[PATCH v2 08/14] objtool: Add elf_create_reloc() helper
From: Peter Zijlstra
Date: Thu Mar 18 2021 - 13:25:24 EST
We have 4 instances of adding a relocation. Create a common helper
to avoid growing even more.
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
tools/objtool/check.c | 76 ++++++----------------------
tools/objtool/elf.c | 90 +++++++++++++++++++++++-----------
tools/objtool/include/objtool/check.h | 7 ++
tools/objtool/include/objtool/elf.h | 10 +++
tools/objtool/orc_gen.c | 57 ++++++++-------------
5 files changed, 119 insertions(+), 121 deletions(-)
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -433,8 +433,7 @@ static int add_dead_ends(struct objtool_
static int create_static_call_sections(struct objtool_file *file)
{
- struct section *sec, *reloc_sec;
- struct reloc *reloc;
+ struct section *sec;
struct static_call_site *site;
struct instruction *insn;
struct symbol *key_sym;
@@ -460,8 +459,7 @@ static int create_static_call_sections(s
if (!sec)
return -1;
- reloc_sec = elf_create_reloc_section(file->elf, sec, SHT_RELA);
- if (!reloc_sec)
+ if (!elf_create_reloc_section(file->elf, sec, SHT_RELA))
return -1;
idx = 0;
@@ -471,26 +469,13 @@ static int create_static_call_sections(s
memset(site, 0, sizeof(struct static_call_site));
/* populate reloc for 'addr' */
- reloc = malloc(sizeof(*reloc));
-
- if (!reloc) {
- perror("malloc");
- return -1;
- }
- memset(reloc, 0, sizeof(*reloc));
-
- insn_to_reloc_sym_addend(insn->sec, insn->offset, reloc);
- if (!reloc->sym) {
- WARN_FUNC("static call tramp: missing containing symbol",
- insn->sec, insn->offset);
+ if (!elf_create_reloc(file->elf, sec, idx * sizeof(struct static_call_site),
+ R_X86_64_PC32,
+ reloc_to_insn, insn, 0)) {
+ WARN_ELF("elf_create_reloc: static_call_site::addr");
return -1;
}
- reloc->type = R_X86_64_PC32;
- reloc->offset = idx * sizeof(struct static_call_site);
- reloc->sec = reloc_sec;
- elf_add_reloc(file->elf, reloc);
-
/* find key symbol */
key_name = strdup(insn->call_dest->name);
if (!key_name) {
@@ -526,18 +511,13 @@ static int create_static_call_sections(s
free(key_name);
/* populate reloc for 'key' */
- reloc = malloc(sizeof(*reloc));
- if (!reloc) {
- perror("malloc");
+ if (!elf_create_reloc(file->elf, sec, idx * sizeof(struct static_call_site) + 4,
+ R_X86_64_PC32,
+ reloc_to_sym, key_sym,
+ is_sibling_call(insn) * STATIC_CALL_SITE_TAIL)) {
+ WARN_ELF("elf_create_reloc: static_call_site::key");
return -1;
}
- memset(reloc, 0, sizeof(*reloc));
- reloc->sym = key_sym;
- reloc->addend = is_sibling_call(insn) ? STATIC_CALL_SITE_TAIL : 0;
- reloc->type = R_X86_64_PC32;
- reloc->offset = idx * sizeof(struct static_call_site) + 4;
- reloc->sec = reloc_sec;
- elf_add_reloc(file->elf, reloc);
idx++;
}
@@ -547,8 +527,7 @@ static int create_static_call_sections(s
static int create_mcount_loc_sections(struct objtool_file *file)
{
- struct section *sec, *reloc_sec;
- struct reloc *reloc;
+ struct section *sec;
unsigned long *loc;
struct instruction *insn;
int idx;
@@ -571,8 +550,7 @@ static int create_mcount_loc_sections(st
if (!sec)
return -1;
- reloc_sec = elf_create_reloc_section(file->elf, sec, SHT_RELA);
- if (!reloc_sec)
+ if (!elf_create_reloc_section(file->elf, sec, SHT_RELA))
return -1;
idx = 0;
@@ -581,32 +559,12 @@ static int create_mcount_loc_sections(st
loc = (unsigned long *)sec->data->d_buf + idx;
memset(loc, 0, sizeof(unsigned long));
- reloc = malloc(sizeof(*reloc));
- if (!reloc) {
- perror("malloc");
+ if (!elf_create_reloc(file->elf, sec, idx * sizeof(unsigned long),
+ R_X86_64_64,
+ reloc_to_insn, insn, 0)) {
+ WARN_ELF("elf_create_reloc: __mcount_loc");
return -1;
}
- memset(reloc, 0, sizeof(*reloc));
-
- if (insn->sec->sym) {
- reloc->sym = insn->sec->sym;
- reloc->addend = insn->offset;
- } else {
- reloc->sym = find_symbol_containing(insn->sec, insn->offset);
-
- if (!reloc->sym) {
- WARN("missing symbol for insn at offset 0x%lx\n",
- insn->offset);
- return -1;
- }
-
- reloc->addend = insn->offset - reloc->sym->offset;
- }
-
- reloc->type = R_X86_64_64;
- reloc->offset = idx * sizeof(unsigned long);
- reloc->sec = reloc_sec;
- elf_add_reloc(file->elf, reloc);
idx++;
}
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -211,32 +211,6 @@ struct reloc *find_reloc_by_dest(const s
return find_reloc_by_dest_range(elf, sec, offset, 1);
}
-void insn_to_reloc_sym_addend(struct section *sec, unsigned long offset,
- struct reloc *reloc)
-{
- if (sec->sym) {
- reloc->sym = sec->sym;
- reloc->addend = offset;
- return;
- }
-
- /*
- * The Clang assembler strips section symbols, so we have to reference
- * the function symbol instead:
- */
- reloc->sym = find_symbol_containing(sec, offset);
- if (!reloc->sym) {
- /*
- * Hack alert. This happens when we need to reference the NOP
- * pad insn immediately after the function.
- */
- reloc->sym = find_symbol_containing(sec, offset - 1);
- }
-
- if (reloc->sym)
- reloc->addend = offset - reloc->sym->offset;
-}
-
static int read_sections(struct elf *elf)
{
Elf_Scn *s = NULL;
@@ -473,7 +447,7 @@ static int read_symbols(struct elf *elf)
return -1;
}
-void elf_add_reloc(struct elf *elf, struct reloc *reloc)
+static void elf_add_reloc(struct elf *elf, struct reloc *reloc)
{
struct section *sec = reloc->sec;
@@ -483,6 +457,68 @@ void elf_add_reloc(struct elf *elf, stru
sec->changed = true;
}
+void reloc_to_sym(struct reloc *reloc, void *dst)
+{
+ struct symbol *sym = dst;
+ reloc->sym = sym;
+}
+
+void __reloc_to_insn(struct reloc *reloc, struct section *sec, unsigned long offset)
+{
+ if (sec->sym) {
+ reloc->sym = sec->sym;
+ reloc->addend = offset;
+ return;
+ }
+
+ /*
+ * The Clang assembler strips section symbols, so we have to reference
+ * the function symbol instead:
+ */
+ reloc->sym = find_symbol_containing(sec, offset);
+ if (!reloc->sym) {
+ /*
+ * Hack alert. This happens when we need to reference the NOP
+ * pad insn immediately after the function.
+ */
+ reloc->sym = find_symbol_containing(sec, offset - 1);
+ }
+
+ if (reloc->sym)
+ reloc->addend = offset - reloc->sym->offset;
+}
+
+struct reloc *elf_create_reloc(struct elf *elf,
+ struct section *sec, unsigned long offset,
+ unsigned int type,
+ void (*set_dest)(struct reloc *, void *), void *dst, int addend)
+{
+ struct reloc *reloc;
+
+ reloc = malloc(sizeof(*reloc));
+ if (!reloc) {
+ perror("malloc");
+ return NULL;
+ }
+ memset(reloc, 0, sizeof(*reloc));
+
+ reloc->sec = sec->reloc;
+ reloc->offset = offset;
+ reloc->type = type;
+
+ set_dest(reloc, dst);
+ if (!reloc->sym) {
+ WARN("failed to create reloc");
+ return NULL;
+ }
+
+ reloc->addend += addend;
+
+ elf_add_reloc(elf, reloc);
+
+ return reloc;
+}
+
static int read_rel_reloc(struct section *sec, int i, struct reloc *reloc, unsigned int *symndx)
{
if (!gelf_getrel(sec->data, i, &reloc->rel)) {
--- a/tools/objtool/include/objtool/check.h
+++ b/tools/objtool/include/objtool/check.h
@@ -9,6 +9,7 @@
#include <stdbool.h>
#include <objtool/cfi.h>
#include <objtool/arch.h>
+#include <objtool/elf.h>
struct insn_state {
struct cfi_state cfi;
@@ -91,4 +92,10 @@ struct instruction *find_insn(struct obj
insn->sec == sec; \
insn = list_next_entry(insn, list))
+static inline void reloc_to_insn(struct reloc *reloc, void *dst)
+{
+ struct instruction *insn = dst;
+ __reloc_to_insn(reloc, insn->sec, insn->offset);
+}
+
#endif /* _CHECK_H */
--- a/tools/objtool/include/objtool/elf.h
+++ b/tools/objtool/include/objtool/elf.h
@@ -123,7 +123,15 @@ static inline u32 reloc_hash(struct relo
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);
struct section *elf_create_reloc_section(struct elf *elf, struct section *base, int reltype);
-void elf_add_reloc(struct elf *elf, struct reloc *reloc);
+
+void reloc_to_sym(struct reloc *reloc, void *sym);
+void __reloc_to_insn(struct reloc *reloc, struct section *sec, unsigned long offset);
+
+struct reloc *elf_create_reloc(struct elf *elf,
+ struct section *sec, unsigned long offset,
+ unsigned int type,
+ void (*set_dest)(struct reloc *reloc, void *), void *dst, int addend);
+
int elf_write_insn(struct elf *elf, struct section *sec,
unsigned long offset, unsigned int len,
const char *insn);
--- a/tools/objtool/orc_gen.c
+++ b/tools/objtool/orc_gen.c
@@ -81,13 +81,25 @@ static int init_orc_entry(struct orc_ent
return 0;
}
+struct orc_list_entry {
+ struct list_head list;
+ struct orc_entry orc;
+ struct section *insn_sec;
+ unsigned long insn_off;
+};
+
+static void reloc_to_orc(struct reloc *reloc, void *dst)
+{
+ struct orc_list_entry *entry = dst;
+ __reloc_to_insn(reloc, entry->insn_sec, entry->insn_off);
+}
+
static int write_orc_entry(struct elf *elf, struct section *orc_sec,
- struct section *ip_rsec, unsigned int idx,
- struct section *insn_sec, unsigned long insn_off,
- struct orc_entry *o)
+ struct section *ip_sec, unsigned int idx,
+ struct orc_list_entry *entry)
{
+ struct orc_entry *o = &entry->orc;
struct orc_entry *orc;
- struct reloc *reloc;
/* populate ORC data */
orc = (struct orc_entry *)orc_sec->data->d_buf + idx;
@@ -96,36 +108,16 @@ static int write_orc_entry(struct elf *e
orc->bp_offset = bswap_if_needed(orc->bp_offset);
/* populate reloc for ip */
- reloc = malloc(sizeof(*reloc));
- if (!reloc) {
- perror("malloc");
- return -1;
- }
- memset(reloc, 0, sizeof(*reloc));
-
- insn_to_reloc_sym_addend(insn_sec, insn_off, reloc);
- if (!reloc->sym) {
- WARN("missing symbol for insn at offset 0x%lx",
- insn_off);
+ if (!elf_create_reloc(elf, ip_sec, idx * sizeof(int),
+ R_X86_64_PC32,
+ reloc_to_orc, entry, 0)) {
+ WARN_ELF("elf_create_reloc: ORC ip");
return -1;
}
- reloc->type = R_X86_64_PC32;
- reloc->offset = idx * sizeof(int);
- reloc->sec = ip_rsec;
-
- elf_add_reloc(elf, reloc);
-
return 0;
}
-struct orc_list_entry {
- struct list_head list;
- struct orc_entry orc;
- struct section *insn_sec;
- unsigned long insn_off;
-};
-
static int orc_list_add(struct list_head *orc_list, struct orc_entry *orc,
struct section *sec, unsigned long offset)
{
@@ -153,7 +145,7 @@ static unsigned long alt_group_len(struc
int orc_create(struct objtool_file *file)
{
- struct section *sec, *ip_rsec, *orc_sec;
+ struct section *sec, *orc_sec;
unsigned int nr = 0, idx = 0;
struct orc_list_entry *entry;
struct list_head orc_list;
@@ -242,15 +234,12 @@ int orc_create(struct objtool_file *file
sec = elf_create_section(file->elf, ".orc_unwind_ip", 0, sizeof(int), nr);
if (!sec)
return -1;
- ip_rsec = elf_create_reloc_section(file->elf, sec, SHT_RELA);
- if (!ip_rsec)
+ if (!elf_create_reloc_section(file->elf, sec, SHT_RELA))
return -1;
/* Write ORC entries to sections: */
list_for_each_entry(entry, &orc_list, list) {
- if (write_orc_entry(file->elf, orc_sec, ip_rsec, idx++,
- entry->insn_sec, entry->insn_off,
- &entry->orc))
+ if (write_orc_entry(file->elf, orc_sec, sec, idx++, entry))
return -1;
}