linux-kernel - [PATCHv6 09/13] kexec_file: Factor out routine to find a symbol in ELF

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Message-ID: <20260119032424.10781-10-piliu@redhat.com>
Date: Mon, 19 Jan 2026 11:24:20 +0800
From: Pingfan Liu <piliu@...hat.com>
To: kexec@...ts.infradead.org
Cc: Pingfan Liu <piliu@...hat.com>,
	"David S. Miller" <davem@...emloft.net>,
	Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	John Fastabend <john.fastabend@...il.com>,
	Andrii Nakryiko <andrii@...nel.org>,
	Martin KaFai Lau <martin.lau@...ux.dev>,
	Eduard Zingerman <eddyz87@...il.com>,
	Song Liu <song@...nel.org>,
	Yonghong Song <yonghong.song@...ux.dev>,
	Jeremy Linton <jeremy.linton@....com>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>,
	Ard Biesheuvel <ardb@...nel.org>,
	Simon Horman <horms@...nel.org>,
	Gerd Hoffmann <kraxel@...hat.com>,
	Vitaly Kuznetsov <vkuznets@...hat.com>,
	Philipp Rudo <prudo@...hat.com>,
	Viktor Malik <vmalik@...hat.com>,
	Jan Hendrik Farr <kernel@...rr.cc>,
	Baoquan He <bhe@...hat.com>,
	Dave Young <dyoung@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	bpf@...r.kernel.org,
	systemd-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org
Subject: [PATCHv6 09/13] kexec_file: Factor out routine to find a symbol in ELF

The routine to search a symbol in ELF can be shared, so split it out.

Signed-off-by: Pingfan Liu <piliu@...hat.com>
Cc: Baoquan He <bhe@...hat.com>
Cc: Dave Young <dyoung@...hat.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Philipp Rudo <prudo@...hat.com>
To: kexec@...ts.infradead.org
---
 kernel/kexec_file.c     | 86 ++++++++++++++++++++++-------------------
 kernel/kexec_internal.h |  1 +
 2 files changed, 47 insertions(+), 40 deletions(-)

diff --git a/kernel/kexec_file.c b/kernel/kexec_file.c
index f9674bb5bd8db..9731019ba2a1a 100644
--- a/kernel/kexec_file.c
+++ b/kernel/kexec_file.c
@@ -889,6 +889,51 @@ static int kexec_calculate_store_digests(struct kimage *image)
 	return ret;
 }
 
+#if defined(CONFIG_ARCH_SUPPORTS_KEXEC_PURGATORY) || defined(CONFIG_KEXEC_BPF)
+const Elf_Sym *elf_find_symbol(const Elf_Ehdr *ehdr, const char *name)
+{
+	const Elf_Shdr *sechdrs;
+	const Elf_Sym *syms;
+	const char *strtab;
+	int i, k;
+
+	sechdrs = (void *)ehdr + ehdr->e_shoff;
+
+	for (i = 0; i < ehdr->e_shnum; i++) {
+		if (sechdrs[i].sh_type != SHT_SYMTAB)
+			continue;
+
+		if (sechdrs[i].sh_link >= ehdr->e_shnum)
+			/* Invalid strtab section number */
+			continue;
+		strtab = (void *)ehdr + sechdrs[sechdrs[i].sh_link].sh_offset;
+		syms = (void *)ehdr + sechdrs[i].sh_offset;
+
+		/* Go through symbols for a match */
+		for (k = 0; k < sechdrs[i].sh_size/sizeof(Elf_Sym); k++) {
+			if (ELF_ST_BIND(syms[k].st_info) != STB_GLOBAL)
+				continue;
+
+			if (strcmp(strtab + syms[k].st_name, name) != 0)
+				continue;
+
+			if (syms[k].st_shndx == SHN_UNDEF ||
+			    syms[k].st_shndx >= ehdr->e_shnum) {
+				pr_debug("Symbol: %s has bad section index %d.\n",
+						name, syms[k].st_shndx);
+				return NULL;
+			}
+
+			/* Found the symbol we are looking for */
+			return &syms[k];
+		}
+	}
+
+	return NULL;
+}
+
+#endif
+
 #ifdef CONFIG_ARCH_SUPPORTS_KEXEC_PURGATORY
 /*
  * kexec_purgatory_setup_kbuf - prepare buffer to load purgatory.
@@ -1146,49 +1191,10 @@ int kexec_load_purgatory(struct kimage *image, struct kexec_buf *kbuf)
 static const Elf_Sym *kexec_purgatory_find_symbol(struct purgatory_info *pi,
 						  const char *name)
 {
-	const Elf_Shdr *sechdrs;
-	const Elf_Ehdr *ehdr;
-	const Elf_Sym *syms;
-	const char *strtab;
-	int i, k;
-
 	if (!pi->ehdr)
 		return NULL;
 
-	ehdr = pi->ehdr;
-	sechdrs = (void *)ehdr + ehdr->e_shoff;
-
-	for (i = 0; i < ehdr->e_shnum; i++) {
-		if (sechdrs[i].sh_type != SHT_SYMTAB)
-			continue;
-
-		if (sechdrs[i].sh_link >= ehdr->e_shnum)
-			/* Invalid strtab section number */
-			continue;
-		strtab = (void *)ehdr + sechdrs[sechdrs[i].sh_link].sh_offset;
-		syms = (void *)ehdr + sechdrs[i].sh_offset;
-
-		/* Go through symbols for a match */
-		for (k = 0; k < sechdrs[i].sh_size/sizeof(Elf_Sym); k++) {
-			if (ELF_ST_BIND(syms[k].st_info) != STB_GLOBAL)
-				continue;
-
-			if (strcmp(strtab + syms[k].st_name, name) != 0)
-				continue;
-
-			if (syms[k].st_shndx == SHN_UNDEF ||
-			    syms[k].st_shndx >= ehdr->e_shnum) {
-				pr_debug("Symbol: %s has bad section index %d.\n",
-						name, syms[k].st_shndx);
-				return NULL;
-			}
-
-			/* Found the symbol we are looking for */
-			return &syms[k];
-		}
-	}
-
-	return NULL;
+	return elf_find_symbol(pi->ehdr, name);
 }
 
 void *kexec_purgatory_get_symbol_addr(struct kimage *image, const char *name)
diff --git a/kernel/kexec_internal.h b/kernel/kexec_internal.h
index ee01d0c8bb377..2e8e0fedbe2a9 100644
--- a/kernel/kexec_internal.h
+++ b/kernel/kexec_internal.h
@@ -40,6 +40,7 @@ extern bool pe_has_bpf_section(const char *file_buf, unsigned long pe_sz);
 extern int pe_get_section(const char *file_buf, const char *sect_name,
 		char **sect_start, unsigned long *sect_sz);
 extern int decompose_kexec_image(struct kimage *image, int extended_fd);
+extern const Elf_Sym *elf_find_symbol(const Elf_Ehdr *ehdr, const char *name);
 #else /* CONFIG_KEXEC_FILE */
 static inline void kimage_file_post_load_cleanup(struct kimage *image) { }
 #endif /* CONFIG_KEXEC_FILE */
-- 
2.49.0