
+ return __get_user(current->thread.fpu.ftop, ftop);
+}
+#endif
+
static int copy_lsx_to_sigcontext(struct lsx_context __user *ctx)
{
int i;
@@ -291,6 +350,41 @@ static int fcsr_pending(unsigned int __user *fcsr)
return err ?: sig;
}

+/*
+ * Wrappers for the assembly _{save,restore}_lbt_context functions.
+ */
+#ifdef CONFIG_CPU_HAS_LBT
+static int save_hw_lbt_context(struct lbt_context __user *ctx)
+{
+ uint64_t __user *regs = (uint64_t *)&ctx->regs;
+ uint32_t __user *eflags = &ctx->eflags;
+
+ return _save_lbt_context(regs, eflags);
+}
+
+static int restore_hw_lbt_context(struct lbt_context __user *ctx)
+{
+ uint64_t __user *regs = (uint64_t *)&ctx->regs;
+ uint32_t __user *eflags = &ctx->eflags;
+
+ return _restore_lbt_context(regs, eflags);
+}
+
+static int save_hw_ftop_context(struct lbt_context __user *ctx)
+{
+ uint32_t __user *ftop = &ctx->ftop;
+
+ return _save_ftop_context(ftop);
+}
+
+static int restore_hw_ftop_context(struct lbt_context __user *ctx)
+{
+ uint32_t __user *ftop = &ctx->ftop;
+
+ return _restore_ftop_context(ftop);
+}
+#endif
+
/*
* Helper routines
*/
@@ -519,6 +613,83 @@ static int protected_restore_lasx_context(struct extctx_layout *extctx)
return err ?: sig;
}

+#ifdef CONFIG_CPU_HAS_LBT
+static int protected_save_lbt_context(struct extctx_layout *extctx)
+{
+ int err = 0;
+ struct sctx_info __user *info = extctx->lbt.addr;
+ struct lbt_context __user *lbt_ctx =
+ (struct lbt_context *)get_ctx_through_ctxinfo(info);
+ uint64_t __user *regs = (uint64_t *)&lbt_ctx->regs;
+ uint32_t __user *eflags = &lbt_ctx->eflags;
+
+ while (1) {
+ lock_lbt_owner();
+ /* save lbt except ftop */
+ if (is_lbt_owner())
+ err |= save_hw_lbt_context(lbt_ctx);
+ else
+ err |= copy_lbt_to_sigcontext(lbt_ctx);
+ /* save ftop */
+ if (is_fpu_owner())
+ err |= save_hw_ftop_context(lbt_ctx);
+ else
+ err |= copy_ftop_to_sigcontext(lbt_ctx);
+ unlock_lbt_owner();
+
+ err |= __put_user(LBT_CTX_MAGIC, &info->magic);
+ err |= __put_user(extctx->lbt.size, &info->size);
+
+ if (likely(!err))
+ break;
+ /* Touch the LBT context and try again */
+ err = __put_user(0, &regs[0]) |
+ __put_user(0, eflags);
+
+ if (err)
+ return err;
+ }
+
+ return err;
+}
+
+static int protected_restore_lbt_context(struct extctx_layout *extctx)
+{
+ int err = 0, tmp __maybe_unused;
+ struct sctx_info __user *info = extctx->lbt.addr;
+ struct lbt_context __user *lbt_ctx =
+ (struct lbt_context *)get_ctx_through_ctxinfo(info);
+ uint64_t __user *regs = (uint64_t *)&lbt_ctx->regs;
+ uint32_t __user *eflags = &lbt_ctx->eflags;
+
+ while (1) {
+ lock_lbt_owner();
+ /* restore lbt except ftop */
+ if (is_lbt_owner())
+ err |= restore_hw_lbt_context(lbt_ctx);
+ else
+ err |= copy_lbt_from_sigcontext(lbt_ctx);
+ /* restore ftop */
+ if (is_fpu_owner())
+ err |= restore_hw_ftop_context(lbt_ctx);
+ else
+ err |= copy_ftop_from_sigcontext(lbt_ctx);
+ unlock_lbt_owner();
+
+ if (likely(!err))
+ break;
+ /* Touch the LBT context and try again */
+ err = __get_user(tmp, &regs[0]) |
+ __get_user(tmp, eflags);
+
+ if (err)
+ return err;
+ }
+
+ return err;
+}
+#endif
+
static int setup_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc,
struct extctx_layout *extctx)
{
@@ -539,6 +710,11 @@ static int setup_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc,
else if (extctx->fpu.addr)
err |= protected_save_fpu_context(extctx);

+#ifdef CONFIG_CPU_HAS_LBT
+ if (extctx->lbt.addr)
+ err |= protected_save_lbt_context(extctx);
+#endif
+
/* Set the "end" magic */
info = (struct sctx_info *)extctx->end.addr;
err |= __put_user(0, &info->magic);
@@ -584,6 +760,13 @@ static int parse_extcontext(struct sigcontext __user *sc, struct extctx_layout *
extctx->lasx.addr = info;
break;

+ case LBT_CTX_MAGIC:
+ if (size < (sizeof(struct sctx_info) +
+ sizeof(struct lbt_context)))
+ goto invalid;
+ extctx->lbt.addr = info;
+ break;
+
default:
goto invalid;
}
@@ -636,6 +819,11 @@ static int restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc
else if (extctx.fpu.addr)
err |= protected_restore_fpu_context(&extctx);

+#ifdef CONFIG_CPU_HAS_LBT
+ if (extctx.lbt.addr)
+ err |= protected_restore_lbt_context(&extctx);
+#endif
+
bad:
return err;
}
@@ -700,6 +888,11 @@ static unsigned long setup_extcontext(struct extctx_layout *extctx, unsigned lon
sizeof(struct fpu_context), FPU_CTX_ALIGN, new_sp);
}

+ if (cpu_has_lbt && thread_lbt_context_live()) {
+ new_sp = extframe_alloc(extctx, &extctx->lbt,
+ sizeof(struct lbt_context), LBT_CTX_ALIGN, new_sp);
+ }
+
return new_sp;
}

diff --git a/arch/loongarch/kernel/traps.c b/arch/loongarch/kernel/traps.c
index 8fb5e7a77145..fd20e22a02b4 100644
--- a/arch/loongarch/kernel/traps.c
+++ b/arch/loongarch/kernel/traps.c
@@ -36,6 +36,7 @@
#include <asm/break.h>
#include <asm/cpu.h>
#include <asm/fpu.h>
+#include <asm/lbt.h>
#include <asm/inst.h>
#include <asm/loongarch.h>
#include <asm/mmu_context.h>
@@ -904,6 +905,24 @@ static void init_restore_lasx(void)
BUG_ON(!is_lasx_enabled());
}

+#ifdef CONFIG_CPU_HAS_LBT
+static void init_restore_lbt(void)
+{
+ if (!thread_lbt_context_live()) {
+ /* First time lbt context user */
+ init_lbt();
+ } else {
+ /* Enable and restore */
+ if (!is_lbt_owner())
+ own_lbt_inatomic(1);
+ }
+
+ BUG_ON(!is_lbt_enabled());
+}
+#else
+static void init_restore_lbt(void) {}
+#endif
+
asmlinkage void noinstr do_fpu(struct pt_regs *regs)
{
irqentry_state_t state = irqentry_enter(regs);
@@ -968,10 +987,29 @@ asmlinkage void noinstr do_lbt(struct pt_regs *regs)
{
irqentry_state_t state = irqentry_enter(regs);

- local_irq_enable();
- force_sig(SIGILL);
- local_irq_disable();
+ /*
+ * BTD (Binary Translation Disable exception) can be triggered
+ * during FP save/restore if TM (Top Mode) is open, which may
+ * cause irq_enable during 'switch_to'. To avoid this situation
+ * (including the user using 'MOVGR2GCSR' to open the TM, which
+ * will not trigger the BTE), we need to check PRMD first.
+ */
+ if (likely(regs->csr_prmd & CSR_PRMD_PIE))
+ local_irq_enable();
+
+ if (!cpu_has_lbt) {
+ force_sig(SIGILL);
+ goto out;
+ }
+
+ BUG_ON(is_lbt_enabled());

+ preempt_disable();
+ init_restore_lbt();
+ preempt_enable();
+
+out:
+ local_irq_disable();
irqentry_exit(regs, state);
}

--
2.40.1