[PATCH 13/20] ARC: entry: rework (non-functional)

From: Vineet Gupta
Date: Mon Aug 14 2023 - 20:49:36 EST

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

Signed-off-by: Vineet Gupta <vgupta@xxxxxxxxxx>
---
arch/arc/include/asm/entry-arcv2.h | 23 ++++++++------
arch/arc/include/asm/entry-compact.h | 3 +-
arch/arc/include/asm/ptrace.h | 2 +-
arch/arc/kernel/asm-offsets.c | 1 +
arch/arc/kernel/entry.S | 45 +++++++++++++---------------
arch/arc/kernel/ptrace.c | 2 +-
6 files changed, 39 insertions(+), 37 deletions(-)

diff --git a/arch/arc/include/asm/entry-arcv2.h b/arch/arc/include/asm/entry-arcv2.h
index 858742feab71..a38ed505b3de 100644
--- a/arch/arc/include/asm/entry-arcv2.h
+++ b/arch/arc/include/asm/entry-arcv2.h
@@ -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
diff --git a/arch/arc/include/asm/entry-compact.h b/arch/arc/include/asm/entry-compact.h
index e3383e1cb040..4e2ae82779ed 100644
--- a/arch/arc/include/asm/entry-compact.h
+++ b/arch/arc/include/asm/entry-compact.h
@@ -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

/*--------------------------------------------------------------
diff --git a/arch/arc/include/asm/ptrace.h b/arch/arc/include/asm/ptrace.h
index e9798f46cdc4..2bf8ea96ea21 100644
--- a/arch/arc/include/asm/ptrace.h
+++ b/arch/arc/include/asm/ptrace.h
@@ -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;
diff --git a/arch/arc/kernel/asm-offsets.c b/arch/arc/kernel/asm-offsets.c
index 5b47d09b925e..e46688975868 100644
--- a/arch/arc/kernel/asm-offsets.c
+++ b/arch/arc/kernel/asm-offsets.c
@@ -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));
diff --git a/arch/arc/kernel/entry.S b/arch/arc/kernel/entry.S
index cd26e0fa5044..f291fc8476d7 100644
--- a/arch/arc/kernel/entry.S
+++ b/arch/arc/kernel/entry.S
@@ -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
diff --git a/arch/arc/kernel/ptrace.c b/arch/arc/kernel/ptrace.c
index 8226df3163fe..14ea7406f5cd 100644
--- a/arch/arc/kernel/ptrace.c
+++ b/arch/arc/kernel/ptrace.c
@@ -339,7 +339,7 @@ long arch_ptrace(struct task_struct *child, long request,
return ret;
}

-asmlinkage int syscall_trace_entry(struct pt_regs *regs)
+asmlinkage int syscall_trace_enter(struct pt_regs *regs)
{
if (test_thread_flag(TIF_SYSCALL_TRACE))
if (ptrace_report_syscall_entry(regs))
--
2.34.1

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