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powerpc/ftrace: Add support for -fpatchable-function-entry
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 <naveen@kernel.org> Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://msgid.link/68586d22981a2c3bb45f27a2b621173d10a7d092.1687166935.git.naveen@kernel.org
This commit is contained in:
Naveen N Rao
Michael Ellerman
parent
c91c5a8286
commit
0f71dcfb4a
@ -186,6 +186,7 @@ config PPC
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select DYNAMIC_FTRACE if FUNCTION_TRACER
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select EDAC_ATOMIC_SCRUB
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select EDAC_SUPPORT
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select FTRACE_MCOUNT_USE_PATCHABLE_FUNCTION_ENTRY if ARCH_USING_PATCHABLE_FUNCTION_ENTRY
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select GENERIC_ATOMIC64 if PPC32
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select GENERIC_CLOCKEVENTS_BROADCAST if SMP
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select GENERIC_CMOS_UPDATE
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@ -227,8 +228,8 @@ config PPC
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select HAVE_DEBUG_KMEMLEAK
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select HAVE_DEBUG_STACKOVERFLOW
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select HAVE_DYNAMIC_FTRACE
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select HAVE_DYNAMIC_FTRACE_WITH_ARGS if MPROFILE_KERNEL || PPC32
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select HAVE_DYNAMIC_FTRACE_WITH_REGS if MPROFILE_KERNEL || PPC32
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select HAVE_DYNAMIC_FTRACE_WITH_ARGS if ARCH_USING_PATCHABLE_FUNCTION_ENTRY || MPROFILE_KERNEL || PPC32
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select HAVE_DYNAMIC_FTRACE_WITH_REGS if ARCH_USING_PATCHABLE_FUNCTION_ENTRY || MPROFILE_KERNEL || PPC32
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select HAVE_EBPF_JIT
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select HAVE_EFFICIENT_UNALIGNED_ACCESS
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select HAVE_FAST_GUP
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@ -256,7 +257,7 @@ config PPC
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select HAVE_MOD_ARCH_SPECIFIC
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select HAVE_NMI if PERF_EVENTS || (PPC64 && PPC_BOOK3S)
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select HAVE_OPTPROBES
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select HAVE_OBJTOOL if PPC32 || MPROFILE_KERNEL
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select HAVE_OBJTOOL if ARCH_USING_PATCHABLE_FUNCTION_ENTRY || MPROFILE_KERNEL || PPC32
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select HAVE_OBJTOOL_MCOUNT if HAVE_OBJTOOL
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select HAVE_PERF_EVENTS
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select HAVE_PERF_EVENTS_NMI if PPC64
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@ -554,6 +555,13 @@ config MPROFILE_KERNEL
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def_bool $(success,$(srctree)/arch/powerpc/tools/gcc-check-mprofile-kernel.sh $(CC) -mlittle-endian) if CPU_LITTLE_ENDIAN
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def_bool $(success,$(srctree)/arch/powerpc/tools/gcc-check-mprofile-kernel.sh $(CC) -mbig-endian) if CPU_BIG_ENDIAN
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config ARCH_USING_PATCHABLE_FUNCTION_ENTRY
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depends on FUNCTION_TRACER && (PPC32 || PPC64_ELF_ABI_V2)
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depends on $(cc-option,-fpatchable-function-entry=2)
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def_bool y if PPC32
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def_bool $(success,$(srctree)/arch/powerpc/tools/gcc-check-fpatchable-function-entry.sh $(CC) -mlittle-endian) if PPC64 && CPU_LITTLE_ENDIAN
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def_bool $(success,$(srctree)/arch/powerpc/tools/gcc-check-fpatchable-function-entry.sh $(CC) -mbig-endian) if PPC64 && CPU_BIG_ENDIAN
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config HOTPLUG_CPU
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bool "Support for enabling/disabling CPUs"
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depends on SMP && (PPC_PSERIES || \
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@ -143,11 +143,16 @@ CFLAGS-$(CONFIG_PPC32) += $(call cc-option, $(MULTIPLEWORD))
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CFLAGS-$(CONFIG_PPC32) += $(call cc-option,-mno-readonly-in-sdata)
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ifdef CONFIG_FUNCTION_TRACER
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ifdef CONFIG_ARCH_USING_PATCHABLE_FUNCTION_ENTRY
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KBUILD_CPPFLAGS += -DCC_USING_PATCHABLE_FUNCTION_ENTRY
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CC_FLAGS_FTRACE := -fpatchable-function-entry=2
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else
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CC_FLAGS_FTRACE := -pg
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ifdef CONFIG_MPROFILE_KERNEL
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CC_FLAGS_FTRACE += -mprofile-kernel
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endif
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endif
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endif
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CFLAGS-$(CONFIG_TARGET_CPU_BOOL) += -mcpu=$(CONFIG_TARGET_CPU)
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AFLAGS-$(CONFIG_TARGET_CPU_BOOL) += -mcpu=$(CONFIG_TARGET_CPU)
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@ -11,7 +11,7 @@
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#define HAVE_FUNCTION_GRAPH_RET_ADDR_PTR
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/* Ignore unused weak functions which will have larger offsets */
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#ifdef CONFIG_MPROFILE_KERNEL
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#if defined(CONFIG_MPROFILE_KERNEL) || defined(CONFIG_ARCH_USING_PATCHABLE_FUNCTION_ENTRY)
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#define FTRACE_MCOUNT_MAX_OFFSET 16
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#elif defined(CONFIG_PPC32)
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#define FTRACE_MCOUNT_MAX_OFFSET 8
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@ -22,7 +22,9 @@ extern void _mcount(void);
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static inline unsigned long ftrace_call_adjust(unsigned long addr)
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{
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/* relocation of mcount call site is the same as the address */
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if (IS_ENABLED(CONFIG_ARCH_USING_PATCHABLE_FUNCTION_ENTRY))
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addr += MCOUNT_INSN_SIZE;
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return addr;
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}
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@ -2,7 +2,9 @@
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#ifndef _ASM_VERMAGIC_H
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#define _ASM_VERMAGIC_H
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#ifdef CONFIG_MPROFILE_KERNEL
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#ifdef CONFIG_ARCH_USING_PATCHABLE_FUNCTION_ENTRY
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#define MODULE_ARCH_VERMAGIC_FTRACE "patchable-function-entry "
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#elif defined(CONFIG_MPROFILE_KERNEL)
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#define MODULE_ARCH_VERMAGIC_FTRACE "mprofile-kernel "
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#else
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#define MODULE_ARCH_VERMAGIC_FTRACE ""
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@ -465,7 +465,7 @@ int module_frob_arch_sections(Elf64_Ehdr *hdr,
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return 0;
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}
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#ifdef CONFIG_MPROFILE_KERNEL
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#if defined(CONFIG_MPROFILE_KERNEL) || defined(CONFIG_ARCH_USING_PATCHABLE_FUNCTION_ENTRY)
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static u32 stub_insns[] = {
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#ifdef CONFIG_PPC_KERNEL_PCREL
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@ -220,7 +220,12 @@ int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec)
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int ret = 0;
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/* Verify instructions surrounding the ftrace location */
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if (IS_ENABLED(CONFIG_PPC32)) {
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if (IS_ENABLED(CONFIG_ARCH_USING_PATCHABLE_FUNCTION_ENTRY)) {
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/* Expect nops */
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ret = ftrace_validate_inst(ip - 4, ppc_inst(PPC_RAW_NOP()));
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if (!ret)
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ret = ftrace_validate_inst(ip, ppc_inst(PPC_RAW_NOP()));
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} else if (IS_ENABLED(CONFIG_PPC32)) {
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/* Expected sequence: 'mflr r0', 'stw r0,4(r1)', 'bl _mcount' */
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ret = ftrace_validate_inst(ip - 8, ppc_inst(PPC_RAW_MFLR(_R0)));
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if (!ret)
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@ -250,7 +255,12 @@ int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec)
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/* Nop-out the ftrace location */
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new = ppc_inst(PPC_RAW_NOP());
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addr = MCOUNT_ADDR;
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if (is_offset_in_branch_range(addr - ip)) {
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if (IS_ENABLED(CONFIG_ARCH_USING_PATCHABLE_FUNCTION_ENTRY)) {
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/* we instead patch-in the 'mflr r0' */
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old = ppc_inst(PPC_RAW_NOP());
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new = ppc_inst(PPC_RAW_MFLR(_R0));
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ret = ftrace_modify_code(ip - 4, old, new);
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} else if (is_offset_in_branch_range(addr - ip)) {
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/* Within range */
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old = ftrace_create_branch_inst(ip, addr, 1);
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ret = ftrace_modify_code(ip, old, new);
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@ -250,6 +250,7 @@ livepatch_handler:
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blr
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#endif /* CONFIG_LIVEPATCH */
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#ifndef CONFIG_ARCH_USING_PATCHABLE_FUNCTION_ENTRY
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_GLOBAL(mcount)
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_GLOBAL(_mcount)
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EXPORT_SYMBOL(_mcount)
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@ -257,6 +258,7 @@ EXPORT_SYMBOL(_mcount)
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mtctr r12
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mtlr r0
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bctr
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#endif
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#ifdef CONFIG_FUNCTION_GRAPH_TRACER
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_GLOBAL(return_to_handler)
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26
arch/powerpc/tools/gcc-check-fpatchable-function-entry.sh
Executable file
26
arch/powerpc/tools/gcc-check-fpatchable-function-entry.sh
Executable file
@ -0,0 +1,26 @@
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#!/bin/bash
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# SPDX-License-Identifier: GPL-2.0
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set -e
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set -o pipefail
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# To debug, uncomment the following line
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# set -x
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# Output from -fpatchable-function-entry can only vary on ppc64 elfv2, so this
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# should not be invoked for other targets. Therefore we can pass in -m64 and
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# -mabi explicitly, to take care of toolchains defaulting to other targets.
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# Test whether the compile option -fpatchable-function-entry exists and
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# generates appropriate code
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echo "int func() { return 0; }" | \
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$* -m64 -mabi=elfv2 -S -x c -O2 -fpatchable-function-entry=2 - -o - 2> /dev/null | \
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grep -q "__patchable_function_entries"
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# Test whether nops are generated after the local entry point
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echo "int x; int func() { return x; }" | \
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$* -m64 -mabi=elfv2 -S -x c -O2 -fpatchable-function-entry=2 - -o - 2> /dev/null | \
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awk 'BEGIN { RS = ";" } /\.localentry.*nop.*\n[[:space:]]*nop/ { print $0 }' | \
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grep -q "func:"
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exit 0
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