clone has some of the quirkiest syscall handling in the kernel, with a
pile of special cases, historical curiosities, and architecture-specific
calling conventions. In particular, clone with CLONE_SETTLS accepts a
parameter "tls" that the C entry point completely ignores and some
assembly entry points overwrite; instead, the low-level arch-specific
code pulls the tls parameter out of the arch-specific register captured
as part of pt_regs on entry to the kernel. That's a massive hack, and
it makes the arch-specific code only work when called via the specific
existing syscall entry points; because of this hack, any new clone-like
system call would have to accept an identical tls argument in exactly
the same arch-specific position, rather than providing a unified system
call entry point across architectures.
The first patch allows architectures to handle the tls argument via
normal C parameter passing, if they opt in by selecting
HAVE_COPY_THREAD_TLS. The second patch makes 32-bit and 64-bit x86 opt
into this.
These two patches came out of the clone4 series, which isn't ready for
this merge window, but these first two cleanup patches were entirely
uncontroversial and have acks. I'd like to go ahead and submit these
two so that other architectures can begin building on top of this and
opting into HAVE_COPY_THREAD_TLS. However, I'm also happy to wait and
send these through the next merge window (along with v3 of clone4) if
anyone would prefer that.
This patch (of 2):
clone with CLONE_SETTLS accepts an argument to set the thread-local
storage area for the new thread. sys_clone declares an int argument
tls_val in the appropriate point in the argument list (based on the
various CLONE_BACKWARDS variants), but doesn't actually use or pass along
that argument. Instead, sys_clone calls do_fork, which calls
copy_process, which calls the arch-specific copy_thread, and copy_thread
pulls the corresponding syscall argument out of the pt_regs captured at
kernel entry (knowing what argument of clone that architecture passes tls
in).
Apart from being awful and inscrutable, that also only works because only
one code path into copy_thread can pass the CLONE_SETTLS flag, and that
code path comes from sys_clone with its architecture-specific
argument-passing order. This prevents introducing a new version of the
clone system call without propagating the same architecture-specific
position of the tls argument.
However, there's no reason to pull the argument out of pt_regs when
sys_clone could just pass it down via C function call arguments.
Introduce a new CONFIG_HAVE_COPY_THREAD_TLS for architectures to opt into,
and a new copy_thread_tls that accepts the tls parameter as an additional
unsigned long (syscall-argument-sized) argument. Change sys_clone's tls
argument to an unsigned long (which does not change the ABI), and pass
that down to copy_thread_tls.
Architectures that don't opt into copy_thread_tls will continue to ignore
the C argument to sys_clone in favor of the pt_regs captured at kernel
entry, and thus will be unable to introduce new versions of the clone
syscall.
Patch co-authored by Josh Triplett and Thiago Macieira.
Signed-off-by: Josh Triplett <josh@joshtriplett.org>
Acked-by: Andy Lutomirski <luto@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Thiago Macieira <thiago.macieira@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
We can't look up the address of the entry point of the function simply
via that function symbol for all architectures.
For PPC64 ABI, actually there is a function descriptors structure.
A function descriptor is a three doubleword data structure that contains
the following values:
* The first doubleword contains the address of the entry point of
the function.
* The second doubleword contains the TOC base address for
the function.
* The third doubleword contains the environment pointer for
languages such as Pascal and PL/1.
So we should call a wapperred dereference_function_descriptor() to get
the address of the entry point of the function.
Note this is also safe for other architecture after refer to
"include/asm-generic/sections.h" since:
dereference_function_descriptor(p) always is (p) if without arched definition.
Signed-off-by: Tiejun Chen <tiejun.chen@windriver.com>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
There has long been a limitation using software breakpoints with a
kernel compiled with CONFIG_DEBUG_RODATA going back to 2.6.26. For
this particular patch, it will apply cleanly and has been tested all
the way back to 2.6.36.
The kprobes code uses the text_poke() function which accommodates
writing a breakpoint into a read-only page. The x86 kgdb code can
solve the problem similarly by overriding the default breakpoint
set/remove routines and using text_poke() directly.
The x86 kgdb code will first attempt to use the traditional
probe_kernel_write(), and next try using a the text_poke() function.
The break point install method is tracked such that the correct break
point removal routine will get called later on.
Cc: x86@kernel.org
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: stable@vger.kernel.org # >= 2.6.36
Inspried-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
The do_fork and sys_open tests have never worked properly on anything
other than a UP configuration with the kgdb test suite. This is
because the test suite did not fully implement the behavior of a real
debugger. A real debugger tracks the state of what thread it asked to
single step and can correctly continue other threads of execution or
conditionally stop while waiting for the original thread single step
request to return.
Below is a simple method to cause a fatal kernel oops with the kgdb
test suite on a 2 processor ARM system:
while [ 1 ] ; do ls > /dev/null 2> /dev/null; done&
while [ 1 ] ; do ls > /dev/null 2> /dev/null; done&
echo V1I1F100 > /sys/module/kgdbts/parameters/kgdbts
Very soon after starting the test the kernel will start warning with
messages like:
kgdbts: BP mismatch c002487c expected c0024878
------------[ cut here ]------------
WARNING: at drivers/misc/kgdbts.c:317 check_and_rewind_pc+0x9c/0xc4()
[<c01f6520>] (check_and_rewind_pc+0x9c/0xc4)
[<c01f595c>] (validate_simple_test+0x3c/0xc4)
[<c01f60d4>] (run_simple_test+0x1e8/0x274)
The kernel will eventually recovers, but the test suite has completely
failed to test anything useful.
This patch implements behavior similar to a real debugger that does
not rely on hardware single stepping by using only software planted
breakpoints.
In order to mimic a real debugger, the kgdb test suite now tracks the
most recent thread that was continued (cont_thread_id), with the
intent to single step just this thread. When the response to the
single step request stops in a different thread that hit the original
break point that thread will now get continued, while the debugger
waits for the thread with the single step pending. Here is a high
level description of the sequence of events.
cont_instead_of_sstep = 0;
1) set breakpoint at do_fork
2) continue
3) Save the thread id where we stop to cont_thread_id
4) Remove breakpoint at do_fork
5) Reset the PC if needed depending on kernel exception type
6) soft single step
7) Check where we stopped
if current thread != cont_thread_id {
if (here for more than 2 times for the same thead) {
### must be a really busy system, start test again ###
goto step 1
}
goto step 5
} else {
cont_instead_of_sstep = 0;
}
8) clean up and run test again if needed
9) Clear out any threads that were waiting on a break point at the
point in time the test is ended with get_cont_catch(). This
happens sometimes because breakpoints are used in place of single
stepping and some threads could have been in the debugger exception
handling queue because breakpoints were hit concurrently on
different CPUs. This also means we wait at least one second before
unplumbing the debugger connection at the very end, so as respond
to any debug threads waiting to be serviced.
Cc: stable@vger.kernel.org # >= 3.0
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
The do_fork and sys_open tests have never worked properly on anything
other than a UP configuration with the kgdb test suite. This is
because the test suite did not fully implement the behavior of a real
debugger. A real debugger tracks the state of what thread it asked to
single step and can correctly continue other threads of execution or
conditionally stop while waiting for the original thread single step
request to return.
Below is a simple method to cause a fatal kernel oops with the kgdb
test suite on a 4 processor x86 system:
while [ 1 ] ; do ls > /dev/null 2> /dev/null; done&
while [ 1 ] ; do ls > /dev/null 2> /dev/null; done&
while [ 1 ] ; do ls > /dev/null 2> /dev/null; done&
while [ 1 ] ; do ls > /dev/null 2> /dev/null; done&
echo V1I1F1000 > /sys/module/kgdbts/parameters/kgdbts
Very soon after starting the test the kernel will oops with a message like:
kgdbts: BP mismatch 3b7da66480 expected ffffffff8106a590
WARNING: at drivers/misc/kgdbts.c:303 check_and_rewind_pc+0xe0/0x100()
Call Trace:
[<ffffffff812994a0>] check_and_rewind_pc+0xe0/0x100
[<ffffffff81298945>] validate_simple_test+0x25/0xc0
[<ffffffff81298f77>] run_simple_test+0x107/0x2c0
[<ffffffff81298a18>] kgdbts_put_char+0x18/0x20
The warn will turn to a hard kernel crash shortly after that because
the pc will not get properly rewound to the right value after hitting
a breakpoint leading to a hard lockup.
This change is broken up into 2 pieces because archs that have hw
single stepping (2.6.26 and up) need different changes than archs that
do not have hw single stepping (3.0 and up). This change implements
the correct behavior for an arch that supports hw single stepping.
A minor defect was fixed where sys_open should be do_sys_open
for the sys_open break point test. This solves the problem of running
a 64 bit with a 32 bit user space. The sys_open() never gets called
when using the 32 bit file system for the kgdb testsuite because the
32 bit binaries invoke the compat_sys_open() call leading to the test
never completing.
In order to mimic a real debugger, the kgdb test suite now tracks the
most recent thread that was continued (cont_thread_id), with the
intent to single step just this thread. When the response to the
single step request stops in a different thread that hit the original
break point that thread will now get continued, while the debugger
waits for the thread with the single step pending. Here is a high
level description of the sequence of events.
cont_instead_of_sstep = 0;
1) set breakpoint at do_fork
2) continue
3) Save the thread id where we stop to cont_thread_id
4) Remove breakpoint at do_fork
5) Reset the PC if needed depending on kernel exception type
6) if (cont_instead_of_sstep) { continue } else { single step }
7) Check where we stopped
if current thread != cont_thread_id {
cont_instead_of_sstep = 1;
goto step 5
} else {
cont_instead_of_sstep = 0;
}
8) clean up and run test again if needed
Cc: stable@vger.kernel.org # >= 2.6.26
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
On x86 the kgdb test suite will oops when the kernel is compiled with
CONFIG_DEBUG_RODATA and you run the tests after boot time. This is
regression has existed since 2.6.26 by commit: b33cb815 (kgdbts: Use
HW breakpoints with CONFIG_DEBUG_RODATA).
The test suite can use hw breakpoints for all the tests, but it has to
execute the hardware breakpoint specific tests first in order to
determine that the hw breakpoints actually work. Specifically the
very first test causes an oops:
# echo V1I1 > /sys/module/kgdbts/parameters/kgdbts
kgdb: Registered I/O driver kgdbts.
kgdbts:RUN plant and detach test
Entering kdb (current=0xffff880017aa9320, pid 1078) on processor 0 due to Keyboard Entry
[0]kdb> kgdbts: ERROR PUT: end of test buffer on 'plant_and_detach_test' line 1 expected OK got $E14#aa
WARNING: at drivers/misc/kgdbts.c:730 run_simple_test+0x151/0x2c0()
[...oops clipped...]
This commit re-orders the running of the tests and puts the RODATA
check into its own function so as to correctly avoid the kernel oops
by detecting and using the hw breakpoints.
Cc: <stable@vger.kernel.org> # >= 2.6.26
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
These files really need the full module.h header file present, but
were just getting it implicitly before. Fix it up in advance so we
avoid build failures once the cleanup commit is present.
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
The new instruction_pointer_set helper is defined for people who have
converted to asm-generic/ptrace.h, so don't use it generally unless
the arch needs it (in which case it has been converted). This should
fix building of kgdb tests for arches not yet converted.
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Acked-by: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Jason Wessel <jason.wessel@windriver.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The Blackfin arch, like the x86 arch, needs to adjust the PC manually
after a breakpoint is hit as normally this is handled by the remote gdb.
However, rather than starting another arch ifdef mess, create a common
GDB_ADJUSTS_BREAK_OFFSET define for any arch to opt-in via their kgdb.h.
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Jason Wessel <jason.wessel@windriver.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Acked-by: Paul Mundt <lethal@linux-sh.org>
Acked-by: Dongdong Deng <dongdong.deng@windriver.com>
Cc: Sergei Shtylyov <sshtylyov@mvista.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This is an off by one because strlen() doesn't count the null
terminator. We strcpy() these strings into an array of size
MAX_CONFIG_LEN.
Signed-off-by: Dan Carpenter <error27@gmail.com>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
The "kgdb_connected" variable of debug_core just indicates whether or
not kgdbts is connected to the debug_core. It does not completely
prevent a script from trying invoke kgdbts again and possibly crashing
the system (see Call Trace below).
The configured variable in kgtbts can be used instead of
kgdb_connected instead of kgdb_connected. The cleanup_kgdbts() can
also be removed because there is no possible way to build kgdbts as a
kernel module that you could unload with rmmod.
Call Trace:
-----------------------------------------------------------------
root:/$ echo kgdbts=V1S1000 > /sys/module/kgdbts/parameters/kgdbts
kgdb: Unregistered I/O driver kgdbts, debugger disabled.
------------[ cut here ]------------
WARNING: at kernel/debug/debug_core.c:1002
kgdb_unregister_io_module+0xec/0x100()
Hardware name: Moon Creek platform
Modules linked in:
Pid: 664, comm: sh Not tainted 2.6.34.1-WR4.0.0.0_standard #58
Call Trace:
[<c103b1ed>] warn_slowpath_common+0x6d/0xa0
[<c1079fdc>] ? kgdb_unregister_io_module+0xec/0x100
[<c1079fdc>] ? kgdb_unregister_io_module+0xec/0x100
[<c10544e0>] ? param_attr_store+0x0/0x20
[<c103b235>] warn_slowpath_null+0x15/0x20
[<c1079fdc>] kgdb_unregister_io_module+0xec/0x100
[<c124e4ea>] cleanup_kgdbts+0x1a/0x20
[<c124eced>] param_set_kgdbts_var+0x6d/0xb0
[<c124ec80>] ? param_set_kgdbts_var+0x0/0xb0
[<c10544f7>] param_attr_store+0x17/0x20
[<c105457c>] module_attr_store+0x2c/0x40
[<c111fe84>] sysfs_write_file+0x94/0xf0
[<c10d42f6>] vfs_write+0x96/0x130
[<c111fdf0>] ? sysfs_write_file+0x0/0xf0
[<c10d44d6>] sys_write+0x46/0xd0
[<c13bf329>] system_call_done+0x0/0x4
---[ end trace 4eb028c6ee43154c ]---
kgdb: Unregistered I/O driver kgdbts, debugger disabled.
-----------------------------------------------------------------
[jason.wessel@windriver.com: remove cleanup_kgdbts() ]
Signed-off-by: Dongdong Deng <dongdong.deng@windriver.com>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
The kgdb test suite mimics the behavior of gdb. For the sh
architecture the pc must be decremented by 2 for software breakpoint.
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Acked-by: Paul Mundt <lethal@linux-sh.org>
Some versions of gcc replace calls to strstr() with single-character
"needle" string parameters by calls to strchr() behind our back.
This causes linking errors if strchr() is defined as an inline function
in <asm/string.h> (e.g. on m68k, which BTW doesn't have kgdb support).
Prevent this by explicitly calling strchr() instead.
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Prevent write to put_buf[BUFMAX] in kgdb test suite.
If put_buf_cnt was BUFMAX - 1 at the earlier test,
`\0' is written to put_buf[BUFMAX].
Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Whenever CONFIG_DEBUG_RODATA is set in the kernel config many kernel
text sections become read-only, and the use of software breakpoints in
the kgdb tests will cause the kernel to fail to complete the start up.
Until such time that there is an official API for modifying read-only
text sections hardware breakpoints must be used to run the do_fork or
sys_open tests or the tests get skipped.
Also fix the duplicated include reported by:
Huang Weiyi <weiyi.huang@gmail.com>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
The single step test is not terribly costly and it should be able to
pass at 1000 loops successfully in under 1 second. A non-kgdb timing
regression was found using this test, but it did not occur frequently
because by default the test was only executed a single time.
This patch changes the default for the single step test to 1000
iterations and allows for individual configuration of the single step
test to further exercise the kgdb subsystem when needed.
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Shadowed variable and integer as NULL pointer fixes:
drivers/misc/kgdbts.c:877:6: warning: symbol 'sys_open_test' shadows an earlier one
drivers/misc/kgdbts.c:537:27: originally declared here
drivers/misc/kgdbts.c:378:22: warning: Using plain integer as NULL pointer
drivers/misc/kgdbts.c:386:22: warning: Using plain integer as NULL pointer
drivers/misc/kgdbts.c:468:30: warning: Using plain integer as NULL pointer
drivers/misc/kgdbts.c:472:15: warning: Using plain integer as NULL pointer
drivers/misc/kgdbts.c:502:30: warning: Using plain integer as NULL pointer
drivers/misc/kgdbts.c:506:30: warning: Using plain integer as NULL pointer
drivers/misc/kgdbts.c:509:30: warning: Using plain integer as NULL pointer
drivers/misc/kgdbts.c:523:20: warning: Using plain integer as NULL pointer
drivers/misc/kgdbts.c:527:20: warning: Using plain integer as NULL pointer
drivers/misc/kgdbts.c:530:15: warning: Using plain integer as NULL pointer
drivers/misc/kgdbts.c:541:21: warning: Using plain integer as NULL pointer
drivers/misc/kgdbts.c:545:21: warning: Using plain integer as NULL pointer
drivers/misc/kgdbts.c:548:15: warning: Using plain integer as NULL pointer
drivers/misc/kgdbts.c:559:30: warning: Using plain integer as NULL pointer
drivers/misc/kgdbts.c:563:15: warning: Using plain integer as NULL pointer
drivers/misc/kgdbts.c:573:16: warning: Using plain integer as NULL pointer
drivers/misc/kgdbts.c:574:19: warning: Using plain integer as NULL pointer
drivers/misc/kgdbts.c:578:15: warning: Using plain integer as NULL pointer
drivers/misc/kgdbts.c:588:16: warning: Using plain integer as NULL pointer
drivers/misc/kgdbts.c:589:19: warning: Using plain integer as NULL pointer
drivers/misc/kgdbts.c:593:15: warning: Using plain integer as NULL pointer
drivers/misc/kgdbts.c:602:16: warning: Using plain integer as NULL pointer
drivers/misc/kgdbts.c:604:15: warning: Using plain integer as NULL pointer
drivers/misc/kgdbts.c:925:3: warning: Using plain integer as NULL pointer
drivers/misc/kgdbts.c:938:3: warning: Using plain integer as NULL pointer
Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
This patch adds in the ability to compile the kgdb internal test
string into the kernel so as to run the tests at boot without changing
the kernel boot arguments. This patch also changes all the error
paths to invoke WARN_ON(1) which will emit the line number of the file
and dump the kernel stack when an error occurs.
You can disable the tests in a kernel that is built this way
using "kgdbts="
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This patch adds regression tests for testing the kgdb core and arch
specific implementation.
The kgdb test suite is designed to be built into the kernel and not as
a module because it uses a number of low level kernel and kgdb
primitives which should not be exported externally.
The kgdb test suite is designed as a KGDB I/O module which
simulates the communications that a debugger would have with kgdb.
The tests are broken up in to a line by line and referenced here as
a "get" which is kgdb requesting input and "put" which is kgdb
sending a response.
The kgdb suite can be invoked from the kernel command line
arguments system or executed dynamically at run time. The test
suite uses the variable "kgdbts" to obtain the information about
which tests to run and to configure the verbosity level. The
following are the various characters you can use with the kgdbts=
line:
When using the "kgdbts=" you only choose one of the following core
test types:
A = Run all the core tests silently
V1 = Run all the core tests with minimal output
V2 = Run all the core tests in debug mode
You can also specify optional tests:
N## = Go to sleep with interrupts of for ## seconds
to test the HW NMI watchdog
F## = Break at do_fork for ## iterations
S## = Break at sys_open for ## iterations
NOTE: that the do_fork and sys_open tests are mutually exclusive.
To invoke the kgdb test suite from boot you use a kernel start
argument as follows:
kgdbts=V1 kgdbwait
Or if you wanted to perform the NMI test for 6 seconds and do_fork
test for 100 forks, you could use:
kgdbts=V1N6F100 kgdbwait
The test suite can also be invoked at run time with:
echo kgdbts=V1N6F100 > /sys/module/kgdbts/parameters/kgdbts
Or as another example:
echo kgdbts=V2 > /sys/module/kgdbts/parameters/kgdbts
When developing a new kgdb arch specific implementation or
using these tests for the purpose of regression testing,
several invocations are required.
1) Boot with the test suite enabled by using the kernel arguments
"kgdbts=V1F100 kgdbwait"
## If kgdb arch specific implementation has NMI use
"kgdbts=V1N6F100
2) After the system boot run the basic test.
echo kgdbts=V1 > /sys/module/kgdbts/parameters/kgdbts
3) Run the concurrency tests. It is best to use n+1
while loops where n is the number of cpus you have
in your system. The example below uses only two
loops.
## This tests break points on sys_open
while [ 1 ] ; do find / > /dev/null 2>&1 ; done &
while [ 1 ] ; do find / > /dev/null 2>&1 ; done &
echo kgdbts=V1S10000 > /sys/module/kgdbts/parameters/kgdbts
fg # and hit control-c
fg # and hit control-c
## This tests break points on do_fork
while [ 1 ] ; do date > /dev/null ; done &
while [ 1 ] ; do date > /dev/null ; done &
echo kgdbts=V1F1000 > /sys/module/kgdbts/parameters/kgdbts
fg # and hit control-c
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
