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Subject[PATCH v4 7/9] riscv: Add uprobes supported
Date
From: Guo Ren <guoren@linux.alibaba.com>

This patch adds support for uprobes on riscv architecture.

Just like kprobe, it support single-step and simulate instructions.

Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Reviewed-by: Pekka Enberg <penberg@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Palmer Dabbelt <palmerdabbelt@google.com>
---
arch/riscv/Kconfig | 3 +
arch/riscv/include/asm/processor.h | 1 +
arch/riscv/include/asm/thread_info.h | 4 +-
arch/riscv/include/asm/uprobes.h | 40 ++++++++
arch/riscv/kernel/probes/Makefile | 1 +
arch/riscv/kernel/probes/uprobes.c | 186 +++++++++++++++++++++++++++++++++++
arch/riscv/kernel/signal.c | 3 +
arch/riscv/kernel/traps.c | 10 ++
arch/riscv/mm/fault.c | 7 ++
9 files changed, 254 insertions(+), 1 deletion(-)
create mode 100644 arch/riscv/include/asm/uprobes.h
create mode 100644 arch/riscv/kernel/probes/uprobes.c

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index feafc9d..4081ecf 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -158,6 +158,9 @@ config ARCH_WANT_GENERAL_HUGETLB
config ARCH_SUPPORTS_DEBUG_PAGEALLOC
def_bool y

+config ARCH_SUPPORTS_UPROBES
+ def_bool y
+
config SYS_SUPPORTS_HUGETLBFS
depends on MMU
def_bool y
diff --git a/arch/riscv/include/asm/processor.h b/arch/riscv/include/asm/processor.h
index bdddcd5..3a24003 100644
--- a/arch/riscv/include/asm/processor.h
+++ b/arch/riscv/include/asm/processor.h
@@ -34,6 +34,7 @@ struct thread_struct {
unsigned long sp; /* Kernel mode stack */
unsigned long s[12]; /* s[0]: frame pointer */
struct __riscv_d_ext_state fstate;
+ unsigned long bad_cause;
};

#define INIT_THREAD { \
diff --git a/arch/riscv/include/asm/thread_info.h b/arch/riscv/include/asm/thread_info.h
index 464a2bb..27240ea 100644
--- a/arch/riscv/include/asm/thread_info.h
+++ b/arch/riscv/include/asm/thread_info.h
@@ -80,6 +80,7 @@ struct thread_info {
#define TIF_SYSCALL_TRACEPOINT 6 /* syscall tracepoint instrumentation */
#define TIF_SYSCALL_AUDIT 7 /* syscall auditing */
#define TIF_SECCOMP 8 /* syscall secure computing */
+#define TIF_UPROBE 9 /* uprobe breakpoint or singlestep */

#define _TIF_SYSCALL_TRACE (1 << TIF_SYSCALL_TRACE)
#define _TIF_NOTIFY_RESUME (1 << TIF_NOTIFY_RESUME)
@@ -88,9 +89,10 @@ struct thread_info {
#define _TIF_SYSCALL_TRACEPOINT (1 << TIF_SYSCALL_TRACEPOINT)
#define _TIF_SYSCALL_AUDIT (1 << TIF_SYSCALL_AUDIT)
#define _TIF_SECCOMP (1 << TIF_SECCOMP)
+#define _TIF_UPROBE (1 << TIF_UPROBE)

#define _TIF_WORK_MASK \
- (_TIF_NOTIFY_RESUME | _TIF_SIGPENDING | _TIF_NEED_RESCHED)
+ (_TIF_NOTIFY_RESUME | _TIF_SIGPENDING | _TIF_NEED_RESCHED | _TIF_UPROBE)

#define _TIF_SYSCALL_WORK \
(_TIF_SYSCALL_TRACE | _TIF_SYSCALL_TRACEPOINT | _TIF_SYSCALL_AUDIT | \
diff --git a/arch/riscv/include/asm/uprobes.h b/arch/riscv/include/asm/uprobes.h
new file mode 100644
index 00000000..f2183e0
--- /dev/null
+++ b/arch/riscv/include/asm/uprobes.h
@@ -0,0 +1,40 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#ifndef _ASM_RISCV_UPROBES_H
+#define _ASM_RISCV_UPROBES_H
+
+#include <asm/probes.h>
+#include <asm/patch.h>
+#include <asm/bug.h>
+
+#define MAX_UINSN_BYTES 8
+
+#ifdef CONFIG_RISCV_ISA_C
+#define UPROBE_SWBP_INSN __BUG_INSN_16
+#define UPROBE_SWBP_INSN_SIZE 2
+#else
+#define UPROBE_SWBP_INSN __BUG_INSN_32
+#define UPROBE_SWBP_INSN_SIZE 4
+#endif
+#define UPROBE_XOL_SLOT_BYTES MAX_UINSN_BYTES
+
+typedef u32 uprobe_opcode_t;
+
+struct arch_uprobe_task {
+ unsigned long saved_cause;
+};
+
+struct arch_uprobe {
+ union {
+ u8 insn[MAX_UINSN_BYTES];
+ u8 ixol[MAX_UINSN_BYTES];
+ };
+ struct arch_probe_insn api;
+ unsigned long insn_size;
+ bool simulate;
+};
+
+bool uprobe_breakpoint_handler(struct pt_regs *regs);
+bool uprobe_single_step_handler(struct pt_regs *regs);
+
+#endif /* _ASM_RISCV_UPROBES_H */
diff --git a/arch/riscv/kernel/probes/Makefile b/arch/riscv/kernel/probes/Makefile
index abbd131..7f0840d 100644
--- a/arch/riscv/kernel/probes/Makefile
+++ b/arch/riscv/kernel/probes/Makefile
@@ -2,4 +2,5 @@
obj-$(CONFIG_KPROBES) += kprobes.o decode-insn.o simulate-insn.o
obj-$(CONFIG_KPROBES) += kprobes_trampoline.o
obj-$(CONFIG_KPROBES_ON_FTRACE) += ftrace.o
+obj-$(CONFIG_UPROBES) += uprobes.o decode-insn.o simulate-insn.o
CFLAGS_REMOVE_simulate-insn.o = $(CC_FLAGS_FTRACE)
diff --git a/arch/riscv/kernel/probes/uprobes.c b/arch/riscv/kernel/probes/uprobes.c
new file mode 100644
index 00000000..7a057b5
--- /dev/null
+++ b/arch/riscv/kernel/probes/uprobes.c
@@ -0,0 +1,186 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <linux/highmem.h>
+#include <linux/ptrace.h>
+#include <linux/uprobes.h>
+
+#include "decode-insn.h"
+
+#define UPROBE_TRAP_NR UINT_MAX
+
+bool is_swbp_insn(uprobe_opcode_t *insn)
+{
+#ifdef CONFIG_RISCV_ISA_C
+ return (*insn & 0xffff) == UPROBE_SWBP_INSN;
+#else
+ return *insn == UPROBE_SWBP_INSN;
+#endif
+}
+
+unsigned long uprobe_get_swbp_addr(struct pt_regs *regs)
+{
+ return instruction_pointer(regs);
+}
+
+int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe, struct mm_struct *mm,
+ unsigned long addr)
+{
+ probe_opcode_t opcode;
+
+ opcode = *(probe_opcode_t *)(&auprobe->insn[0]);
+
+ auprobe->insn_size = GET_INSN_LENGTH(opcode);
+
+ switch (riscv_probe_decode_insn(&opcode, &auprobe->api)) {
+ case INSN_REJECTED:
+ return -EINVAL;
+
+ case INSN_GOOD_NO_SLOT:
+ auprobe->simulate = true;
+ break;
+
+ case INSN_GOOD:
+ auprobe->simulate = false;
+ break;
+
+ default:
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
+int arch_uprobe_pre_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
+{
+ struct uprobe_task *utask = current->utask;
+
+ utask->autask.saved_cause = current->thread.bad_cause;
+ current->thread.bad_cause = UPROBE_TRAP_NR;
+
+ instruction_pointer_set(regs, utask->xol_vaddr);
+
+ regs->status &= ~SR_SPIE;
+
+ return 0;
+}
+
+int arch_uprobe_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
+{
+ struct uprobe_task *utask = current->utask;
+
+ WARN_ON_ONCE(current->thread.bad_cause != UPROBE_TRAP_NR);
+
+ instruction_pointer_set(regs, utask->vaddr + auprobe->insn_size);
+
+ regs->status |= SR_SPIE;
+
+ return 0;
+}
+
+bool arch_uprobe_xol_was_trapped(struct task_struct *t)
+{
+ if (t->thread.bad_cause != UPROBE_TRAP_NR)
+ return true;
+
+ return false;
+}
+
+bool arch_uprobe_skip_sstep(struct arch_uprobe *auprobe, struct pt_regs *regs)
+{
+ probe_opcode_t insn;
+ unsigned long addr;
+
+ if (!auprobe->simulate)
+ return false;
+
+ insn = *(probe_opcode_t *)(&auprobe->insn[0]);
+ addr = instruction_pointer(regs);
+
+ if (auprobe->api.handler)
+ auprobe->api.handler(insn, addr, regs);
+
+ return true;
+}
+
+void arch_uprobe_abort_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
+{
+ struct uprobe_task *utask = current->utask;
+
+ /*
+ * Task has received a fatal signal, so reset back to probbed
+ * address.
+ */
+ instruction_pointer_set(regs, utask->vaddr);
+
+ regs->status &= ~SR_SPIE;
+}
+
+bool arch_uretprobe_is_alive(struct return_instance *ret, enum rp_check ctx,
+ struct pt_regs *regs)
+{
+ if (ctx == RP_CHECK_CHAIN_CALL)
+ return regs->sp <= ret->stack;
+ else
+ return regs->sp < ret->stack;
+}
+
+unsigned long
+arch_uretprobe_hijack_return_addr(unsigned long trampoline_vaddr,
+ struct pt_regs *regs)
+{
+ unsigned long ra;
+
+ ra = regs->ra;
+
+ regs->ra = trampoline_vaddr;
+
+ return ra;
+}
+
+int arch_uprobe_exception_notify(struct notifier_block *self,
+ unsigned long val, void *data)
+{
+ return NOTIFY_DONE;
+}
+
+bool uprobe_breakpoint_handler(struct pt_regs *regs)
+{
+ if (uprobe_pre_sstep_notifier(regs))
+ return true;
+
+ return false;
+}
+
+bool uprobe_single_step_handler(struct pt_regs *regs)
+{
+ if (uprobe_post_sstep_notifier(regs))
+ return true;
+
+ return false;
+}
+
+void arch_uprobe_copy_ixol(struct page *page, unsigned long vaddr,
+ void *src, unsigned long len)
+{
+ /* Initialize the slot */
+ void *kaddr = kmap_atomic(page);
+ void *dst = kaddr + (vaddr & ~PAGE_MASK);
+
+ memcpy(dst, src, len);
+
+ /* Add ebreak behind opcode to simulate singlestep */
+ if (vaddr) {
+ dst += GET_INSN_LENGTH(*(probe_opcode_t *)src);
+ *(uprobe_opcode_t *)dst = __BUG_INSN_32;
+ }
+
+ kunmap_atomic(kaddr);
+
+ /*
+ * We probably need flush_icache_user_page() but it needs vma.
+ * This should work on most of architectures by default. If
+ * architecture needs to do something different it can define
+ * its own version of the function.
+ */
+ flush_dcache_page(page);
+}
diff --git a/arch/riscv/kernel/signal.c b/arch/riscv/kernel/signal.c
index e996e08..3c169ff 100644
--- a/arch/riscv/kernel/signal.c
+++ b/arch/riscv/kernel/signal.c
@@ -309,6 +309,9 @@ static void do_signal(struct pt_regs *regs)
asmlinkage __visible void do_notify_resume(struct pt_regs *regs,
unsigned long thread_info_flags)
{
+ if (thread_info_flags & _TIF_UPROBE)
+ uprobe_notify_resume(regs);
+
/* Handle pending signal delivery */
if (thread_info_flags & _TIF_SIGPENDING)
do_signal(regs);
diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
index 19a788a..2bca2fa 100644
--- a/arch/riscv/kernel/traps.c
+++ b/arch/riscv/kernel/traps.c
@@ -76,6 +76,8 @@ void do_trap(struct pt_regs *regs, int signo, int code, unsigned long addr)
static void do_trap_error(struct pt_regs *regs, int signo, int code,
unsigned long addr, const char *str)
{
+ current->thread.bad_cause = regs->cause;
+
if (user_mode(regs)) {
do_trap(regs, signo, code, addr);
} else {
@@ -153,6 +155,14 @@ asmlinkage __visible void do_trap_break(struct pt_regs *regs)
if (kprobe_breakpoint_handler(regs))
return;
#endif
+#ifdef CONFIG_UPROBES
+ if (uprobe_single_step_handler(regs))
+ return;
+
+ if (uprobe_breakpoint_handler(regs))
+ return;
+#endif
+ current->thread.bad_cause = regs->cause;

if (user_mode(regs))
force_sig_fault(SIGTRAP, TRAP_BRKPT, (void __user *)regs->epc);
diff --git a/arch/riscv/mm/fault.c b/arch/riscv/mm/fault.c
index 6afd59d..c186455 100644
--- a/arch/riscv/mm/fault.c
+++ b/arch/riscv/mm/fault.c
@@ -155,11 +155,14 @@ asmlinkage void do_page_fault(struct pt_regs *regs)
mmap_read_unlock(mm);
/* User mode accesses just cause a SIGSEGV */
if (user_mode(regs)) {
+ tsk->thread.bad_cause = cause;
do_trap(regs, SIGSEGV, code, addr);
return;
}

no_context:
+ tsk->thread.bad_cause = cause;
+
/* Are we prepared to handle this kernel fault? */
if (fixup_exception(regs))
return;
@@ -180,6 +183,8 @@ asmlinkage void do_page_fault(struct pt_regs *regs)
* (which will retry the fault, or kill us if we got oom-killed).
*/
out_of_memory:
+ tsk->thread.bad_cause = cause;
+
mmap_read_unlock(mm);
if (!user_mode(regs))
goto no_context;
@@ -187,6 +192,8 @@ asmlinkage void do_page_fault(struct pt_regs *regs)
return;

do_sigbus:
+ tsk->thread.bad_cause = cause;
+
mmap_read_unlock(mm);
/* Kernel mode? Handle exceptions or die */
if (!user_mode(regs))
--
2.7.4
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