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

[Muhammad Usama Anjum]

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@xxxxxxx>
> ---
>  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@xxxxxxx>
> + *
> + * 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().

> +}
> +
> +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();
> +}

-- 
BR,
Muhammad Usama Anjum