Commit c505b0da authored May 19, 2020 by Vineet Gupta

ARC: entry: rework (non-functional)



 - comments update
 - rename syscall_trace_entry
 - use PT_xxx in entry code

Signed-off-by: Vineet Gupta <vgupta@kernel.org>

parent fd476197

arch/arc/include/asm/entry-arcv2.h

+14 −9

Original line number	Diff line number	Diff line
		@@ -48,14 +48,18 @@
		/------------------------------------------------------------------------/
		.macro INTERRUPT_PROLOGUE

		; (A) Before jumping to Interrupt Vector, hardware micro-ops did following:
		; Before jumping to Interrupt Vector, hardware micro-ops did following:
		; 1. SP auto-switched to kernel mode stack
		; 2. STATUS32.Z flag set if in U mode at time of interrupt (U:1,K:0)
		; 3. Auto save: (mandatory) Push PC and STAT32 on stack
		; hardware does even if CONFIG_ARC_IRQ_NO_AUTOSAVE
		; 4. Auto save: (optional) r0-r11, blink, LPE,LPS,LPC, JLI,LDI,EI
		; 4a. Auto save: (optional) r0-r11, blink, LPE,LPS,LPC, JLI,LDI,EI
		;
		; (B) Manually saved some regs: r12,r30, sp,fp,gp, ACCL pair
		; Now
		; 4b. If Auto-save (optional) not enabled in hw, manually save them
		; 5. Manually save: r12,r30, sp,fp,gp, ACCL pair
		;
		; At the end, SP points to pt_regs

		#ifdef CONFIG_ARC_IRQ_NO_AUTOSAVE
		; carve pt_regs on stack (case #3), PC/STAT32 already on stack
		@@ -73,13 +77,14 @@
		/------------------------------------------------------------------------/
		.macro EXCEPTION_PROLOGUE

		; (A) Before jumping to Exception Vector, hardware micro-ops did following:
		; Before jumping to Exception Vector, hardware micro-ops did following:
		; 1. SP auto-switched to kernel mode stack
		; 2. STATUS32.Z flag set if in U mode at time of exception (U:1,K:0)
		;
		; (B) Manually save the complete reg file below
		; Now manually save rest of reg file
		; At the end, SP points to pt_regs

		sub sp, sp, SZ_PT_REGS ; carve pt_regs
		sub sp, sp, SZ_PT_REGS ; carve space for pt_regs

		; _HARD saves r10 clobbered by _SOFT as scratch hence comes first

		@@ -136,8 +141,8 @@

		ST2 gp, fp, PT_r26 ; gp (r26), fp (r27)

		st r12, [sp, PT_sp + 4]
		st r30, [sp, PT_sp + 8]
		st r12, [sp, PT_r12]
		st r30, [sp, PT_r30]

		; Saving pt_regs->sp correctly requires some extra work due to the way
		; Auto stack switch works
		@@ -244,7 +249,7 @@

		btst r0, STATUS_U_BIT ; Z flag set if K, used in restoring SP

		ld r10, [sp, PT_event + 4]
		ld r10, [sp, PT_bta]
		sr r10, [erbta]

		LD2 r10, r11, PT_ret

arch/arc/include/asm/entry-compact.h

+2 −1

Original line number	Diff line number	Diff line
		@@ -170,12 +170,13 @@
		PUSHAX erbta

		lr r10, [ecr]
		st r10, [sp, PT_event] /* EV_Trap expects r10 to have ECR */
		st r10, [sp, PT_event]

		#ifdef CONFIG_ARC_CURR_IN_REG
		/* gp already saved on stack: now load with "current" */
		GET_CURR_TASK_ON_CPU gp
		#endif
		; OUTPUT: r10 has ECR expected by EV_Trap
		.endm

		/*--------------------------------------------------------------

arch/arc/include/asm/ptrace.h

+1 −1

Original line number	Diff line number	Diff line
		@@ -75,7 +75,7 @@ struct pt_regs {
		unsigned long event;
		};

		unsigned long bta; /* bta_l1, bta_l2, erbta */
		unsigned long bta; /* erbta */

		unsigned long r26; /* gp */
		unsigned long fp;

arch/arc/kernel/asm-offsets.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -47,6 +47,7 @@ int main(void)

		DEFINE(PT_status32, offsetof(struct pt_regs, status32));
		DEFINE(PT_event, offsetof(struct pt_regs, event));
		DEFINE(PT_bta, offsetof(struct pt_regs, bta));
		DEFINE(PT_sp, offsetof(struct pt_regs, sp));
		DEFINE(PT_r0, offsetof(struct pt_regs, r0));
		DEFINE(PT_r1, offsetof(struct pt_regs, r1));

arch/arc/kernel/entry.S

+20 −25

Original line number	Diff line number	Diff line
		@@ -160,20 +160,19 @@ END(EV_Extension)
		; syscall Tracing
		; ---------------------------------------------
		tracesys:
		; save EFA in case tracer wants the PC of traced task
		; using ERET won't work since next-PC has already committed
		; safekeep EFA (r12) if syscall tracer wanted PC
		; for traps, ERET is pre-commit so points to next-PC
		GET_CURR_TASK_FIELD_PTR TASK_THREAD, r11
		st r12, [r11, THREAD_FAULT_ADDR] ; thread.fault_address

		; PRE Sys Call Ptrace hook
		mov r0, sp ; pt_regs needed
		bl @syscall_trace_entry
		; PRE syscall trace hook
		mov r0, sp ; pt_regs
		bl @syscall_trace_enter

		; Tracing code now returns the syscall num (orig or modif)
		mov r8, r0

		; Do the Sys Call as we normally would.
		; Validate the Sys Call number
		cmp r8, NR_syscalls - 1
		mov.hi r0, -ENOSYS
		bhi tracesys_exit
		@@ -190,36 +189,36 @@ tracesys:
		ld r6, [sp, PT_r6]
		ld r7, [sp, PT_r7]
		ld.as r9, [sys_call_table, r8]
		jl [r9] ; Entry into Sys Call Handler
		jl [r9]

		tracesys_exit:
		st r0, [sp, PT_r0] ; sys call return value in pt_regs
		st r0, [sp, PT_r0]

		;POST Sys Call Ptrace Hook
		; POST syscall trace hook
		mov r0, sp ; pt_regs needed
		bl @syscall_trace_exit
		b ret_from_exception ; NOT ret_from_system_call at is saves r0 which
		; we'd done before calling post hook above

		; don't call ret_from_system_call as it saves r0, already done above
		b ret_from_exception

		; ---------------------------------------------
		; Breakpoint TRAP
		; ---------------------------------------------
		trap_with_param:
		mov r0, r12 ; EFA in case ptracer/gdb wants stop_pc
		mov r1, sp
		mov r1, sp ; pt_regs

		; Save callee regs in case gdb wants to have a look
		; SP will grow up by size of CALLEE Reg-File
		; save callee regs in case tracer/gdb wants to peek
		SAVE_CALLEE_SAVED_USER

		; save location of saved Callee Regs @ thread_struct->pc
		; safekeep ref to callee regs
		GET_CURR_TASK_FIELD_PTR TASK_THREAD, r10
		st sp, [r10, THREAD_CALLEE_REG]

		; Call the trap handler
		; call the non syscall trap handler
		bl do_non_swi_trap

		; unwind stack to discard Callee saved Regs
		; unwind stack to discard callee regs
		DISCARD_CALLEE_SAVED_USER

		b ret_from_exception
		@@ -237,31 +236,27 @@ ENTRY(EV_Trap)

		FAKE_RET_FROM_EXCPN

		;============ TRAP 1 :breakpoints
		; Check ECR for trap with arg (PROLOGUE ensures r10 has ECR)
		;============ TRAP N : breakpoints, kprobes etc
		bmsk.f 0, r10, 7
		bnz trap_with_param

		;============ TRAP (no param): syscall top level
		;============ TRAP 0 (no param): syscall

		; If syscall tracing ongoing, invoke pre-post-hooks
		; syscall tracing ongoing, invoke pre-post-hooks around syscall
		GET_CURR_THR_INFO_FLAGS r10
		and.f 0, r10, _TIF_SYSCALL_WORK
		bnz tracesys ; this never comes back

		;============ Normal syscall case

		; syscall num shd not exceed the total system calls avail
		cmp r8, NR_syscalls - 1
		mov.hi r0, -ENOSYS
		bhi .Lret_from_system_call

		; Offset into the syscall_table and call handler
		ld.as r9,[sys_call_table, r8]
		jl [r9] ; Entry into Sys Call Handler
		jl [r9]

		.Lret_from_system_call:

		st r0, [sp, PT_r0] ; sys call return value in pt_regs

		; fall through to ret_from_exception