WIP: BPF support for ARCv2 and ARCv3

arch/arc/Kconfig

@@ -38,8 +38,10 @@ config ARC
 	select HAVE_KERNEL_LZMA
 	select HAVE_KPROBES
 	select HAVE_KRETPROBES
+	select HAVE_REGS_AND_STACK_ACCESS_API
 	select HAVE_MOD_ARCH_SPECIFIC
 	select HAVE_PERF_EVENTS
+	select HAVE_SYSCALL_TRACEPOINTS
 	select IRQ_DOMAIN
 	select MODULES_USE_ELF_RELA
 	select OF

arch/arc/include/asm/perf_event.h

@@ -65,6 +65,10 @@ struct arc_reg_cc_build {
 
 #define PERF_COUNT_ARC_HW_MAX	(PERF_COUNT_HW_MAX + 8)
 
+#ifdef CONFIG_PERF_EVENTS
+#define perf_arch_bpf_user_pt_regs(regs) (struct user_regs_struct *)regs
+#endif
+
 /*
  * Some ARC pct quirks:
  *

arch/arc/include/asm/ptrace.h

@@ -8,6 +8,7 @@
 #define __ASM_ARC_PTRACE_H
 
 #include <uapi/asm/ptrace.h>
+#include <linux/compiler.h>
 
 #ifndef __ASSEMBLY__
 
@@ -53,6 +54,8 @@ struct pt_regs {
 	ecr_reg ecr;
 };
 
+#define MAX_REG_OFFSET offsetof(struct pt_regs, ecr)
+
 struct callee_regs {
 	unsigned long r25, r24, r23, r22, r21, r20, r19, r18, r17, r16, r15, r14, r13;
 };
@@ -95,6 +98,8 @@ struct pt_regs {
 	unsigned long status32;
 };
 
+#define MAX_REG_OFFSET offsetof(struct pt_regs, status32)
+
 struct callee_regs {
 	unsigned long r25, r24, r23, r22, r21, r20, r19, r18, r17, r16, r15, r14, r13;
 };
@@ -119,6 +124,8 @@ struct pt_regs {
 	unsigned long status32;
 };
 
+#define MAX_REG_OFFSET offsetof(struct pt_regs, status32)
+
 /* ARCv3 callee regs start from r14; gp is r30 not r26 */
 struct callee_regs {
 	unsigned long r14, r15, r16, r17, r18, r19, r20, r21, r22, r23, r24, r25, r26;
@@ -170,6 +177,27 @@ static inline void instruction_pointer_set(struct pt_regs *regs,
 {
 	instruction_pointer(regs) = val;
 }
+
+static inline unsigned long kernel_stack_pointer(struct pt_regs *regs)
+{
+	return regs->sp;
+}
+
+extern int regs_query_register_offset(const char *name);
+extern const char *regs_query_register_name(unsigned int offset);
+extern bool regs_within_kernel_stack(struct pt_regs *regs, unsigned long addr);
+extern unsigned long regs_get_kernel_stack_nth(struct pt_regs *regs,
+					       unsigned int n);
+
+static inline unsigned long regs_get_register(struct pt_regs *regs,
+					      unsigned int offset)
+{
+	if (unlikely(offset > MAX_REG_OFFSET))
+		return 0;
+
+	return *(unsigned long *)((unsigned long)regs + offset);
+}
+
 #endif /* !__ASSEMBLY__ */
 
 #endif /* __ASM_PTRACE_H */

arch/arc/include/asm/syscall.h

@@ -12,6 +12,8 @@
 #include <asm/unistd.h>
 #include <asm/ptrace.h>		/* in_syscall() */
 
+extern void *sys_call_table[];
+
 static inline long
 syscall_get_nr(struct task_struct *task, struct pt_regs *regs)
 {

arch/arc/include/asm/thread_info.h

@@ -82,6 +82,7 @@ static inline __attribute_const__ struct thread_info *current_thread_info(void)
 #define TIF_NOTIFY_SIGNAL	5	/* signal notifications exist */
 #define TIF_SYSCALL_TRACE	15	/* syscall trace active */
 #define TIF_MEMDIE		16
+#define TIF_SYSCALL_TRACEPOINT	17	/* syscall tracepoint instrumentation */
 
 #define _TIF_SYSCALL_TRACE	(1<<TIF_SYSCALL_TRACE)
 #define _TIF_NOTIFY_RESUME	(1<<TIF_NOTIFY_RESUME)
@@ -91,11 +92,14 @@ static inline __attribute_const__ struct thread_info *current_thread_info(void)
 #define _TIF_NOTIFY_SIGNAL	(1<<TIF_NOTIFY_SIGNAL)
 #define _TIF_SYSCALL_TRACE	(1<<TIF_SYSCALL_TRACE)
 #define _TIF_MEMDIE		(1<<TIF_MEMDIE)
+#define _TIF_SYSCALL_TRACEPOINT	(1<<TIF_SYSCALL_TRACEPOINT)
 
 /* work to do on interrupt/exception return */
 #define _TIF_WORK_MASK		(_TIF_NEED_RESCHED | _TIF_SIGPENDING | \
 				 _TIF_NOTIFY_RESUME | _TIF_NOTIFY_SIGNAL)
 
+#define _TIF_SYSCALL_WORK	(_TIF_SYSCALL_TRACE | _TIF_SYSCALL_TRACEPOINT)
+
 /*
  * _TIF_ALLWORK_MASK includes SYSCALL_TRACE, but we don't need it.
  * SYSCALL_TRACE is anyway seperately/unconditionally tested right after a

arch/arc/include/uapi/asm/bpf_perf_event.h

@@ -0,0 +1,9 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+#ifndef _UAPI__ASM_BPF_PERF_EVENT_H__
+#define _UAPI__ASM_BPF_PERF_EVENT_H__
+
+#include <asm/ptrace.h>
+
+typedef struct user_regs_struct bpf_user_pt_regs_t;
+
+#endif /* _UAPI__ASM_BPF_PERF_EVENT_H__ */

arch/arc/kernel/disasm.c

@@ -434,18 +434,60 @@ long __kprobes get_reg(int reg, struct pt_regs *regs,
 {
 	long *p;
 
+#if defined(CONFIG_ISA_ARCOMPACT)
 	if (reg <= 12) {
 		p = &regs->r0;
 		return p[-reg];
 	}
 
 	if (cregs && (reg <= 25)) {
 		p = &cregs->r13;
-		return p[13-reg];
+		return p[13 - reg];
 	}
 
 	if (reg == 26)
 		return regs->gp;
+
+#elif defined(CONFIG_ISA_ARCV2)
+	if (reg <= 11) {
+		p = &regs->r0;
+		return p[reg];
+	}
+
+	if (reg == 12)
+		return regs->r12;
+
+	if (cregs && (reg <= 25)) {
+		p = &cregs->r13;
+		return p[13 - reg];
+	}
+
+	if (reg == 26)
+		return regs->gp;
+	if (reg == 30)
+		return regs->r30;
+#ifdef CONFIG_ARC_HAS_ACCL_REGS
+	if (reg == 58)
+		return regs->r58;
+	if (reg == 59)
+		return regs->r59;
+#endif
+
+#else /* CONFIG_ISA_ARCV3 */
+	if (reg <= 13) {
+		p = &regs->r0;
+		return p[reg];
+	}
+
+	if (cregs && (reg <= 26)) {
+		p = &cregs->r14;
+		return p[reg - 14];
+	}
+
+	if (reg == 30)
+		return regs->gp;
+#endif
+
 	if (reg == 27)
 		return regs->fp;
 	if (reg == 28)
@@ -461,6 +503,7 @@ void __kprobes set_reg(int reg, long val, struct pt_regs *regs,
 {
 	long *p;
 
+#if defined(CONFIG_ISA_ARCOMPACT)
 	switch (reg) {
 	case 0 ... 12:
 		p = &regs->r0;
@@ -469,7 +512,7 @@ void __kprobes set_reg(int reg, long val, struct pt_regs *regs,
 	case 13 ... 25:
 		if (cregs) {
 			p = &cregs->r13;
-			p[13-reg] = val;
+			p[13 - reg] = val;
 		}
 		break;
 	case 26:
@@ -487,6 +530,76 @@ void __kprobes set_reg(int reg, long val, struct pt_regs *regs,
 	default:
 		break;
 	}
+#elif defined(CONFIG_ISA_ARCV2)
+	switch (reg) {
+	case 0 ... 11:
+		p = &regs->r0;
+		p[reg] = val;
+		break;
+	case 12:
+		regs->r12 = val;
+		break;
+	case 13 ... 25:
+		if (cregs) {
+			p = &cregs->r13;
+			p[13 - reg] = val;
+		}
+		break;
+	case 26:
+		regs->gp = val;
+		break;
+	case 27:
+		regs->fp = val;
+		break;
+	case 28:
+		regs->sp = val;
+		break;
+	case 30:
+		regs->r30 = val;
+		break;
+	case 31:
+		regs->blink = val;
+		break;
+#ifdef CONFIG_ARC_HAS_ACCL_REGS
+	case 58:
+		regs->r58 = val;
+		break;
+	case 59:
+		regs->r59 = val;
+		break;
+#endif
+	default:
+		break;
+	}
+#else /* CONFIG_ISA_ARCV3 */
+	switch (reg) {
+	case 0 ... 13:
+		p = &regs->r0;
+		p[reg] = val;
+		break;
+	case 14 ... 26:
+		if (cregs) {
+			p = &cregs->r14;
+			p[reg - 14] = val;
+		}
+		break;
+	case 27:
+		regs->fp = val;
+		break;
+	case 28:
+		regs->sp = val;
+		break;
+	case 30:
+		regs->gp = val;
+		break;
+	case 31:
+		regs->blink = val;
+		break;
+	default:
+		break;
+	}
+
+#endif
 }
 
 /*

arch/arc/kernel/entry.S

@@ -29,8 +29,8 @@ ENTRY(sys_clone_wrapper)
 	DISCARD_CALLEE_SAVED_USER
 
 	GET_CURR_THR_INFO_FLAGS   r10
-	btst r10, TIF_SYSCALL_TRACE
-	bnz  tracesys_exit
+	and.f 0, r10, _TIF_SYSCALL_WORK
+	bnz   tracesys_exit
 
 	b .Lret_from_system_call
 END(sys_clone_wrapper)
@@ -41,8 +41,8 @@ ENTRY(sys_clone3_wrapper)
 	DISCARD_CALLEE_SAVED_USER
 
 	GET_CURR_THR_INFO_FLAGS   r10
-	btst r10, TIF_SYSCALL_TRACE
-	bnz  tracesys_exit
+	and.f 0, r10, _TIF_SYSCALL_WORK
+	bnz   tracesys_exit
 
 	b .Lret_from_system_call
 END(sys_clone3_wrapper)
@@ -175,6 +175,7 @@ tracesys_exit:
 	STR  r0, sp, PT_r0
 
 	; POST syscall trace hook
+	MOVR r0, sp				; pt_regs
 	bl  @syscall_trace_exit
 
 	; don't call ret_from_system_call as it saves r0, already done above
@@ -223,8 +224,8 @@ ENTRY(EV_Trap)
 
 	; syscall tracing ongoing, invoke pre-post-hooks around syscall
 	GET_CURR_THR_INFO_FLAGS   r10
-	btst r10, TIF_SYSCALL_TRACE
-	bnz tracesys  ; this never comes back
+	and.f 0, r10, _TIF_SYSCALL_WORK
+	bnz   tracesys  ; this never comes back
 
 	;============ Normal syscall case