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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
        "Peter Zijlstra (Intel)" <peterz@infradead.org>
Subject: [PATCH 5.4 46/58] selftests/rseq: Remove arm/mips asm goto compiler work-around
Date:   Tue,  5 Jul 2022 13:58:22 +0200
Message-Id: <20220705115611.594384517@linuxfoundation.org>
In-Reply-To: <20220705115610.236040773@linuxfoundation.org>
References: <20220705115610.236040773@linuxfoundation.org>
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From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

commit 94c5cf2a0e193afffef8de48ddc42de6df7cac93 upstream.

The arm and mips work-around for asm goto size guess issues are not
properly documented, and lack reference to specific compiler versions,
upstream compiler bug tracker entry, and reproducer.

I can only find a loosely documented patch in my original LKML rseq post
refering to gcc < 7 on ARM, but it does not appear to be sufficient to
track the exact issue. Also, I am not sure MIPS really has the same
limitation.

Therefore, remove the work-around until we can properly document this.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/lkml/20171121141900.18471-17-mathieu.desnoyers@efficios.com/
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 tools/testing/selftests/rseq/rseq-arm.h  |   37 -------------------------------
 tools/testing/selftests/rseq/rseq-mips.h |   37 -------------------------------
 2 files changed, 74 deletions(-)

--- a/tools/testing/selftests/rseq/rseq-arm.h
+++ b/tools/testing/selftests/rseq/rseq-arm.h
@@ -147,14 +147,11 @@ do {									\
 		teardown						\
 		"b %l[" __rseq_str(cmpfail_label) "]\n\t"
 
-#define rseq_workaround_gcc_asm_size_guess()	__asm__ __volatile__("")
-
 static inline __attribute__((always_inline))
 int rseq_cmpeqv_storev(intptr_t *v, intptr_t expect, intptr_t newv, int cpu)
 {
 	RSEQ_INJECT_C(9)
 
-	rseq_workaround_gcc_asm_size_guess();
 	__asm__ __volatile__ goto (
 		RSEQ_ASM_DEFINE_TABLE(9, 1f, 2f, 4f) /* start, commit, abort */
 		RSEQ_ASM_DEFINE_EXIT_POINT(1f, %l[cmpfail])
@@ -198,14 +195,11 @@ int rseq_cmpeqv_storev(intptr_t *v, intp
 		  , error1, error2
 #endif
 	);
-	rseq_workaround_gcc_asm_size_guess();
 	return 0;
 abort:
-	rseq_workaround_gcc_asm_size_guess();
 	RSEQ_INJECT_FAILED
 	return -1;
 cmpfail:
-	rseq_workaround_gcc_asm_size_guess();
 	return 1;
 #ifdef RSEQ_COMPARE_TWICE
 error1:
@@ -221,7 +215,6 @@ int rseq_cmpnev_storeoffp_load(intptr_t
 {
 	RSEQ_INJECT_C(9)
 
-	rseq_workaround_gcc_asm_size_guess();
 	__asm__ __volatile__ goto (
 		RSEQ_ASM_DEFINE_TABLE(9, 1f, 2f, 4f) /* start, commit, abort */
 		RSEQ_ASM_DEFINE_EXIT_POINT(1f, %l[cmpfail])
@@ -270,14 +263,11 @@ int rseq_cmpnev_storeoffp_load(intptr_t
 		  , error1, error2
 #endif
 	);
-	rseq_workaround_gcc_asm_size_guess();
 	return 0;
 abort:
-	rseq_workaround_gcc_asm_size_guess();
 	RSEQ_INJECT_FAILED
 	return -1;
 cmpfail:
-	rseq_workaround_gcc_asm_size_guess();
 	return 1;
 #ifdef RSEQ_COMPARE_TWICE
 error1:
@@ -292,7 +282,6 @@ int rseq_addv(intptr_t *v, intptr_t coun
 {
 	RSEQ_INJECT_C(9)
 
-	rseq_workaround_gcc_asm_size_guess();
 	__asm__ __volatile__ goto (
 		RSEQ_ASM_DEFINE_TABLE(9, 1f, 2f, 4f) /* start, commit, abort */
 #ifdef RSEQ_COMPARE_TWICE
@@ -328,10 +317,8 @@ int rseq_addv(intptr_t *v, intptr_t coun
 		  , error1
 #endif
 	);
-	rseq_workaround_gcc_asm_size_guess();
 	return 0;
 abort:
-	rseq_workaround_gcc_asm_size_guess();
 	RSEQ_INJECT_FAILED
 	return -1;
 #ifdef RSEQ_COMPARE_TWICE
@@ -347,7 +334,6 @@ int rseq_cmpeqv_trystorev_storev(intptr_
 {
 	RSEQ_INJECT_C(9)
 
-	rseq_workaround_gcc_asm_size_guess();
 	__asm__ __volatile__ goto (
 		RSEQ_ASM_DEFINE_TABLE(9, 1f, 2f, 4f) /* start, commit, abort */
 		RSEQ_ASM_DEFINE_EXIT_POINT(1f, %l[cmpfail])
@@ -398,14 +384,11 @@ int rseq_cmpeqv_trystorev_storev(intptr_
 		  , error1, error2
 #endif
 	);
-	rseq_workaround_gcc_asm_size_guess();
 	return 0;
 abort:
-	rseq_workaround_gcc_asm_size_guess();
 	RSEQ_INJECT_FAILED
 	return -1;
 cmpfail:
-	rseq_workaround_gcc_asm_size_guess();
 	return 1;
 #ifdef RSEQ_COMPARE_TWICE
 error1:
@@ -422,7 +405,6 @@ int rseq_cmpeqv_trystorev_storev_release
 {
 	RSEQ_INJECT_C(9)
 
-	rseq_workaround_gcc_asm_size_guess();
 	__asm__ __volatile__ goto (
 		RSEQ_ASM_DEFINE_TABLE(9, 1f, 2f, 4f) /* start, commit, abort */
 		RSEQ_ASM_DEFINE_EXIT_POINT(1f, %l[cmpfail])
@@ -474,14 +456,11 @@ int rseq_cmpeqv_trystorev_storev_release
 		  , error1, error2
 #endif
 	);
-	rseq_workaround_gcc_asm_size_guess();
 	return 0;
 abort:
-	rseq_workaround_gcc_asm_size_guess();
 	RSEQ_INJECT_FAILED
 	return -1;
 cmpfail:
-	rseq_workaround_gcc_asm_size_guess();
 	return 1;
 #ifdef RSEQ_COMPARE_TWICE
 error1:
@@ -498,7 +477,6 @@ int rseq_cmpeqv_cmpeqv_storev(intptr_t *
 {
 	RSEQ_INJECT_C(9)
 
-	rseq_workaround_gcc_asm_size_guess();
 	__asm__ __volatile__ goto (
 		RSEQ_ASM_DEFINE_TABLE(9, 1f, 2f, 4f) /* start, commit, abort */
 		RSEQ_ASM_DEFINE_EXIT_POINT(1f, %l[cmpfail])
@@ -554,14 +532,11 @@ int rseq_cmpeqv_cmpeqv_storev(intptr_t *
 		  , error1, error2, error3
 #endif
 	);
-	rseq_workaround_gcc_asm_size_guess();
 	return 0;
 abort:
-	rseq_workaround_gcc_asm_size_guess();
 	RSEQ_INJECT_FAILED
 	return -1;
 cmpfail:
-	rseq_workaround_gcc_asm_size_guess();
 	return 1;
 #ifdef RSEQ_COMPARE_TWICE
 error1:
@@ -582,7 +557,6 @@ int rseq_cmpeqv_trymemcpy_storev(intptr_
 
 	RSEQ_INJECT_C(9)
 
-	rseq_workaround_gcc_asm_size_guess();
 	__asm__ __volatile__ goto (
 		RSEQ_ASM_DEFINE_TABLE(9, 1f, 2f, 4f) /* start, commit, abort */
 		RSEQ_ASM_DEFINE_EXIT_POINT(1f, %l[cmpfail])
@@ -678,21 +652,16 @@ int rseq_cmpeqv_trymemcpy_storev(intptr_
 		  , error1, error2
 #endif
 	);
-	rseq_workaround_gcc_asm_size_guess();
 	return 0;
 abort:
-	rseq_workaround_gcc_asm_size_guess();
 	RSEQ_INJECT_FAILED
 	return -1;
 cmpfail:
-	rseq_workaround_gcc_asm_size_guess();
 	return 1;
 #ifdef RSEQ_COMPARE_TWICE
 error1:
-	rseq_workaround_gcc_asm_size_guess();
 	rseq_bug("cpu_id comparison failed");
 error2:
-	rseq_workaround_gcc_asm_size_guess();
 	rseq_bug("expected value comparison failed");
 #endif
 }
@@ -706,7 +675,6 @@ int rseq_cmpeqv_trymemcpy_storev_release
 
 	RSEQ_INJECT_C(9)
 
-	rseq_workaround_gcc_asm_size_guess();
 	__asm__ __volatile__ goto (
 		RSEQ_ASM_DEFINE_TABLE(9, 1f, 2f, 4f) /* start, commit, abort */
 		RSEQ_ASM_DEFINE_EXIT_POINT(1f, %l[cmpfail])
@@ -803,21 +771,16 @@ int rseq_cmpeqv_trymemcpy_storev_release
 		  , error1, error2
 #endif
 	);
-	rseq_workaround_gcc_asm_size_guess();
 	return 0;
 abort:
-	rseq_workaround_gcc_asm_size_guess();
 	RSEQ_INJECT_FAILED
 	return -1;
 cmpfail:
-	rseq_workaround_gcc_asm_size_guess();
 	return 1;
 #ifdef RSEQ_COMPARE_TWICE
 error1:
-	rseq_workaround_gcc_asm_size_guess();
 	rseq_bug("cpu_id comparison failed");
 error2:
-	rseq_workaround_gcc_asm_size_guess();
 	rseq_bug("expected value comparison failed");
 #endif
 }
--- a/tools/testing/selftests/rseq/rseq-mips.h
+++ b/tools/testing/selftests/rseq/rseq-mips.h
@@ -154,14 +154,11 @@ do {									\
 		teardown \
 		"b %l[" __rseq_str(cmpfail_label) "]\n\t"
 
-#define rseq_workaround_gcc_asm_size_guess()	__asm__ __volatile__("")
-
 static inline __attribute__((always_inline))
 int rseq_cmpeqv_storev(intptr_t *v, intptr_t expect, intptr_t newv, int cpu)
 {
 	RSEQ_INJECT_C(9)
 
-	rseq_workaround_gcc_asm_size_guess();
 	__asm__ __volatile__ goto (
 		RSEQ_ASM_DEFINE_TABLE(9, 1f, 2f, 4f) /* start, commit, abort */
 		RSEQ_ASM_DEFINE_EXIT_POINT(1f, %l[cmpfail])
@@ -203,14 +200,11 @@ int rseq_cmpeqv_storev(intptr_t *v, intp
 		  , error1, error2
 #endif
 	);
-	rseq_workaround_gcc_asm_size_guess();
 	return 0;
 abort:
-	rseq_workaround_gcc_asm_size_guess();
 	RSEQ_INJECT_FAILED
 	return -1;
 cmpfail:
-	rseq_workaround_gcc_asm_size_guess();
 	return 1;
 #ifdef RSEQ_COMPARE_TWICE
 error1:
@@ -226,7 +220,6 @@ int rseq_cmpnev_storeoffp_load(intptr_t
 {
 	RSEQ_INJECT_C(9)
 
-	rseq_workaround_gcc_asm_size_guess();
 	__asm__ __volatile__ goto (
 		RSEQ_ASM_DEFINE_TABLE(9, 1f, 2f, 4f) /* start, commit, abort */
 		RSEQ_ASM_DEFINE_EXIT_POINT(1f, %l[cmpfail])
@@ -273,14 +266,11 @@ int rseq_cmpnev_storeoffp_load(intptr_t
 		  , error1, error2
 #endif
 	);
-	rseq_workaround_gcc_asm_size_guess();
 	return 0;
 abort:
-	rseq_workaround_gcc_asm_size_guess();
 	RSEQ_INJECT_FAILED
 	return -1;
 cmpfail:
-	rseq_workaround_gcc_asm_size_guess();
 	return 1;
 #ifdef RSEQ_COMPARE_TWICE
 error1:
@@ -295,7 +285,6 @@ int rseq_addv(intptr_t *v, intptr_t coun
 {
 	RSEQ_INJECT_C(9)
 
-	rseq_workaround_gcc_asm_size_guess();
 	__asm__ __volatile__ goto (
 		RSEQ_ASM_DEFINE_TABLE(9, 1f, 2f, 4f) /* start, commit, abort */
 #ifdef RSEQ_COMPARE_TWICE
@@ -331,10 +320,8 @@ int rseq_addv(intptr_t *v, intptr_t coun
 		  , error1
 #endif
 	);
-	rseq_workaround_gcc_asm_size_guess();
 	return 0;
 abort:
-	rseq_workaround_gcc_asm_size_guess();
 	RSEQ_INJECT_FAILED
 	return -1;
 #ifdef RSEQ_COMPARE_TWICE
@@ -350,7 +337,6 @@ int rseq_cmpeqv_trystorev_storev(intptr_
 {
 	RSEQ_INJECT_C(9)
 
-	rseq_workaround_gcc_asm_size_guess();
 	__asm__ __volatile__ goto (
 		RSEQ_ASM_DEFINE_TABLE(9, 1f, 2f, 4f) /* start, commit, abort */
 		RSEQ_ASM_DEFINE_EXIT_POINT(1f, %l[cmpfail])
@@ -399,14 +385,11 @@ int rseq_cmpeqv_trystorev_storev(intptr_
 		  , error1, error2
 #endif
 	);
-	rseq_workaround_gcc_asm_size_guess();
 	return 0;
 abort:
-	rseq_workaround_gcc_asm_size_guess();
 	RSEQ_INJECT_FAILED
 	return -1;
 cmpfail:
-	rseq_workaround_gcc_asm_size_guess();
 	return 1;
 #ifdef RSEQ_COMPARE_TWICE
 error1:
@@ -423,7 +406,6 @@ int rseq_cmpeqv_trystorev_storev_release
 {
 	RSEQ_INJECT_C(9)
 
-	rseq_workaround_gcc_asm_size_guess();
 	__asm__ __volatile__ goto (
 		RSEQ_ASM_DEFINE_TABLE(9, 1f, 2f, 4f) /* start, commit, abort */
 		RSEQ_ASM_DEFINE_EXIT_POINT(1f, %l[cmpfail])
@@ -473,14 +455,11 @@ int rseq_cmpeqv_trystorev_storev_release
 		  , error1, error2
 #endif
 	);
-	rseq_workaround_gcc_asm_size_guess();
 	return 0;
 abort:
-	rseq_workaround_gcc_asm_size_guess();
 	RSEQ_INJECT_FAILED
 	return -1;
 cmpfail:
-	rseq_workaround_gcc_asm_size_guess();
 	return 1;
 #ifdef RSEQ_COMPARE_TWICE
 error1:
@@ -497,7 +476,6 @@ int rseq_cmpeqv_cmpeqv_storev(intptr_t *
 {
 	RSEQ_INJECT_C(9)
 
-	rseq_workaround_gcc_asm_size_guess();
 	__asm__ __volatile__ goto (
 		RSEQ_ASM_DEFINE_TABLE(9, 1f, 2f, 4f) /* start, commit, abort */
 		RSEQ_ASM_DEFINE_EXIT_POINT(1f, %l[cmpfail])
@@ -549,14 +527,11 @@ int rseq_cmpeqv_cmpeqv_storev(intptr_t *
 		  , error1, error2, error3
 #endif
 	);
-	rseq_workaround_gcc_asm_size_guess();
 	return 0;
 abort:
-	rseq_workaround_gcc_asm_size_guess();
 	RSEQ_INJECT_FAILED
 	return -1;
 cmpfail:
-	rseq_workaround_gcc_asm_size_guess();
 	return 1;
 #ifdef RSEQ_COMPARE_TWICE
 error1:
@@ -577,7 +552,6 @@ int rseq_cmpeqv_trymemcpy_storev(intptr_
 
 	RSEQ_INJECT_C(9)
 
-	rseq_workaround_gcc_asm_size_guess();
 	__asm__ __volatile__ goto (
 		RSEQ_ASM_DEFINE_TABLE(9, 1f, 2f, 4f) /* start, commit, abort */
 		RSEQ_ASM_DEFINE_EXIT_POINT(1f, %l[cmpfail])
@@ -670,21 +644,16 @@ int rseq_cmpeqv_trymemcpy_storev(intptr_
 		  , error1, error2
 #endif
 	);
-	rseq_workaround_gcc_asm_size_guess();
 	return 0;
 abort:
-	rseq_workaround_gcc_asm_size_guess();
 	RSEQ_INJECT_FAILED
 	return -1;
 cmpfail:
-	rseq_workaround_gcc_asm_size_guess();
 	return 1;
 #ifdef RSEQ_COMPARE_TWICE
 error1:
-	rseq_workaround_gcc_asm_size_guess();
 	rseq_bug("cpu_id comparison failed");
 error2:
-	rseq_workaround_gcc_asm_size_guess();
 	rseq_bug("expected value comparison failed");
 #endif
 }
@@ -698,7 +667,6 @@ int rseq_cmpeqv_trymemcpy_storev_release
 
 	RSEQ_INJECT_C(9)
 
-	rseq_workaround_gcc_asm_size_guess();
 	__asm__ __volatile__ goto (
 		RSEQ_ASM_DEFINE_TABLE(9, 1f, 2f, 4f) /* start, commit, abort */
 		RSEQ_ASM_DEFINE_EXIT_POINT(1f, %l[cmpfail])
@@ -792,21 +760,16 @@ int rseq_cmpeqv_trymemcpy_storev_release
 		  , error1, error2
 #endif
 	);
-	rseq_workaround_gcc_asm_size_guess();
 	return 0;
 abort:
-	rseq_workaround_gcc_asm_size_guess();
 	RSEQ_INJECT_FAILED
 	return -1;
 cmpfail:
-	rseq_workaround_gcc_asm_size_guess();
 	return 1;
 #ifdef RSEQ_COMPARE_TWICE
 error1:
-	rseq_workaround_gcc_asm_size_guess();
 	rseq_bug("cpu_id comparison failed");
 error2:
-	rseq_workaround_gcc_asm_size_guess();
 	rseq_bug("expected value comparison failed");
 #endif
 }