kernel.git/arch/mips/kernel/traps.c, branch linux-4.14.y

exit: Add and use make_task_dead.

2023-02-06T06:46:33Z

commit 0e25498f8cd43c1b5aa327f373dd094e9a006da7 upstream. There are two big uses of do_exit. The first is it's design use to be the guts of the exit(2) system call. The second use is to terminate a task after something catastrophic has happened like a NULL pointer in kernel code. Add a function make_task_dead that is initialy exactly the same as do_exit to cover the cases where do_exit is called to handle catastrophic failure. In time this can probably be reduced to just a light wrapper around do_task_dead. For now keep it exactly the same so that there will be no behavioral differences introducing this new concept. Replace all of the uses of do_exit that use it for catastraphic task cleanup with make_task_dead to make it clear what the code is doing. As part of this rename rewind_stack_do_exit rewind_stack_and_make_dead. Signed-off-by: "Eric W. Biederman" Signed-off-by: Eric Biggers Signed-off-by: Greg Kroah-Hartman

MIPS: fix fortify panic when copying asm exception handlers

2022-04-20T07:08:27Z

[ Upstream commit d17b66417308996e7e64b270a3c7f3c1fbd4cfc8 ] With KCFLAGS="-O3", I was able to trigger a fortify-source memcpy() overflow panic on set_vi_srs_handler(). Although O3 level is not supported in the mainline, under some conditions that may've happened with any optimization settings, it's just a matter of inlining luck. The panic itself is correct, more precisely, 50/50 false-positive and not at the same time. From the one side, no real overflow happens. Exception handler defined in asm just gets copied to some reserved places in the memory. But the reason behind is that C code refers to that exception handler declares it as `char`, i.e. something of 1 byte length. It's obvious that the asm function itself is way more than 1 byte, so fortify logics thought we are going to past the symbol declared. The standard way to refer to asm symbols from C code which is not supposed to be called from C is to declare them as `extern const u8[]`. This is fully correct from any point of view, as any code itself is just a bunch of bytes (including 0 as it is for syms like _stext/_etext/etc.), and the exact size is not known at the moment of compilation. Adjust the type of the except_vec_vi_*() and related variables. Make set_handler() take `const` as a second argument to avoid cast-away warnings and give a little more room for optimization. Signed-off-by: Alexander Lobakin Signed-off-by: Thomas Bogendoerfer Signed-off-by: Sasha Levin

MIPS: Add missing EHB in mtc0 -> mfc0 sequence for DSPen

2020-07-09T07:36:32Z

commit fcec538ef8cca0ad0b84432235dccd9059c8e6f8 upstream. This resolves the hazard between the mtc0 in the change_c0_status() and the mfc0 in configure_exception_vector(). Without resolving this hazard configure_exception_vector() could read an old value and would restore this old value again. This would revert the changes change_c0_status() did. I checked this by printing out the read_c0_status() at the end of per_cpu_trap_init() and the ST0_MX is not set without this patch. The hazard is documented in the MIPS Architecture Reference Manual Vol. III: MIPS32/microMIPS32 Privileged Resource Architecture (MD00088), rev 6.03 table 8.1 which includes: Producer | Consumer | Hazard ----------|----------|---------------------------- mtc0 | mfc0 | any coprocessor 0 register I saw this hazard on an Atheros AR9344 rev 2 SoC with a MIPS 74Kc CPU. There the change_c0_status() function would activate the DSPen by setting ST0_MX in the c0_status register. This was reverted and then the system got a DSP exception when the DSP registers were saved in save_dsp() in the first process switch. The crash looks like this: [ 0.089999] Mount-cache hash table entries: 1024 (order: 0, 4096 bytes, linear) [ 0.097796] Mountpoint-cache hash table entries: 1024 (order: 0, 4096 bytes, linear) [ 0.107070] Kernel panic - not syncing: Unexpected DSP exception [ 0.113470] Rebooting in 1 seconds.. We saw this problem in OpenWrt only on the MIPS 74Kc based Atheros SoCs, not on the 24Kc based SoCs. We only saw it with kernel 5.4 not with kernel 4.19, in addition we had to use GCC 8.4 or 9.X, with GCC 8.3 it did not happen. In the kernel I bisected this problem to commit 9012d011660e ("compiler: allow all arches to enable CONFIG_OPTIMIZE_INLINING"), but when this was reverted it also happened after commit 172dcd935c34b ("MIPS: Always allocate exception vector for MIPSr2+"). Commit 0b24cae4d535 ("MIPS: Add missing EHB in mtc0 -> mfc0 sequence.") does similar changes to a different file. I am not sure if there are more places affected by this problem. Signed-off-by: Hauke Mehrtens Cc: Signed-off-by: Thomas Bogendoerfer Signed-off-by: Greg Kroah-Hartman

MIPS: Call dump_stack() from show_regs()

2018-07-17T09:39:23Z

commit 5a267832c2ec47b2dad0fdb291a96bb5b8869315 upstream. The generic nmi_cpu_backtrace() function calls show_regs() when a struct pt_regs is available, and dump_stack() otherwise. If we were to make use of the generic nmi_cpu_backtrace() with MIPS' current implementation of show_regs() this would mean that we see only register data with no accompanying stack information, in contrast with our current implementation which calls dump_stack() regardless of whether register state is available. In preparation for making use of the generic nmi_cpu_backtrace() to implement arch_trigger_cpumask_backtrace(), have our implementation of show_regs() call dump_stack() and drop the explicit dump_stack() call in arch_dump_stack() which is invoked by arch_trigger_cpumask_backtrace(). This will allow the output we produce to remain the same after a later patch switches to using nmi_cpu_backtrace(). It may mean that we produce extra stack output in other uses of show_regs(), but this: 1) Seems harmless. 2) Is good for consistency between arch_trigger_cpumask_backtrace() and other users of show_regs(). 3) Matches the behaviour of the ARM & PowerPC architectures. Marked for stable back to v4.9 as a prerequisite of the following patch "MIPS: Call dump_stack() from show_regs()". Signed-off-by: Paul Burton Patchwork: https://patchwork.linux-mips.org/patch/19596/ Cc: James Hogan Cc: Ralf Baechle Cc: Huacai Chen Cc: linux-mips@linux-mips.org Cc: stable@vger.kernel.org # v4.9+ Signed-off-by: Greg Kroah-Hartman

MIPS: CPS: Have asm/mips-cps.h include CM & CPC headers

2017-08-29T22:57:27Z

With Coherence Manager (CM) 3.5 information about the topology of the system, which has previously only been available through & accessed from the CM, is now also provided by the Cluster Power Controller (CPC). This includes a new CPC_CONFIG register mirroring GCR_CONFIG, and similarly a new CPC_Cx_CONFIG register mirroring GCR_Cx_CONFIG. In preparation for adjusting functions such as mips_cm_numcores(), which have previously only needed to access the CM, to also access the CPC this patch modifies the way we use the various CPS headers. Rather than having users include asm/mips-cm.h or asm/mips-cpc.h individually we instead have users include asm/mips-cps.h which in turn includes asm/mips-cm.h & asm/mips-cpc.h. This means that users will gain access to both CM & CPC registers by including one header, and most importantly it makes asm/mips-cps.h an ideal location for helper functions which need to access the various components of the CPS. Signed-off-by: Paul Burton Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/17015/ Patchwork: https://patchwork.linux-mips.org/patch/17217/ Signed-off-by: Ralf Baechle

MIPS: CM: Use BIT/GENMASK for register fields, order & drop shifts

2017-08-29T13:21:57Z

There's no reason for us not to use BIT() & GENMASK() in asm/mips-cm.h when declaring macros corresponding to register fields. This patch modifies our definitions to do so. The *_SHF definitions are removed entirely - they duplicate information found in the masks, are infrequently used & can be replaced with use of __ffs() where needed. The *_MSK definitions then lose their _MSK suffix which is now somewhat redundant, and users are modified to match. The field definitions are moved to follow the appropriate register's accessor functions, which helps to keep the field definitions in order & to find the appropriate fields for a given register. Whilst here a comment is added describing each register & including its name, which is helpful both for linking the register back to hardware documentation & for grepping purposes. This also cleans up a couple of issues that became obvious as a result of making the changes described above: - We previously had definitions for GCR_Cx_RESET_EXT_BASE & a phony copy of that named GCR_RESET_EXT_BASE - a register which does not exist. The bad definitions were added by commit 497e803ebf98 ("MIPS: smp-cps: Ensure secondary cores start with EVA disabled") and made use of from boot_core(), which is now modified to use the GCR_Cx_RESET_EXT_BASE definitions. - We had a typo in CM_GCR_ERROR_CAUSE_ERRINGO_MSK - we now correctly define this as inFo rather than inGo. Now that we don't duplicate field information between _SHF & _MSK definitions, and keep the fields next to the register accessors, it will be much easier to spot & prevent any similar oddities being introduced in the future. Signed-off-by: Paul Burton Acked-by: Thomas Gleixner

MIPS: signal: Remove unreachable code from force_fcr31_sig().

2017-08-29T13:21:52Z

Based on discussion with Linus remove the impossible to reach code rather than replacing it with a BUG(). Signed-off-by: Ralf Baechle Link: http://lkml.kernel.org/r/20170718140651.15973-4-ebiederm@xmission.com

MIPS: Remove unused R6000 support

2017-08-29T13:21:51Z

The kernel contains a small amount of incomplete code aimed at supporting old R6000 CPUs. This is: - Unused, as no machine selects CONFIG_SYS_HAS_CPU_R6000. - Broken, since there are glaring errors such as r6000_fpu.S moving the FCSR register to t1, then ignoring it & instead saving t0 into struct sigcontext... - A maintenance headache, since it's code that nobody can test which nevertheless imposes constraints on code which it shares with other machines. Remove this incomplete & broken R6000 CPU support in order to clean up and in preparation for changes which will no longer need to consider dragging the pretense of R6000 support along with them. Signed-off-by: Paul Burton Cc: linux-mips@linux-mips.org Patchwork: https://patchwork.linux-mips.org/patch/16236/ Signed-off-by: Ralf Baechle

lib/extable.c: use bsearch() library function in search_extable()

2017-07-10T23:32:35Z

[thomas@m3y3r.de: v3: fix arch specific implementations] Link: http://lkml.kernel.org/r/1497890858.12931.7.camel@m3y3r.de Signed-off-by: Thomas Meyer Cc: Rasmus Villemoes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

MIPS: Avoid accidental raw backtrace

2017-06-30T02:42:15Z

Since commit 81a76d7119f6 ("MIPS: Avoid using unwind_stack() with usermode") show_backtrace() invokes the raw backtracer when cp0_status & ST0_KSU indicates user mode to fix issues on EVA kernels where user and kernel address spaces overlap. However this is used by show_stack() which creates its own pt_regs on the stack and leaves cp0_status uninitialised in most of the code paths. This results in the non deterministic use of the raw back tracer depending on the previous stack content. show_stack() deals exclusively with kernel mode stacks anyway, so explicitly initialise regs.cp0_status to KSU_KERNEL (i.e. 0) to ensure we get a useful backtrace. Fixes: 81a76d7119f6 ("MIPS: Avoid using unwind_stack() with usermode") Signed-off-by: James Hogan Cc: linux-mips@linux-mips.org Cc: # 3.15+ Patchwork: https://patchwork.linux-mips.org/patch/16656/ Signed-off-by: Ralf Baechle