Re: [RFC][PATCH] objtool,x86_64: Replace recordmcount with objtool
From: Sami Tolvanen <samitolvanen@google.com>
Date: 2020-06-25 22:40:54
Also in:
linux-arch, linux-kbuild, linux-pci, lkml
On Thu, Jun 25, 2020 at 10:02:35PM +0200, Peter Zijlstra wrote:
quoted hunk ↗ jump to hunk
On Thu, Jun 25, 2020 at 09:15:03AM -0700, Sami Tolvanen wrote:quoted
On Thu, Jun 25, 2020 at 09:45:30AM +0200, Peter Zijlstra wrote:quoted
quoted
At least for x86_64 I can do a really quick take for a recordmcount pass in objtool, but I suppose you also need this for ARM64 ?Sure, sounds good. arm64 uses -fpatchable-function-entry with clang, so we don't need recordmcount there.This is on top of my local pile: git://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git master which notably includes the static_call series. Not boot tested, but it generates the required sections and they look more or less as expected, ymmv. --- arch/x86/Kconfig | 1 - scripts/Makefile.build | 3 ++ scripts/link-vmlinux.sh | 2 +- tools/objtool/builtin-check.c | 9 ++--- tools/objtool/builtin.h | 2 +- tools/objtool/check.c | 81 +++++++++++++++++++++++++++++++++++++++++++ tools/objtool/check.h | 1 + tools/objtool/objtool.h | 1 + 8 files changed, 91 insertions(+), 9 deletions(-)diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index a291823f3f26..189575c12434 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig@@ -174,7 +174,6 @@ config X86 select HAVE_EXIT_THREAD select HAVE_FAST_GUP select HAVE_FENTRY if X86_64 || DYNAMIC_FTRACE - select HAVE_FTRACE_MCOUNT_RECORD select HAVE_FUNCTION_GRAPH_TRACER select HAVE_FUNCTION_TRACER select HAVE_GCC_PLUGINS
This breaks DYNAMIC_FTRACE according to kernel/trace/ftrace.c: #ifndef CONFIG_FTRACE_MCOUNT_RECORD # error Dynamic ftrace depends on MCOUNT_RECORD #endif And the build errors after that seem to confirm this. It looks like we might need another flag to skip recordmcount. Anyway, since objtool is run before recordmcount, I just left this unchanged for testing and ignored the recordmcount warnings about __mcount_loc already existing. Something is a bit off still though, I see this at boot: ------------[ ftrace bug ]------------ ftrace failed to modify [<ffffffff81000660>] __tracepoint_iter_initcall_level+0x0/0x40 actual: 0f:1f:44:00:00 Initializing ftrace call sites ftrace record flags: 0 (0) expected tramp: ffffffff81056500 ------------[ cut here ]------------ Otherwise, this looks pretty good. Sami _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel