Messages in this thread Patch in this message | | | From | Yinan Liu <> | Subject | [PATCH v2 2/2] scripts: ftrace - move the nop-processing in ftrace_init to compile time | Date | Tue, 16 Nov 2021 10:49:42 +0800 |
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In some business scenarios, GCC versions are so old that optimizations in ftrace cannot be completed, such as -mrecord-mcount and -mnop-mcount. The recordmCount in the kernel is actually used. In this case, ftrace_init will consume a period of time, usually around 9~12ms. Do nop substitution in recordmcount.c to speed up ftrace_init.
Signed-off-by: Yinan Liu <yinan@linux.alibaba.com> --- kernel/trace/ftrace.c | 7 +++++++ scripts/recordmcount.h | 14 ++++++++++++++ 2 files changed, 21 insertions(+)
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c index c776a2956237..ccc690e81556 100644 --- a/kernel/trace/ftrace.c +++ b/kernel/trace/ftrace.c @@ -6478,6 +6478,13 @@ static int ftrace_process_locs(struct module *mod, * until we are finished with it, and there's no * reason to cause large interrupt latencies while we do it. */ +#ifdef CONFIG_FTRACE_MCOUNT_USE_RECORDMCOUNT +#ifdef CONFIG_HAVE_C_RECORDMCOUNT + ret = 0; + goto out; +#endif +#endif + if (!mod) local_irq_save(flags); ftrace_update_code(mod, start_pg); diff --git a/scripts/recordmcount.h b/scripts/recordmcount.h index 1e9baa5c4fc6..152311639a0b 100644 --- a/scripts/recordmcount.h +++ b/scripts/recordmcount.h @@ -406,6 +406,8 @@ static uint_t *sift_rel_mcount(uint_t *mlocp, uint_t const recval, unsigned const reltype) { + Elf_Shdr *const shdr0 = (Elf_Shdr *)(_w(ehdr->e_shoff) + (void *)ehdr); + Elf_Shdr const *const shdr = &shdr0[w(relhdr->sh_info)]; uint_t *const mloc0 = mlocp; Elf_Rel *mrelp = *mrelpp; Elf_Sym const *sym0; @@ -419,6 +421,7 @@ static uint_t *sift_rel_mcount(uint_t *mlocp, get_sym_str_and_relp(relhdr, ehdr, &sym0, &str0, &relp); for (t = nrel; t; --t) { + int ret = -1; if (!mcountsym) mcountsym = get_mcountsym(sym0, relp, str0); @@ -436,6 +439,17 @@ static uint_t *sift_rel_mcount(uint_t *mlocp, *mlocp++ = addend; mrelp = (Elf_Rel *)(rel_entsize + (void *)mrelp); + /* convert mcount into nop */ + if (make_nop) + ret = make_nop((void *)ehdr, + _w(shdr->sh_offset) + _w(relp->r_offset)); + if (!ret) { + Elf_Rel rel; + rel = *(Elf_Rel *)relp; + Elf_r_info(&rel, Elf_r_sym(relp), rel_type_nop); + ulseek(fd_map, (void *)relp - (void *)ehdr, SEEK_SET); + uwrite(fd_map, &rel, sizeof(rel)); + } } relp = (Elf_Rel const *)(rel_entsize + (void *)relp); } -- 2.14.4.44.g2045bb6
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