From fbf6c73c5b264c25484fa9f449b5546569fe11f0 Mon Sep 17 00:00:00 2001 From: Mark Rutland Date: Wed, 16 Oct 2019 17:51:10 +0100 Subject: ftrace: add ftrace_init_nop() Architectures may need to perform special initialization of ftrace callsites, and today they do so by special-casing ftrace_make_nop() when the expected branch address is MCOUNT_ADDR. In some cases (e.g. for patchable-function-entry), we don't have an mcount-like symbol and don't want a synthetic MCOUNT_ADDR, but we may need to perform some initialization of callsites. To make it possible to separate initialization from runtime modification, and to handle cases without an mcount-like symbol, this patch adds an optional ftrace_init_nop() function that architectures can implement, which does not pass a branch address. Where an architecture does not provide ftrace_init_nop(), we will fall back to the existing behaviour of calling ftrace_make_nop() with MCOUNT_ADDR. At the same time, ftrace_code_disable() is renamed to ftrace_nop_initialize() to make it clearer that it is intended to intialize a callsite into a disabled state, and is not for disabling a callsite that has been runtime enabled. The kerneldoc description of rec arguments is updated to cover non-mcount callsites. Signed-off-by: Mark Rutland Reviewed-by: Amit Daniel Kachhap Reviewed-by: Ard Biesheuvel Reviewed-by: Miroslav Benes Reviewed-by: Steven Rostedt (VMware) Reviewed-by: Torsten Duwe Tested-by: Amit Daniel Kachhap Tested-by: Sven Schnelle Tested-by: Torsten Duwe Cc: Ingo Molnar --- include/linux/ftrace.h | 35 ++++++++++++++++++++++++++++++++--- 1 file changed, 32 insertions(+), 3 deletions(-) (limited to 'include/linux/ftrace.h') diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h index 8a8cb3c401b2..9867d90d635e 100644 --- a/include/linux/ftrace.h +++ b/include/linux/ftrace.h @@ -499,7 +499,7 @@ static inline int ftrace_disable_ftrace_graph_caller(void) { return 0; } /** * ftrace_make_nop - convert code into nop * @mod: module structure if called by module load initialization - * @rec: the mcount call site record + * @rec: the call site record (e.g. mcount/fentry) * @addr: the address that the call site should be calling * * This is a very sensitive operation and great care needs @@ -520,9 +520,38 @@ static inline int ftrace_disable_ftrace_graph_caller(void) { return 0; } extern int ftrace_make_nop(struct module *mod, struct dyn_ftrace *rec, unsigned long addr); + +/** + * ftrace_init_nop - initialize a nop call site + * @mod: module structure if called by module load initialization + * @rec: the call site record (e.g. mcount/fentry) + * + * This is a very sensitive operation and great care needs + * to be taken by the arch. The operation should carefully + * read the location, check to see if what is read is indeed + * what we expect it to be, and then on success of the compare, + * it should write to the location. + * + * The code segment at @rec->ip should contain the contents created by + * the compiler + * + * Return must be: + * 0 on success + * -EFAULT on error reading the location + * -EINVAL on a failed compare of the contents + * -EPERM on error writing to the location + * Any other value will be considered a failure. + */ +#ifndef ftrace_init_nop +static inline int ftrace_init_nop(struct module *mod, struct dyn_ftrace *rec) +{ + return ftrace_make_nop(mod, rec, MCOUNT_ADDR); +} +#endif + /** * ftrace_make_call - convert a nop call site into a call to addr - * @rec: the mcount call site record + * @rec: the call site record (e.g. mcount/fentry) * @addr: the address that the call site should call * * This is a very sensitive operation and great care needs @@ -545,7 +574,7 @@ extern int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr); #ifdef CONFIG_DYNAMIC_FTRACE_WITH_REGS /** * ftrace_modify_call - convert from one addr to another (no nop) - * @rec: the mcount call site record + * @rec: the call site record (e.g. mcount/fentry) * @old_addr: the address expected to be currently called to * @addr: the address to change to * -- cgit v1.2.3 From a1326b17ac03a9012cb3d01e434aacb4d67a416c Mon Sep 17 00:00:00 2001 From: Mark Rutland Date: Wed, 16 Oct 2019 18:17:11 +0100 Subject: module/ftrace: handle patchable-function-entry When using patchable-function-entry, the compiler will record the callsites into a section named "__patchable_function_entries" rather than "__mcount_loc". Let's abstract this difference behind a new FTRACE_CALLSITE_SECTION, so that architectures don't have to handle this explicitly (e.g. with custom module linker scripts). As parisc currently handles this explicitly, it is fixed up accordingly, with its custom linker script removed. Since FTRACE_CALLSITE_SECTION is only defined when DYNAMIC_FTRACE is selected, the parisc module loading code is updated to only use the definition in that case. When DYNAMIC_FTRACE is not selected, modules shouldn't have this section, so this removes some redundant work in that case. To make sure that this is keep up-to-date for modules and the main kernel, a comment is added to vmlinux.lds.h, with the existing ifdeffery simplified for legibility. I built parisc generic-{32,64}bit_defconfig with DYNAMIC_FTRACE enabled, and verified that the section made it into the .ko files for modules. Signed-off-by: Mark Rutland Acked-by: Helge Deller Acked-by: Steven Rostedt (VMware) Reviewed-by: Ard Biesheuvel Reviewed-by: Torsten Duwe Tested-by: Amit Daniel Kachhap Tested-by: Sven Schnelle Tested-by: Torsten Duwe Cc: Ingo Molnar Cc: James E.J. Bottomley Cc: Jessica Yu Cc: linux-parisc@vger.kernel.org --- arch/parisc/Makefile | 1 - arch/parisc/kernel/module.c | 10 +++++++--- arch/parisc/kernel/module.lds | 7 ------- include/asm-generic/vmlinux.lds.h | 14 +++++++------- include/linux/ftrace.h | 5 +++++ kernel/module.c | 2 +- 6 files changed, 20 insertions(+), 19 deletions(-) delete mode 100644 arch/parisc/kernel/module.lds (limited to 'include/linux/ftrace.h') diff --git a/arch/parisc/Makefile b/arch/parisc/Makefile index 36b834f1c933..dca8f2de8cf5 100644 --- a/arch/parisc/Makefile +++ b/arch/parisc/Makefile @@ -60,7 +60,6 @@ KBUILD_CFLAGS += -DCC_USING_PATCHABLE_FUNCTION_ENTRY=1 \ -DFTRACE_PATCHABLE_FUNCTION_SIZE=$(NOP_COUNT) CC_FLAGS_FTRACE := -fpatchable-function-entry=$(NOP_COUNT),$(shell echo $$(($(NOP_COUNT)-1))) -KBUILD_LDS_MODULE += $(srctree)/arch/parisc/kernel/module.lds endif OBJCOPY_FLAGS =-O binary -R .note -R .comment -S diff --git a/arch/parisc/kernel/module.c b/arch/parisc/kernel/module.c index ac5f34993b53..1c50093e2ebe 100644 --- a/arch/parisc/kernel/module.c +++ b/arch/parisc/kernel/module.c @@ -43,6 +43,7 @@ #include #include #include +#include #include #include #include @@ -862,7 +863,7 @@ int module_finalize(const Elf_Ehdr *hdr, const char *strtab = NULL; const Elf_Shdr *s; char *secstrings; - int err, symindex = -1; + int symindex = -1; Elf_Sym *newptr, *oldptr; Elf_Shdr *symhdr = NULL; #ifdef DEBUG @@ -946,11 +947,13 @@ int module_finalize(const Elf_Ehdr *hdr, /* patch .altinstructions */ apply_alternatives(aseg, aseg + s->sh_size, me->name); +#ifdef CONFIG_DYNAMIC_FTRACE /* For 32 bit kernels we're compiling modules with * -ffunction-sections so we must relocate the addresses in the - *__mcount_loc section. + * ftrace callsite section. */ - if (symindex != -1 && !strcmp(secname, "__mcount_loc")) { + if (symindex != -1 && !strcmp(secname, FTRACE_CALLSITE_SECTION)) { + int err; if (s->sh_type == SHT_REL) err = apply_relocate((Elf_Shdr *)sechdrs, strtab, symindex, @@ -962,6 +965,7 @@ int module_finalize(const Elf_Ehdr *hdr, if (err) return err; } +#endif } return 0; } diff --git a/arch/parisc/kernel/module.lds b/arch/parisc/kernel/module.lds deleted file mode 100644 index 1a9a92aca5c8..000000000000 --- a/arch/parisc/kernel/module.lds +++ /dev/null @@ -1,7 +0,0 @@ -/* SPDX-License-Identifier: GPL-2.0 */ - -SECTIONS { - __mcount_loc : { - *(__patchable_function_entries) - } -} diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h index dae64600ccbf..a9c4e4721434 100644 --- a/include/asm-generic/vmlinux.lds.h +++ b/include/asm-generic/vmlinux.lds.h @@ -110,17 +110,17 @@ #endif #ifdef CONFIG_FTRACE_MCOUNT_RECORD -#ifdef CC_USING_PATCHABLE_FUNCTION_ENTRY -#define MCOUNT_REC() . = ALIGN(8); \ - __start_mcount_loc = .; \ - KEEP(*(__patchable_function_entries)) \ - __stop_mcount_loc = .; -#else +/* + * The ftrace call sites are logged to a section whose name depends on the + * compiler option used. A given kernel image will only use one, AKA + * FTRACE_CALLSITE_SECTION. We capture all of them here to avoid header + * dependencies for FTRACE_CALLSITE_SECTION's definition. + */ #define MCOUNT_REC() . = ALIGN(8); \ __start_mcount_loc = .; \ KEEP(*(__mcount_loc)) \ + KEEP(*(__patchable_function_entries)) \ __stop_mcount_loc = .; -#endif #else #define MCOUNT_REC() #endif diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h index 9867d90d635e..9141f2263286 100644 --- a/include/linux/ftrace.h +++ b/include/linux/ftrace.h @@ -738,6 +738,11 @@ static inline unsigned long get_lock_parent_ip(void) #ifdef CONFIG_FTRACE_MCOUNT_RECORD extern void ftrace_init(void); +#ifdef CC_USING_PATCHABLE_FUNCTION_ENTRY +#define FTRACE_CALLSITE_SECTION "__patchable_function_entries" +#else +#define FTRACE_CALLSITE_SECTION "__mcount_loc" +#endif #else static inline void ftrace_init(void) { } #endif diff --git a/kernel/module.c b/kernel/module.c index ff2d7359a418..acf7962936c4 100644 --- a/kernel/module.c +++ b/kernel/module.c @@ -3222,7 +3222,7 @@ static int find_module_sections(struct module *mod, struct load_info *info) #endif #ifdef CONFIG_FTRACE_MCOUNT_RECORD /* sechdrs[0].sh_size is always zero */ - mod->ftrace_callsites = section_objs(info, "__mcount_loc", + mod->ftrace_callsites = section_objs(info, FTRACE_CALLSITE_SECTION, sizeof(*mod->ftrace_callsites), &mod->num_ftrace_callsites); #endif -- cgit v1.2.3