[Crash-utility] Re: [Crash-Utility][PATCH v2 06/13] Fix gdb_interface: restore gdb's output streams at end of gdb_interface
Hi Tao,
Thanks for sending the series.
Maybe you missed CCing people ?
Also this patch's 'author' line is missing, maybe while editing the
commit it messed up ?
I will proceed with testing the series, might do it later, currently my
mails got messed up, I got some mails in Inbox (those patches with me in
Cc), and others in my crash-utility folder (those with Cc: crash-utility).
Thanks,
Aditya Gupta
On 28/04/24 09:32, Tao Liu wrote:
> 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>
> 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);
> + }
> +
> + /*