linux-kernel - Re: [PATCH 3/4] selftests/arm: Add elf test

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Message-ID: <15a24a03-6e83-4a25-803a-5c5efcd393fd@arm.com>
Date: Wed, 10 Apr 2024 09:41:00 +0530
From: Dev Jain <dev.jain@....com>
To: Muhammad Usama Anjum <usama.anjum@...labora.com>, shuah@...nel.org,
 linux-arm-kernel@...ts.infradead.org
Cc: linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org,
 Anshuman.Khandual@....com, suzuki.poulose@....com, ryan.roberts@....com,
 rob.herring@....com, Catalin.Marinas@....com, broonie@...nel.org,
 will@...nel.org, mark.rutland@....com
Subject: Re: [PATCH 3/4] selftests/arm: Add elf test


On 4/7/24 03:00, Muhammad Usama Anjum wrote:
> On 4/5/24 1:44 PM, Dev Jain wrote:
>> This patch introduces an ELF parsing test; the 5th byte of the ELF header
>> must be 0x01 for a 32-bit process. A basic sanity check is required to ensure
>> that we are actually testing a 32-bit build.
>>
>> Signed-off-by: Dev Jain <dev.jain@....com>
>> ---
>>   tools/testing/selftests/arm/elf/parse_elf.c | 75 +++++++++++++++++++++
>>   1 file changed, 75 insertions(+)
>>   create mode 100644 tools/testing/selftests/arm/elf/parse_elf.c
>>
>> diff --git a/tools/testing/selftests/arm/elf/parse_elf.c b/tools/testing/selftests/arm/elf/parse_elf.c
>> new file mode 100644
>> index 000000000000..decd65699858
>> --- /dev/null
>> +++ b/tools/testing/selftests/arm/elf/parse_elf.c
>> @@ -0,0 +1,75 @@
>> +// SPDX-License-Identifier: GPL-2.0
>> +/*
>> + * Copyright (C) 2024 ARM Limited
>> + *
>> + * Author : Dev Jain <dev.jain@....com>
>> + *
>> + * Parse elf header to confirm 32-bit process
>> + */
>> +
>> +#define _GNU_SOURCE
>> +#include <stdio.h>
>> +#include <unistd.h>
>> +#include <stdlib.h>
>> +#include <elf.h>
>> +#include <stdint.h>
>> +
>> +#include <kselftest.h>
>> +
>> +/* The ELF file header.  This appears at the start of every ELF file. */
>> +
>> +struct elf_header {
>> +	unsigned char	e_ident[16];	/* Magic number and other info */
>> +	uint16_t	e_type;		/* Object file type */
>> +	uint16_t	e_machine;	/* Architecture */
>> +	uint32_t	e_version;	/* Object file version */
>> +	uint64_t	e_entry;	/* Entry point virtual address */
>> +	uint64_t	e_phoff;	/* Program header table file offset */
>> +	uint64_t	e_shoff;	/* Section header table file offset */
>> +	uint32_t	e_flags;	/* Processor-specific flags */
>> +	uint16_t	e_ehsize;	/* ELF header size in bytes */
>> +	uint16_t	e_phentsize;	/* Program header table entry size */
>> +	uint16_t	e_phnum;	/* Program header table entry count */
>> +	uint16_t	e_shentsize;	/* Section header table entry size */
>> +	uint16_t	e_shnum;	/* Section header table entry count */
>> +	uint16_t	e_shstrndx;	/* Section header string table index */
>> +};
>> +
>> +static int read_elf_header(const char  *elfFile)
>> +{
>> +	struct elf_header header;
>> +	FILE *file;
>> +
>> +	file = fopen(elfFile, "r");
>> +	if (file) {
>> +
>> +		/* store header in struct */
>> +		fread(&header, 1, sizeof(header), file);
>> +		fclose(file);
>> +
>> +		/* sanity check: does it really follow ELF format */
>> +		if (header.e_ident[0] == 0x7f &&
>> +		    header.e_ident[1] == 'E' &&
>> +		    header.e_ident[2] == 'L' &&
>> +		    header.e_ident[3] == 'F') {
>> +			if (header.e_ident[4] == 0x01)
>> +				return 0;
>> +			return 1;
>> +		}
>> +		ksft_exit_fail_msg("Cannot parse /proc/self/exe\n");
>> +	}
>> +	ksft_exit_fail_msg("Cannot open /proc/self/exe\n");
>> +	exit(EXIT_FAILURE);
> Instead of failing and exiting multiple times here, use ksft_print_msg,
> return error or -1 from here and fail the test case in ksft_test_result().
Thanks for the suggestion.
>
>> +}
>> +
>> +int main(int argc, char *argv[])
>> +{
>> +	const char *file_name;
>> +
>> +	ksft_print_header();
>> +	ksft_set_plan(1);
>> +
>> +	file_name = "/proc/self/exe";
>> +	ksft_test_result(read_elf_header(file_name) == 0, "ELF is 32 bit\n");
>> +	ksft_finished();
>> +}