From: Naveen N Rao <naveen@xxxxxxxxxx> Function tracer on powerpc can only work with vmlinux having a .text size of up to ~64MB due to powerpc branch instruction having a limited relative branch range of 32MB. Today, this is only detected on kernel boot when ftrace is init'ed. Add a post-link script to check the size of .text so that we can detect this at build time, and break the build if necessary. We add a dependency on !COMPILE_TEST for CONFIG_HAVE_FUNCTION_TRACER so that allyesconfig and other test builds can continue to work without enabling ftrace. Signed-off-by: Naveen N Rao <naveen@xxxxxxxxxx> Signed-off-by: Hari Bathini <hbathini@xxxxxxxxxxxxx> --- arch/powerpc/Kconfig | 2 +- arch/powerpc/Makefile.postlink | 8 +++++ arch/powerpc/tools/ftrace_check.sh | 50 ++++++++++++++++++++++++++++++ 3 files changed, 59 insertions(+), 1 deletion(-) create mode 100755 arch/powerpc/tools/ftrace_check.sh diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig index 6aaca48955a3..bb99ec9da63c 100644 --- a/arch/powerpc/Kconfig +++ b/arch/powerpc/Kconfig @@ -243,7 +243,7 @@ config PPC select HAVE_FUNCTION_DESCRIPTORS if PPC64_ELF_ABI_V1 select HAVE_FUNCTION_ERROR_INJECTION select HAVE_FUNCTION_GRAPH_TRACER - select HAVE_FUNCTION_TRACER if PPC64 || (PPC32 && CC_IS_GCC) + select HAVE_FUNCTION_TRACER if !COMPILE_TEST && (PPC64 || (PPC32 && CC_IS_GCC)) select HAVE_GCC_PLUGINS if GCC_VERSION >= 50200 # plugin support on gcc <= 5.1 is buggy on PPC select HAVE_GENERIC_VDSO select HAVE_HARDLOCKUP_DETECTOR_ARCH if PPC_BOOK3S_64 && SMP diff --git a/arch/powerpc/Makefile.postlink b/arch/powerpc/Makefile.postlink index ae5a4256b03d..bb601be36173 100644 --- a/arch/powerpc/Makefile.postlink +++ b/arch/powerpc/Makefile.postlink @@ -24,6 +24,9 @@ else $(CONFIG_SHELL) $(srctree)/arch/powerpc/tools/relocs_check.sh "$(OBJDUMP)" "$(NM)" "$@" endif +quiet_cmd_ftrace_check = CHKFTRC $@ + cmd_ftrace_check = $(CONFIG_SHELL) $(srctree)/arch/powerpc/tools/ftrace_check.sh "$(NM)" "$@" + # `@true` prevents complaint when there is nothing to be done vmlinux: FORCE @@ -34,6 +37,11 @@ endif ifdef CONFIG_RELOCATABLE $(call if_changed,relocs_check) endif +ifdef CONFIG_FUNCTION_TRACER +ifndef CONFIG_PPC64_ELF_ABI_V1 + $(call cmd,ftrace_check) +endif +endif clean: rm -f .tmp_symbols.txt diff --git a/arch/powerpc/tools/ftrace_check.sh b/arch/powerpc/tools/ftrace_check.sh new file mode 100755 index 000000000000..405e7e306617 --- /dev/null +++ b/arch/powerpc/tools/ftrace_check.sh @@ -0,0 +1,50 @@ +#!/bin/bash +# SPDX-License-Identifier: GPL-2.0-or-later +# +# This script checks vmlinux to ensure that all functions can call ftrace_caller() either directly, +# or through the stub, ftrace_tramp_text, at the end of kernel text. + +# Error out if any command fails +set -e + +# Allow for verbose output +if [ "$V" = "1" ]; then + set -x +fi + +if [ $# -lt 2 ]; then + echo "$0 [path to nm] [path to vmlinux]" 1>&2 + exit 1 +fi + +# Have Kbuild supply the path to nm so we handle cross compilation. +nm="$1" +vmlinux="$2" + +stext_addr=$($nm "$vmlinux" | grep -e " [TA] _stext$" | \ + cut -d' ' -f1 | tr '[:lower:]' '[:upper:]') +ftrace_caller_addr=$($nm "$vmlinux" | grep -e " T ftrace_caller$" | \ + cut -d' ' -f1 | tr '[:lower:]' '[:upper:]') +ftrace_tramp_addr=$($nm "$vmlinux" | grep -e " T ftrace_tramp_text$" | \ + cut -d' ' -f1 | tr '[:lower:]' '[:upper:]') + +ftrace_caller_offset=$(echo "ibase=16;$ftrace_caller_addr - $stext_addr" | bc) +ftrace_tramp_offset=$(echo "ibase=16;$ftrace_tramp_addr - $ftrace_caller_addr" | bc) +sz_32m=$(printf "%d" 0x2000000) +sz_64m=$(printf "%d" 0x4000000) + +# ftrace_caller - _stext < 32M +if [ "$ftrace_caller_offset" -ge "$sz_32m" ]; then + echo "ERROR: ftrace_caller (0x$ftrace_caller_addr) is beyond 32MiB of _stext" 1>&2 + echo "ERROR: consider disabling CONFIG_FUNCTION_TRACER, or reducing the size \ + of kernel text" 1>&2 + exit 1 +fi + +# ftrace_tramp_text - ftrace_caller < 64M +if [ "$ftrace_tramp_offset" -ge "$sz_64m" ]; then + echo "ERROR: kernel text extends beyond 64MiB from ftrace_caller" 1>&2 + echo "ERROR: consider disabling CONFIG_FUNCTION_TRACER, or reducing the size \ + of kernel text" 1>&2 + exit 1 +fi -- 2.47.0
