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Date: Thu, 18 Jun 2020 13:38:30 -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 44/51] objtool: mcount: Keep lists locations and relocations
To reduce the need for an initial pass through the sections
we need to keep lists of mcount call locations and suitable
relocations. A subsequent patch will eliminate the need for
the first pass entirely.
Introduce a new list for the locations and reuse objtool's
relocation lists respectively.
Signed-off-by: Matt Helsley <mhelsley@...are.com>
---
tools/objtool/mcount.c | 133 +++++++++++++++++++++++------------------
1 file changed, 75 insertions(+), 58 deletions(-)
diff --git a/tools/objtool/mcount.c b/tools/objtool/mcount.c
index 7fbde6ce6eb8..7d7843f7cd44 100644
--- a/tools/objtool/mcount.c
+++ b/tools/objtool/mcount.c
@@ -43,9 +43,15 @@
#define R_ARM_THM_CALL 10
+struct mcount_loc {
+ struct list_head list;
+ GElf_Addr loc;
+};
+
extern int warn_on_notrace_sect; /* warn when section has mcount not being recorded */
static struct elf *lf;
+static struct list_head mcount_locs;
static const char ip_relative_call_x86[5] = { 0xe8, 0x00, 0x00, 0x00, 0x00 };
static const char ideal_nop5_x86_64[5] = { 0x0f, 0x1f, 0x44, 0x00, 0x00 };
@@ -294,20 +300,17 @@ static char const *has_rel_mcount(const struct section * const rels)
return txts->name;
}
-static unsigned tot_relsize(unsigned int *rel_entsize)
+static void tot_relsize(unsigned int *rel_entsize)
{
const struct section *sec;
- unsigned totrelsz = 0;
char const *txtname;
list_for_each_entry(sec, &lf->sections, list) {
txtname = has_rel_mcount(sec);
if (!(txtname && is_mcounted_section_name(txtname)))
continue;
- totrelsz += sec->sh.sh_size;
*rel_entsize = sec->sh.sh_entsize;
}
- return totrelsz;
}
/* zero or a small negative offset added to get the start of the call
@@ -323,55 +326,89 @@ static size_t loc_size;
* Accumulate the section offsets that are found, and their relocation info,
* onto the end of the existing arrays.
*/
-static void sift_rel_mcount(GElf_Addr **mlocpp,
- GElf_Sxword *r_offsetp,
- void **const mrelpp,
+static void sift_rel_mcount(GElf_Sxword *r_offsetp,
const struct section * const rels,
+ struct section *mc_relocs,
+ struct section *mc_locs,
unsigned const recsym_index,
unsigned long const recval,
unsigned const reltype,
bool is_rela)
{
- GElf_Rel *mrelp = *mrelpp;
- GElf_Rela *mrelap = *mrelpp;
struct reloc *reloc;
list_for_each_entry(reloc, &rels->reloc_list, list) {
unsigned long addend;
+ struct mcount_loc *mc_loc;
+ struct reloc *mc_reloc;
+
+ if (reloc->sym->class != SYM_MCOUNT || is_fake_mcount(reloc))
+ continue;
- if (reloc->sym->class == SYM_MCOUNT || is_fake_mcount(reloc))
+ mc_loc = malloc(sizeof(*mc_loc));
+ if (!mc_loc) {
+ perror("malloc");
continue;
+ }
+ mc_reloc = malloc(sizeof(*mc_reloc));
+ if (!mc_reloc) {
+ perror("malloc");
+ free(mc_loc);
+ continue;
+ }
+ memset(mc_reloc, 0, sizeof(*mc_reloc));
+ memset(mc_loc, 0, sizeof(*mc_loc));
+ mc_reloc->sec = mc_relocs;
addend = reloc->offset - recval + mcount_adjust;
if (is_rela) {
- mrelap->r_offset = *r_offsetp;
- mrelap->r_info = GELF_R_INFO(recsym_index, reltype);
- mrelap->r_addend = addend;
- mrelap++;
- **mlocpp = 0;
+ mc_reloc->rela.r_offset = *r_offsetp;
+ mc_reloc->rela.r_info = GELF_R_INFO(recsym_index, reltype);
+ mc_reloc->rela.r_addend = addend;
+ mc_loc->loc = 0;
} else {
- mrelp->r_offset = *r_offsetp;
- mrelp->r_info = GELF_R_INFO(recsym_index, reltype);
- mrelp++;
- **mlocpp = addend;
+ mc_reloc->rel.r_offset = *r_offsetp;
+ mc_reloc->rel.r_info = GELF_R_INFO(recsym_index, reltype);
+ mc_loc->loc = addend;
}
- (*mlocpp)++;
+ mc_reloc->offset = *r_offsetp;
+ mc_reloc->type = reltype;
+ mc_reloc->sec = mc_locs;
+ elf_add_reloc(lf, mc_reloc);
+
+ list_add_tail(&mc_loc->list, &mcount_locs);
*r_offsetp += loc_size;
}
- *mrelpp = is_rela ? (void *)mrelap : (void *)mrelp;
}
-/* Overall supervision for Elf32 ET_REL file. */
-static int do_mcount(unsigned const reltype, size_t rela_size)
+/* Convert list of mcount locations to an array/buffer for libelf */
+static void fill_mcount_locs(GElf_Sxword r_offset, GElf_Addr **rbuf,
+ size_t *rsize)
{
- /* Upper bound on space: assume all relevant relocs are for mcount. */
- unsigned totrelsz;
+ GElf_Addr *buf, *loc;
+ struct mcount_loc *entry, *next;
+ size_t size = sizeof(*loc) * r_offset / loc_size;
+
+ buf = malloc(size);
+ if (!buf) {
+ perror("malloc");
+ return;
+ }
- void *mrel0;
- void *mrelp;
+ loc = buf;
+ list_for_each_entry_safe(entry, next, &mcount_locs, list) {
+ *loc = entry->loc;
+ list_del(&entry->list);
+ free(entry);
+ loc++;
+ }
+ *rbuf = buf;
+ *rsize = size;
+}
- GElf_Addr *mloc0;
- GElf_Addr *mlocp;
+/* Overall supervision for Elf32 ET_REL file. */
+static int do_mcount(unsigned const reltype, size_t rela_size)
+{
GElf_Sxword r_offset = 0;
struct section *sec, *mlocs, *mrels;
@@ -384,33 +421,16 @@ static int do_mcount(unsigned const reltype, size_t rela_size)
if (find_section_by_name(lf, "__mcount_loc") != NULL)
return 0;
- totrelsz = tot_relsize(&rel_entsize);
- if (totrelsz == 0)
- return 0;
-
- mrel0 = malloc(totrelsz);
- mrelp = mrel0;
- if (!mrel0)
- return -1;
-
- /* 2*sizeof(address) <= sizeof(Elf_Rel) */
- mloc0 = malloc(totrelsz>>1);
- mlocp = mloc0;
- if (!mloc0) {
- free(mrel0);
- return -1;
- }
-
+ tot_relsize(&rel_entsize);
is_rela = (rela_size == rel_entsize);
/* add section: __mcount_loc */
- mlocs = elf_create_section(lf, mc_name, sizeof(*mloc0), 0);
+ mlocs = elf_create_section(lf, mc_name, sizeof(GElf_Addr), 0);
if (!mlocs)
goto out;
mlocs->sh.sh_link = 0;
mlocs->sh.sh_info = 0;
mlocs->sh.sh_addralign = 8;
- mlocs->data->d_buf = mloc0;
mlocs->data->d_type = ELF_T_ADDR; /* elf_xlatetof() conversion */
/* add section .rel[a]__mcount_loc */
@@ -419,7 +439,6 @@ static int do_mcount(unsigned const reltype, size_t rela_size)
if (!mrels)
goto out;
mrels->sh.sh_flags = 0; /* clear SHF_INFO_LINK */
- mrels->data->d_buf = mrel0;
list_for_each_entry(sec, &lf->sections, list) {
char const *txtname;
@@ -433,7 +452,7 @@ static int do_mcount(unsigned const reltype, size_t rela_size)
txtname, &recval, &recsym))
goto out;
- sift_rel_mcount(&mlocp, &r_offset, &mrelp, sec,
+ sift_rel_mcount(&r_offset, sec, mrels, mlocs,
recsym, recval, reltype, is_rela);
} else if (txtname && (warn_on_notrace_sect || make_nop)) {
/*
@@ -445,25 +464,21 @@ static int do_mcount(unsigned const reltype, size_t rela_size)
}
}
- if (mloc0 != mlocp) {
+ if (!list_empty(&mcount_locs)) {
+ fill_mcount_locs(r_offset, (GElf_Addr **)&mlocs->data->d_buf,
+ &mlocs->sh.sh_size);
/* Update the section size and Elf_Data size */
- mlocs->sh.sh_size = (void *)mlocp - (void *)mloc0;
mlocs->len = mlocs->sh.sh_size;
mlocs->data->d_size = mlocs->len;
elf_flagdata(mlocs->data, ELF_C_SET, ELF_F_DIRTY);
- mrels->sh.sh_size = mrelp - mrel0;
- mrels->len = mrels->sh.sh_size;
- mrels->data->d_size = mrels->len;
- elf_flagdata(mrels->data, ELF_C_SET, ELF_F_DIRTY);
+ elf_rebuild_reloc_section(lf, mrels);
/* overwrite the ELF file */
result = elf_write(lf);
} else
result = 0;
out:
- free(mrel0);
- free(mloc0);
return result;
}
@@ -490,6 +505,8 @@ static int do_file(char const *const fname)
goto out;
}
+ INIT_LIST_HEAD(&mcount_locs);
+
switch (lf->ehdr.e_ident[EI_DATA]) {
default:
fprintf(stderr, "unrecognized ELF data encoding %d: %s\n",
--
2.20.1
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