linux.git/arch/sh/kernel/entry-common.S, branch v6.8

sh: fix syscall tracing

2020-09-14T01:22:55+00:00

Addition of SECCOMP_FILTER exposed a longstanding bug in
do_syscall_trace_enter, whereby r0 (the 5th argument register) was
mistakenly used where r3 (syscall_nr) was intended. By overwriting r0
rather than r3 with -1 when attempting to block a syscall, the
existing code would instead have caused the syscall to execute with an
argument clobbered.

Commit 0bb605c2c7f2b4b3 then introduced skipping of the syscall when
do_syscall_trace_enter returns -1, so that the return value set by
seccomp filters would not be clobbered by -ENOSYS. This eliminated the
clobbering of the 5th argument register, but instead caused syscalls
made with a 5th argument of -1 to be misinterpreted as a request by
do_syscall_trace_enter to suppress the syscall.

Fixes: 0bb605c2c7f2b4b3 ("sh: Add SECCOMP_FILTER")
Fixes: ab99c733ae73cce3 ("sh: Make syscall tracer use tracehook notifiers, add TIF_NOTIFY_RESUME.")
Tested-by: John Paul Adrian Glaubitz 
Signed-off-by: Rich Felker

sh: Add SECCOMP_FILTER

2020-08-15T02:05:19+00:00

Port sh to use the new SECCOMP_FILTER code.

Signed-off-by: Michael Karcher 
Tested-by: John Paul Adrian Glaubitz 
Signed-off-by: Rich Felker

sh: Rearrange blocks in entry-common.S

2020-08-15T02:05:19+00:00

This avoids out-of-range jumps that get auto-replaced by the assembler
and prepares for the changes needed to implement SECCOMP_FILTER cleanly.

Signed-off-by: Michael Karcher 
Tested-by: John Paul Adrian Glaubitz 
Signed-off-by: Rich Felker

sh: Fix validation of system call number

2020-07-27T20:12:49+00:00

The slow path for traced system call entries accessed a wrong memory
location to get the number of the maximum allowed system call number.
Renumber the numbered "local" label for the correct location to avoid
collisions with actual local labels.

Signed-off-by: Michael Karcher 
Tested-by: John Paul Adrian Glaubitz 
Fixes: f3a8308864f920d2 ("sh: Add a few missing irqflags tracing markers.")
Signed-off-by: Rich Felker

sched/rt, sh: Use CONFIG_PREEMPTION

2019-12-08T13:37:35+00:00

CONFIG_PREEMPTION is selected by CONFIG_PREEMPT and by CONFIG_PREEMPT_RT.
Both PREEMPT and PREEMPT_RT require the same functionality which today
depends on CONFIG_PREEMPT.

Switch the entry code over to use CONFIG_PREEMPTION.

[bigeasy: +Kconfig]

Signed-off-by: Thomas Gleixner 
Signed-off-by: Sebastian Andrzej Siewior 
Signed-off-by: Thomas Gleixner 
Cc: Linus Torvalds 
Cc: Peter Zijlstra 
Cc: Rich Felker 
Cc: Yoshinori Sato 
Cc: linux-sh@vger.kernel.org
Link: https://lore.kernel.org/r/20191015191821.11479-19-bigeasy@linutronix.de
Signed-off-by: Ingo Molnar

sh: kernel: convert to SPDX identifiers

2018-12-28T20:11:45+00:00

Update license to use SPDX-License-Identifier instead of verbose license
text.

Link: http://lkml.kernel.org/r/8736rccswn.wl-kuninori.morimoto.gx@renesas.com
Signed-off-by: Kuninori Morimoto 
Reviewed-by: Simon Horman 
Cc: Rich Felker 
Cc: Yoshinori Sato 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

sh: fix debug trap failure to process signals before return to user

2018-04-12T23:47:52+00:00

When responding to a debug trap (breakpoint) in userspace, the
kernel's trap handler raised SIGTRAP but returned from the trap via a
code path that ignored pending signals, resulting in an infinite loop
re-executing the trapping instruction.

Signed-off-by: Rich Felker

sh: provide unified syscall trap compatible with all SH models

2016-03-17T19:46:06+00:00

Historically SH-2 Linux (and originally uClinux) used a syscall
calling convention incompatible with the established SH-3/4 Linux ABI.
This choice was made because the trap range used by the existing ABI,
0x10-0x17, overlaps with the hardware exception/interrupt trap range
reserved by SH-2, and in particular, with the SH-2A divide-by-zero and
division-overflow exceptions.

Despite the documented syscall convention using the low bits of the
trap number to signal the number of arguments the kernel should
expect, no version of the kernel has ever used this information, nor
is it useful; all of the registers need to be saved anyway. Therefore,
it is possible to pick a new trap number, 0x1f, that is both supported
by all existing SH-3/4 kernels and unassigned as a hardware trap in
the SH-2 range. This makes it possible to produce SH-2 application
binaries that are forwards-compatible with running on SH-3/4 kernels
and to treat SH as a unified platform with varying ISA support levels
rather than multiple gratuitously-incompatible platforms.

This patch adjusts the range checking SH-2 and SH-2A kernels make for
the syscall trap to accept the range 0x1f-0x2f rather than just
0x20-0x2f. As a result, trap 0x1f now acts as a syscall for all SH
models.

Signed-off-by: Rich Felker

sh: push extra copy of r0-r2 for syscall parameters

2014-04-03T23:20:52+00:00

When invoking syscall handlers on sh32, the saved userspace registers
are at the top of the stack.  This seems to have been intentional, as it
is an easy way to pass r0, r1, ...  to the handler as parameters 5, 6,
...

It causes problems, however, because the compiler is allowed to generate
code for a function which clobbers that function's own parameters.  For
example, gcc generates the following code for clone:

    :
        mov.l   8c020714 ,r1  ! 8c020540 
        mov.l   r7,@r15
        mov     r6,r7
        jmp     @r1
        mov     #0,r6
        nop
        .word 0x0540
        .word 0x8c02

The `mov.l r7,@r15` clobbers the saved value of r0 passed from
userspace.  For most system calls, this might not be a problem, because
we'll be overwriting r0 with the return value anyway.  But in the case
of clone, copy_thread will need the original value of r0 if the
CLONE_SETTLS flag was specified.

The first patch in this series fixes this issue for system calls by
pushing to the stack and extra copy of r0-r2 before invoking the
handler.  We discard this copy before restoring the userspace registers,
so it is not a problem if they are clobbered.

Exception handlers also receive the userspace register values in a
similar manner, and may hit the same problem.  The second patch removes
the do_fpu_error handler, which looks susceptible to this problem and
which, as far as I can tell, has not been used in some time.  The third
patch addresses other exception handlers.

This patch (of 3):

The userspace registers are stored at the top of the stack when the
syscall handler is invoked, which allows r0-r2 to act as parameters 5-7.
Parameters passed on the stack may be clobbered by the syscall handler.
The solution is to push an extra copy of the registers which might be
used as syscall parameters to the stack, so that the authoritative set
of saved register values does not get clobbered.

A few system call handlers are also updated to get the userspace
registers using current_pt_regs() instead of from the stack.

Signed-off-by: Bobby Bingham 
Cc: Paul Mundt 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

preempt: Make PREEMPT_ACTIVE generic

2013-11-13T19:21:47+00:00

No point in having this bit defined by architecture.

Signed-off-by: Thomas Gleixner 
Acked-by: Peter Zijlstra 
Link: http://lkml.kernel.org/r/20130917183629.090698799@linutronix.de