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Message-Id: <20230208100837.2451-3-zhangqing@loongson.cn>
Date: Wed, 8 Feb 2023 18:08:37 +0800
From: Qing Zhang <zhangqing@...ngson.cn>
To: Huacai Chen <chenhuacai@...nel.org>,
Oleg Nesterov <oleg@...hat.com>,
WANG Xuerui <kernel@...0n.name>
Cc: Jiaxun Yang <jiaxun.yang@...goat.com>, loongarch@...ts.linux.dev,
linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] LoongArch: Add ptrace single step support
Use the generic ptrace_resume code for PTRACE_SYSCALL, PTRACE_CONT,
PTRACE_KILL and PTRACE_SINGLESTEP. This implies defining
arch_has_single_step in and implementing the
user_enable_single_step and user_disable_single_step functions.
LongArch has no hardware single-step register. the hardware single-step
function multiplex fetch instruction watchpoint(FWPS) and specifies that
the next instruction must trigger the watch exception by setting the mask bit.
Signed-off-by: Qing Zhang <zhangqing@...ngson.cn>
---
arch/loongarch/include/asm/ptrace.h | 2 +
arch/loongarch/kernel/hw_breakpoint.c | 13 ++++-
arch/loongarch/kernel/ptrace.c | 68 +++++++++++++++++++++++++++
arch/loongarch/kernel/traps.c | 27 +++++++++--
4 files changed, 103 insertions(+), 7 deletions(-)
diff --git a/arch/loongarch/include/asm/ptrace.h b/arch/loongarch/include/asm/ptrace.h
index 58596c4f8a0f..66a0e6c480a3 100644
--- a/arch/loongarch/include/asm/ptrace.h
+++ b/arch/loongarch/include/asm/ptrace.h
@@ -150,4 +150,6 @@ static inline void user_stack_pointer_set(struct pt_regs *regs,
regs->regs[3] = val;
}
+#define arch_has_single_step() (1)
+
#endif /* _ASM_PTRACE_H */
diff --git a/arch/loongarch/kernel/hw_breakpoint.c b/arch/loongarch/kernel/hw_breakpoint.c
index 4ba1e730f3e9..bcecc076b420 100644
--- a/arch/loongarch/kernel/hw_breakpoint.c
+++ b/arch/loongarch/kernel/hw_breakpoint.c
@@ -497,9 +497,18 @@ arch_initcall(arch_hw_breakpoint_init);
void hw_breakpoint_thread_switch(struct task_struct *next)
{
struct pt_regs *regs = task_pt_regs(next);
+ u64 addr, mask;
- /* Update breakpoints/watchpoints. */
- update_bp_registers(regs, 1);
+ if (test_bit(TIF_SINGLESTEP, &task_thread_info(next)->flags)) {
+ addr = read_wb_reg(CSR_CFG_ADDR, 0, 0);
+ mask = read_wb_reg(CSR_CFG_MASK, 0, 0);
+ if ((task_pt_regs(next)->csr_era & ~mask) == (addr & ~mask))
+ csr_write32(0x10000, LOONGARCH_CSR_FWPS);
+ regs->csr_prmd |= CSR_PRMD_PWE;
+ } else {
+ /* Update breakpoints/watchpoints. */
+ update_bp_registers(regs, 1);
+ }
}
void hw_breakpoint_pmu_read(struct perf_event *bp)
diff --git a/arch/loongarch/kernel/ptrace.c b/arch/loongarch/kernel/ptrace.c
index bee4194177fd..52a3ee4366f4 100644
--- a/arch/loongarch/kernel/ptrace.c
+++ b/arch/loongarch/kernel/ptrace.c
@@ -20,6 +20,7 @@
#include <linux/context_tracking.h>
#include <linux/elf.h>
#include <linux/errno.h>
+#include <linux/hw_breakpoint.h>
#include <linux/mm.h>
#include <linux/ptrace.h>
#include <linux/regset.h>
@@ -30,6 +31,7 @@
#include <linux/stddef.h>
#include <linux/seccomp.h>
#include <linux/uaccess.h>
+#include <linux/thread_info.h>
#include <asm/byteorder.h>
#include <asm/cpu.h>
@@ -39,6 +41,7 @@
#include <asm/page.h>
#include <asm/pgtable.h>
#include <asm/processor.h>
+#include <asm/ptrace.h>
#include <asm/reg.h>
#include <asm/syscall.h>
@@ -541,3 +544,68 @@ long arch_ptrace(struct task_struct *child, long request,
return ret;
}
+
+void ptrace_triggered(struct perf_event *bp,
+ struct perf_sample_data *data, struct pt_regs *regs)
+{
+ struct perf_event_attr attr;
+
+ attr = bp->attr;
+ attr.disabled = true;
+ modify_user_hw_breakpoint(bp, &attr);
+}
+
+static int set_single_step(struct task_struct *tsk, unsigned long addr)
+{
+ struct thread_struct *thread = &tsk->thread;
+ struct perf_event *bp;
+ struct perf_event_attr attr;
+ struct arch_hw_breakpoint *info;
+
+ bp = thread->hbp_break[0];
+ if (!bp) {
+ ptrace_breakpoint_init(&attr);
+
+ attr.bp_addr = addr;
+ attr.bp_len = HW_BREAKPOINT_LEN_8;
+ attr.bp_type = HW_BREAKPOINT_X;
+
+ bp = register_user_hw_breakpoint(&attr, ptrace_triggered,
+ NULL, tsk);
+ if (IS_ERR(bp))
+ return PTR_ERR(bp);
+
+ thread->hbp_break[0] = bp;
+ } else {
+ int err;
+
+ attr = bp->attr;
+ attr.bp_addr = addr;
+ /* reenable breakpoint */
+ attr.disabled = false;
+ err = modify_user_hw_breakpoint(bp, &attr);
+ if (unlikely(err))
+ return err;
+
+ csr_write64(attr.bp_addr, LOONGARCH_CSR_IB0ADDR);
+ }
+ info = counter_arch_bp(bp);
+ info->mask = 0xffffffffffff;
+
+ return 0;
+}
+
+/* ptrace API */
+void user_enable_single_step(struct task_struct *task)
+{
+ struct thread_info *ti = task_thread_info(task);
+
+ set_single_step(task, task_pt_regs(task)->csr_era);
+ task->thread.single_step = task_pt_regs(task)->csr_era;
+ set_ti_thread_flag(ti, TIF_SINGLESTEP);
+}
+
+void user_disable_single_step(struct task_struct *task)
+{
+ clear_tsk_thread_flag(task, TIF_SINGLESTEP);
+}
diff --git a/arch/loongarch/kernel/traps.c b/arch/loongarch/kernel/traps.c
index 70085d83476d..0c4c6dcf9a4e 100644
--- a/arch/loongarch/kernel/traps.c
+++ b/arch/loongarch/kernel/traps.c
@@ -512,13 +512,30 @@ asmlinkage void noinstr do_watch(struct pt_regs *regs)
prev_state = exception_enter();
+ if (test_tsk_thread_flag(current, TIF_SINGLESTEP)) {
+ int llbit = (csr_read32(LOONGARCH_CSR_LLBCTL) & 0x1);
+ unsigned long pc = regs->csr_era;
+
+ if (llbit) {
+ csr_write32(0x10000, LOONGARCH_CSR_FWPS);
+ csr_write32(0x4, LOONGARCH_CSR_LLBCTL);
+ } else if (pc == current->thread.single_step) {
+ csr_write32(0x10000, LOONGARCH_CSR_FWPS);
+ } else {
+ csr_write32(0x10000, LOONGARCH_CSR_FWPS);
+ pr_info("Single step in progress\n");
+ force_sig(SIGTRAP);
+ }
+ } else {
#ifdef CONFIG_HAVE_HW_BREAKPOINT
- if (breakpoint_handler(regs))
- return;
- if (watchpoint_handler(regs))
- return;
+ if (breakpoint_handler(regs))
+ return;
+ if (watchpoint_handler(regs))
+ return;
+ force_sig(SIGTRAP);
#endif
- force_sig(SIGTRAP);
+ }
+
exception_exit(prev_state);
return;
}
--
2.36.0
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