ftrace: Have architectures opt-in for mcount build time sorting

First S390 complained that the sorting of the mcount sections at build
time caused the kernel to crash on their architecture. Now PowerPC is
complaining about it too. And also ARM64 appears to be having issues.

It may be necessary to also update the relocation table for the values
in the mcount table. Not only do we have to sort the table, but also
update the relocations that may be applied to the items in the table.

If the system is not relocatable, then it is fine to sort, but if it is,
some architectures may have issues (although x86 does not as it shifts all
addresses the same).

Add a HAVE_BUILDTIME_MCOUNT_SORT that an architecture can set to say it is
safe to do the sorting at build time.

Also update the config to compile in build time sorting in the sorttable
code in scripts/ to depend on CONFIG_BUILDTIME_MCOUNT_SORT.

Link: https://lore.kernel.org/all/944D10DA-8200-4BA9-8D0A-3BED9AA99F82@linux.ibm.com/
Link: https://lkml.kernel.org/r/20220127153821.3bc1ac6e@gandalf.local.home
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Yinan Liu <yinan@linux.alibaba.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Kees Cook <keescook@chromium.org>
Reported-by: Sachin Sant <sachinp@linux.ibm.com>
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Mark Rutland <mark.rutland@arm.com> [arm64]
Tested-by: Sachin Sant <sachinp@linux.ibm.com>
Fixes: 72b3942a173c ("scripts: ftrace - move the sort-processing in ftrace_init")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index fabe39169b120ca6c11fb3037b2c134f0faa7b5c..4c97cb40eebb632eafc036ee6d4f8c4dce570b35 100644 (file)
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -83,6 +83,7 @@ config ARM
        select HAVE_EBPF_JIT if !CPU_ENDIAN_BE32
        select HAVE_CONTEXT_TRACKING
        select HAVE_C_RECORDMCOUNT
+       select HAVE_BUILDTIME_MCOUNT_SORT
        select HAVE_DEBUG_KMEMLEAK if !XIP_KERNEL
        select HAVE_DMA_CONTIGUOUS if MMU
        select HAVE_DYNAMIC_FTRACE if !XIP_KERNEL && !CPU_ENDIAN_BE32 && MMU

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index ebe8fc76949af1b8415f47daa3ee2869b34ffccd..9f5bd41bf660c7b024e6cf0838e6b7a3cf31b54e 100644 (file)
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -186,6 +186,7 @@ config X86
        select HAVE_CONTEXT_TRACKING_OFFSTACK   if HAVE_CONTEXT_TRACKING
        select HAVE_C_RECORDMCOUNT
        select HAVE_OBJTOOL_MCOUNT              if STACK_VALIDATION
+       select HAVE_BUILDTIME_MCOUNT_SORT
        select HAVE_DEBUG_KMEMLEAK
        select HAVE_DMA_CONTIGUOUS
        select HAVE_DYNAMIC_FTRACE

diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index 752ed89a293bd3e57b59781958b2fd2d8bb6499b..a5eb5e7fd624a033d00a6c59b9f8ce2b7c67f252 100644 (file)
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -70,10 +70,16 @@ config HAVE_C_RECORDMCOUNT
        help
          C version of recordmcount available?
 
+config HAVE_BUILDTIME_MCOUNT_SORT
+       bool
+       help
+         An architecture selects this if it sorts the mcount_loc section
+        at build time.
+
 config BUILDTIME_MCOUNT_SORT
        bool
        default y
-       depends on BUILDTIME_TABLE_SORT && !S390
+       depends on HAVE_BUILDTIME_MCOUNT_SORT && DYNAMIC_FTRACE
        help
          Sort the mcount_loc section at build time.
 

diff --git a/scripts/Makefile b/scripts/Makefile
index ecd3acacd0ec5209569400851e8832e8c295d809..ce5aa9030b740a65c731c8013973e24f76f2687b 100644 (file)
--- a/scripts/Makefile
+++ b/scripts/Makefile
@@ -25,7 +25,7 @@ HOSTCFLAGS_sorttable.o += -I$(srctree)/tools/arch/x86/include
 HOSTCFLAGS_sorttable.o += -DUNWINDER_ORC_ENABLED
 endif
 
-ifdef CONFIG_DYNAMIC_FTRACE
+ifdef CONFIG_BUILDTIME_MCOUNT_SORT
 HOSTCFLAGS_sorttable.o += -DMCOUNT_SORT_ENABLED
 endif