linux-kernel - [PATCH v2] rseq/selftests: fix parametrized test with -fpie

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Date:   Thu, 27 Sep 2018 14:39:19 -0400
From:   Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To:     Shuah Khan <shuah@...nel.org>
Cc:     linux-kernel@...r.kernel.org,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        stable@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Joel Fernandes <joelaf@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Dave Watson <davejwatson@...com>,
        Will Deacon <will.deacon@....com>,
        Andi Kleen <andi@...stfloor.org>,
        linux-kselftest@...r.kernel.org, "H . Peter Anvin" <hpa@...or.com>,
        Chris Lameter <cl@...ux.com>,
        Russell King <linux@....linux.org.uk>,
        Michael Kerrisk <mtk.manpages@...il.com>,
        "Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>,
        Paul Turner <pjt@...gle.com>,
        Boqun Feng <boqun.feng@...il.com>,
        Josh Triplett <josh@...htriplett.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Maurer <bmaurer@...com>,
        Andy Lutomirski <luto@...capital.net>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH v2] rseq/selftests: fix parametrized test with -fpie

On x86-64, the parametrized selftest code for rseq crashes with a
segmentation fault when compiled with -fpie. This happens when the
param_test binary is loaded at an address beyond 32-bit on x86-64.

The issue is caused by use of a 32-bit register to hold the address
of the loop counter variable.

Fix this by using a 64-bit register to calculate the address of the
loop counter variables as an offset from rip.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Acked-by: "Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>
Cc: <stable@...r.kernel.org> # v4.18
Cc: Shuah Khan <shuah@...nel.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Joel Fernandes <joelaf@...gle.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Catalin Marinas <catalin.marinas@....com>
Cc: Dave Watson <davejwatson@...com>
Cc: Will Deacon <will.deacon@....com>
Cc: Andi Kleen <andi@...stfloor.org>
Cc: linux-kselftest@...r.kernel.org
Cc: "H . Peter Anvin" <hpa@...or.com>
Cc: Chris Lameter <cl@...ux.com>
Cc: Russell King <linux@....linux.org.uk>
Cc: Michael Kerrisk <mtk.manpages@...il.com>
Cc: "Paul E . McKenney" <paulmck@...ux.vnet.ibm.com>
Cc: Paul Turner <pjt@...gle.com>
Cc: Boqun Feng <boqun.feng@...il.com>
Cc: Josh Triplett <josh@...htriplett.org>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Ben Maurer <bmaurer@...com>
Cc: Andy Lutomirski <luto@...capital.net>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
---
Changes since v1:
- Update email address for Shuah Khan based on updated MAINTAINERS
  email address,
- Rebase on v4.19-rc5.
---
 tools/testing/selftests/rseq/param_test.c | 19 ++++++++++---------
 1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/tools/testing/selftests/rseq/param_test.c b/tools/testing/selftests/rseq/param_test.c
index 642d4e12abea..eec2663261f2 100644
--- a/tools/testing/selftests/rseq/param_test.c
+++ b/tools/testing/selftests/rseq/param_test.c
@@ -56,15 +56,13 @@ unsigned int yield_mod_cnt, nr_abort;
 			printf(fmt, ## __VA_ARGS__);	\
 	} while (0)
 
-#if defined(__x86_64__) || defined(__i386__)
+#ifdef __i386__
 
 #define INJECT_ASM_REG	"eax"
 
 #define RSEQ_INJECT_CLOBBER \
 	, INJECT_ASM_REG
 
-#ifdef __i386__
-
 #define RSEQ_INJECT_ASM(n) \
 	"mov asm_loop_cnt_" #n ", %%" INJECT_ASM_REG "\n\t" \
 	"test %%" INJECT_ASM_REG ",%%" INJECT_ASM_REG "\n\t" \
@@ -76,9 +74,16 @@ unsigned int yield_mod_cnt, nr_abort;
 
 #elif defined(__x86_64__)
 
+#define INJECT_ASM_REG_P	"rax"
+#define INJECT_ASM_REG		"eax"
+
+#define RSEQ_INJECT_CLOBBER \
+	, INJECT_ASM_REG_P \
+	, INJECT_ASM_REG
+
 #define RSEQ_INJECT_ASM(n) \
-	"lea asm_loop_cnt_" #n "(%%rip), %%" INJECT_ASM_REG "\n\t" \
-	"mov (%%" INJECT_ASM_REG "), %%" INJECT_ASM_REG "\n\t" \
+	"lea asm_loop_cnt_" #n "(%%rip), %%" INJECT_ASM_REG_P "\n\t" \
+	"mov (%%" INJECT_ASM_REG_P "), %%" INJECT_ASM_REG "\n\t" \
 	"test %%" INJECT_ASM_REG ",%%" INJECT_ASM_REG "\n\t" \
 	"jz 333f\n\t" \
 	"222:\n\t" \
@@ -86,10 +91,6 @@ unsigned int yield_mod_cnt, nr_abort;
 	"jnz 222b\n\t" \
 	"333:\n\t"
 
-#else
-#error "Unsupported architecture"
-#endif
-
 #elif defined(__s390__)
 
 #define RSEQ_INJECT_INPUT \
-- 
2.17.1