From 4c2c7ac69d7318d61a5c0e4f5ddcee1c1597f4e0 Mon Sep 17 00:00:00 2001 From: Markus Metzger Date: Mon, 30 Jan 2017 09:16:27 +0100 Subject: [PATCH] btrace: preserve call stack on function switch On 64-bit FC25, the _dl_runtime_resolve function uses a conditional branch to 'call' a particular variant optimized for that system: (gdb) disas _dl_runtime_resolve_avx_opt Dump of assembler code for function _dl_runtime_resolve_avx_opt: 0x00007ffff7deeb60 <+0>: push %rax 0x00007ffff7deeb61 <+1>: push %rcx 0x00007ffff7deeb62 <+2>: push %rdx 0x00007ffff7deeb63 <+3>: mov $0x1,%ecx 0x00007ffff7deeb68 <+8>: xgetbv 0x00007ffff7deeb6b <+11>: mov %eax,%r11d 0x00007ffff7deeb6e <+14>: pop %rdx 0x00007ffff7deeb6f <+15>: pop %rcx 0x00007ffff7deeb70 <+16>: pop %rax 0x00007ffff7deeb71 <+17>: and $0x4,%r11d 0x00007ffff7deeb75 <+21>: bnd je 0x7ffff7def4a0 <_dl_runtime_resolve_sse_vex> End of assembler dump. When computing the function-level trace, btrace treats this as a switch from _dl_runtime_resolve_avx_opt to _dl_runtime_resolve_sse_vex. We know that we switched functions but we can't really say in which caller/callee relationship those two functions are. In addition to preserving the indentaion level, also preserve the caller information. This is a heuristic since we don't really know. But at least in this case, this seems to be the right thing to do. This fixes a fail in gdb.btrace/rn-dl-bind.exp on 64-bit FC25. gdb/ * btrace.c (ftrace_new_switch): Preserve up link and flags. --- gdb/ChangeLog | 4 ++++ gdb/btrace.c | 6 ++++-- 2 files changed, 8 insertions(+), 2 deletions(-) diff --git a/gdb/ChangeLog b/gdb/ChangeLog index e274191663..ae33435346 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,7 @@ +2017-02-14 Markus Metzger + + * btrace.c (ftrace_new_switch): Preserve up link and flags. + 2017-02-13 Luis Machado * symfile (_initialize_symfile): Add usage text to the load command's diff --git a/gdb/btrace.c b/gdb/btrace.c index 6d621e4ecf..ddf6692d18 100644 --- a/gdb/btrace.c +++ b/gdb/btrace.c @@ -448,9 +448,11 @@ ftrace_new_switch (struct btrace_function *prev, { struct btrace_function *bfun; - /* This is an unexplained function switch. The call stack will likely - be wrong at this point. */ + /* This is an unexplained function switch. We can't really be sure about the + call stack, yet the best I can think of right now is to preserve it. */ bfun = ftrace_new_function (prev, mfun, fun); + bfun->up = prev->up; + bfun->flags = prev->flags; ftrace_debug (bfun, "new switch"); -- 2.34.1