From: Eduard Zingerman <eddyz87@xxxxxxxxx>
Update btf_parse_elf() to check if .BTF.base section is present.
The logic is as follows:
if .BTF.base section exists:
distilled_base := btf_new(.BTF.base)
if distilled_base:
btf := btf_new(.BTF, .base_btf=distilled_base)
if base_btf:
btf_relocate(btf, base_btf)
else:
btf := btf_new(.BTF)
return btf
In other words:
- if .BTF.base section exists, load BTF from it and use it as a base
for .BTF load;
- if base_btf is specified and .BTF.base section exist, relocate newly
loaded .BTF against base_btf.
Signed-off-by: Eduard Zingerman <eddyz87@xxxxxxxxx>
Signed-off-by: Alan Maguire <alan.maguire@xxxxxxxxxx>
---
tools/lib/bpf/btf.c | 164 +++++++++++++++++++++++++++++---------------
tools/lib/bpf/btf.h | 1 +
2 files changed, 111 insertions(+), 54 deletions(-)
diff --git a/tools/lib/bpf/btf.c b/tools/lib/bpf/btf.c
index 5e20354fbcfa..ef1b2f573c1b 100644
--- a/tools/lib/bpf/btf.c
+++ b/tools/lib/bpf/btf.c
@@ -116,6 +116,9 @@ struct btf {
/* whether strings are already deduplicated */
bool strs_deduped;
+ /* whether base_btf should be freed in btf_free for this instance */
+ bool owns_base;
+
/* BTF object FD, if loaded into kernel */
int fd;
@@ -969,6 +972,8 @@ void btf__free(struct btf *btf)
free(btf->raw_data);
free(btf->raw_data_swapped);
free(btf->type_offs);
+ if (btf->owns_base)
+ btf__free(btf->base_btf);
free(btf);
}
@@ -1084,53 +1089,38 @@ struct btf *btf__new_split(const void *data, __u32 size, struct btf *base_btf)
return libbpf_ptr(btf_new(data, size, base_btf));
}
-static struct btf *btf_parse_elf(const char *path, struct btf *base_btf,
- struct btf_ext **btf_ext)
+struct btf_elf_secs {
+ Elf_Data *btf_data;
+ Elf_Data *btf_ext_data;
+ Elf_Data *btf_base_data;
+};
+
+static int btf_find_elf_sections(Elf *elf, const char *path, struct btf_elf_secs *secs)
{
- Elf_Data *btf_data = NULL, *btf_ext_data = NULL;
- int err = 0, fd = -1, idx = 0;
- struct btf *btf = NULL;
Elf_Scn *scn = NULL;
- Elf *elf = NULL;
+ Elf_Data *data;
GElf_Ehdr ehdr;
size_t shstrndx;
+ int idx = 0;
- if (elf_version(EV_CURRENT) == EV_NONE) {
- pr_warn("failed to init libelf for %s\n", path);
- return ERR_PTR(-LIBBPF_ERRNO__LIBELF);
- }
-
- fd = open(path, O_RDONLY | O_CLOEXEC);
- if (fd < 0) {
- err = -errno;
- pr_warn("failed to open %s: %s\n", path, strerror(errno));
- return ERR_PTR(err);
- }
-
- err = -LIBBPF_ERRNO__FORMAT;
-
- elf = elf_begin(fd, ELF_C_READ, NULL);
- if (!elf) {
- pr_warn("failed to open %s as ELF file\n", path);
- goto done;
- }
if (!gelf_getehdr(elf, &ehdr)) {
pr_warn("failed to get EHDR from %s\n", path);
- goto done;
+ goto err;
}
if (elf_getshdrstrndx(elf, &shstrndx)) {
pr_warn("failed to get section names section index for %s\n",
path);
- goto done;
+ goto err;
}
if (!elf_rawdata(elf_getscn(elf, shstrndx), NULL)) {
pr_warn("failed to get e_shstrndx from %s\n", path);
- goto done;
+ goto err;
}
while ((scn = elf_nextscn(elf, scn)) != NULL) {
+ Elf_Data **field;
GElf_Shdr sh;
char *name;
@@ -1138,42 +1128,102 @@ static struct btf *btf_parse_elf(const char *path, struct btf *base_btf,
if (gelf_getshdr(scn, &sh) != &sh) {
pr_warn("failed to get section(%d) header from %s\n",
idx, path);
- goto done;
+ goto err;
}
name = elf_strptr(elf, shstrndx, sh.sh_name);
if (!name) {
pr_warn("failed to get section(%d) name from %s\n",
idx, path);
- goto done;
+ goto err;
}
- if (strcmp(name, BTF_ELF_SEC) == 0) {
- btf_data = elf_getdata(scn, 0);
- if (!btf_data) {
- pr_warn("failed to get section(%d, %s) data from %s\n",
- idx, name, path);
- goto done;
- }
- continue;
- } else if (btf_ext && strcmp(name, BTF_EXT_ELF_SEC) == 0) {
- btf_ext_data = elf_getdata(scn, 0);
- if (!btf_ext_data) {
- pr_warn("failed to get section(%d, %s) data from %s\n",
- idx, name, path);
- goto done;
- }
+
+ if (strcmp(name, BTF_ELF_SEC) == 0)
+ field = &secs->btf_data;
+ else if (strcmp(name, BTF_EXT_ELF_SEC) == 0)
+ field = &secs->btf_ext_data;
+ else if (strcmp(name, BTF_BASE_ELF_SEC) == 0)
+ field = &secs->btf_base_data;
+ else
continue;
+
+ data = elf_getdata(scn, 0);
+ if (!data) {
+ pr_warn("failed to get section(%d, %s) data from %s\n",
+ idx, name, path);
+ goto err;
}
+ *field = data;
+ }
+
+ return 0;
+
+err:
+ return -LIBBPF_ERRNO__FORMAT;
+}
+
+static struct btf *btf_parse_elf(const char *path, struct btf *base_btf,
+ struct btf_ext **btf_ext)
+{
+ struct btf_elf_secs secs = {};
+ struct btf *dist_base_btf = NULL;
+ struct btf *btf = NULL;
+ int err = 0, fd = -1;
+ Elf *elf = NULL;
+
+ if (elf_version(EV_CURRENT) == EV_NONE) {
+ pr_warn("failed to init libelf for %s\n", path);
+ return ERR_PTR(-LIBBPF_ERRNO__LIBELF);
+ }
+
+ fd = open(path, O_RDONLY | O_CLOEXEC);
+ if (fd < 0) {
+ err = -errno;
+ pr_warn("failed to open %s: %s\n", path, strerror(errno));
+ return ERR_PTR(err);
}
- if (!btf_data) {
+ elf = elf_begin(fd, ELF_C_READ, NULL);
+ if (!elf) {
+ pr_warn("failed to open %s as ELF file\n", path);
+ goto done;
+ }
+
+ err = btf_find_elf_sections(elf, path, &secs);
+ if (err)
+ goto done;
+
+ if (!secs.btf_data) {
pr_warn("failed to find '%s' ELF section in %s\n", BTF_ELF_SEC, path);
err = -ENODATA;
goto done;
}
- btf = btf_new(btf_data->d_buf, btf_data->d_size, base_btf);
- err = libbpf_get_error(btf);
- if (err)
+
+ if (secs.btf_base_data) {
+ dist_base_btf = btf_new(secs.btf_base_data->d_buf, secs.btf_base_data->d_size,
+ NULL);
+ if (IS_ERR(dist_base_btf)) {
+ err = PTR_ERR(dist_base_btf);
+ dist_base_btf = NULL;
+ goto done;
+ }
+ }
+
+ btf = btf_new(secs.btf_data->d_buf, secs.btf_data->d_size,
+ dist_base_btf ?: base_btf);
+ if (IS_ERR(btf)) {
+ err = PTR_ERR(btf);
goto done;
+ }
+ if (dist_base_btf && base_btf) {
+ err = btf__relocate(btf, base_btf);
+ if (err)
+ goto done;
+ btf__free(dist_base_btf);
+ dist_base_btf = NULL;
+ }
+
+ if (dist_base_btf)
+ btf->owns_base = true;
switch (gelf_getclass(elf)) {
case ELFCLASS32:
@@ -1187,11 +1237,12 @@ static struct btf *btf_parse_elf(const char *path, struct btf *base_btf,
break;
}
- if (btf_ext && btf_ext_data) {
- *btf_ext = btf_ext__new(btf_ext_data->d_buf, btf_ext_data->d_size);
- err = libbpf_get_error(*btf_ext);
- if (err)
+ if (btf_ext && secs.btf_ext_data) {
+ *btf_ext = btf_ext__new(secs.btf_ext_data->d_buf, secs.btf_ext_data->d_size);
+ if (IS_ERR(*btf_ext)) {
+ err = PTR_ERR(*btf_ext);
goto done;
+ }
} else if (btf_ext) {
*btf_ext = NULL;
}
@@ -1205,6 +1256,7 @@ static struct btf *btf_parse_elf(const char *path, struct btf *base_btf,
if (btf_ext)
btf_ext__free(*btf_ext);
+ btf__free(dist_base_btf);
btf__free(btf);
return ERR_PTR(err);
@@ -5598,5 +5650,9 @@ void btf_set_base_btf(struct btf *btf, const struct btf *base_btf)
int btf__relocate(struct btf *btf, const struct btf *base_btf)
{
- return libbpf_err(btf_relocate(btf, base_btf, NULL));
+ int err = btf_relocate(btf, base_btf, NULL);
+
+ if (!err)
+ btf->owns_base = false;
+ return libbpf_err(err);
}
diff --git a/tools/lib/bpf/btf.h b/tools/lib/bpf/btf.h
index 8a93120b7385..b68d216837a9 100644
--- a/tools/lib/bpf/btf.h
+++ b/tools/lib/bpf/btf.h
@@ -18,6 +18,7 @@ extern "C" {
#define BTF_ELF_SEC ".BTF"
#define BTF_EXT_ELF_SEC ".BTF.ext"
+#define BTF_BASE_ELF_SEC ".BTF.base"
#define MAPS_ELF_SEC ".maps"
struct btf;
--
2.31.1
