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* [glibc/fw/unwind-link] s390: Remove backchain-based fallback from backtrace
@ 2020-02-10 17:08 Florian Weimer
0 siblings, 0 replies; only message in thread
From: Florian Weimer @ 2020-02-10 17:08 UTC (permalink / raw)
To: glibc-cvs
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=c7d1a41c54e746fb256aec82f3c09b977b4379d1
commit c7d1a41c54e746fb256aec82f3c09b977b4379d1
Author: Florian Weimer <fweimer@redhat.com>
Date: Mon Feb 10 16:21:32 2020 +0100
s390: Remove backchain-based fallback from backtrace
This backtrace variant is used when _Unwind_Backtrace is not found in
libgcc_s. It still depends on _Unwind_GetIP from libgcc_s, so it does
not work if loading libgcc_s fails. Therefore, as long as libgcc_s
provides a definition of _Unwind_Backtrace, the fallback is not useful.
After this change, the implementation is the same on s390 and s390x
and can be shared.
Diff:
---
sysdeps/s390/{s390-32 => }/backtrace.c | 58 +------------
sysdeps/s390/s390-64/backtrace.c | 147 ---------------------------------
2 files changed, 1 insertion(+), 204 deletions(-)
diff --git a/sysdeps/s390/s390-32/backtrace.c b/sysdeps/s390/backtrace.c
similarity index 60%
rename from sysdeps/s390/s390-32/backtrace.c
rename to sysdeps/s390/backtrace.c
index 497e4f8..5801e5e 100644
--- a/sysdeps/s390/s390-32/backtrace.c
+++ b/sysdeps/s390/backtrace.c
@@ -24,36 +24,6 @@
#include <stdlib.h>
#include <unwind.h>
-/* This is a global variable set at program start time. It marks the
- highest used stack address. */
-extern void *__libc_stack_end;
-
-
-/* This is the stack layout we see for every non-leaf function.
- size offset
- %r15 -> +------------------+
- 4 | back chain | 0
- 4 | end of stack | 4
- 8 | glue | 8
- 8 | scratch | 16
- 40 | save area r6-r15 | 24
- 16 | save area f4,f6 | 64
- 16 | empty | 80
- +------------------+
- r14 in the save area holds the return address.
-*/
-
-struct layout
-{
- int back_chain;
- int end_of_stack;
- int glue[2];
- int scratch[2];
- int save_grps[10];
- int save_fp[4];
- int empty[2];
-};
-
struct trace_arg
{
void **array;
@@ -77,32 +47,6 @@ init (void)
if (unwind_getip == NULL)
unwind_backtrace = NULL;
}
-
-static int
-__backchain_backtrace (void **array, int size)
-{
- /* We assume that all the code is generated with frame pointers set. */
- struct layout *stack;
- int cnt = 0;
-
- __asm__ ("LR %0,%%r15" : "=d" (stack) );
- /* We skip the call to this function, it makes no sense to record it. */
- stack = (struct layout *) stack->back_chain;
- while (cnt < size)
- {
- if (stack == NULL || (void *) stack > __libc_stack_end)
- /* This means the address is out of range. Note that for the
- toplevel we see a frame pointer with value NULL which clearly is
- out of range. */
- break;
-
- array[cnt++] = (void *) (stack->save_grps[8] & 0x7fffffff);
-
- stack = (struct layout *) stack->back_chain;
- }
-
- return cnt;
-}
#else
# define unwind_backtrace _Unwind_Backtrace
# define unwind_getip _Unwind_GetIP
@@ -136,7 +80,7 @@ __backtrace (void **array, int size)
__libc_once (once, init);
if (unwind_backtrace == NULL)
- return __backchain_backtrace (array, size);
+ return 0;
#endif
unwind_backtrace (backtrace_helper, &arg);
diff --git a/sysdeps/s390/s390-64/backtrace.c b/sysdeps/s390/s390-64/backtrace.c
deleted file mode 100644
index 5d14e01..0000000
--- a/sysdeps/s390/s390-64/backtrace.c
+++ /dev/null
@@ -1,147 +0,0 @@
-/* Return backtrace of current program state. 64 bit S/390 version.
- Copyright (C) 2001-2020 Free Software Foundation, Inc.
- Contributed by Martin Schwidefsky <schwidefsky@de.ibm.com>.
- 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
- <https://www.gnu.org/licenses/>. */
-
-#include <libc-lock.h>
-#include <dlfcn.h>
-#include <execinfo.h>
-#include <stddef.h>
-#include <stdlib.h>
-#include <unwind.h>
-
-
-/* This is a global variable set at program start time. It marks the
- highest used stack address. */
-extern void *__libc_stack_end;
-
-
-/* This is the stack layout we see for every non-leaf function.
- size offset
- %r15 -> +------------------+
- 8 | back chain | 0
- 8 | end of stack | 8
- 32 | scratch | 16
- 80 | save area r6-r15 | 48
- 16 | save area f4,f6 | 128
- 16 | empty | 144
- +------------------+
- r14 in the save area holds the return address.
-*/
-
-struct layout
-{
- long back_chain;
- long end_of_stack;
- long scratch[4];
- long save_grps[10];
- long save_fp[2];
- long empty[2];
-};
-
-struct trace_arg
-{
- void **array;
- int cnt, size;
-};
-
-#ifdef SHARED
-static _Unwind_Reason_Code (*unwind_backtrace) (_Unwind_Trace_Fn, void *);
-static _Unwind_Ptr (*unwind_getip) (struct _Unwind_Context *);
-
-static void
-init (void)
-{
- void *handle = __libc_dlopen ("libgcc_s.so.1");
-
- if (handle == NULL)
- return;
-
- unwind_backtrace = __libc_dlsym (handle, "_Unwind_Backtrace");
- unwind_getip = __libc_dlsym (handle, "_Unwind_GetIP");
- if (unwind_getip == NULL)
- unwind_backtrace = NULL;
-}
-
-static int
-__backchain_backtrace (void **array, int size)
-{
- /* We assume that all the code is generated with frame pointers set. */
- struct layout *stack;
- int cnt = 0;
-
- __asm__ ("LGR %0,%%r15" : "=d" (stack) );
- /* We skip the call to this function, it makes no sense to record it. */
- stack = (struct layout *) stack->back_chain;
- while (cnt < size)
- {
- if (stack == NULL || (void *) stack > __libc_stack_end)
- /* This means the address is out of range. Note that for the
- toplevel we see a frame pointer with value NULL which clearly is
- out of range. */
- break;
-
- array[cnt++] = (void *) stack->save_grps[8];
-
- stack = (struct layout *) stack->back_chain;
- }
-
- return cnt;
-}
-#else
-# define unwind_backtrace _Unwind_Backtrace
-# define unwind_getip _Unwind_GetIP
-#endif
-
-static _Unwind_Reason_Code
-backtrace_helper (struct _Unwind_Context *ctx, void *a)
-{
- struct trace_arg *arg = a;
-
- /* We are first called with address in the __backtrace function.
- Skip it. */
- if (arg->cnt != -1)
- arg->array[arg->cnt] = (void *) unwind_getip (ctx);
- if (++arg->cnt == arg->size)
- return _URC_END_OF_STACK;
- return _URC_NO_REASON;
-}
-
-int
-__backtrace (void **array, int size)
-{
- struct trace_arg arg = { .array = array, .size = size, .cnt = -1 };
-
- if (size <= 0)
- return 0;
-
-#ifdef SHARED
- __libc_once_define (static, once);
-
- __libc_once (once, init);
-
- if (unwind_backtrace == NULL)
- return __backchain_backtrace (array, size);
-#endif
-
- unwind_backtrace (backtrace_helper, &arg);
-
- return arg.cnt != -1 ? arg.cnt : 0;
-}
-
-weak_alias (__backtrace, backtrace)
-libc_hidden_def (__backtrace)
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