user/sven/linux.git/arch/arc/kernel/entry.S, branch v4.9.254

Revert "ARC: entry: fix potential EFA clobber when TIF_SYSCALL_TRACE"

2020-11-10T09:24:04Z

This reverts commit 00fdec98d9881bf5173af09aebd353ab3b9ac729. (but only from 5.2 and prior kernels) The original commit was a preventive fix based on code-review and was auto-picked for stable back-port (for better or worse). It was OK for v5.3+ kernels, but turned up needing an implicit change 68e5c6f073bcf70 "(ARC: entry: EV_Trap expects r10 (vs. r9) to have exception cause)" merged in v5.3 which itself was not backported. So to summarize the stable backport of this patch for v5.2 and prior kernels is busted and it won't boot. The obvious solution is backport 68e5c6f073bcf70 but that is a pain as it doesn't revert cleanly and each of affected kernels (so far v4.19, v4.14, v4.9, v4.4) needs a slightly different massaged varaint. So the easier fix is to simply revert the backport from 5.2 and prior. The issue was not a big deal as it would cause strace to sporadically not work correctly. Waldemar Brodkorb first reported this when running ARC uClibc regressions on latest stable kernels (with offending backport). Once he bisected it, the analysis was trivial, so thx to him for this. Reported-by: Waldemar Brodkorb Bisected-by: Waldemar Brodkorb Cc: stable # 5.2 and prior Signed-off-by: Vineet Gupta Signed-off-by: Greg Kroah-Hartman

ARC: entry: fix potential EFA clobber when TIF_SYSCALL_TRACE

2020-07-22T07:10:47Z

commit 00fdec98d9881bf5173af09aebd353ab3b9ac729 upstream. Trap handler for syscall tracing reads EFA (Exception Fault Address), in case strace wants PC of trap instruction (EFA is not part of pt_regs as of current code). However this EFA read is racy as it happens after dropping to pure kernel mode (re-enabling interrupts). A taken interrupt could context-switch, trigger a different task's trap, clobbering EFA for this execution context. Fix this by reading EFA early, before re-enabling interrupts. A slight side benefit is de-duplication of FAKE_RET_FROM_EXCPN in trap handler. The trap handler is common to both ARCompact and ARCv2 builds too. This just came out of code rework/review and no real problem was reported but is clearly a potential problem specially for strace. Cc: Signed-off-by: Vineet Gupta Signed-off-by: Greg Kroah-Hartman

ARC: Re-enable MMU upon Machine Check exception

2017-09-27T12:39:23Z

commit 1ee55a8f7f6b7ca4c0c59e0b4b4e3584a085c2d3 upstream. I recently came upon a scenario where I would get a double fault machine check exception tiriggered by a kernel module. However the ensuing crash stacktrace (ksym lookup) was not working correctly. Turns out that machine check auto-disables MMU while modules are allocated in kernel vaddr spapce. This patch re-enables the MMU before start printing the stacktrace making stacktracing of modules work upon a fatal exception. Signed-off-by: Jose Abreu Reviewed-by: Alexey Brodkin Signed-off-by: Vineet Gupta [vgupta: moved code into low level handler to avoid in 2 places] Signed-off-by: Greg Kroah-Hartman

ARC: entry: make ret_from_system_call local label

2016-09-30T21:48:21Z

This essentially removes ENTRY() assembler annotation for this symbol since it didn't have a pairing END() This in ahead of introducing cfi pseudo ops in ENTRY/END which expects paired cfi_startproc/cfi_endproc | ../arch/arc/kernel/entry.S: Assembler messages: | ../arch/arc/kernel/entry.S:270: Error: previous CFI entry not closed (missing .cfi_endproc) | ../scripts/Makefile.build:326: recipe for target 'arch/arc/kernel/entry-arcv2.o' failed | make[4]: *** [arch/arc/kernel/entry-arcv2.o] Error 1 Signed-off-by: Vineet Gupta

ARC: dw2 unwind: switch to .eh_frame based unwinding

2016-09-30T21:48:20Z

So finally after almost 8 years of dealing with .debug_frame, we are finally switching to .eh_frame. The reason being stripped kernel binaries had non-functional unwinder as .debug_frame was gone. Also, in general .eh_frame seems more common way of doing unwinding. This also folds a revert of f52e126cc747 ("ARC: unwind: ensure that .debug_frame is generated (vs. .eh_frame)") to ensure that we start getting .eh_frame Reported-by: Daniel Mentz Signed-off-by: Vineet Gupta

ARC: [arcompact] Handle bus error from userspace as Interrupt not exception

2015-11-14T07:42:20Z

Bus errors from userspace on ARCompact based cores are handled by core as a high priority L2 interrupt but current code treated it as interrupt Handling an interrupt like exception is certainly not going to go unnoticed. (and it worked so far as we never saw a Bus error from userspace until IPPK guys tested a DDR controller with ECC error detection etc hence needed to explicitly trigger/handle such errors) - So move mem_service exception handler from common code into ARCv2 code. - In ARCompact code, define mem_service as L2 interrupt handler which just drops down to pure kernel mode and goes of to enqueue SIGBUS Reported-by: Nelson Pereira Tested-by: Ana Martins Signed-off-by: Vineet Gupta

ARC: change some branchs to jumps to resolve linkage errors

2015-08-20T13:23:15Z

When kernel's binary becomes large enough (32M and more) errors may occur during the final linkage stage. It happens because the build system uses short relocations for ARC by default. This problem may be easily resolved by passing -mlong-calls option to GCC to use long absolute jumps (j) instead of short relative branchs (b). But there are fragments of pure assembler code exist which use branchs in inappropriate places and cause a linkage error because of relocations overflow. First of these fragments is .fixup insertion in futex.h and unaligned.c. It inserts a code in the separate section (.fixup) with branch instruction. It leads to the linkage error when kernel becomes large. Second of these fragments is calling scheduler's functions (common kernel code) from entry.S of ARC's code. When kernel's binary becomes large it may lead to the linkage error because scheduler may occur far enough from ARC's code in the final binary. Signed-off-by: Yuriy Kolerov Signed-off-by: Vineet Gupta

ARC: entry.S: micro-optimize Trap handler

2015-06-19T12:39:39Z

Elide the need to re-read ECR in Trap handler by ensuring that EXCEPTION_PROLOGUE does that at the very end just before returning to Trap handler ARCv2 EXCEPTION_PROLOGUE already did that, so same for ARcompact and the common trap handler adjusted to use cached ECR Signed-off-by: Vineet Gupta

ARC: entry.S: move some code around for cache locality in return path

2015-06-19T12:39:38Z

Signed-off-by: Vineet Gupta

ARC: entry.S: split into ARCompact ISA specific, common bits

2015-06-19T12:39:38Z

Signed-off-by: Vineet Gupta