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Message-ID: <6be5c941-07b0-64d5-7f36-fe5770fb5244@csgroup.eu>
Date: Tue, 24 May 2022 09:35:36 +0000
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: Sathvika Vasireddy <sv@...ux.ibm.com>,
"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"jpoimboe@...hat.com" <jpoimboe@...hat.com>,
"peterz@...radead.org" <peterz@...radead.org>,
"mbenes@...e.cz" <mbenes@...e.cz>, "aik@...abs.ru" <aik@...abs.ru>,
"mpe@...erman.id.au" <mpe@...erman.id.au>,
"rostedt@...dmis.org" <rostedt@...dmis.org>,
"naveen.n.rao@...ux.vnet.ibm.com" <naveen.n.rao@...ux.vnet.ibm.com>
Subject: Re: [RFC PATCH 4/4] objtool/powerpc: Add --mcount specific
implementation
Le 23/05/2022 à 19:55, Sathvika Vasireddy a écrit :
> This patch enables objtool --mcount on powerpc, and
> adds implementation specific to powerpc.
>
> Signed-off-by: Sathvika Vasireddy <sv@...ux.ibm.com>
> ---
> arch/powerpc/Kconfig | 1 +
> tools/objtool/arch/powerpc/decode.c | 14 ++++++++++++++
> tools/objtool/check.c | 12 +++++++-----
> tools/objtool/elf.c | 13 +++++++++++++
> tools/objtool/include/objtool/elf.h | 1 +
> 5 files changed, 36 insertions(+), 5 deletions(-)
>
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index 732a3f91ee5e..3373d44a1298 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -233,6 +233,7 @@ config PPC
> select HAVE_NMI if PERF_EVENTS || (PPC64 && PPC_BOOK3S)
> select HAVE_OPTPROBES
> select HAVE_OBJTOOL if PPC64
> + select HAVE_OBJTOOL_MCOUNT if HAVE_OBJTOOL
> select HAVE_PERF_EVENTS
> select HAVE_PERF_EVENTS_NMI if PPC64
> select HAVE_PERF_REGS
> diff --git a/tools/objtool/arch/powerpc/decode.c b/tools/objtool/arch/powerpc/decode.c
> index e3b77a6ce357..ad3d79fffac2 100644
> --- a/tools/objtool/arch/powerpc/decode.c
> +++ b/tools/objtool/arch/powerpc/decode.c
> @@ -40,12 +40,26 @@ int arch_decode_instruction(struct objtool_file *file, const struct section *sec
> struct list_head *ops_list)
> {
> u32 insn;
> + unsigned int opcode;
>
> *immediate = 0;
> memcpy(&insn, sec->data->d_buf+offset, 4);
> *len = 4;
> *type = INSN_OTHER;
>
> + opcode = (insn >> 26);
You dont need the brackets here.
> +
> + switch (opcode) {
> + case 18: /* bl */
> + if ((insn & 3) == 1) {
> + *type = INSN_CALL;
> + *immediate = insn & 0x3fffffc;
> + if (*immediate & 0x2000000)
> + *immediate -= 0x4000000;
> + }
> + break;
> + }
> +
> return 0;
> }
>
> diff --git a/tools/objtool/check.c b/tools/objtool/check.c
> index 056302d58e23..fd8bad092f89 100644
> --- a/tools/objtool/check.c
> +++ b/tools/objtool/check.c
> @@ -832,7 +832,7 @@ static int create_mcount_loc_sections(struct objtool_file *file)
>
> if (elf_add_reloc_to_insn(file->elf, sec,
> idx * sizeof(unsigned long),
> - R_X86_64_64,
> + elf_reloc_type_long(file->elf),
> insn->sec, insn->offset))
> return -1;
>
> @@ -2183,7 +2183,7 @@ static int classify_symbols(struct objtool_file *file)
> if (arch_is_retpoline(func))
> func->retpoline_thunk = true;
>
> - if (!strcmp(func->name, "__fentry__"))
> + if ((!strcmp(func->name, "__fentry__")) || (!strcmp(func->name, "_mcount")))
> func->fentry = true;
>
> if (is_profiling_func(func->name))
> @@ -2259,9 +2259,11 @@ static int decode_sections(struct objtool_file *file)
> * Must be before add_jump_destinations(), which depends on 'func'
> * being set for alternatives, to enable proper sibling call detection.
> */
> - ret = add_special_section_alts(file);
> - if (ret)
> - return ret;
> + if (opts.stackval || opts.orc || opts.uaccess || opts.noinstr) {
> + ret = add_special_section_alts(file);
> + if (ret)
> + return ret;
> + }
I think this change should be a patch by itself, it's not related to
powerpc.
>
> ret = add_jump_destinations(file);
> if (ret)
> diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
> index c25e957c1e52..95763060d551 100644
> --- a/tools/objtool/elf.c
> +++ b/tools/objtool/elf.c
> @@ -793,6 +793,19 @@ elf_create_section_symbol(struct elf *elf, struct section *sec)
> return sym;
> }
>
> +int elf_reloc_type_long(struct elf *elf)
Not sure it's a good name, because for 32 bits we have to use 'int'.
> +{
> + switch (elf->ehdr.e_machine) {
> + case EM_X86_64:
> + return R_X86_64_64;
> + case EM_PPC64:
> + return R_PPC64_ADDR64;
> + default:
> + WARN("unknown machine...");
> + exit(-1);
> + }
> +}
Wouldn't it be better to make that function arch specific ?
> +
> int elf_add_reloc_to_insn(struct elf *elf, struct section *sec,
> unsigned long offset, unsigned int type,
> struct section *insn_sec, unsigned long insn_off)
> diff --git a/tools/objtool/include/objtool/elf.h b/tools/objtool/include/objtool/elf.h
> index adebfbc2b518..c43e23c0b3c8 100644
> --- a/tools/objtool/include/objtool/elf.h
> +++ b/tools/objtool/include/objtool/elf.h
> @@ -144,6 +144,7 @@ static inline bool has_multiple_files(struct elf *elf)
> struct elf *elf_open_read(const char *name, int flags);
> struct section *elf_create_section(struct elf *elf, const char *name, unsigned int sh_flags, size_t entsize, int nr);
>
> +int elf_reloc_type_long(struct elf *elf);
> int elf_add_reloc(struct elf *elf, struct section *sec, unsigned long offset,
> unsigned int type, struct symbol *sym, s64 addend);
> int elf_add_reloc_to_insn(struct elf *elf, struct section *sec,
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