From: Giuliano Procida <gprocida@google.com>
To: dwarves@vger.kernel.org
Cc: acme@kernel.org, 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 v2 3/4] btf_encoder: Add .BTF as a loadable segment
Date: Mon, 1 Feb 2021 17:25:29 +0000 [thread overview]
Message-ID: <20210201172530.1141087-4-gprocida@google.com> (raw)
In-Reply-To: <20210201172530.1141087-1-gprocida@google.com>
In addition to adding .BTF to the Section Header Table, we also need
to add it to the Program Header Table and rewrite the PHT's
description of itself.
The segment as loadbale, at address 0 and read-only.
Signed-off-by: Giuliano Procida <gprocida@google.com>
---
libbtf.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 44 insertions(+)
diff --git a/libbtf.c b/libbtf.c
index 6e06a58..048a873 100644
--- a/libbtf.c
+++ b/libbtf.c
@@ -699,6 +699,7 @@ static int btf_elf__write(const char *filename, struct btf *btf)
int fd, err = -1;
size_t strndx;
void *str_table = NULL;
+ GElf_Phdr *pht = NULL;
fd = open(filename, O_RDWR);
if (fd < 0) {
@@ -900,6 +901,47 @@ static int btf_elf__write(const char *filename, struct btf *btf)
goto out;
}
+ size_t phnum = 0;
+ if (!elf_getphdrnum(elf, &phnum)) {
+ pht = malloc((phnum + 1) * sizeof(GElf_Phdr));
+ if (!pht) {
+ fprintf(stderr, "%s: malloc (PHT) failed\n", __func__);
+ goto out;
+ }
+ for (size_t ix = 0; ix < phnum; ++ix) {
+ if (!gelf_getphdr(elf, ix, &pht[ix])) {
+ fprintf(stderr,
+ "%s: gelf_getphdr(%zu) failed: %s\n",
+ __func__, ix, elf_errmsg(elf_errno()));
+ goto out;
+ }
+ if (pht[ix].p_type == PT_PHDR) {
+ size_t fsize = gelf_fsize(elf, ELF_T_PHDR,
+ phnum+1, EV_CURRENT);
+ pht[ix].p_memsz = pht[ix].p_filesz = fsize;
+ }
+ }
+ pht[phnum].p_type = PT_LOAD;
+ pht[phnum].p_offset = btf_shdr->sh_offset;
+ pht[phnum].p_memsz = pht[phnum].p_filesz = btf_shdr->sh_size;
+ pht[phnum].p_vaddr = pht[phnum].p_paddr = 0;
+ pht[phnum].p_flags = PF_R;
+ void *phdr = gelf_newphdr(elf, phnum+1);
+ if (!phdr) {
+ fprintf(stderr, "%s: gelf_newphdr failed: %s\n",
+ __func__, elf_errmsg(elf_errno()));
+ goto out;
+ }
+ for (size_t ix = 0; ix < phnum+1; ++ix) {
+ if (!gelf_update_phdr(elf, ix, &pht[ix])) {
+ fprintf(stderr,
+ "%s: gelf_update_phdr(%zu) failed: %s\n",
+ __func__, ix, elf_errmsg(elf_errno()));
+ goto out;
+ }
+ }
+ }
+
if (elf_update(elf, ELF_C_WRITE) < 0) {
fprintf(stderr, "%s: elf_update (write) failed: %s\n",
__func__, elf_errmsg(elf_errno()));
@@ -908,6 +950,8 @@ static int btf_elf__write(const char *filename, struct btf *btf)
err = 0;
out:
+ if (pht)
+ free(pht);
if (str_table)
free(str_table);
if (fd != -1)
--
2.30.0.365.g02bc693789-goog
next prev parent reply other threads:[~2021-02-01 17:27 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 ` Giuliano Procida [this message]
2021-02-02 10:54 ` [PATCH dwarves v2 3/4] btf_encoder: Add .BTF as a loadable segment 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 ` [PATCH dwarves v4 2/5] btf_encoder: Do not use both structs and pointers for the same data Giuliano Procida
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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