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From: Andrii Nakryiko <andrii@kernel.org>
To: <dwarves@vger.kernel.org>
Cc: <bpf@vger.kernel.org>, <kernel-team@fb.com>, <ast@kernel.org>,
	Andrii Nakryiko <andrii@kernel.org>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Andrii Nakryiko <andriin@fb.com>
Subject: [PATCH v2 dwarves 8/8] btf_encoder: support cross-compiled ELF binaries with different endianness
Date: Thu, 8 Oct 2020 16:40:00 -0700
Message-ID: <20201008234000.740660-9-andrii@kernel.org> (raw)
In-Reply-To: <20201008234000.740660-1-andrii@kernel.org>

From: Andrii Nakryiko <andriin@fb.com>

Ensure that output BTF endianness corresponds to target ELF's endianness. This
makes it finally possible to use pahole to generate BTF for cross-compiled
kernels with different endianness.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
---
 libbtf.c | 24 ++++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

diff --git a/libbtf.c b/libbtf.c
index 27aa3e5a986e..babf4fe8cd9e 100644
--- a/libbtf.c
+++ b/libbtf.c
@@ -87,6 +87,8 @@ struct btf_elf *btf_elf__new(const char *filename, Elf *elf)
 		btfe->raw_btf  = true;
 		btfe->wordsize = sizeof(long);
 		btfe->is_big_endian = BYTE_ORDER == BIG_ENDIAN;
+		btf__set_endianness(btfe->btf,
+				    btfe->is_big_endian ? BTF_BIG_ENDIAN : BTF_LITTLE_ENDIAN);
 		return btfe;
 	}
 
@@ -118,8 +120,14 @@ struct btf_elf *btf_elf__new(const char *filename, Elf *elf)
 	}
 
 	switch (btfe->ehdr.e_ident[EI_DATA]) {
-	case ELFDATA2LSB: btfe->is_big_endian = false; break;
-	case ELFDATA2MSB: btfe->is_big_endian = true;  break;
+	case ELFDATA2LSB:
+		btfe->is_big_endian = false;
+		btf__set_endianness(btfe->btf, BTF_LITTLE_ENDIAN);
+		break;
+	case ELFDATA2MSB:
+		btfe->is_big_endian = true;
+		btf__set_endianness(btfe->btf, BTF_BIG_ENDIAN);
+		break;
 	default:
 		fprintf(stderr, "%s: unknown elf endianness.\n", __func__);
 		goto errout;
@@ -704,6 +712,18 @@ static int btf_elf__write(const char *filename, struct btf *btf)
 		goto out;
 	}
 
+	switch (ehdr_mem.e_ident[EI_DATA]) {
+	case ELFDATA2LSB:
+		btf__set_endianness(btf, BTF_LITTLE_ENDIAN);
+		break;
+	case ELFDATA2MSB:
+		btf__set_endianness(btf, BTF_BIG_ENDIAN);
+		break;
+	default:
+		fprintf(stderr, "%s: unknown elf endianness.\n", __func__);
+		goto out;
+	}
+
 	/*
 	 * First we look if there was already a .BTF section to overwrite.
 	 */
-- 
2.24.1


  parent reply index

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-08 23:39 [PATCH v2 dwarves 0/8] Switch BTF loading and encoding to libbpf APIs Andrii Nakryiko
2020-10-08 23:39 ` [PATCH v2 dwarves 1/8] btf_loader: use libbpf to load BTF Andrii Nakryiko
2020-10-09 14:53   ` Arnaldo Carvalho de Melo
2020-10-09 17:49     ` Andrii Nakryiko
2020-10-08 23:39 ` [PATCH v2 dwarves 2/8] btf_encoder: use libbpf APIs to encode BTF type info Andrii Nakryiko
2020-10-08 23:39 ` [PATCH v2 dwarves 3/8] btf_encoder: fix emitting __ARRAY_SIZE_TYPE__ as index range type Andrii Nakryiko
2020-10-08 23:39 ` [PATCH v2 dwarves 4/8] btf_encoder: discard CUs after BTF encoding Andrii Nakryiko
2020-10-09 15:47   ` Arnaldo Carvalho de Melo
2020-10-08 23:39 ` [PATCH v2 dwarves 5/8] btf_encoder: revamp how per-CPU variables are encoded Andrii Nakryiko
2020-10-09 15:53   ` Arnaldo Carvalho de Melo
2020-10-08 23:39 ` [PATCH v2 dwarves 6/8] dwarf_loader: increase the size of lookup hash map Andrii Nakryiko
2020-10-08 23:39 ` [PATCH v2 dwarves 7/8] strings: use BTF's string APIs for strings management Andrii Nakryiko
2020-10-08 23:40 ` Andrii Nakryiko [this message]
2020-10-09 16:22 ` [PATCH v2 dwarves 0/8] Switch BTF loading and encoding to libbpf APIs Arnaldo Carvalho de Melo
2020-10-09 17:59   ` Andrii Nakryiko

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