linux-kernel - KGDB fails to pass selft tests on x86-64 (v2.6.26)

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Date:	Thu, 24 Jul 2008 15:24:07 +0200
From:	"Francis Moreau" <francis.moro@...il.com>
To:	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>
Subject: KGDB fails to pass selft tests on x86-64 (v2.6.26)

Hello.

I wanted to give kgdb a try on a v2.6.26 kernel. My cpu is an
x86-64.

So the first thing I did is to enable kgdb support and also the
kgdb self tests:

CONFIG_HAVE_ARCH_KGDB=y
CONFIG_KGDB=y
CONFIG_KGDB_SERIAL_CONSOLE=y
CONFIG_KGDB_TESTS=y
# CONFIG_KGDB_TESTS_ON_BOOT is not set

Once compiled I booted this kernel through qemu and got the following:

...
kgdb: Registered I/O driver kgdbts.
kgdb: Waiting for connection from remote gdb...
kgdbts:RUN plant and detach test
kgdbts:RUN sw breakpoint test
kgdbts:RUN bad memory access test
kgdbts:RUN singlestep test 1000 iterations
kgdbts:RUN singlestep [0/1000]
kgdbts:RUN singlestep [100/1000]
kgdbts:RUN singlestep [200/1000]
kgdbts:RUN singlestep [300/1000]
kgdbts:RUN singlestep [400/1000]
kgdbts:RUN singlestep [500/1000]
kgdbts:RUN singlestep [600/1000]
kgdbts:RUN singlestep [700/1000]
kgdbts:RUN singlestep [800/1000]
kgdbts:RUN singlestep [900/1000]
kgdbts:RUN hw breakpoint test
kgdbts: BP mismatch ffffffff810677e3 expected ffffffff811b4e1f
------------[ cut here ]------------
WARNING: at drivers/misc/kgdbts.c:302 check_and_rewind_pc+0xbf/0xde()
Modules linked in:
Pid: 1, comm: swapper Tainted: G        W 2.6.26 #9

Call Trace:
 <#DB>  [<ffffffff8102f607>] warn_on_slowpath+0x58/0x94
 [<ffffffff810677e3>] ? kgdb_breakpoint+0x12/0x21
 [<ffffffff811b4e1f>] ? kgdbts_break_test+0x0/0x22
 [<ffffffff811b4ce8>] ? fill_get_buf+0xc9/0xd1
 [<ffffffff811b4e1f>] ? kgdbts_break_test+0x0/0x22
 [<ffffffff81073608>] ? probe_kernel_write+0x38/0x68
 [<ffffffff810677e3>] ? kgdb_breakpoint+0x12/0x21
 [<ffffffff811b4e1f>] ? kgdbts_break_test+0x0/0x22
 [<ffffffff811b554e>] check_and_rewind_pc+0xbf/0xde
 [<ffffffff811b4a69>] validate_simple_test+0x25/0x75
 [<ffffffff811b50df>] run_simple_test+0x1e1/0x255
 [<ffffffff811b4aee>] kgdbts_put_char+0x18/0x1a
 [<ffffffff81067616>] put_packet+0x79/0xd9
 [<ffffffff81068c39>] kgdb_handle_exception+0xdd3/0xf02
 [<ffffffff81018e48>] ? touch_nmi_watchdog+0x5e/0x62
 [<ffffffff811b4e1f>] ? kgdbts_break_test+0x0/0x22
 [<ffffffff8101c34a>] kgdb_notify+0x14c/0x166
 [<ffffffff812aa477>] notifier_call_chain+0x33/0x5b
 [<ffffffff812aa4c1>] atomic_notifier_call_chain+0x13/0x15
 [<ffffffff81045900>] notify_die+0x2e/0x30
 [<ffffffff812a8aa5>] do_int3+0x32/0x8f
 [<ffffffff812a82a3>] int3+0x93/0xb0
 [<ffffffff810677e3>] ? kgdb_breakpoint+0x12/0x21
 <<EOE>>  [<ffffffff811b5267>] ? run_breakpoint_test+0x5b/0x9c
 [<ffffffff811b5a20>] ? configure_kgdbts+0x254/0x45d
 [<ffffffff81138399>] ? blk_register_region+0x2a/0x2c
 [<ffffffff8147ffb6>] ? init_kgdbts+0x0/0x16
 [<ffffffff8147ffca>] ? init_kgdbts+0x14/0x16
 [<ffffffff814606d3>] ? kernel_init+0x15f/0x2b3
 [<ffffffff8100ccf8>] ? child_rip+0xa/0x12
 [<ffffffff81460574>] ? kernel_init+0x0/0x2b3
 [<ffffffff8100ccee>] ? child_rip+0x0/0x12

---[ end trace 4eaa2a86a8e2da22 ]---
kgdbts: ERROR PUT: end of test buffer on 'hw_breakpoint_test' line 3
expected kgdbts_break_test got
$d8fa4a81ffffffff0090b57f0081ffff000000000000000001000000000000001000000000000000286a5481ffffffff201e8a0f0081ffff201e8a0f0081ffffc01c8a0f0081ffff��J�����
------------[ cut here ]------------
WARNING: at drivers/misc/kgdbts.c:721 run_simple_test+0x22b/0x255()
Modules linked in:
Pid: 1, comm: swapper Tainted: G        W 2.6.26 #9

Call Trace:
 <#DB>  [<ffffffff8102f607>] warn_on_slowpath+0x58/0x94
 [<ffffffff811b4ce8>] ? fill_get_buf+0xc9/0xd1
 [<ffffffff81073608>] ? probe_kernel_write+0x38/0x68
 [<ffffffff810677e3>] ? kgdb_breakpoint+0x12/0x21
 [<ffffffff811b4e1f>] ? kgdbts_break_test+0x0/0x22
 [<ffffffff811b554e>] ? check_and_rewind_pc+0xbf/0xde
 [<ffffffff811b5129>] run_simple_test+0x22b/0x255
 [<ffffffff811b4aee>] kgdbts_put_char+0x18/0x1a
 [<ffffffff81067616>] put_packet+0x79/0xd9
 [<ffffffff81068c39>] kgdb_handle_exception+0xdd3/0xf02
 [<ffffffff81018e48>] ? touch_nmi_watchdog+0x5e/0x62
 [<ffffffff811b4e1f>] ? kgdbts_break_test+0x0/0x22
 [<ffffffff8101c34a>] kgdb_notify+0x14c/0x166
 [<ffffffff812aa477>] notifier_call_chain+0x33/0x5b
 [<ffffffff812aa4c1>] atomic_notifier_call_chain+0x13/0x15
 [<ffffffff81045900>] notify_die+0x2e/0x30
 [<ffffffff812a8aa5>] do_int3+0x32/0x8f
 [<ffffffff812a82a3>] int3+0x93/0xb0
 [<ffffffff810677e3>] ? kgdb_breakpoint+0x12/0x21
 <<EOE>>  [<ffffffff811b5267>] ? run_breakpoint_test+0x5b/0x9c
 [<ffffffff811b5a20>] ? configure_kgdbts+0x254/0x45d
 [<ffffffff81138399>] ? blk_register_region+0x2a/0x2c
 [<ffffffff8147ffb6>] ? init_kgdbts+0x0/0x16
 [<ffffffff8147ffca>] ? init_kgdbts+0x14/0x16
 [<ffffffff814606d3>] ? kernel_init+0x15f/0x2b3
 [<ffffffff8100ccf8>] ? child_rip+0xa/0x12
 [<ffffffff81460574>] ? kernel_init+0x0/0x2b3
 [<ffffffff8100ccee>] ? child_rip+0x0/0x12

---[ end trace 4eaa2a86a8e2da22 ]---
kgdbts: ERROR hw_breakpoint_test test failed
------------[ cut here ]------------
WARNING: at drivers/misc/kgdbts.c:783 run_breakpoint_test+0x8a/0x9c()
Modules linked in:
Pid: 1, comm: swapper Tainted: G        W 2.6.26 #9

Call Trace:
 [<ffffffff8102f607>] warn_on_slowpath+0x58/0x94
 [<ffffffff810677e3>] ? kgdb_breakpoint+0x12/0x21
 [<ffffffff811b5296>] run_breakpoint_test+0x8a/0x9c
 [<ffffffff811b5a20>] configure_kgdbts+0x254/0x45d
 [<ffffffff81138399>] ? blk_register_region+0x2a/0x2c
 [<ffffffff8147ffb6>] ? init_kgdbts+0x0/0x16
 [<ffffffff8147ffca>] init_kgdbts+0x14/0x16
 [<ffffffff814606d3>] kernel_init+0x15f/0x2b3
 [<ffffffff8100ccf8>] child_rip+0xa/0x12
 [<ffffffff81460574>] ? kernel_init+0x0/0x2b3
 [<ffffffff8100ccee>] ? child_rip+0x0/0x12

---[ end trace 4eaa2a86a8e2da22 ]---
kgdbts:RUN hw write breakpoint test
kgdbts: ERROR hw_write_break_test test failed
------------[ cut here ]------------
WARNING: at drivers/misc/kgdbts.c:815 run_hw_break_test+0xd4/0xe3()
Modules linked in:
Pid: 1, comm: swapper Tainted: G        W 2.6.26 #9

Call Trace:
 [<ffffffff8102f607>] warn_on_slowpath+0x58/0x94
 [<ffffffff810677e3>] ? kgdb_breakpoint+0x12/0x21
 [<ffffffff811b537c>] run_hw_break_test+0xd4/0xe3
 [<ffffffff811b5a41>] configure_kgdbts+0x275/0x45d
 [<ffffffff81138399>] ? blk_register_region+0x2a/0x2c
 [<ffffffff8147ffb6>] ? init_kgdbts+0x0/0x16
 [<ffffffff8147ffca>] init_kgdbts+0x14/0x16
 [<ffffffff814606d3>] kernel_init+0x15f/0x2b3
 [<ffffffff8100ccf8>] child_rip+0xa/0x12
 [<ffffffff81460574>] ? kernel_init+0x0/0x2b3
 [<ffffffff8100ccee>] ? child_rip+0x0/0x12

---[ end trace 4eaa2a86a8e2da22 ]---
kgdbts:RUN access write breakpoint test
kgdbts: ERROR hw_access_break_test test failed
------------[ cut here ]------------
WARNING: at drivers/misc/kgdbts.c:815 run_hw_break_test+0xd4/0xe3()
Modules linked in:
Pid: 1, comm: swapper Tainted: G        W 2.6.26 #9

Call Trace:
 [<ffffffff8102f607>] warn_on_slowpath+0x58/0x94
 [<ffffffff811b537c>] run_hw_break_test+0xd4/0xe3
 [<ffffffff811b5a5f>] configure_kgdbts+0x293/0x45d
 [<ffffffff81138399>] ? blk_register_region+0x2a/0x2c
 [<ffffffff8147ffb6>] ? init_kgdbts+0x0/0x16
 [<ffffffff8147ffca>] init_kgdbts+0x14/0x16
 [<ffffffff814606d3>] kernel_init+0x15f/0x2b3
 [<ffffffff8100ccf8>] child_rip+0xa/0x12
 [<ffffffff81460574>] ? kernel_init+0x0/0x2b3
 [<ffffffff8100ccee>] ? child_rip+0x0/0x12

---[ end trace 4eaa2a86a8e2da22 ]---
kgdb: Unregistered I/O driver kgdbts, debugger disabled.

I assumed that the tests failed, so I thought that the best thing to
do was to post
this on LKML.

So the question is "what's wrong ?"

Thanks
-- 
Francis