BMC/Intel-BMC/linux.git/arch/s390/kernel/ftrace.c, branch dev

s390/maccess: remove potentially broken probe_kernel_write()

2015-03-25T10:49:43+00:00

Remove the s390 architecture implementation of probe_kernel_write() and instead use a new function s390_kernel_write() to modify kernel text and data everywhere. The s390 implementation of probe_kernel_write() was potentially broken since it modified memory in a read-modify-write fashion, which read four bytes, modified the requested bytes within those four bytes and wrote the result back. If two cpus would modify the same four byte area at different locations within that area, this could lead to corruption. Right now the only places which called probe_kernel_write() did run within stop_machine_run. Therefore the scenario can't happen right now, however that might change at any time. To fix this rename probe_kernel_write() to s390_kernel_write() which can have special semantics, like only call it while running within stop_machine(). Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky

s390/ftrace: fix compile error if CONFIG_KPROBES is disabled

2015-03-13T11:15:44+00:00

Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky

s390/ftrace: hotpatch support for function tracing

2015-01-29T08:19:25+00:00

Make use of gcc's hotpatch support to generate better code for ftrace function tracing. The generated code now contains only a six byte nop in each function prologue instead of a 24 byte code block which will be runtime patched to support function tracing. With the new code generation the runtime overhead for supporting function tracing is close to zero, while the original code did show a significant performance impact. Acked-by: Steven Rostedt Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky

s390/ftrace: add code replacement sanity checks

2015-01-08T09:02:46+00:00

Always verify that the to be replaced code matches what we expect to see. Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky

Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux

2014-12-12T01:30:55+00:00

Pull s390 updates from Martin Schwidefsky: "The most notable change for this pull request is the ftrace rework from Heiko. It brings a small performance improvement and the ground work to support a new gcc option to replace the mcount blocks with a single nop. Two new s390 specific system calls are added to emulate user space mmio for PCI, an artifact of the how PCI memory is accessed. Two patches for the memory management with changes to common code. For KVM mm_forbids_zeropage is added which disables the empty zero page for an mm that is used by a KVM process. And an optimization, pmdp_get_and_clear_full is added analog to ptep_get_and_clear_full. Some micro optimization for the cmpxchg and the spinlock code. And as usual bug fixes and cleanups" * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux: (46 commits) s390/cputime: fix 31-bit compile s390/scm_block: make the number of reqs per HW req configurable s390/scm_block: handle multiple requests in one HW request s390/scm_block: allocate aidaw pages only when necessary s390/scm_block: use mempool to manage aidaw requests s390/eadm: change timeout value s390/mm: fix memory leak of ptlock in pmd_free_tlb s390: use local symbol names in entry[64].S s390/ptrace: always include vector registers in core files s390/simd: clear vector register pointer on fork/clone s390: translate cputime magic constants to macros s390/idle: convert open coded idle time seqcount s390/idle: add missing irq off lockdep annotation s390/debug: avoid function call for debug_sprintf_* s390/kprobes: fix instruction copy for out of line execution s390: remove diag 44 calls from cpu_relax() s390/dasd: retry partition detection s390/dasd: fix list corruption for sleep_on requests s390/dasd: fix infinite term I/O loop s390/dasd: remove unused code ...

s390/ftrace: add ftrace_graph_is_dead() check

2014-10-28T08:24:12+00:00

Add an ftrace_graph_is_dead() check to prepare_ftrace_return() in order to detect an internal ftrace graph error. This allows to prevent further ftrace graph handling and hopefully keeps the kernel alive. This patch is the same like for all other architectures. For unkown reasons s390 was left out. Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky

s390/kprobes: make use of NOKPROBE_SYMBOL()

2014-10-27T12:27:28+00:00

Use NOKPROBE_SYMBOL() instead of __kprobes annotation. Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky

s390/ftrace,kprobes: allow to patch first instruction

2014-10-27T12:27:27+00:00

If the function tracer is enabled, allow to set kprobes on the first instruction of a function (which is the function trace caller): If no kprobe is set handling of enabling and disabling function tracing of a function simply patches the first instruction. Either it is a nop (right now it's an unconditional branch, which skips the mcount block), or it's a branch to the ftrace_caller() function. If a kprobe is being placed on a function tracer calling instruction we encode if we actually have a nop or branch in the remaining bytes after the breakpoint instruction (illegal opcode). This is possible, since the size of the instruction used for the nop and branch is six bytes, while the size of the breakpoint is only two bytes. Therefore the first two bytes contain the illegal opcode and the last four bytes contain either "0" for nop or "1" for branch. The kprobes code will then execute/simulate the correct instruction. Instruction patching for kprobes and function tracer is always done with stop_machine(). Therefore we don't have any races where an instruction is patched concurrently on a different cpu. Besides that also the program check handler which executes the function trace caller instruction won't be executed concurrently to any stop_machine() execution. This allows to keep full fault based kprobes handling which generates correct pt_regs contents automatically. Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky

s390/ftrace: simplify enabling/disabling of ftrace_graph_caller

2014-10-09T07:14:20+00:00

We can simply patch the mask field within the branch relative on condition instruction at the beginning of the ftrace_graph_caller code block. This makes the logic even simpler and we get rid of the displacement calculation. Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky

s390/ftrace: remove 31 bit ftrace support

2014-10-09T07:14:18+00:00

31 bit and 64 bit diverge more and more and it is rather painful to keep both parts running. To make things simpler just remove the 31 bit support which nobody uses anyway. Signed-off-by: Heiko Carstens Signed-off-by: Martin Schwidefsky