diff options
| author | Helge Deller <deller@gmx.de> | 2017-03-25 11:59:15 +0100 |
|---|---|---|
| committer | Helge Deller <deller@gmx.de> | 2017-03-29 21:50:36 +0200 |
| commit | d19f5e41b344a057bb2450024a807476f30978d2 (patch) | |
| tree | 4f7f4fa52e5e845ec0abe38d1906404d575ca8ab /arch/parisc/mm | |
| parent | 554bfeceb8a22d448cd986fc9efce25e833278a1 (diff) | |
parisc: Clean up fixup routines for get_user()/put_user()
Al Viro noticed that userspace accesses via get_user()/put_user() can be
simplified a lot with regard to usage of the exception handling.
This patch implements a fixup routine for get_user() and put_user() in such
that the exception handler will automatically load -EFAULT into the register
%r8 (the error value) in case on a fault on userspace. Additionally the fixup
routine will zero the target register on fault in case of a get_user() call.
The target register is extracted out of the faulting assembly instruction.
This patch brings a few benefits over the old implementation:
1. Exception handling gets much cleaner, easier and smaller in size.
2. Helper functions like fixup_get_user_skip_1 (all of fixup.S) can be dropped.
3. No need to hardcode %r9 as target register for get_user() any longer. This
helps the compiler register allocator and thus creates less assembler
statements.
4. No dependency on the exception_data contents any longer.
5. Nested faults will be handled cleanly.
Reported-by: Al Viro <viro@ZenIV.linux.org.uk>
Cc: <stable@vger.kernel.org> # v4.9+
Signed-off-by: Helge Deller <deller@gmx.de>
Diffstat (limited to 'arch/parisc/mm')
| -rw-r--r-- | arch/parisc/mm/fault.c | 17 |
1 files changed, 17 insertions, 0 deletions
diff --git a/arch/parisc/mm/fault.c b/arch/parisc/mm/fault.c index deab89a8915a..32ec22146141 100644 --- a/arch/parisc/mm/fault.c +++ b/arch/parisc/mm/fault.c @@ -150,6 +150,23 @@ int fixup_exception(struct pt_regs *regs) d->fault_space = regs->isr; d->fault_addr = regs->ior; + /* + * Fix up get_user() and put_user(). + * ASM_EXCEPTIONTABLE_ENTRY_EFAULT() sets the least-significant + * bit in the relative address of the fixup routine to indicate + * that %r8 should be loaded with -EFAULT to report a userspace + * access error. + */ + if (fix->fixup & 1) { + regs->gr[8] = -EFAULT; + + /* zero target register for get_user() */ + if (parisc_acctyp(0, regs->iir) == VM_READ) { + int treg = regs->iir & 0x1f; + regs->gr[treg] = 0; + } + } + regs->iaoq[0] = (unsigned long)&fix->fixup + fix->fixup; regs->iaoq[0] &= ~3; /* |