From 776e5d41d7a8e9da2bab67d6e9f10c34fc11a6a9 Mon Sep 17 00:00:00 2001
From: Marc Hartmayer <mhartmay@linux.ibm.com>
Date: Wed, 17 Nov 2021 15:01:06 +0100
Subject: [PATCH] zdump: dfi_elf: factor out some ELF functionalities
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This makes them reuseable and testable.

Signed-off-by: Marc Hartmayer <mhartmay@linux.ibm.com>
Reviewed-by: Steffen Eiden <seiden@linux.ibm.com>
Reviewed-by: Alexander Egorenkov <egorenar@linux.ibm.com>
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>
---
 zdump/df_elf.c  | 16 ++++++++++++++++
 zdump/df_elf.h  | 16 ++++++++++++++++
 zdump/dfi_elf.c |  7 +++----
 3 files changed, 35 insertions(+), 4 deletions(-)

diff --git a/zdump/df_elf.c b/zdump/df_elf.c
index 013385d7..69965979 100644
--- a/zdump/df_elf.c
+++ b/zdump/df_elf.c
@@ -34,6 +34,22 @@ void *ehdr_init(Elf64_Ehdr *ehdr, Elf64_Half phnum)
 	return ehdr + 1;
 }
 
+bool ehdr_is_elf_object(const Elf64_Ehdr *ehdr)
+{
+	return (memcmp(ehdr->e_ident, ELFMAG, SELFMAG) == 0);
+}
+
+bool ehdr_is_vmcore(const Elf64_Ehdr *ehdr)
+{
+	return ehdr->e_type == ET_CORE;
+}
+
+bool ehdr_is_s390x(const Elf64_Ehdr *ehdr)
+{
+	return ehdr->e_machine == EM_S390 &&
+	       ehdr->e_ident[EI_CLASS] == ELFCLASS64;
+}
+
 void *nt_init(void *buf, Elf64_Word type, const void *desc, int d_len,
 	      const char *name)
 {
diff --git a/zdump/df_elf.h b/zdump/df_elf.h
index 7b5cfc75..6862fc32 100644
--- a/zdump/df_elf.h
+++ b/zdump/df_elf.h
@@ -14,6 +14,7 @@
 
 #include <elf.h>
 #include <linux/types.h>
+#include <stdbool.h>
 
 #include "lib/zt_common.h"
 
@@ -127,6 +128,21 @@ static inline void df_elf_ensure_s390x(void)
  */
 void *ehdr_init(Elf64_Ehdr *ehdr, Elf64_Half phnum);
 
+/*
+ * Checks whether @ehdr is a ELF object
+ */
+bool ehdr_is_elf_object(const Elf64_Ehdr *ehdr);
+
+/*
+ * Checks whether @ehdr is a vmcore
+ */
+bool ehdr_is_vmcore(const Elf64_Ehdr *ehdr);
+
+/*
+ * Checks whether @ehdr is a s390x header
+ */
+bool ehdr_is_s390x(const Elf64_Ehdr *ehdr);
+
 /*
  * Initialize ELF note
  */
diff --git a/zdump/dfi_elf.c b/zdump/dfi_elf.c
index 63d531fb..0067984d 100644
--- a/zdump/dfi_elf.c
+++ b/zdump/dfi_elf.c
@@ -289,11 +289,10 @@ static int read_elf_hdr(Elf64_Ehdr *ehdr)
 	if (zg_size(g.fh) < sizeof(*ehdr))
 		return -ENODEV;
 	zg_read(g.fh, ehdr, sizeof(*ehdr), ZG_CHECK);
-	if (memcmp(ehdr->e_ident, ELFMAG, SELFMAG) != 0)
+
+	if (!ehdr_is_elf_object(ehdr) || !ehdr_is_vmcore(ehdr))
 		return -ENODEV;
-	if (ehdr->e_type != ET_CORE)
-		return -ENODEV;
-	if (ehdr->e_machine != EM_S390 || ehdr->e_ident[EI_CLASS] != ELFCLASS64)
+	if (!ehdr_is_s390x(ehdr))
 		ERR_EXIT("Only s390x (64 bit) core dump files are supported");
 	return 0;
 }