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perf dso: Add support for reading the e_machine type for a dso

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For ELF file dsos read the e_machine from the ELF header. For kernel
types assume the e_machine matches the perf tool. In other cases
return EM_NONE.

When reading from the ELF header use DSO__SWAP that may need
dso->needs_swap initializing. Factor out dso__swap_init to allow this.

Signed-off-by: Ian Rogers <irogers@google.com>
Reviewed-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Arnaldo Carvalho de Melo <acme@kernel.org>
Link: https://lore.kernel.org/r/20250319050741.269828-7-irogers@google.com
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
This commit is contained in:
Ian Rogers
2025-03-18 22:07:33 -07:00
committed by Namhyung Kim
parent 5c2938fe78
commit afffec6f03
3 changed files with 92 additions and 27 deletions
Download Patch File Download Diff File Expand all files Collapse all files
tools/perf/util/dso.c
+89
View File
@@ -1194,6 +1194,68 @@ ssize_t dso__data_read_offset(struct dso *dso, struct machine *machine,
return data_read_write_offset(dso, machine, offset, data, size, true);
}
uint16_t dso__e_machine(struct dso *dso, struct machine *machine)
{
uint16_t e_machine = EM_NONE;
int fd;
switch (dso__binary_type(dso)) {
case DSO_BINARY_TYPE__KALLSYMS:
case DSO_BINARY_TYPE__GUEST_KALLSYMS:
case DSO_BINARY_TYPE__VMLINUX:
case DSO_BINARY_TYPE__GUEST_VMLINUX:
case DSO_BINARY_TYPE__GUEST_KMODULE:
case DSO_BINARY_TYPE__GUEST_KMODULE_COMP:
case DSO_BINARY_TYPE__SYSTEM_PATH_KMODULE:
case DSO_BINARY_TYPE__SYSTEM_PATH_KMODULE_COMP:
case DSO_BINARY_TYPE__KCORE:
case DSO_BINARY_TYPE__GUEST_KCORE:
case DSO_BINARY_TYPE__BPF_PROG_INFO:
case DSO_BINARY_TYPE__BPF_IMAGE:
case DSO_BINARY_TYPE__OOL:
case DSO_BINARY_TYPE__JAVA_JIT:
return EM_HOST;
case DSO_BINARY_TYPE__DEBUGLINK:
case DSO_BINARY_TYPE__BUILD_ID_CACHE:
case DSO_BINARY_TYPE__BUILD_ID_CACHE_DEBUGINFO:
case DSO_BINARY_TYPE__GNU_DEBUGDATA:
case DSO_BINARY_TYPE__SYSTEM_PATH_DSO:
case DSO_BINARY_TYPE__OPENEMBEDDED_DEBUGINFO:
case DSO_BINARY_TYPE__FEDORA_DEBUGINFO:
case DSO_BINARY_TYPE__UBUNTU_DEBUGINFO:
case DSO_BINARY_TYPE__MIXEDUP_UBUNTU_DEBUGINFO:
case DSO_BINARY_TYPE__BUILDID_DEBUGINFO:
break;
case DSO_BINARY_TYPE__NOT_FOUND:
default:
return EM_NONE;
}
mutex_lock(dso__data_open_lock());
/*
* dso__data(dso)->fd might be closed if other thread opened another
* file (dso) due to open file limit (RLIMIT_NOFILE).
*/
try_to_open_dso(dso, machine);
fd = dso__data(dso)->fd;
if (fd >= 0) {
_Static_assert(offsetof(Elf32_Ehdr, e_machine) == 18, "Unexpected offset");
_Static_assert(offsetof(Elf64_Ehdr, e_machine) == 18, "Unexpected offset");
if (dso__needs_swap(dso) == DSO_SWAP__UNSET) {
unsigned char eidata;
if (pread(fd, &eidata, sizeof(eidata), EI_DATA) == sizeof(eidata))
dso__swap_init(dso, eidata);
}
if (dso__needs_swap(dso) != DSO_SWAP__UNSET &&
pread(fd, &e_machine, sizeof(e_machine), 18) == sizeof(e_machine))
e_machine = DSO__SWAP(dso, uint16_t, e_machine);
}
mutex_unlock(dso__data_open_lock());
return e_machine;
}
/**
* dso__data_read_addr - Read data from dso address
* @dso: dso object
@@ -1549,6 +1611,33 @@ void dso__put(struct dso *dso)
RC_CHK_PUT(dso);
}
int dso__swap_init(struct dso *dso, unsigned char eidata)
{
static unsigned int const endian = 1;
dso__set_needs_swap(dso, DSO_SWAP__NO);
switch (eidata) {
case ELFDATA2LSB:
/* We are big endian, DSO is little endian. */
if (*(unsigned char const *)&endian != 1)
dso__set_needs_swap(dso, DSO_SWAP__YES);
break;
case ELFDATA2MSB:
/* We are little endian, DSO is big endian. */
if (*(unsigned char const *)&endian != 0)
dso__set_needs_swap(dso, DSO_SWAP__YES);
break;
default:
pr_err("unrecognized DSO data encoding %d\n", eidata);
return -EINVAL;
}
return 0;
}
void dso__set_build_id(struct dso *dso, struct build_id *bid)
{
RC_CHK_ACCESS(dso)->bid = *bid;
tools/perf/util/dso.h
+3
View File
@@ -737,6 +737,8 @@ bool dso__sorted_by_name(const struct dso *dso);
void dso__set_sorted_by_name(struct dso *dso);
void dso__sort_by_name(struct dso *dso);
int dso__swap_init(struct dso *dso, unsigned char eidata);
void dso__set_build_id(struct dso *dso, struct build_id *bid);
bool dso__build_id_equal(const struct dso *dso, struct build_id *bid);
void dso__read_running_kernel_build_id(struct dso *dso,
@@ -826,6 +828,7 @@ int dso__data_file_size(struct dso *dso, struct machine *machine);
off_t dso__data_size(struct dso *dso, struct machine *machine);
ssize_t dso__data_read_offset(struct dso *dso, struct machine *machine,
u64 offset, u8 *data, ssize_t size);
uint16_t dso__e_machine(struct dso *dso, struct machine *machine);
ssize_t dso__data_read_addr(struct dso *dso, struct map *map,
struct machine *machine, u64 addr,
u8 *data, ssize_t size);
tools/perf/util/symbol-elf.c
-27
View File
@@ -1174,33 +1174,6 @@ out:
#endif
static int dso__swap_init(struct dso *dso, unsigned char eidata)
{
static unsigned int const endian = 1;
dso__set_needs_swap(dso, DSO_SWAP__NO);
switch (eidata) {
case ELFDATA2LSB:
/* We are big endian, DSO is little endian. */
if (*(unsigned char const *)&endian != 1)
dso__set_needs_swap(dso, DSO_SWAP__YES);
break;
case ELFDATA2MSB:
/* We are little endian, DSO is big endian. */
if (*(unsigned char const *)&endian != 0)
dso__set_needs_swap(dso, DSO_SWAP__YES);
break;
default:
pr_err("unrecognized DSO data encoding %d\n", eidata);
return -EINVAL;
}
return 0;
}
bool symsrc__possibly_runtime(struct symsrc *ss)
{
return ss->dynsym || ss->opdsec;