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Message-ID: <8bc94dfae5969002d946b1aad2f831474d4649fd.1592510545.git.mhelsley@vmware.com>
Date: Thu, 18 Jun 2020 13:38:31 -0700
From: Matt Helsley <mhelsley@...are.com>
To: <linux-kernel@...r.kernel.org>
CC: Josh Poimboeuf <jpoimboe@...hat.com>,
Peter Zijlstra <peterz@...radead.org>,
Steven Rostedt <rostedt@...dmis.org>,
Julien Thierry <jthierry@...hat.com>,
Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>,
Matt Helsley <mhelsley@...are.com>
Subject: [RFC][PATCH v5 45/51] objtool: mcount: Move mcount section test to objtool ELF
In preparation for removing this first pass by mcount move
the test for whether a section is mcountable into objtool's
ELF read code, much like we did with the symbol name. A
subsequent patch will eliminate the tot_relsize() function
and thereby reduce the number of passes through the ELF
data.
Signed-off-by: Matt Helsley <mhelsley@...are.com>
---
tools/objtool/elf.c | 16 ++++++++++++++++
tools/objtool/elf.h | 2 +-
tools/objtool/mcount.c | 36 +++++++++++-------------------------
3 files changed, 28 insertions(+), 26 deletions(-)
diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index 666cbc01c332..dffdc3264a25 100644
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -308,6 +308,20 @@ struct reloc *find_reloc_by_dest(const struct elf *elf, struct section *sec, uns
return find_reloc_by_dest_range(elf, sec, offset, 1);
}
+/* Names of the sections that could contain calls to mcount. */
+static int is_mcounted_section_name(char const *const txtname)
+{
+ return strncmp(".text", txtname, 5) == 0 ||
+ strcmp(".init.text", txtname) == 0 ||
+ strcmp(".ref.text", txtname) == 0 ||
+ strcmp(".sched.text", txtname) == 0 ||
+ strcmp(".spinlock.text", txtname) == 0 ||
+ strcmp(".irqentry.text", txtname) == 0 ||
+ strcmp(".softirqentry.text", txtname) == 0 ||
+ strcmp(".kprobes.text", txtname) == 0 ||
+ strcmp(".cpuidle.text", txtname) == 0;
+}
+
static int read_sections(struct elf *elf)
{
Elf_Scn *s = NULL;
@@ -370,6 +384,8 @@ static int read_sections(struct elf *elf)
}
sec->len = sec->sh.sh_size;
+ sec->mcounted = is_mcounted_section_name(sec->name);
+
list_add_tail(&sec->list, &elf->sections);
elf_hash_add(elf->section_hash, &sec->hash, sec->idx);
elf_hash_add(elf->section_name_hash, &sec->name_hash, str_hash(sec->name));
diff --git a/tools/objtool/elf.h b/tools/objtool/elf.h
index f0b02824f9d3..db207e93a1e6 100644
--- a/tools/objtool/elf.h
+++ b/tools/objtool/elf.h
@@ -39,7 +39,7 @@ struct section {
char *name;
int idx;
unsigned int len;
- bool changed, text, rodata, noinstr;
+ bool changed, text, rodata, noinstr, mcounted;
};
enum symbol_class {
diff --git a/tools/objtool/mcount.c b/tools/objtool/mcount.c
index 7d7843f7cd44..a75d918a9fa5 100644
--- a/tools/objtool/mcount.c
+++ b/tools/objtool/mcount.c
@@ -144,20 +144,6 @@ static int make_nop_arm64(struct section *txts, size_t const offset)
return elf_write_insn(lf, txts, offset, 4, ideal_nop);
}
-/* Names of the sections that could contain calls to mcount. */
-static int is_mcounted_section_name(char const *const txtname)
-{
- return strncmp(".text", txtname, 5) == 0 ||
- strcmp(".init.text", txtname) == 0 ||
- strcmp(".ref.text", txtname) == 0 ||
- strcmp(".sched.text", txtname) == 0 ||
- strcmp(".spinlock.text", txtname) == 0 ||
- strcmp(".irqentry.text", txtname) == 0 ||
- strcmp(".softirqentry.text", txtname) == 0 ||
- strcmp(".kprobes.text", txtname) == 0 ||
- strcmp(".cpuidle.text", txtname) == 0;
-}
-
/*
* MIPS mcount long call has 2 _mcount symbols, only the position of the 1st
* _mcount symbol is needed for dynamic function tracer, with it, to disable
@@ -288,7 +274,7 @@ static int nop_mcount(struct section * const rels,
return 0;
}
-static char const *has_rel_mcount(const struct section * const rels)
+static struct section const *has_rel_mcount(const struct section * const rels)
{
const struct section *txts;
if (rels->sh.sh_type != SHT_REL && rels->sh.sh_type != SHT_RELA)
@@ -297,17 +283,17 @@ static char const *has_rel_mcount(const struct section * const rels)
if ((txts->sh.sh_type != SHT_PROGBITS) ||
!(txts->sh.sh_flags & SHF_EXECINSTR))
return NULL;
- return txts->name;
+ return txts;
}
static void tot_relsize(unsigned int *rel_entsize)
{
const struct section *sec;
- char const *txtname;
+ const struct section *txts;
list_for_each_entry(sec, &lf->sections, list) {
- txtname = has_rel_mcount(sec);
- if (!(txtname && is_mcounted_section_name(txtname)))
+ txts = has_rel_mcount(sec);
+ if (!(txts && txts->mcounted))
continue;
*rel_entsize = sec->sh.sh_entsize;
}
@@ -441,25 +427,25 @@ static int do_mcount(unsigned const reltype, size_t rela_size)
mrels->sh.sh_flags = 0; /* clear SHF_INFO_LINK */
list_for_each_entry(sec, &lf->sections, list) {
- char const *txtname;
+ struct section const *txts;
- txtname = has_rel_mcount(sec);
- if (txtname && is_mcounted_section_name(txtname)) {
+ txts = has_rel_mcount(sec);
+ if (txts && txts->mcounted) {
unsigned long recval = 0;
unsigned int recsym;
if (find_section_sym_index(sec->sh.sh_info,
- txtname, &recval, &recsym))
+ txts->name, &recval, &recsym))
goto out;
sift_rel_mcount(&r_offset, sec, mrels, mlocs,
recsym, recval, reltype, is_rela);
- } else if (txtname && (warn_on_notrace_sect || make_nop)) {
+ } else if (txts && (warn_on_notrace_sect || make_nop)) {
/*
* This section is ignored by ftrace, but still
* has mcount calls. Convert them to nops now.
*/
- if (nop_mcount(sec, txtname) < 0)
+ if (nop_mcount(sec, txts->name) < 0)
goto out;
}
}
--
2.20.1
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