[Crash-utility] [PATCH v3 06/16] Fix gdb_interface: restore gdb's output streams at end of gdb_interface
Currently for most gdb_interface call, in which a non-null file pointer
is passed, GDB's output stream is replaced with the passed file pointer
Due to this, 'info threads', which is a gdb passthrough, doesn't print any
thread, after support was added to get registers from crash_target:
crash> info threads
Id Target Id Frame
This empty output of 'info threads' was due to a subtle bug in
gdb_interface.
After this gdb passthrough is run, 'datatype_info' is called, with file
pointer set to null_fp (pointing to /dev/null). And after
'datatype_info' returns, any output by gdb goes to /dev/null, and hence
the output is lost.
Fix this by restoring the original output streams, after gdb_interface
has handled the output
After this patch:
crash> info threads
Id Target Id Frame
* 1 2131 bash 0xc000000000051e40 in crash_fadump (regs=0x0,
str=0xc000000002c60510 <buf> "sysrq triggered crash") at
arch/powerpc/kernel/fadump.c:735
Cc: Sourabh Jain <sourabhjain(a)linux.ibm.com>
Cc: Hari Bathini <hbathini(a)linux.ibm.com>
Cc: Mahesh J Salgaonkar <mahesh(a)linux.ibm.com>
Cc: Naveen N. Rao <naveen.n.rao(a)linux.vnet.ibm.com>
Cc: Lianbo Jiang <lijiang(a)redhat.com>
Cc: HAGIO KAZUHITO(萩尾 一仁) <k-hagio-ab(a)nec.com>
Cc: Tao Liu <ltao(a)redhat.com>
Cc: Alexey Makhalov <alexey.makhalov(a)broadcom.com>
Signed-off-by: Aditya Gupta <adityag(a)linux.ibm.com>
Signed-off-by: Tao Liu <ltao(a)redhat.com>
---
gdb-10.2.patch | 53 ++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 53 insertions(+)
diff --git a/gdb-10.2.patch b/gdb-10.2.patch
index 3694b13..0bed96a 100644
--- a/gdb-10.2.patch
+++ b/gdb-10.2.patch
@@ -16118,3 +16118,56 @@ exit 0
subclass (SYMBOL_NONE)
{
/* We can't use an initializer list for members of a base class, and
+--- gdb-10.2/gdb/ui-file.h.orig
++++ gdb-10.2/gdb/ui-file.h
+@@ -195,6 +195,7 @@ public:
+
+ bool can_emit_style_escape () override;
+
++ FILE *get_stream(void);
+ /* Sets the internal stream to FILE, and saves the FILE's file
+ descriptor in M_FD. */
+ void set_stream (FILE *file);
+--- gdb-10.2/gdb/ui-file.c.orig
++++ gdb-10.2/gdb/ui-file.c
+@@ -161,6 +161,12 @@ stdio_file::~stdio_file ()
+ fclose (m_file);
+ }
+
++FILE*
++stdio_file::get_stream(void)
++{
++ return m_file;
++}
++
+ void
+ stdio_file::set_stream (FILE *file)
+ {
+--- gdb-10.2/gdb/symtab.c.orig
++++ gdb-10.2/gdb/symtab.c
+@@ -6964,8 +6964,12 @@ void
+ gdb_command_funnel_1(struct gnu_request *req)
+ {
+ struct symbol *sym;
++ FILE *original_stdout_stream = nullptr;
++ FILE *original_stderr_stream = nullptr;
+
+ if (req->command != GNU_VERSION && req->command !=
GNU_USER_PRINT_OPTION) {
++ original_stdout_stream = (dynamic_cast< stdio_file *
>gdb_stdout)->get_stream();
++ original_stderr_stream = (dynamic_cast< stdio_file *
>gdb_stderr)->get_stream();
+ (dynamic_cast<stdio_file
*>gdb_stdout)->set_stream(req->fp);
+ (dynamic_cast<stdio_file
*>gdb_stderr)->set_stream(req->fp);
+ }
+@@ -7068,6 +7072,12 @@ gdb_command_funnel_1(struct gnu_request *req)
+ req->flags |= GNU_COMMAND_FAILED;
+ break;
+ }
++
++ /* Restore the streams gdb output was using */
++ if (original_stdout_stream)
++ (dynamic_cast<stdio_file
*>gdb_stdout)->set_stream(original_stdout_stream);
++ if (original_stderr_stream)
++ (dynamic_cast<stdio_file
*>gdb_stderr)->set_stream(original_stderr_stream);
+ }
+
+ /*
--
2.40.1