compel: add error constants

For tests, we need to know if elf file parsing was interrupted
in a proper place (and thus meaningful error numbers).

Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
Reviewed-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

compel/arch/aarch64/handle-elf.c

 #include <string.h>
 
 #include "piegen.h"
+#include "uapi/piegen-err.h"
 #include "handle-elf.h"
 
 int handle_binary(void *mem, size_t size)
@@ -16,5 +17,5 @@ int handle_binary(void *mem, size_t size)
 		return handle_elf_aarch64(mem, size);
 
 	pr_err("Unsupported Elf format detected\n");
-	return -1;
+	return -E_NOT_ELF;
 }

compel/arch/arm/handle-elf.c

 #include <string.h>
 
 #include "piegen.h"
+#include "uapi/piegen-err.h"
 #include "handle-elf.h"
 
 int handle_binary(void *mem, size_t size)
@@ -9,5 +10,5 @@ int handle_binary(void *mem, size_t size)
 		return handle_elf_arm(mem, size);
 
 	pr_err("Unsupported Elf format detected\n");
-	return -1;
+	return -E_NOT_ELF;
 }

compel/arch/ppc64/handle-elf.c

 #include <string.h>
 
 #include "piegen.h"
+#include "uapi/piegen-err.h"
 #include "handle-elf.h"
 
 int handle_binary(void *mem, size_t size)
@@ -16,5 +17,5 @@ int handle_binary(void *mem, size_t size)
 		return handle_elf_ppc64(mem, size);
 
 	pr_err("Unsupported Elf format detected\n");
-	return -1;
+	return -E_NOT_ELF;
 }

compel/arch/x86/handle-elf.c

 #include <string.h>
 
 #include "piegen.h"
+#include "uapi/piegen-err.h"
 #include "handle-elf.h"
 
 int handle_binary(void *mem, size_t size)
@@ -11,5 +12,5 @@ int handle_binary(void *mem, size_t size)
 		return handle_elf_x86_64(mem, size);
 
 	pr_err("Unsupported Elf format detected\n");
-	return -1;
+	return -E_NOT_ELF;
 }

compel/handle-elf.c

@@ -13,6 +13,7 @@
 
 #include "asm-generic/int.h"
 
+#include "uapi/piegen-err.h"
 #include "piegen.h"
 #include "handle-elf.h"
 
@@ -142,6 +143,7 @@ int __handle_elf(void *mem, size_t size)
 #ifdef ELF_PPC64
 	s64 toc_offset = 0;
 #endif
+	int ret = -E_UNKNOWN;
 
 	pr_debug("Header\n");
 	pr_debug("------------\n");
@@ -150,18 +152,22 @@ int __handle_elf(void *mem, size_t size)
 
 	if (!is_header_supported(hdr)) {
 		pr_err("Unsupported header detected\n");
+		ret = -E_NOT_ELF;
 		goto err;
 	}
 
 	sec_hdrs = malloc(sizeof(*sec_hdrs) * hdr->e_shnum);
 	if (!sec_hdrs) {
 		pr_err("No memory for section headers\n");
+		ret = -E_NOMEM;
 		goto err;
 	}
 
 	secstrings = get_strings_section(hdr, (uintptr_t)mem, size);
-	if (!secstrings)
+	if (!secstrings) {
+		ret = -E_NO_STR_SEC;
 		goto err;
+	}
 
 	pr_debug("Sections\n");
 	pr_debug("------------\n");
@@ -563,5 +569,5 @@ int __handle_elf(void *mem, size_t size)
 	return 0;
 err:
 	free(sec_hdrs);
-	return -1;
+	return ret;
 }

compel/include/uapi/piegen-err.h

+#ifndef __PIEGEN_ERR_H__
+#define __PIEGEN_ERR_H__
+
+/* Error numbers for piegen. Success is 0, so errors should differ. */
+#define E_UNKNOWN	1
+#define E_NOMEM		2
+#define E_NOT_ELF	3
+#define E_NO_STR_SEC	4
+
+#endif /* __PIEGEN_ERR_H__ */