From: Giuliano Procida <gprocida@google.com>
To: dwarves@vger.kernel.org, acme@kernel.org
Cc: andrii@kernel.org, ast@kernel.org, gprocida@google.com,
maennich@google.com, kernel-team@android.com, kernel-team@fb.com,
bpf@vger.kernel.org
Subject: [PATCH dwarves v4 2/5] btf_encoder: Do not use both structs and pointers for the same data
Date: Wed, 17 Feb 2021 11:08:01 +0000 [thread overview]
Message-ID: <20210217110804.75923-3-gprocida@google.com> (raw)
In-Reply-To: <20210217110804.75923-1-gprocida@google.com>
Many operations in the libelf API return a pointer to a user-provided
struct (on success) or NULL (on failure).
There are a couple of places in btf_elf__write where both structs and
pointers to the same structs are used. Holding on to the pointers
raises ownership and lifetime issues unnecessarily and the code is
cleaner with only a single access path for these data.
The code now treats the returned pointers as booleans.
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Giuliano Procida <gprocida@google.com>
---
libbtf.c | 14 ++++++--------
1 file changed, 6 insertions(+), 8 deletions(-)
diff --git a/libbtf.c b/libbtf.c
index 7bc49ba..ace8896 100644
--- a/libbtf.c
+++ b/libbtf.c
@@ -698,8 +698,7 @@ int32_t btf_elf__add_datasec_type(struct btf_elf *btfe, const char *section_name
static int btf_elf__write(const char *filename, struct btf *btf)
{
- GElf_Shdr shdr_mem, *shdr;
- GElf_Ehdr ehdr_mem, *ehdr;
+ GElf_Ehdr ehdr;
Elf_Data *btf_data = NULL;
Elf_Scn *scn = NULL;
Elf *elf = NULL;
@@ -727,13 +726,12 @@ static int btf_elf__write(const char *filename, struct btf *btf)
elf_flagelf(elf, ELF_C_SET, ELF_F_DIRTY);
- ehdr = gelf_getehdr(elf, &ehdr_mem);
- if (ehdr == NULL) {
+ if (!gelf_getehdr(elf, &ehdr)) {
elf_error("elf_getehdr failed");
goto out;
}
- switch (ehdr_mem.e_ident[EI_DATA]) {
+ switch (ehdr.e_ident[EI_DATA]) {
case ELFDATA2LSB:
btf__set_endianness(btf, BTF_LITTLE_ENDIAN);
break;
@@ -751,10 +749,10 @@ static int btf_elf__write(const char *filename, struct btf *btf)
elf_getshdrstrndx(elf, &strndx);
while ((scn = elf_nextscn(elf, scn)) != NULL) {
- shdr = gelf_getshdr(scn, &shdr_mem);
- if (shdr == NULL)
+ GElf_Shdr shdr;
+ if (!gelf_getshdr(scn, &shdr))
continue;
- char *secname = elf_strptr(elf, strndx, shdr->sh_name);
+ char *secname = elf_strptr(elf, strndx, shdr.sh_name);
if (strcmp(secname, ".BTF") == 0) {
btf_data = elf_getdata(scn, btf_data);
break;
--
2.30.0.478.g8a0d178c01-goog
next prev parent reply other threads:[~2021-02-17 11:10 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <87a83353155506cc02141e6e4108d89aa4e7d284>
2021-02-01 17:25 ` [PATCH dwarves v2 0/4] BTF ELF writing changes Giuliano Procida
2021-02-01 17:25 ` [PATCH dwarves v2 1/4] btf_encoder: Add .BTF section using libelf Giuliano Procida
2021-02-04 4:10 ` Andrii Nakryiko
2021-02-04 18:29 ` Giuliano Procida
2021-02-01 17:25 ` [PATCH dwarves v2 2/4] btf_encoder: Manually lay out updated ELF sections Giuliano Procida
2021-02-04 4:13 ` Andrii Nakryiko
2021-02-04 18:34 ` Giuliano Procida
2021-02-04 23:06 ` Andrii Nakryiko
2021-02-01 17:25 ` [PATCH dwarves v2 3/4] btf_encoder: Add .BTF as a loadable segment Giuliano Procida
2021-02-02 10:54 ` Giuliano Procida
2021-02-01 17:25 ` [PATCH dwarves v2 4/4] btf_encoder: Align .BTF section/segment to 8 bytes Giuliano Procida
2021-02-04 4:10 ` Andrii Nakryiko
2021-02-04 15:11 ` Giuliano Procida
2021-02-04 15:11 ` [PATCH] btf_encoder: Align .BTF section " Giuliano Procida
2021-02-05 13:42 ` [PATCH dwarves v3 0/5] ELF writing changes Giuliano Procida
2021-02-05 13:42 ` [PATCH dwarves v3 1/5] btf_encoder: Funnel ELF error reporting through a macro Giuliano Procida
2021-02-08 22:20 ` Andrii Nakryiko
2021-02-05 13:42 ` [PATCH dwarves v3 2/5] btf_encoder: Do not use both structs and pointers for the same data Giuliano Procida
2021-02-08 22:23 ` Andrii Nakryiko
2021-02-09 14:52 ` Giuliano Procida
2021-02-05 13:42 ` [PATCH dwarves v3 3/5] btf_encoder: Traverse sections using a for-loop Giuliano Procida
2021-02-08 22:24 ` Andrii Nakryiko
2021-02-09 14:59 ` Giuliano Procida
2021-02-05 13:42 ` [PATCH dwarves v3 4/5] btf_encoder: Add .BTF section using libelf Giuliano Procida
2021-02-08 22:29 ` Andrii Nakryiko
2021-02-09 15:04 ` Giuliano Procida
2021-02-05 13:42 ` [PATCH dwarves v3 5/5] btf_encoder: Align .BTF section to 8 bytes Giuliano Procida
2021-02-08 22:29 ` Andrii Nakryiko
2021-02-09 15:05 ` Giuliano Procida
2021-02-17 11:07 ` [PATCH dwarves v4 0/5] ELF writing changes Giuliano Procida
2021-02-17 11:08 ` [PATCH dwarves v4 1/5] btf_encoder: Funnel ELF error reporting through a macro Giuliano Procida
2021-02-17 11:08 ` Giuliano Procida [this message]
2021-02-17 11:08 ` [PATCH dwarves v4 3/5] btf_encoder: Traverse sections using a for-loop Giuliano Procida
2021-02-17 11:08 ` [PATCH dwarves v4 4/5] btf_encoder: Add .BTF section using libelf Giuliano Procida
2021-02-17 11:08 ` [PATCH dwarves v4 5/5] btf_encoder: Align .BTF section to 8 bytes Giuliano Procida
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