linux-kernel - [PATCH 10/15] binfmt_flat: make support for old format binaries optional

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Message-Id: <20190610212015.9157-11-hch@lst.de>
Date:   Mon, 10 Jun 2019 23:20:10 +0200
From:   Christoph Hellwig <hch@....de>
To:     Greg Ungerer <gerg@...ux-m68k.org>
Cc:     Michal Simek <monstr@...str.eu>,
        linux-arm-kernel@...ts.infradead.org, linux-c6x-dev@...ux-c6x.org,
        uclinux-h8-devel@...ts.sourceforge.jp,
        linux-m68k@...ts.linux-m68k.org, linux-riscv@...ts.infradead.org,
        linux-sh@...r.kernel.org, linux-xtensa@...ux-xtensa.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 10/15] binfmt_flat: make support for old format binaries optional

No need to carry the extra code around, given that systems using flat
binaries are generally very resource constrained.

Signed-off-by: Christoph Hellwig <hch@....de>
---
 fs/Kconfig.binfmt |  7 +++++++
 fs/binfmt_flat.c  | 29 +++++++++++++++++++++--------
 2 files changed, 28 insertions(+), 8 deletions(-)

diff --git a/fs/Kconfig.binfmt b/fs/Kconfig.binfmt
index 286b425b30b9..62dc4f577ba1 100644
--- a/fs/Kconfig.binfmt
+++ b/fs/Kconfig.binfmt
@@ -106,6 +106,13 @@ config BINFMT_FLAT_ARGVP_ENVP_ON_STACK
 config BINFMT_FLAT_OLD_ALWAYS_RAM
 	bool
 
+config BINFMT_FLAT_OLD
+	bool "Enable support for very old legacy flat binaries"
+	depends on BINFMT_FLAT
+	help
+	  Support decade old uClinux FLAT format binaries.  Unless you know
+	  you have some of those say N here.
+
 config BINFMT_ZFLAT
 	bool "Enable ZFLAT support"
 	depends on BINFMT_FLAT
diff --git a/fs/binfmt_flat.c b/fs/binfmt_flat.c
index 6c1848dee724..ed7d969593d2 100644
--- a/fs/binfmt_flat.c
+++ b/fs/binfmt_flat.c
@@ -374,6 +374,7 @@ calc_reloc(unsigned long r, struct lib_info *p, int curid, int internalp)
 
 /****************************************************************************/
 
+#ifdef CONFIG_BINFMT_FLAT_OLD
 static void old_reloc(unsigned long rl)
 {
 	static const char *segment[] = { "TEXT", "DATA", "BSS", "*UNKNOWN*" };
@@ -411,6 +412,7 @@ static void old_reloc(unsigned long rl)
 
 	pr_debug("Relocation became %lx\n", val);
 }
+#endif /* CONFIG_BINFMT_FLAT_OLD */
 
 /****************************************************************************/
 
@@ -461,6 +463,7 @@ static int load_flat_file(struct linux_binprm *bprm,
 	if (flags & FLAT_FLAG_KTRACE)
 		pr_info("Loading file: %s\n", bprm->filename);
 
+#ifdef CONFIG_BINFMT_FLAT_OLD
 	if (rev != FLAT_VERSION && rev != OLD_FLAT_VERSION) {
 		pr_err("bad flat file version 0x%x (supported 0x%lx and 0x%lx)\n",
 		       rev, FLAT_VERSION, OLD_FLAT_VERSION);
@@ -476,6 +479,22 @@ static int load_flat_file(struct linux_binprm *bprm,
 		goto err;
 	}
 
+	/*
+	 * fix up the flags for the older format,  there were all kinds
+	 * of endian hacks,  this only works for the simple cases
+	 */
+	if (IS_ENABLED(CONFIG_BINFMT_FLAT_OLD_ALWAYS_RAM) &&
+	    rev == OLD_FLAT_VERSION)
+		flags = FLAT_FLAG_RAM;
+#else /* CONFIG_BINFMT_FLAT_OLD */
+	if (rev != FLAT_VERSION) {
+		pr_err("bad flat file version 0x%x (supported 0x%lx)\n",
+		       rev, FLAT_VERSION);
+		ret = -ENOEXEC;
+		goto err;
+	}
+#endif /* !CONFIG_BINFMT_FLAT_OLD */
+
 	/*
 	 * Make sure the header params are sane.
 	 * 28 bits (256 MB) is way more than reasonable in this case.
@@ -487,14 +506,6 @@ static int load_flat_file(struct linux_binprm *bprm,
 		goto err;
 	}
 
-	/*
-	 * fix up the flags for the older format,  there were all kinds
-	 * of endian hacks,  this only works for the simple cases
-	 */
-	if (IS_ENABLED(CONFIG_BINFMT_FLAT_OLD_ALWAYS_RAM) &&
-	    rev == OLD_FLAT_VERSION)
-		flags = FLAT_FLAG_RAM;
-
 #ifndef CONFIG_BINFMT_ZFLAT
 	if (flags & (FLAT_FLAG_GZIP|FLAT_FLAG_GZDATA)) {
 		pr_err("Support for ZFLAT executables is not enabled.\n");
@@ -833,6 +844,7 @@ static int load_flat_file(struct linux_binprm *bprm,
 					goto err;
 			}
 		}
+#ifdef CONFIG_BINFMT_FLAT_OLD
 	} else {
 		for (i = 0; i < relocs; i++) {
 			__be32 relval;
@@ -840,6 +852,7 @@ static int load_flat_file(struct linux_binprm *bprm,
 				return -EFAULT;
 			old_reloc(ntohl(relval));
 		}
+#endif /* CONFIG_BINFMT_FLAT_OLD */
 	}
 
 	flush_icache_range(start_code, end_code);
-- 
2.20.1