Le 19/06/2023 à 11:47, Naveen N Rao a écrit : > GCC v13.1 updated support for -fpatchable-function-entry on ppc64le to > emit nops after the local entry point, rather than before it. This > allows us to use this in the kernel for ftrace purposes. A new script is > added under arch/powerpc/tools/ to help detect if nops are emitted after > the function local entry point, or before the global entry point. > > With -fpatchable-function-entry, we no longer have the profiling > instructions generated at function entry, so we only need to validate > the presence of two nops at the ftrace location in ftrace_init_nop(). We > patch the preceding instruction with 'mflr r0' to match the > -mprofile-kernel ABI for subsequent ftrace use. > > This changes the profiling instructions used on ppc32. The default -pg > option emits an additional 'stw' instruction after 'mflr r0' and before > the branch to _mcount 'bl _mcount'. This is very similar to the original > -mprofile-kernel implementation on ppc64le, where an additional 'std' > instruction was used to save LR to its save location in the caller's > stackframe. Subsequently, this additional store was removed in later > compiler versions for performance reasons. The same reasons apply for > ppc32 so we only patch in a 'mflr r0'. > > Signed-off-by: Naveen N Rao <nav...@kernel.org>
Reviewed-by: Christophe Leroy <christophe.le...@csgroup.eu> Nit below > --- > arch/powerpc/Kconfig | 14 +++++++--- > arch/powerpc/Makefile | 5 ++++ > arch/powerpc/include/asm/ftrace.h | 6 +++-- > arch/powerpc/include/asm/vermagic.h | 4 ++- > arch/powerpc/kernel/module_64.c | 2 +- > arch/powerpc/kernel/trace/ftrace.c | 14 ++++++++-- > arch/powerpc/kernel/trace/ftrace_entry.S | 2 ++ > .../gcc-check-fpatchable-function-entry.sh | 26 +++++++++++++++++++ > 8 files changed, 64 insertions(+), 9 deletions(-) > create mode 100755 arch/powerpc/tools/gcc-check-fpatchable-function-entry.sh > > diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig > index bff5820b7cda14..9352d8e68152e1 100644 > --- a/arch/powerpc/Kconfig > +++ b/arch/powerpc/Kconfig > @@ -187,6 +187,7 @@ config PPC > select DYNAMIC_FTRACE if FUNCTION_TRACER > select EDAC_ATOMIC_SCRUB > select EDAC_SUPPORT > + select FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY if > ARCH_USING_PATCHABLE_FUNCTION_ENTRY > select GENERIC_ATOMIC64 if PPC32 > select GENERIC_CLOCKEVENTS_BROADCAST if SMP > select GENERIC_CMOS_UPDATE > @@ -227,8 +228,8 @@ config PPC > select HAVE_DEBUG_KMEMLEAK > select HAVE_DEBUG_STACKOVERFLOW > select HAVE_DYNAMIC_FTRACE > - select HAVE_DYNAMIC_FTRACE_WITH_ARGS if MPROFILE_KERNEL || PPC32 > - select HAVE_DYNAMIC_FTRACE_WITH_REGS if MPROFILE_KERNEL || PPC32 > + select HAVE_DYNAMIC_FTRACE_WITH_ARGS if > ARCH_USING_PATCHABLE_FUNCTION_ENTRY || MPROFILE_KERNEL || PPC32 > + select HAVE_DYNAMIC_FTRACE_WITH_REGS if > ARCH_USING_PATCHABLE_FUNCTION_ENTRY || MPROFILE_KERNEL || PPC32 ARCH_USING_PATCHABLE_FUNCTION_ENTRY defaults to y if PPC32, so you can remove PPC32 from the condition here. > select HAVE_EBPF_JIT > select HAVE_EFFICIENT_UNALIGNED_ACCESS > select HAVE_FAST_GUP > @@ -256,7 +257,7 @@ config PPC > select HAVE_MOD_ARCH_SPECIFIC > select HAVE_NMI if PERF_EVENTS || (PPC64 && > PPC_BOOK3S) > select HAVE_OPTPROBES > - select HAVE_OBJTOOL if PPC32 || MPROFILE_KERNEL > + select HAVE_OBJTOOL if > ARCH_USING_PATCHABLE_FUNCTION_ENTRY || MPROFILE_KERNEL || PPC32 Same > select HAVE_OBJTOOL_MCOUNT if HAVE_OBJTOOL > select HAVE_PERF_EVENTS > select HAVE_PERF_EVENTS_NMI if PPC64 > @@ -550,6 +551,13 @@ config MPROFILE_KERNEL > depends on PPC64 && CPU_LITTLE_ENDIAN && FUNCTION_TRACER > def_bool > $(success,$(srctree)/arch/powerpc/tools/gcc-check-mprofile-kernel.sh $(CC) > -I$(srctree)/include -D__KERNEL__) > > +config ARCH_USING_PATCHABLE_FUNCTION_ENTRY > + depends on FUNCTION_TRACER && (PPC32 || PPC64_ELF_ABI_V2) > + depends on $(cc-option,-fpatchable-function-entry=2) > + def_bool y if PPC32 > + def_bool > $(success,$(srctree)/arch/powerpc/tools/gcc-check-fpatchable-function-entry.sh > $(CC) -mlittle-endian) if PPC64 && CPU_LITTLE_ENDIAN > + def_bool > $(success,$(srctree)/arch/powerpc/tools/gcc-check-fpatchable-function-entry.sh > $(CC) -mbig-endian) if PPC64 && CPU_BIG_ENDIAN > + > config HOTPLUG_CPU > bool "Support for enabling/disabling CPUs" > depends on SMP && (PPC_PSERIES || \ > diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile > index dca73f673d7046..de39478b1c9e9f 100644 > --- a/arch/powerpc/Makefile > +++ b/arch/powerpc/Makefile > @@ -148,11 +148,16 @@ CFLAGS-$(CONFIG_PPC32) += $(call cc-option, > $(MULTIPLEWORD)) > CFLAGS-$(CONFIG_PPC32) += $(call cc-option,-mno-readonly-in-sdata) > > ifdef CONFIG_FUNCTION_TRACER > +ifdef CONFIG_ARCH_USING_PATCHABLE_FUNCTION_ENTRY > +KBUILD_CPPFLAGS += -DCC_USING_PATCHABLE_FUNCTION_ENTRY > +CC_FLAGS_FTRACE := -fpatchable-function-entry=2 > +else > CC_FLAGS_FTRACE := -pg > ifdef CONFIG_MPROFILE_KERNEL > CC_FLAGS_FTRACE += -mprofile-kernel > endif > endif > +endif > > CFLAGS-$(CONFIG_TARGET_CPU_BOOL) += -mcpu=$(CONFIG_TARGET_CPU) > AFLAGS-$(CONFIG_TARGET_CPU_BOOL) += -mcpu=$(CONFIG_TARGET_CPU) > diff --git a/arch/powerpc/include/asm/ftrace.h > b/arch/powerpc/include/asm/ftrace.h > index ef9f0b97670d1c..9e5a39b6a3114b 100644 > --- a/arch/powerpc/include/asm/ftrace.h > +++ b/arch/powerpc/include/asm/ftrace.h > @@ -11,7 +11,7 @@ > #define HAVE_FUNCTION_GRAPH_RET_ADDR_PTR > > /* Ignore unused weak functions which will have larger offsets */ > -#ifdef CONFIG_MPROFILE_KERNEL > +#if defined(CONFIG_MPROFILE_KERNEL) || > defined(CONFIG_ARCH_USING_PATCHABLE_FUNCTION_ENTRY) > #define FTRACE_MCOUNT_MAX_OFFSET 16 > #elif defined(CONFIG_PPC32) > #define FTRACE_MCOUNT_MAX_OFFSET 8 > @@ -22,7 +22,9 @@ extern void _mcount(void); > > static inline unsigned long ftrace_call_adjust(unsigned long addr) > { > - /* relocation of mcount call site is the same as the address */ > + if (IS_ENABLED(CONFIG_ARCH_USING_PATCHABLE_FUNCTION_ENTRY)) > + addr += MCOUNT_INSN_SIZE; > + > return addr; > } > > diff --git a/arch/powerpc/include/asm/vermagic.h > b/arch/powerpc/include/asm/vermagic.h > index b054a8576e5deb..6f250fe506bd1c 100644 > --- a/arch/powerpc/include/asm/vermagic.h > +++ b/arch/powerpc/include/asm/vermagic.h > @@ -2,7 +2,9 @@ > #ifndef _ASM_VERMAGIC_H > #define _ASM_VERMAGIC_H > > -#ifdef CONFIG_MPROFILE_KERNEL > +#ifdef CONFIG_ARCH_USING_PATCHABLE_FUNCTION_ENTRY > +#define MODULE_ARCH_VERMAGIC_FTRACE "patchable-function-entry " > +#elif defined(CONFIG_MPROFILE_KERNEL) > #define MODULE_ARCH_VERMAGIC_FTRACE "mprofile-kernel " > #else > #define MODULE_ARCH_VERMAGIC_FTRACE "" > diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c > index 92570289ce08f5..7112adc597a80b 100644 > --- a/arch/powerpc/kernel/module_64.c > +++ b/arch/powerpc/kernel/module_64.c > @@ -465,7 +465,7 @@ int module_frob_arch_sections(Elf64_Ehdr *hdr, > return 0; > } > > -#ifdef CONFIG_MPROFILE_KERNEL > +#if defined(CONFIG_MPROFILE_KERNEL) || > defined(CONFIG_ARCH_USING_PATCHABLE_FUNCTION_ENTRY) > > static u32 stub_insns[] = { > #ifdef CONFIG_PPC_KERNEL_PCREL > diff --git a/arch/powerpc/kernel/trace/ftrace.c > b/arch/powerpc/kernel/trace/ftrace.c > index cf9dce77527920..82010629cf887c 100644 > --- a/arch/powerpc/kernel/trace/ftrace.c > +++ b/arch/powerpc/kernel/trace/ftrace.c > @@ -220,7 +220,12 @@ int ftrace_init_nop(struct module *mod, struct > dyn_ftrace *rec) > int ret = 0; > > /* Verify instructions surrounding the ftrace location */ > - if (IS_ENABLED(CONFIG_PPC32)) { > + if (IS_ENABLED(CONFIG_ARCH_USING_PATCHABLE_FUNCTION_ENTRY)) { > + /* Expect nops */ > + ret = ftrace_validate_inst(ip - 4, ppc_inst(PPC_RAW_NOP())); > + if (!ret) > + ret = ftrace_validate_inst(ip, ppc_inst(PPC_RAW_NOP())); > + } else if (IS_ENABLED(CONFIG_PPC32)) { > /* Expected sequence: 'mflr r0', 'stw r0,4(r1)', 'bl _mcount' */ > ret = ftrace_validate_inst(ip - 8, ppc_inst(PPC_RAW_MFLR(_R0))); > if (!ret) > @@ -250,7 +255,12 @@ int ftrace_init_nop(struct module *mod, struct > dyn_ftrace *rec) > /* Nop-out the ftrace location */ > new = ppc_inst(PPC_RAW_NOP()); > addr = MCOUNT_ADDR; > - if (is_offset_in_branch_range(addr - ip)) { > + if (IS_ENABLED(CONFIG_ARCH_USING_PATCHABLE_FUNCTION_ENTRY)) { > + /* we instead patch-in the 'mflr r0' */ > + old = ppc_inst(PPC_RAW_NOP()); > + new = ppc_inst(PPC_RAW_MFLR(_R0)); > + ret = ftrace_modify_code(ip - 4, old, new); > + } else if (is_offset_in_branch_range(addr - ip)) { > /* Within range */ > old = ftrace_create_branch_inst(ip, addr, 1); > ret = ftrace_modify_code(ip, old, new); > diff --git a/arch/powerpc/kernel/trace/ftrace_entry.S > b/arch/powerpc/kernel/trace/ftrace_entry.S > index e8339706e735b1..bab3ab1368a33f 100644 > --- a/arch/powerpc/kernel/trace/ftrace_entry.S > +++ b/arch/powerpc/kernel/trace/ftrace_entry.S > @@ -250,6 +250,7 @@ livepatch_handler: > blr > #endif /* CONFIG_LIVEPATCH */ > > +#ifndef CONFIG_ARCH_USING_PATCHABLE_FUNCTION_ENTRY > _GLOBAL(mcount) > _GLOBAL(_mcount) > EXPORT_SYMBOL(_mcount) > @@ -257,6 +258,7 @@ EXPORT_SYMBOL(_mcount) > mtctr r12 > mtlr r0 > bctr > +#endif > > #ifdef CONFIG_FUNCTION_GRAPH_TRACER > _GLOBAL(return_to_handler) > diff --git a/arch/powerpc/tools/gcc-check-fpatchable-function-entry.sh > b/arch/powerpc/tools/gcc-check-fpatchable-function-entry.sh > new file mode 100755 > index 00000000000000..06706903503b6c > --- /dev/null > +++ b/arch/powerpc/tools/gcc-check-fpatchable-function-entry.sh > @@ -0,0 +1,26 @@ > +#!/bin/bash > +# SPDX-License-Identifier: GPL-2.0 > + > +set -e > +set -o pipefail > + > +# To debug, uncomment the following line > +# set -x > + > +# Output from -fpatchable-function-entry can only vary on ppc64 elfv2, so > this > +# should not be invoked for other targets. Therefore we can pass in -m64 and > +# -mabi explicitly, to take care of toolchains defaulting to other targets. > + > +# Test whether the compile option -fpatchable-function-entry exists and > +# generates appropriate code > +echo "int func() { return 0; }" | \ > + $* -m64 -mabi=elfv2 -S -x c -O2 -fpatchable-function-entry=2 - -o - 2> > /dev/null | \ > + grep -q "__patchable_function_entries" > + > +# Test whether nops are generated after the local entry point > +echo "int x; int func() { return x; }" | \ > + $* -m64 -mabi=elfv2 -S -x c -O2 -fpatchable-function-entry=2 - -o - 2> > /dev/null | \ > + awk 'BEGIN { RS = ";" } /\.localentry.*nop.*\n[[:space:]]*nop/ { print > $0 }' | \ > + grep -q "func:" > + > +exit 0