Date: Wed, 31 Jan 2018 15:09:55 +0000 From: Roger Pau =?iso-8859-1?Q?Monn=E9?= <roger.pau@citrix.com> To: Wojciech Macek <wma@FreeBSD.org> Cc: <src-committers@freebsd.org>, <svn-src-all@freebsd.org>, <svn-src-head@freebsd.org> Subject: Re: svn commit: r328536 - in head/stand: common powerpc/kboot Message-ID: <20180131150955.trc5tkkykgxuwf4f@MacBook-Pro-de-Roger.local> In-Reply-To: <201801290924.w0T9OSix008403@repo.freebsd.org>
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On Mon, Jan 29, 2018 at 09:24:28AM +0000, Wojciech Macek wrote:
> Modified: head/stand/common/load_elf.c
> ==============================================================================
> --- head/stand/common/load_elf.c Mon Jan 29 09:21:08 2018 (r328535)
> +++ head/stand/common/load_elf.c Mon Jan 29 09:24:28 2018 (r328536)
> @@ -29,6 +29,7 @@
> __FBSDID("$FreeBSD$");
>
> #include <sys/param.h>
> +#include <sys/endian.h>
> #include <sys/exec.h>
> #include <sys/linker.h>
> #include <sys/module.h>
> @@ -118,15 +119,72 @@ __elfN(load_elf_header)(char *filename, elf_file_t ef)
> err = EFTYPE;
> goto error;
> }
> +
> if (ehdr->e_ident[EI_CLASS] != ELF_TARG_CLASS || /* Layout ? */
> ehdr->e_ident[EI_DATA] != ELF_TARG_DATA ||
So here you force EI_DATA == ELF_TARG_DATA in order to continue...
> - ehdr->e_ident[EI_VERSION] != EV_CURRENT || /* Version ? */
> - ehdr->e_version != EV_CURRENT ||
> - ehdr->e_machine != ELF_TARG_MACH) { /* Machine ? */
> + ehdr->e_ident[EI_VERSION] != EV_CURRENT) /* Version ? */ {
> err = EFTYPE;
> goto error;
> }
>
> + /*
> + * Fixup ELF endianness.
> + *
> + * The Xhdr structure was loaded using block read call to
> + * optimize file accesses. It might happen, that the endianness
> + * of the system memory is different that endianness of
> + * the ELF header.
> + * Swap fields here to guarantee that Xhdr always contain
> + * valid data regardless of architecture.
> + */
> + if (ehdr->e_ident[EI_DATA] == ELFDATA2MSB) {
> + ehdr->e_type = be16toh(ehdr->e_type);
... yet here you check for EI_DATA == ELFDATA2MSB which AFAICT it's not
possible given the check above, so the following if branch is dead
code.
> + ehdr->e_machine = be16toh(ehdr->e_machine);
> + ehdr->e_version = be32toh(ehdr->e_version);
> + if (ehdr->e_ident[EI_CLASS] == ELFCLASS64) {
> + ehdr->e_entry = be64toh(ehdr->e_entry);
> + ehdr->e_phoff = be64toh(ehdr->e_phoff);
> + ehdr->e_shoff = be64toh(ehdr->e_shoff);
> + } else {
> + ehdr->e_entry = be32toh(ehdr->e_entry);
> + ehdr->e_phoff = be32toh(ehdr->e_phoff);
> + ehdr->e_shoff = be32toh(ehdr->e_shoff);
> + }
> + ehdr->e_flags = be32toh(ehdr->e_flags);
> + ehdr->e_ehsize = be16toh(ehdr->e_ehsize);
> + ehdr->e_phentsize = be16toh(ehdr->e_phentsize);
> + ehdr->e_phnum = be16toh(ehdr->e_phnum);
> + ehdr->e_shentsize = be16toh(ehdr->e_shentsize);
> + ehdr->e_shnum = be16toh(ehdr->e_shnum);
> + ehdr->e_shstrndx = be16toh(ehdr->e_shstrndx);
> +
> + } else {
> + ehdr->e_type = le16toh(ehdr->e_type);
> + ehdr->e_machine = le16toh(ehdr->e_machine);
> + ehdr->e_version = le32toh(ehdr->e_version);
> + if (ehdr->e_ident[EI_CLASS] == ELFCLASS64) {
> + ehdr->e_entry = le64toh(ehdr->e_entry);
> + ehdr->e_phoff = le64toh(ehdr->e_phoff);
> + ehdr->e_shoff = le64toh(ehdr->e_shoff);
> + } else {
> + ehdr->e_entry = le32toh(ehdr->e_entry);
> + ehdr->e_phoff = le32toh(ehdr->e_phoff);
> + ehdr->e_shoff = le32toh(ehdr->e_shoff);
> + }
> + ehdr->e_flags = le32toh(ehdr->e_flags);
> + ehdr->e_ehsize = le16toh(ehdr->e_ehsize);
> + ehdr->e_phentsize = le16toh(ehdr->e_phentsize);
> + ehdr->e_phnum = le16toh(ehdr->e_phnum);
> + ehdr->e_shentsize = le16toh(ehdr->e_shentsize);
> + ehdr->e_shnum = le16toh(ehdr->e_shnum);
> + ehdr->e_shstrndx = le16toh(ehdr->e_shstrndx);
> + }
I think this chunk (and all the similar ones below) should be put on a
macro in order to avoid such big chunks of code repetition. It's also
fairly easy to forget to change one of the branches in the future.
Roger.
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