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[PATCH] S390: Fix backtrace in vdso functions.

From: Stefan Liebler <stli at linux dot vnet dot ibm dot com>
To: GNU C Library <libc-alpha at sourceware dot org>
Date: Tue, 28 Nov 2017 13:44:30 +0100
Subject: [PATCH] S390: Fix backtrace in vdso functions.
Authentication-results: sourceware.org; auth=none

Hi,

On s390, GDB fails to show the complete backtrace from within vdsofunctions. The macro INTERNAL_VSYSCALL_CALL saves the return address inr14 to r10 before branching to the vdso function. The branch-instructionupdates r14 in order to let the vdso function return. Then the originaladdress in r14 is restored from r10. Unfortunately, there are nocfi-rules and GDB fails.

Furthermore the call of the vdso function does not comply with the s390ABI as no stack-frame for the vdso-function is generated.

This patch removes the s390 specific macro INTERNAL_VSYSCALL_CALL andthe common implementation in sysdeps/unix/sysv/linux/sysdep-vdso.h isused. Then the vdso function is called via function-pointer and GCCgenerates a new stack-frame and emits all needed cfi-rules.

The defines CLOBBER_[0-6] are removed as they were only used in macroINTERNAL_VSYSCALL_CALL.

The macro INTERNAL_VSYSCALL_NO_SYSCALL_FALLBACK is not used on s390. Theonly user is power. Thus it is removed from s390 sysdep.h.


ChangeLog:

	* sysdeps/unix/sysv/linux/s390/s390-64/sysdep.h
	(INTERNAL_VSYSCALL_CALL, CLOBBER_0, CLOBBER_1, CLOBBER_2,
	 CLOBBER_3, CLOBBER_4, CLOBBER_5, CLOBBER_6,
	INTERNAL_VSYSCALL_NO_SYSCALL_FALLBACK): Remove.
	* sysdeps/unix/sysv/linux/s390/s390-32/sysdep.h: Likewise.

commit a1000218276c4cfb9a72e53f17b144b137faf334
Author: Stefan Liebler <stli@linux.vnet.ibm.com>
Date:   Mon Nov 27 11:24:45 2017 +0100

    S390: Fix backtrace in vdso functions.
    
    On s390, GDB fails to show the complete backtrace from within vdso functions.
    The macro INTERNAL_VSYSCALL_CALL saves the return address in r14 to r10
    before branching to the vdso function. The branch-instruction updates r14
    in order to let the vdso function return. Then the original address in r14 is
    restored from r10. Unfortunately, there are no cfi-rules and GDB fails.
    
    Furthermore the call of the vdso function does not comply with the s390 ABI
    as no stack-frame for the vdso-function is generated.
    
    This patch removes the s390 specific macro INTERNAL_VSYSCALL_CALL
    and the common implementation in sysdeps/unix/sysv/linux/sysdep-vdso.h is used.
    Then the vdso function is called via function-pointer and GCC generates a
    new stack-frame and emits all needed cfi-rules.
    
    The defines CLOBBER_[0-6] are removed as they  were only used in macro
    INTERNAL_VSYSCALL_CALL.
    
    The macro INTERNAL_VSYSCALL_NO_SYSCALL_FALLBACK is not used on s390.
    The only user is power. Thus it is removed from s390 sysdep.h.
    
    ChangeLog:
    
    	* sysdeps/unix/sysv/linux/s390/s390-64/sysdep.h
    	(INTERNAL_VSYSCALL_CALL, CLOBBER_0, CLOBBER_1, CLOBBER_2,
    	 CLOBBER_3, CLOBBER_4, CLOBBER_5, CLOBBER_6,
    	INTERNAL_VSYSCALL_NO_SYSCALL_FALLBACK): Remove.
    	* sysdeps/unix/sysv/linux/s390/s390-32/sysdep.h: Likewise.

diff --git a/sysdeps/unix/sysv/linux/s390/s390-32/sysdep.h b/sysdeps/unix/sysv/linux/s390/s390-32/sysdep.h
index e56fc32..644b83c 100644
--- a/sysdeps/unix/sysv/linux/s390/s390-32/sysdep.h
+++ b/sysdeps/unix/sysv/linux/s390/s390-32/sysdep.h
@@ -271,48 +271,12 @@
 #define ASMFMT_5 , "0" (gpr2), "d" (gpr3), "d" (gpr4), "d" (gpr5), "d" (gpr6)
 #define ASMFMT_6 , "0" (gpr2), "d" (gpr3), "d" (gpr4), "d" (gpr5), "d" (gpr6), "d" (gpr7)
 
-#define CLOBBER_0 , "3", "4", "5"
-#define CLOBBER_1 , "3", "4", "5"
-#define CLOBBER_2 , "4", "5"
-#define CLOBBER_3 , "5"
-#define CLOBBER_4
-#define CLOBBER_5
-#define CLOBBER_6
-
 /* List of system calls which are supported as vsyscalls.  */
 #define HAVE_CLOCK_GETRES_VSYSCALL	1
 #define HAVE_CLOCK_GETTIME_VSYSCALL	1
 #define HAVE_GETTIMEOFDAY_VSYSCALL	1
 #define HAVE_GETCPU_VSYSCALL		1
 
-/* This version is for internal uses when there is no desire
-   to set errno */
-#define INTERNAL_VSYSCALL_NO_SYSCALL_FALLBACK(name, err, nr, args...)	      \
-  ({									      \
-    long int _ret = ENOSYS;						      \
-									      \
-    __typeof (__vdso_##name) vdsop = __vdso_##name;			      \
-    PTR_DEMANGLE (vdsop);						      \
-    if (vdsop != NULL)							      \
-      _ret = INTERNAL_VSYSCALL_CALL (vdsop, err, nr, ##args);		      \
-    else								      \
-      err = 1 << 28;							      \
-    _ret;								      \
-  })
-
-#define INTERNAL_VSYSCALL_CALL(fn, err, nr, args...)			      \
-  ({									      \
-    DECLARGS_##nr(args)							      \
-    register long _ret __asm__("2");					      \
-    __asm__ __volatile__ (						      \
-			  "lr 10,14\n\t"				      \
-			  "basr 14,%1\n\t"				      \
-			  "lr 14,10\n\t"				      \
-			  : "=d" (_ret)					      \
-			  : "d" (fn) ASMFMT_##nr			      \
-			  : "cc", "memory", "0", "1", "10" CLOBBER_##nr);     \
-    _ret; })
-
 /* Pointer mangling support.  */
 #if IS_IN (rtld)
 /* We cannot use the thread descriptor because in ld.so we use setjmp
diff --git a/sysdeps/unix/sysv/linux/s390/s390-64/sysdep.h b/sysdeps/unix/sysv/linux/s390/s390-64/sysdep.h
index 622991d..18ed339 100644
--- a/sysdeps/unix/sysv/linux/s390/s390-64/sysdep.h
+++ b/sysdeps/unix/sysv/linux/s390/s390-64/sysdep.h
@@ -277,14 +277,6 @@
 #define ASMFMT_5 , "0" (gpr2), "d" (gpr3), "d" (gpr4), "d" (gpr5), "d" (gpr6)
 #define ASMFMT_6 , "0" (gpr2), "d" (gpr3), "d" (gpr4), "d" (gpr5), "d" (gpr6), "d" (gpr7)
 
-#define CLOBBER_0 , "3", "4", "5"
-#define CLOBBER_1 , "3", "4", "5"
-#define CLOBBER_2 , "4", "5"
-#define CLOBBER_3 , "5"
-#define CLOBBER_4
-#define CLOBBER_5
-#define CLOBBER_6
-
 /* List of system calls which are supported as vsyscalls.  */
 #define HAVE_CLOCK_GETRES_VSYSCALL	1
 #define HAVE_CLOCK_GETTIME_VSYSCALL	1
@@ -293,34 +285,6 @@
 
 #define SINGLE_THREAD_BY_GLOBAL		1
 
-/* This version is for internal uses when there is no desire
-   to set errno */
-#define INTERNAL_VSYSCALL_NO_SYSCALL_FALLBACK(name, err, nr, args...)	      \
-  ({									      \
-    long int _ret = ENOSYS;						      \
-									      \
-    __typeof (__vdso_##name) vdsop = __vdso_##name;			      \
-    PTR_DEMANGLE (vdsop);						      \
-    if (vdsop != NULL)							      \
-      _ret = INTERNAL_VSYSCALL_CALL (vdsop, err, nr, ##args);		      \
-    else								      \
-      err = 1 << 28;							      \
-    _ret;								      \
-  })
-
-#define INTERNAL_VSYSCALL_CALL(fn, err, nr, args...)			      \
-  ({									      \
-    DECLARGS_##nr(args)							      \
-    register long _ret __asm__("2");					      \
-    __asm__ __volatile__ (						      \
-			  "lgr 10,14\n\t"				      \
-			  "basr 14,%1\n\t"				      \
-			  "lgr 14,10\n\t"				      \
-			  : "=d" (_ret)					      \
-			  : "a" (fn) ASMFMT_##nr			      \
-			  : "cc", "memory", "0", "1", "10" CLOBBER_##nr);     \
-    _ret; })
-
 /* Pointer mangling support.  */
 #if IS_IN (rtld)
 /* We cannot use the thread descriptor because in ld.so we use setjmp

Follow-Ups:
- Re: [PATCH] S390: Fix backtrace in vdso functions.
  - From: Adhemerval Zanella

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