kernel/arch/mips/math-emu, branch linux-5.1.y

mips: math-emu: no need to check return value of debugfs_create functions

2019-01-22T19:17:20Z

When calling debugfs functions, there is no need to ever check the return value. The function can work or not, but the code logic should never do something different based on this. Cc: Ralf Baechle Cc: Paul Burton Cc: James Hogan Cc: Yangtao Li Cc: linux-mips@vger.kernel.org Signed-off-by: Greg Kroah-Hartman Signed-off-by: Paul Burton

Remove 'type' argument from access_ok() function

2019-01-04T02:57:57Z

Nobody has actually used the type (VERIFY_READ vs VERIFY_WRITE) argument of the user address range verification function since we got rid of the old racy i386-only code to walk page tables by hand. It existed because the original 80386 would not honor the write protect bit when in kernel mode, so you had to do COW by hand before doing any user access. But we haven't supported that in a long time, and these days the 'type' argument is a purely historical artifact. A discussion about extending 'user_access_begin()' to do the range checking resulted this patch, because there is no way we're going to move the old VERIFY_xyz interface to that model. And it's best done at the end of the merge window when I've done most of my merges, so let's just get this done once and for all. This patch was mostly done with a sed-script, with manual fix-ups for the cases that weren't of the trivial 'access_ok(VERIFY_xyz' form. There were a couple of notable cases: - csky still had the old "verify_area()" name as an alias. - the iter_iov code had magical hardcoded knowledge of the actual values of VERIFY_{READ,WRITE} (not that they mattered, since nothing really used it) - microblaze used the type argument for a debug printout but other than those oddities this should be a total no-op patch. I tried to fix up all architectures, did fairly extensive grepping for access_ok() uses, and the changes are trivial, but I may have missed something. Any missed conversion should be trivially fixable, though. Signed-off-by: Linus Torvalds

MIPS: math-emu: Write-protect delay slot emulation pages

2018-12-20T18:00:01Z

Mapping the delay slot emulation page as both writeable & executable presents a security risk, in that if an exploit can write to & jump into the page then it can be used as an easy way to execute arbitrary code. Prevent this by mapping the page read-only for userland, and using access_process_vm() with the FOLL_FORCE flag to write to it from mips_dsemul(). This will likely be less efficient due to copy_to_user_page() performing cache maintenance on a whole page, rather than a single line as in the previous use of flush_cache_sigtramp(). However this delay slot emulation code ought not to be running in any performance critical paths anyway so this isn't really a problem, and we can probably do better in copy_to_user_page() anyway in future. A major advantage of this approach is that the fix is small & simple to backport to stable kernels. Reported-by: Andy Lutomirski Signed-off-by: Paul Burton Fixes: 432c6bacbd0c ("MIPS: Use per-mm page to execute branch delay slot instructions") Cc: stable@vger.kernel.org # v4.8+ Cc: linux-mips@vger.kernel.org Cc: linux-kernel@vger.kernel.org Cc: Rich Felker Cc: David Daney

MIPS: Ensure emulated FP sets PF_USED_MATH

2018-11-09T18:23:14Z

Emulated floating point instructions don't ensure that the PF_USED_MATH flag is set for the task. This results in a couple of inconsistencies: - ptrace will return the default initial state of FP registers rather than the values actually stored in struct thread_struct, hiding state that has been updated by emulated floating point instructions. - If a task migrates to a CPU with an FPU after having emulated floating point instructions then its floating point register state will be reset to the default ~0 bit pattern, losing state from the emulated instructions. Fix this by calling init_fp_ctx() from fpu_emulator_cop1Handler() to consistently initialize FP state if it was previously uninitialized, setting the PF_USED_MATH flag in the process. All callers of fpu_emulator_cop1Handler() either call lose_fpu(1) before it in order to save any live FPU registers to struct thread_struct, or in the case of do_cpu() already know that the task does not own an FPU so lose_fpu(1) would be a no-op. Since we know that saving FP context will be unnecessary in the case where FP context was just initialized we move this call into fpu_emulator_cop1Handler() too, providing consistency & avoiding needless duplication. Calls to own_fpu(1) are common after return from fpu_emulator_cop1Handler() too, but this would not be a no-op in the do_cpu() case so these are left as-is. A potential future improvement could be to have fpu_emulator_cop1Handler() restore FPU state automatically only if it saved it, though this may not be optimal if some callers are better off without their current calls to own_fpu(1). One potential example of this could be mipsr2_decoder() which as-is could end up saving & restoring FP context repeatedly & unnecessarily if emulating multiple FP instructions. Signed-off-by: Paul Burton Patchwork: https://patchwork.linux-mips.org/patch/21003/ Cc: linux-mips@linux-mips.org

MIPS: math-emu: Change to use DEFINE_SHOW_ATTRIBUTE macro

2018-11-05T18:13:21Z

Use DEFINE_SHOW_ATTRIBUTE macro to simplify the code. Signed-off-by: Yangtao Li Signed-off-by: Paul Burton Patchwork: https://patchwork.linux-mips.org/patch/20988/ Cc: ralf@linux-mips.org Cc: jhogan@kernel.org Cc: linux-mips@linux-mips.org Cc: linux-kernel@vger.kernel.org

MIPS: math-emu: Mark fall throughs in switch statements with a comment

2017-12-12T16:20:20Z

Mark intentional fall throughs in switch statements with a consistent comment. In most of the cases, a new comment line containing text "fall through" is inserted. In some of the cases, existing comment contained a variation of the text "fall through" (for example, "FALL THROUGH" or "drop through"). In such cases, the existing comment is modified to contain "fall through". Lastly, in two cases, code segments were described in comments as "fall througs", but were in reality "breaks out" of switch statement. In such cases, existing comments are accordingly modified. Apart from making code easier to follow and debug, this change enables some static code analysers to interpret newly inserted comments as their annotations (and, therefore, not issue warnings of type "fall through in switch statement", which is desireable, since marked fallthroughs are intentional). Signed-off-by: Aleksandar Markovic Cc: Douglas Leung Cc: Goran Ferenc Cc: James Hogan Cc: Maciej W. Rozycki Cc: Manuel Lauss Cc: Miodrag Dinic Cc: Paul Burton Cc: Petar Jovanovic Cc: Raghu Gandham Cc: linux-kernel@vger.kernel.org Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/17588/ Signed-off-by: Ralf Baechle

MIPS: math-emu: Avoid multiple assignment

2017-12-12T16:20:20Z

Replace several instances of multiple assignment with individual assignments. Signed-off-by: Aleksandar Markovic Cc: Douglas Leung Cc: Goran Ferenc Cc: James Hogan Cc: Maciej W. Rozycki Cc: Manuel Lauss Cc: Miodrag Dinic Cc: Paul Burton Cc: Petar Jovanovic Cc: Raghu Gandham Cc: linux-mips@linux-mips.org Cc: linux-kernel@vger.kernel.org Patchwork: https://patchwork.linux-mips.org/patch/17587/ Signed-off-by: Ralf Baechle

MIPS: math-emu: Avoid an assignment within if statement condition

2017-12-12T16:20:20Z

Move invocation of fpu_emu() to be out of if statement condition. This makes code easier to follow and debug, and fixes a checkpatch warning. Signed-off-by: Aleksandar Markovic Cc: Douglas Leung Cc: Goran Ferenc Cc: James Hogan Cc: Maciej W. Rozycki Cc: Miodrag Dinic Cc: Paul Burton Cc: Petar Jovanovic Cc: Raghu Gandham Cc: linux-mips@linux-mips.org Cc: linux-kernel@vger.kernel.org Patchwork: https://patchwork.linux-mips.org/patch/17586/ Signed-off-by: Ralf Baechle

MIPS: math-emu: Declare function srl128() as static

2017-12-12T16:20:19Z

Declare function srl128() as static, since it it used just locally to the source file. This also removes a sparse warning for corresponding file. Signed-off-by: Aleksandar Markovic Cc: Douglas Leung Cc: Goran Ferenc Cc: James Hogan Cc: Miodrag Dinic Cc: Paul Burton Cc: Petar Jovanovic Cc: Raghu Gandham Cc: linux-mips@linux-mips.org Cc: linux-kernel@vger.kernel.org Patchwork: https://patchwork.linux-mips.org/patch/17585/ Signed-off-by: Ralf Baechle

MIPS: math-emu: Avoid definition duplication for macro DPXMULT()

2017-12-12T16:20:19Z

Avoid duplicate definition of macro DPXMULT(). Move its definition to a header. Signed-off-by: Aleksandar Markovic Cc: Douglas Leung Cc: Goran Ferenc Cc: James Hogan Cc: Miodrag Dinic Cc: Paul Burton Cc: Petar Jovanovic Cc: Raghu Gandham Cc: linux-mips@linux-mips.org Cc: linux-kernel@vger.kernel.org Patchwork: https://patchwork.linux-mips.org/patch/17584/ Signed-off-by: Ralf Baechle