BMC/Intel-BMC/linux.git/arch/powerpc/kernel/ftrace.c, branch dev-4.6

powerpc/ftrace: Add support for -mprofile-kernel ftrace ABI

2016-03-07T03:53:55+00:00

The gcc switch -mprofile-kernel defines a new ABI for calling _mcount() very early in the function with minimal overhead. Although mprofile-kernel has been available since GCC 3.4, there were bugs which were only fixed recently. Currently it is known to work in GCC 4.9, 5 and 6. Additionally there are two possible code sequences generated by the flag, the first uses mflr/std/bl and the second is optimised to omit the std. Currently only gcc 6 has the optimised sequence. This patch supports both sequences. Initial work started by Vojtech Pavlik, used with permission. Key changes: - rework _mcount() to work for both the old and new ABIs. - implement new versions of ftrace_caller() and ftrace_graph_caller() which deal with the new ABI. - updates to __ftrace_make_nop() to recognise the new mcount calling sequence. - updates to __ftrace_make_call() to recognise the nop'ed sequence. - implement ftrace_modify_call(). - updates to the module loader to surpress the toc save in the module stub when calling mcount with the new ABI. Reviewed-by: Balbir Singh Signed-off-by: Torsten Duwe Signed-off-by: Michael Ellerman

powerpc/ftrace: Use generic ftrace_modify_all_code()

2016-03-07T03:53:54+00:00

Convert powerpc's arch_ftrace_update_code() from its own version to use the generic default functionality (without stop_machine -- our instructions are properly aligned and the replacements atomic). With this we gain error checking and the much-needed function_trace_op handling. Reviewed-by: Balbir Singh Reviewed-by: Kamalesh Babulal Signed-off-by: Torsten Duwe Signed-off-by: Michael Ellerman

powerpc/module: Mark module stubs with a magic value

2016-03-07T03:53:53+00:00

When a module is loaded, calls out to the kernel go via a stub which is generated at runtime. One of these stubs is used to call _mcount(), which is the default target of tracing calls generated by the compiler with -pg. If dynamic ftrace is enabled (which it typically is), another stub is used to call ftrace_caller(), which is the target of tracing calls when ftrace is actually active. ftrace then wants to disable the calls to _mcount() at module startup, and enable/disable the calls to ftrace_caller() when enabling/disabling tracing - all of these it does by patching the code. As part of that code patching, the ftrace code wants to confirm that the branch it is about to modify, is in fact a call to a module stub which calls _mcount() or ftrace_caller(). Currently it does that by inspecting the instructions and confirming they are what it expects. Although that works, the code to do it is pretty intricate because it requires lots of knowledge about the exact format of the stub. We can make that process easier by marking the generated stubs with a magic value, and then looking for that magic value. Altough this is not as rigorous as the current method, I believe it is sufficient in practice. Reviewed-by: Balbir Singh Reviewed-by: Torsten Duwe Signed-off-by: Michael Ellerman

Merge tag 'powerpc-3.19-1' of git://git.kernel.org/pub/scm/linux/kernel/git/mpe/linux

2014-12-12T01:48:14+00:00

Pull powerpc updates from Michael Ellerman: "Some nice cleanups like removing bootmem, and removal of __get_cpu_var(). There is one patch to mm/gup.c. This is the generic GUP implementation, but is only used by us and arm(64). We have an ack from Steve Capper, and although we didn't get an ack from Andrew he told us to take the patch through the powerpc tree. There's one cxl patch. This is in drivers/misc, but Greg said he was happy for us to manage fixes for it. There is an infrastructure patch to support an IPMI driver for OPAL. There is also an RTC driver for OPAL. We weren't able to get any response from the RTC maintainer, Alessandro Zummo, so in the end we just merged the driver. The usual batch of Freescale updates from Scott" * tag 'powerpc-3.19-1' of git://git.kernel.org/pub/scm/linux/kernel/git/mpe/linux: (101 commits) powerpc/powernv: Return to cpu offline loop when finished in KVM guest powerpc/book3s: Fix partial invalidation of TLBs in MCE code. powerpc/mm: don't do tlbie for updatepp request with NO HPTE fault powerpc/xmon: Cleanup the breakpoint flags powerpc/xmon: Enable HW instruction breakpoint on POWER8 powerpc/mm/thp: Use tlbiel if possible powerpc/mm/thp: Remove code duplication powerpc/mm/hugetlb: Sanity check gigantic hugepage count powerpc/oprofile: Disable pagefaults during user stack read powerpc/mm: Check for matching hpte without taking hpte lock powerpc: Drop useless warning in eeh_init() powerpc/powernv: Cleanup unused MCE definitions/declarations. powerpc/eeh: Dump PHB diag-data early powerpc/eeh: Recover EEH error on ownership change for BCM5719 powerpc/eeh: Set EEH_PE_RESET on PE reset powerpc/eeh: Refactor eeh_reset_pe() powerpc: Remove more traces of bootmem powerpc/pseries: Initialise nvram_pstore_info's buf_lock cxl: Name interrupts in /proc/interrupt cxl: Return error to PSL if IRQ demultiplexing fails & print clearer warning ...

ftrace: Add more information to ftrace_bug() output

2014-11-11T17:42:13+00:00

With the introduction of the dynamic trampolines, it is useful that if things go wrong that ftrace_bug() produces more information about what the current state is. This can help debug issues that may arise. Ftrace has lots of checks to make sure that the state of the system it touchs is exactly what it expects it to be. When it detects an abnormality it calls ftrace_bug() and disables itself to prevent any further damage. It is crucial that ftrace_bug() produces sufficient information that can be used to debug the situation. Cc: Benjamin Herrenschmidt Acked-by: Borislav Petkov Tested-by: Masami Hiramatsu Tested-by: Jiri Kosina Signed-off-by: Steven Rostedt

powerpc/ftrace: simplify prepare_ftrace_return

2014-11-09T22:59:28+00:00

Instead of passing in the stack address of the link register to be modified, just pass in the old value and return the new value and rely on ftrace_graph_caller to do the modification. This removes the exception handling around the stack update - it isn't needed and we weren't consistent about it. Later on we would do an unprotected modification: if (!ftrace_graph_entry(&trace)) { *parent = old; Signed-off-by: Anton Blanchard Signed-off-by: Michael Ellerman

powerpc/ftrace: Remove mod_return_to_handler

2014-11-09T22:59:27+00:00

mod_return_to_handler is the same as return_to_handler, except it handles the change of the TOC (r2). Add this into return_to_handler and remove mod_return_to_handler. Signed-off-by: Anton Blanchard Signed-off-by: Michael Ellerman

powerpc/ftrace: Add call to ftrace_graph_is_dead() in function graph code

2014-07-18T17:56:56+00:00

ftrace_stop() is going away as it disables parts of function tracing that affects users that should not be affected. But ftrace_graph_stop() is built on ftrace_stop(). Here's another example of killing all of function tracing because something went wrong with function graph tracing. Instead of disabling all users of function tracing on function graph error, disable only function graph tracing. To do this, the arch code must call ftrace_graph_is_dead() before it implements function graph. Cc: Anton Blanchard Acked-by: Benjamin Herrenschmidt Signed-off-by: Steven Rostedt

powerpc/ftrace: Use pr_fmt() to namespace error messages

2014-06-24T04:05:50+00:00

The printks() in our ftrace code have no prefix, so they appear on the console with very little context, eg: Branch out of range Use pr_fmt() & pr_err() to add a prefix. While we're at it, collapse a few split lines that don't need to be, and add a missing newline to one message. Signed-off-by: Michael Ellerman Signed-off-by: Benjamin Herrenschmidt

powerpc/ftrace: Fix nop of modules on 64bit LE (ABIv2)

2014-06-24T04:05:46+00:00

There is a bug in the handling of the function entry when we are nopping out a branch from a module in ftrace. We compare the result of module_trampoline_target() with the value of ppc_function_entry(), and expect them to be true. But they never will be. module_trampoline_target() will always return the global entry point of the function, whereas ppc_function_entry() will always return the local. Fix it by using the newly added ppc_global_function_entry(). Signed-off-by: Michael Ellerman Signed-off-by: Benjamin Herrenschmidt