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    SubjectRe: [RFC PATCH 4/4] objtool/powerpc: Add --mcount specific implementation
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    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@linux.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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