Patchwork [RFC] powerpc: restore TOC when static longjmp to shared object

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Submitter rcardoso@linux.vnet.ibm.com
Date June 4, 2018, 2:34 p.m.
Message ID <4de7760b-04a9-855c-34ac-1565c5532fb9@linux.vnet.ibm.com>
Download mbox | patch
Permalink /patch/27615/
State Superseded
Delegated to: Florian Weimer
Headers show

Comments

rcardoso@linux.vnet.ibm.com - June 4, 2018, 2:34 p.m.
This is v3 of patch.  As pointed out by Alexander Monakov we can't rely 
on  alloca/memset since gcc can optimize this out or it can save the 
registers on the stack and the test will no longer make sense.

Now I use small asm code to deliberately overwrite TOC area on caller 
frame with zero. If the TOC is not restored by longjmp the test will 
fail and them I removed alloca/memset since it's no longer necessary for 
the test itself.

Em 25-05-2018 16:39, Rogerio Alves escreveu:
> 
> 
> Em 23-05-2018 11:24, Alexander Monakov escreveu:
>> On Wed, 23 May 2018, Rogerio Alves wrote:
>>> I don't think that alloca/memset should destroy the caller stack like is
>>> happening but, also I think we have to restore TOC to the caller 
>>> frame after
>>> the longjmp in that case also. I don't know if there's any other more 
>>> direct
>>> and robust ways to checking if TOC is correctly restored. I can't 
>>> think in
>>> anything easier than always restore.
>>
>> I'm not challenging the idea that "always restoring" is an appropriate 
>> fix.
>> My question was about *verifying* that TOC register is restored as it 
>> ought
>> to, i.e. how the testcase needs to work. Right now, the test uses my code
>> from Bugzilla that worked okay for demonstration purposes, but has 
>> issues as
>> a long-term testsuite addition:
>>
>> * it demonstrates the issue in a very intransparent fashion, relying on
>>    non-obvious interaction with alloca-memset part of the test;
>>
>> * when GCC manages to optimize out the alloca-memset part, the test
>>    will cease to work for the intended purpose.
>>
>> Alexander
>>
> 
> Ok. I understand your concern. Let me see if I can change this test to 
> check if the TOC was been restored.
> 
> Rogerio
Florian Weimer - June 4, 2018, 2:38 p.m.
On 06/04/2018 04:34 PM, Rogerio Alves wrote:
> diff --git a/setjmp/tst-setjmp-bug21895-static.c b/setjmp/tst-setjmp-bug21895-static.c
> new file mode 100644
> index 0000000..6ab5340
> --- /dev/null
> +++ b/setjmp/tst-setjmp-bug21895-static.c

> +  /* Destroy TOC area on caller frame.  */
> +  asm volatile(
> +    "li 14, 0\n\t"
> +    "std 14, 24(%0)"
> +    :
> +    : "r" (jb->__jmpbuf[20])
> +  );

Sorry, this test is now very POWER-specific and needs to be moved into a 
POWER sysdeps directory (preferably the most generic one where the test 
is expected to be valid and pass).

Thanks,
Florian

Patch

From 0b59a0e92f56901a3512069441d46778fc97c719 Mon Sep 17 00:00:00 2001
From: Rogerio Alves <rcardoso@linux.vnet.ibm.com>
Date: Wed, 16 May 2018 14:20:53 -0500
Subject: [PATCH v3] powerpc: Always restore TOC on longjmp.

This patch change longjmp to always restore the TOC pointer (r2 register)
to the caller frame on powerpc. This is related to bug 21895[1] that reports
a situation where you have a static longjmp to a shared object file.

[1] https://sourceware.org/bugzilla/show_bug.cgi?id=21895

2018-05-16 Rogerio A. Cardoso <rcardoso@linux.vnet.ibm.com>

	*sysdeps/powerpc/powerpc64/__longjmp-common.S: Remove condition code for
	restore r2 on longjmp.
	*setjmp/Makefile: Added tst-setjmp-bug21895-static to test list.
	Added rules to build test tst-setjmp-bug21895-static
	Added module setjmp-bug21895 and rules to build a shared object from it.
	*setjmp/setjmp-bug21895.c: New test file.
	*setjmp/tst-setjmp-bug21895-static.c: New test file.
---
 Changes in v3: as pointed out by Alexander Monakov we can't rely on
alloca/memset since gcc can optimize this out or it can save the
registers on the stack and the test will no longer make sense. Now I use
a small asm code to deliberately overwrite TOC area on caller frame with
zero. If the TOC is not restored by longjmp the test will fail.

 Changes in v2: Per Adhemerval Zanella. Fix test fail using the suggestions
given. Fix changelog. Fix copyright and indentation for new tests. Change
tests to use libsupport instead old test-skeleton. Fix a extra space
in  __longjmp-common.

 setjmp/Makefile                              | 16 +++++-
 setjmp/setjmp-bug21895.c                     | 41 +++++++++++++++
 setjmp/tst-setjmp-bug21895-static.c          | 75 ++++++++++++++++++++++++++++
 sysdeps/powerpc/powerpc64/__longjmp-common.S |  5 +-
 4 files changed, 132 insertions(+), 5 deletions(-)
 create mode 100644 setjmp/setjmp-bug21895.c
 create mode 100644 setjmp/tst-setjmp-bug21895-static.c

diff --git a/setjmp/Makefile b/setjmp/Makefile
index dc2fcc6..d70daa2 100644
--- a/setjmp/Makefile
+++ b/setjmp/Makefile
@@ -29,9 +29,23 @@  routines	:= setjmp sigjmp bsd-setjmp bsd-_setjmp \
 
 tests		:= tst-setjmp jmpbug bug269-setjmp tst-setjmp-fp \
 		   tst-sigsetjmp tst-setjmp-static
-tests-static	:= tst-setjmp-static
 
+tests-static	:= tst-setjmp-static tst-setjmp-bug21895-static
+
+modules-names = setjmp-bug21895
 
 include ../Rules
 
 $(objpfx)tst-setjmp-fp: $(libm)
+
+test-modules = $(addprefix $(objpfx),$(addsuffix .so,$(modules-names)))
+
+ifeq ($(build-shared),yes)
+tests: $(test-modules)
+endif
+
+$(objpfx)tst-setjmp-bug21895-static: $(common-objpfx)dlfcn/libdl.a
+$(objpfx)tst-setjmp-bug21895-static.out: $(objpfx)setjmp-bug21895.so
+
+tst-setjmp-bug21895-static-ENV = \
+	LD_LIBRARY_PATH=$(objpfx):$(common-objpfx):$(common-objpfx)setjmp:$(common-objpfx)elf
diff --git a/setjmp/setjmp-bug21895.c b/setjmp/setjmp-bug21895.c
new file mode 100644
index 0000000..d7c0133
--- /dev/null
+++ b/setjmp/setjmp-bug21895.c
@@ -0,0 +1,41 @@ 
+/* Shared object part of test for setjmp interoperability with static
+   dlopen BZ #21895.
+   Copyright (C) 2017-2018 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <alloca.h>
+#include <string.h>
+#include <setjmp.h>
+
+jmp_buf jb;
+void (*bar)(jmp_buf);
+
+void
+lbar (void)
+{
+  bar(jb);
+  for(;;);
+}
+
+void
+foo (void)
+{
+  setjmp(jb);
+  lbar();
+
+  for(;;);
+}
diff --git a/setjmp/tst-setjmp-bug21895-static.c b/setjmp/tst-setjmp-bug21895-static.c
new file mode 100644
index 0000000..6ab5340
--- /dev/null
+++ b/setjmp/tst-setjmp-bug21895-static.c
@@ -0,0 +1,75 @@ 
+/* Test setjmp interoperability with static dlopen BZ #21895.
+   Copyright (C) 2017-2018 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#include <setjmp.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <dlfcn.h>
+
+static void
+bar (jmp_buf jb)
+{
+  static int i;
+  if (i++==1)
+    exit(0);	/* Success.  */
+
+  /* Destroy TOC area on caller frame.  */
+  asm volatile(
+    "li 14, 0\n\t"
+    "std 14, 24(%0)"
+    :
+    : "r" (jb->__jmpbuf[20])
+  );
+
+  longjmp(jb, i);
+}
+
+static int
+do_test (void)
+{
+  void *h = dlopen("setjmp-bug21895.so", RTLD_NOW);
+  if (!h)
+    {
+      puts(dlerror());
+      return 1;
+    }
+
+  void (*pfoo)(void) = dlsym(h, "foo");
+  if (!pfoo)
+    {
+      puts(dlerror());
+      return 1;
+    }
+
+  void (**ppbar)(jmp_buf) = dlsym(h, "bar");
+  if (!ppbar)
+    {
+      puts(dlerror());
+      return 1;
+    }
+
+  *ppbar = bar;
+  pfoo();
+
+  for(;;);
+}
+
+/* Make sure the test will not stuck if jmp fails and fall into one of
+   for(;;).  */
+#define TIMEOUT 100
+#include <support/test-driver.c>
diff --git a/sysdeps/powerpc/powerpc64/__longjmp-common.S b/sysdeps/powerpc/powerpc64/__longjmp-common.S
index 0e10b8d..99c17c5 100644
--- a/sysdeps/powerpc/powerpc64/__longjmp-common.S
+++ b/sysdeps/powerpc/powerpc64/__longjmp-common.S
@@ -130,9 +130,6 @@  L(no_vmx):
 	ld r0,(JB_LR*8)(r3)
 	ld r14,((JB_GPRS+0)*8)(r3)
 	lfd fp14,((JB_FPRS+0)*8)(r3)
-#if defined SHARED && !IS_IN (rtld)
-	std r2,FRAME_TOC_SAVE(r1)	/* Restore the callers TOC save area.  */
-#endif
 	ld r15,((JB_GPRS+1)*8)(r3)
 	lfd fp15,((JB_FPRS+1)*8)(r3)
 	ld r16,((JB_GPRS+2)*8)(r3)
@@ -152,7 +149,7 @@  L(no_vmx):
 	second argument (-4@4), and target address (8@0), respectively.  */
 	LIBC_PROBE (longjmp, 3, 8@3, -4@4, 8@0)
 	mtlr r0
-/* 	std r2,FRAME_TOC_SAVE(r1)	Restore the TOC save area.  */
+	std r2,FRAME_TOC_SAVE(r1)	/* Restore the TOC save area.  */
 	ld r21,((JB_GPRS+7)*8)(r3)
 	lfd fp21,((JB_FPRS+7)*8)(r3)
 	ld r22,((JB_GPRS+8)*8)(r3)
-- 
2.7.4