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linux/arch/powerpc/platforms/pseries/hvCall.S
Nicholas Piggin 61d7ebe037 powerpc/pseries: Remove unused hcall tracing instruction 
When JUMP_LABEL=n, the tracepoint refcount test in the pre-call stores
the refcount value to the stack, so the same value can be used for the
post-call (presumably to avoid racing with the value concurrently
changing).

On little-endian (ELFv2) that might have just worked by luck, because
32(r1) is STK_PARAM(R3) there and so the value save gets clobbered by
the tracing code when it's non-zero, but fortunately r3 is the hcall
number and 0 is an invalid hcall number so it should get clobbered by
another non-zero value. In any case, commit cc1adb5f32
("powerpc/pseries: Use jump labels for hcall tracepoints") removed the
code that actually used the value stored, so now it's just dead code.

It's fragile to be storing to the stack like this, and confusing. Better
remove it.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230509091600.70994-2-npiggin@gmail.com
2023-08-25 08:39:30 +10:00

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/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
* This file contains the generic code to perform a call to the
* pSeries LPAR hypervisor.
*/
#include <linux/jump_label.h>
#include <asm/hvcall.h>
#include <asm/processor.h>
#include <asm/ppc_asm.h>
#include <asm/asm-offsets.h>
#include <asm/ptrace.h>
#include <asm/feature-fixups.h>
.section ".text"
#ifdef CONFIG_TRACEPOINTS
#ifndef CONFIG_JUMP_LABEL
.data
.globl hcall_tracepoint_refcount
hcall_tracepoint_refcount:
.8byte 0
.section ".text"
#endif
/*
* precall must preserve all registers. use unused STK_PARAM()
* areas to save snapshots and opcode. STK_PARAM() in the caller's
* frame will be available even on ELFv2 because these are all
* variadic functions.
*/
#define HCALL_INST_PRECALL(FIRST_REG) \
mflr r0; \
std r3,STK_PARAM(R3)(r1); \
std r4,STK_PARAM(R4)(r1); \
std r5,STK_PARAM(R5)(r1); \
std r6,STK_PARAM(R6)(r1); \
std r7,STK_PARAM(R7)(r1); \
std r8,STK_PARAM(R8)(r1); \
std r9,STK_PARAM(R9)(r1); \
std r10,STK_PARAM(R10)(r1); \
std r0,16(r1); \
addi r4,r1,STK_PARAM(FIRST_REG); \
stdu r1,-STACK_FRAME_MIN_SIZE(r1); \
bl CFUNC(__trace_hcall_entry); \
ld r3,STACK_FRAME_MIN_SIZE+STK_PARAM(R3)(r1); \
ld r4,STACK_FRAME_MIN_SIZE+STK_PARAM(R4)(r1); \
ld r5,STACK_FRAME_MIN_SIZE+STK_PARAM(R5)(r1); \
ld r6,STACK_FRAME_MIN_SIZE+STK_PARAM(R6)(r1); \
ld r7,STACK_FRAME_MIN_SIZE+STK_PARAM(R7)(r1); \
ld r8,STACK_FRAME_MIN_SIZE+STK_PARAM(R8)(r1); \
ld r9,STACK_FRAME_MIN_SIZE+STK_PARAM(R9)(r1); \
ld r10,STACK_FRAME_MIN_SIZE+STK_PARAM(R10)(r1)
/*
* postcall is performed immediately before function return which
* allows liberal use of volatile registers.
*/
#define __HCALL_INST_POSTCALL \
ld r0,STACK_FRAME_MIN_SIZE+STK_PARAM(R3)(r1); \
std r3,STACK_FRAME_MIN_SIZE+STK_PARAM(R3)(r1); \
mr r4,r3; \
mr r3,r0; \
bl CFUNC(__trace_hcall_exit); \
ld r0,STACK_FRAME_MIN_SIZE+16(r1); \
addi r1,r1,STACK_FRAME_MIN_SIZE; \
ld r3,STK_PARAM(R3)(r1); \
mtlr r0
#define HCALL_INST_POSTCALL_NORETS \
li r5,0; \
__HCALL_INST_POSTCALL
#define HCALL_INST_POSTCALL(BUFREG) \
mr r5,BUFREG; \
__HCALL_INST_POSTCALL
#ifdef CONFIG_JUMP_LABEL
#define HCALL_BRANCH(LABEL) \
ARCH_STATIC_BRANCH(LABEL, hcall_tracepoint_key)
#else
/*
* We branch around this in early init (eg when populating the MMU
* hashtable) by using an unconditional cpu feature.
*/
#define HCALL_BRANCH(LABEL) \
BEGIN_FTR_SECTION; \
b 1f; \
END_FTR_SECTION(0, 1); \
LOAD_REG_ADDR(r12, hcall_tracepoint_refcount) ; \
ld r12,0(r12); \
cmpdi r12,0; \
bne- LABEL; \
1:
#endif
#else
#define HCALL_INST_PRECALL(FIRST_ARG)
#define HCALL_INST_POSTCALL_NORETS
#define HCALL_INST_POSTCALL(BUFREG)
#define HCALL_BRANCH(LABEL)
#endif
_GLOBAL_TOC(plpar_hcall_norets_notrace)
HMT_MEDIUM
mfcr r0
stw r0,8(r1)
HVSC /* invoke the hypervisor */
li r4,0
stb r4,PACASRR_VALID(r13)
lwz r0,8(r1)
mtcrf 0xff,r0
blr /* return r3 = status */
_GLOBAL_TOC(plpar_hcall_norets)
HMT_MEDIUM
mfcr r0
stw r0,8(r1)
HCALL_BRANCH(plpar_hcall_norets_trace)
HVSC /* invoke the hypervisor */
li r4,0
stb r4,PACASRR_VALID(r13)
lwz r0,8(r1)
mtcrf 0xff,r0
blr /* return r3 = status */
#ifdef CONFIG_TRACEPOINTS
plpar_hcall_norets_trace:
HCALL_INST_PRECALL(R4)
HVSC
HCALL_INST_POSTCALL_NORETS
li r4,0
stb r4,PACASRR_VALID(r13)
lwz r0,8(r1)
mtcrf 0xff,r0
blr
#endif
_GLOBAL_TOC(plpar_hcall)
HMT_MEDIUM
mfcr r0
stw r0,8(r1)
HCALL_BRANCH(plpar_hcall_trace)
std r4,STK_PARAM(R4)(r1) /* Save ret buffer */
mr r4,r5
mr r5,r6
mr r6,r7
mr r7,r8
mr r8,r9
mr r9,r10
HVSC /* invoke the hypervisor */
ld r12,STK_PARAM(R4)(r1)
std r4, 0(r12)
std r5, 8(r12)
std r6, 16(r12)
std r7, 24(r12)
li r4,0
stb r4,PACASRR_VALID(r13)
lwz r0,8(r1)
mtcrf 0xff,r0
blr /* return r3 = status */
#ifdef CONFIG_TRACEPOINTS
plpar_hcall_trace:
HCALL_INST_PRECALL(R5)
std r4,STK_PARAM(R4)(r1)
mr r0,r4
mr r4,r5
mr r5,r6
mr r6,r7
mr r7,r8
mr r8,r9
mr r9,r10
HVSC
ld r12,STK_PARAM(R4)(r1)
std r4,0(r12)
std r5,8(r12)
std r6,16(r12)
std r7,24(r12)
HCALL_INST_POSTCALL(r12)
li r4,0
stb r4,PACASRR_VALID(r13)
lwz r0,8(r1)
mtcrf 0xff,r0
blr
#endif
/*
* plpar_hcall_raw can be called in real mode. kexec/kdump need some
* hypervisor calls to be executed in real mode. So plpar_hcall_raw
* does not access the per cpu hypervisor call statistics variables,
* since these variables may not be present in the RMO region.
*/
_GLOBAL(plpar_hcall_raw)
HMT_MEDIUM
mfcr r0
stw r0,8(r1)
std r4,STK_PARAM(R4)(r1) /* Save ret buffer */
mr r4,r5
mr r5,r6
mr r6,r7
mr r7,r8
mr r8,r9
mr r9,r10
HVSC /* invoke the hypervisor */
ld r12,STK_PARAM(R4)(r1)
std r4, 0(r12)
std r5, 8(r12)
std r6, 16(r12)
std r7, 24(r12)
li r4,0
stb r4,PACASRR_VALID(r13)
lwz r0,8(r1)
mtcrf 0xff,r0
blr /* return r3 = status */
_GLOBAL_TOC(plpar_hcall9)
HMT_MEDIUM
mfcr r0
stw r0,8(r1)
HCALL_BRANCH(plpar_hcall9_trace)
std r4,STK_PARAM(R4)(r1) /* Save ret buffer */
mr r4,r5
mr r5,r6
mr r6,r7
mr r7,r8
mr r8,r9
mr r9,r10
ld r10,STK_PARAM(R11)(r1) /* put arg7 in R10 */
ld r11,STK_PARAM(R12)(r1) /* put arg8 in R11 */
ld r12,STK_PARAM(R13)(r1) /* put arg9 in R12 */
HVSC /* invoke the hypervisor */
mr r0,r12
ld r12,STK_PARAM(R4)(r1)
std r4, 0(r12)
std r5, 8(r12)
std r6, 16(r12)
std r7, 24(r12)
std r8, 32(r12)
std r9, 40(r12)
std r10,48(r12)
std r11,56(r12)
std r0, 64(r12)
li r4,0
stb r4,PACASRR_VALID(r13)
lwz r0,8(r1)
mtcrf 0xff,r0
blr /* return r3 = status */
#ifdef CONFIG_TRACEPOINTS
plpar_hcall9_trace:
HCALL_INST_PRECALL(R5)
std r4,STK_PARAM(R4)(r1)
mr r0,r4
mr r4,r5
mr r5,r6
mr r6,r7
mr r7,r8
mr r8,r9
mr r9,r10
ld r10,STACK_FRAME_MIN_SIZE+STK_PARAM(R11)(r1)
ld r11,STACK_FRAME_MIN_SIZE+STK_PARAM(R12)(r1)
ld r12,STACK_FRAME_MIN_SIZE+STK_PARAM(R13)(r1)
HVSC
mr r0,r12
ld r12,STACK_FRAME_MIN_SIZE+STK_PARAM(R4)(r1)
std r4,0(r12)
std r5,8(r12)
std r6,16(r12)
std r7,24(r12)
std r8,32(r12)
std r9,40(r12)
std r10,48(r12)
std r11,56(r12)
std r0,64(r12)
HCALL_INST_POSTCALL(r12)
li r4,0
stb r4,PACASRR_VALID(r13)
lwz r0,8(r1)
mtcrf 0xff,r0
blr
#endif
/* See plpar_hcall_raw to see why this is needed */
_GLOBAL(plpar_hcall9_raw)
HMT_MEDIUM
mfcr r0
stw r0,8(r1)
std r4,STK_PARAM(R4)(r1) /* Save ret buffer */
mr r4,r5
mr r5,r6
mr r6,r7
mr r7,r8
mr r8,r9
mr r9,r10
ld r10,STK_PARAM(R11)(r1) /* put arg7 in R10 */
ld r11,STK_PARAM(R12)(r1) /* put arg8 in R11 */
ld r12,STK_PARAM(R13)(r1) /* put arg9 in R12 */
HVSC /* invoke the hypervisor */
mr r0,r12
ld r12,STK_PARAM(R4)(r1)
std r4, 0(r12)
std r5, 8(r12)
std r6, 16(r12)
std r7, 24(r12)
std r8, 32(r12)
std r9, 40(r12)
std r10,48(r12)
std r11,56(r12)
std r0, 64(r12)
li r4,0
stb r4,PACASRR_VALID(r13)
lwz r0,8(r1)
mtcrf 0xff,r0
blr /* return r3 = status */
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