Groups > linux.kernel > #1449168 > unrolled thread

[PATCH v5 00/15] allow BFLT executables on systems with a MMU

Started by	Nicolas Pitre <nicolas.pitre@linaro.org>
First post	2016-07-24 17:40 +0200
Last post	2016-07-26 03:00 +0200
Articles	6 — 2 participants

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  [PATCH v5 00/15] allow BFLT executables on systems with a MMU Nicolas Pitre <nicolas.pitre@linaro.org> - 2016-07-24 17:40 +0200
    [PATCH v5 09/15] binfmt_flat: use clear_user() rather than memset() to clear .bss Nicolas Pitre <nicolas.pitre@linaro.org> - 2016-07-24 17:40 +0200
    [PATCH v5 02/15] binfmt_flat: convert printk invocations to their modern form Nicolas Pitre <nicolas.pitre@linaro.org> - 2016-07-24 17:40 +0200
    [PATCH v5 04/15] elf_fdpic_transfer_args_to_stack(): make it generic Nicolas Pitre <nicolas.pitre@linaro.org> - 2016-07-24 17:40 +0200
    [PATCH v5 13/15] m68k: fix bFLT executable running on MMU enabled systems Nicolas Pitre <nicolas.pitre@linaro.org> - 2016-07-24 17:40 +0200
    Re: [PATCH v5 00/15] allow BFLT executables on systems with a MMU Greg Ungerer <gerg@linux-m68k.org> - 2016-07-26 03:00 +0200

#1449168 — [PATCH v5 00/15] allow BFLT executables on systems with a MMU

From	Nicolas Pitre <nicolas.pitre@linaro.org>
Date	2016-07-24 17:40 +0200
Subject	[PATCH v5 00/15] allow BFLT executables on systems with a MMU
Message-ID	<rYtFw-19R-9@gated-at.bofh.it>

This series provides the necessary changes to allow "flat" executable
binaries meant for no-MMU systems to actually run on systems with a MMU.
Also thrown in are various cleanups to binfmt_flat.c.

This can also be found in the following git repo:

	git://git.linaro.org/people/nicolas.pitre/linux binfmt_flat_with_mmu

*Why?*

Because developing and testing natively on a large system with lots of
RAM makes it so much more convenient to use all the existing profiling
tools and debugging facilities that a kernel with lots of RAM can give.
And incidentally, those systems with lots of RAM all have a MMU.

*Why not use elf_fdpic?*

The flat executable format is simple with very small footprint
overhead, either in the executables themselves or kernel support.
This makes the flat format more suitable than elf_fdpic for very small
single user-app embedded systems.

And while elf_fdpic binaries can run on MMU systems, flat binaries still
couldn't, which just felt wrong.

So here it is. The no-MMU support should remain unaffected, confirmed by
Greg Ungerer. Tested with MMU on ARM and M68K.

Changes since v4:

- Isolated architecture specific changes in their own patches for easier
  review through their own path to mainline.

- Added needed m68k register fixup from Greg Ungerer.

Changes since v3:

- Small cosmetic changes to pr_*().

- Addressed most important checkpatch complaints on the whole source file
  and patches in this seris.

Changes since  v2:

- Added protection against a corrupted header that could have caused nasty
  overflows etc. Suggested by Alan Cox.

- printk() modernization. Suggested by Greg Ungerer / Geert Uytterhoeven.

- Added Greg Ungerer's reviewed-by tag.

Changes since v1:

- Removed SuperH and Xtensa from the Kconfig rule as they fail to build
  due to lack of get/put_unaligned_user().

- Clarified some commit logs a bit.

diffstat:

 arch/arm/include/asm/flat.h       |   5 +-
 arch/m68k/include/asm/flat.h      |  11 +-
 arch/m68k/include/asm/processor.h |   2 -
 fs/Kconfig.binfmt                 |   3 +-
 fs/binfmt_elf_fdpic.c             |  38 +--
 fs/binfmt_flat.c                  | 525 ++++++++++++++++++--------------
 fs/exec.c                         |  33 ++
 include/linux/binfmts.h           |   2 +
 8 files changed, 345 insertions(+), 274 deletions(-)

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#1449169 — [PATCH v5 09/15] binfmt_flat: use clear_user() rather than memset() to clear .bss

From	Nicolas Pitre <nicolas.pitre@linaro.org>
Date	2016-07-24 17:40 +0200
Subject	[PATCH v5 09/15] binfmt_flat: use clear_user() rather than memset() to clear .bss
Message-ID	<rYtFx-19R-35@gated-at.bofh.it>
In reply to	#1449168

This is needed on systems with a MMU.

Signed-off-by: Nicolas Pitre <nico@linaro.org>
Reviewed-by: Greg Ungerer <gerg@linux-m68k.org>
---
 fs/binfmt_flat.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/fs/binfmt_flat.c b/fs/binfmt_flat.c
index 63756ca6a7..92c1530a2c 100644
--- a/fs/binfmt_flat.c
+++ b/fs/binfmt_flat.c
@@ -795,10 +795,11 @@ static int load_flat_file(struct linux_binprm *bprm,
 	flush_icache_range(start_code, end_code);
 
 	/* zero the BSS,  BRK and stack areas */
-	memset((void *)(datapos + data_len), 0, bss_len +
-			(memp + memp_size - stack_len -		/* end brk */
-			libinfo->lib_list[id].start_brk) +	/* start brk */
-			stack_len);
+	if (clear_user((void __user *)(datapos + data_len), bss_len +
+		       (memp + memp_size - stack_len -		/* end brk */
+		       libinfo->lib_list[id].start_brk) +	/* start brk */
+		       stack_len))
+		return -EFAULT;
 
 	return 0;
 err:
-- 
2.7.4

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#1449170 — [PATCH v5 02/15] binfmt_flat: convert printk invocations to their modern form

From	Nicolas Pitre <nicolas.pitre@linaro.org>
Date	2016-07-24 17:40 +0200
Subject	[PATCH v5 02/15] binfmt_flat: convert printk invocations to their modern form
Message-ID	<rYtFx-19R-41@gated-at.bofh.it>
In reply to	#1449168

Signed-off-by: Nicolas Pitre <nico@linaro.org>
---
 fs/binfmt_flat.c | 118 ++++++++++++++++++++++++-------------------------------
 1 file changed, 51 insertions(+), 67 deletions(-)

diff --git a/fs/binfmt_flat.c b/fs/binfmt_flat.c
index 892dba62bf..c3ccdefdea 100644
--- a/fs/binfmt_flat.c
+++ b/fs/binfmt_flat.c
@@ -15,6 +15,8 @@
  *	JAN/99 -- coded full program relocation (gerg@snapgear.com)
  */
 
+#define pr_fmt(fmt)	KBUILD_MODNAME ": " fmt
+
 #include <linux/kernel.h>
 #include <linux/sched.h>
 #include <linux/mm.h>
@@ -40,16 +42,6 @@
 
 /****************************************************************************/
 
-#if 0
-#define DEBUG 1
-#endif
-
-#ifdef DEBUG
-#define	DBG_FLT(a...)	printk(a)
-#else
-#define	DBG_FLT(a...)
-#endif
-
 /*
  * User data (data section and bss) needs to be aligned.
  * We pick 0x20 here because it is the max value elf2flt has always
@@ -102,8 +94,8 @@ static struct linux_binfmt flat_format = {
 
 static int flat_core_dump(struct coredump_params *cprm)
 {
-	printk("Process %s:%d received signr %d and should have core dumped\n",
-			current->comm, current->pid, cprm->siginfo->si_signo);
+	pr_warn("Process %s:%d received signr %d and should have core dumped\n",
+		current->comm, current->pid, cprm->siginfo->si_signo);
 	return 1;
 }
 
@@ -186,17 +178,17 @@ static int decompress_exec(
 	loff_t fpos;
 	int ret, retval;
 
-	DBG_FLT("decompress_exec(offset=%lx,buf=%p,len=%lx)\n", offset, dst, len);
+	pr_debug("decompress_exec(offset=%lx,buf=%p,len=%lx)\n", offset, dst, len);
 
 	memset(&strm, 0, sizeof(strm));
 	strm.workspace = kmalloc(zlib_inflate_workspacesize(), GFP_KERNEL);
 	if (strm.workspace == NULL) {
-		DBG_FLT("binfmt_flat: no memory for decompress workspace\n");
+		pr_debug("no memory for decompress workspace\n");
 		return -ENOMEM;
 	}
 	buf = kmalloc(LBUFSIZE, GFP_KERNEL);
 	if (buf == NULL) {
-		DBG_FLT("binfmt_flat: no memory for read buffer\n");
+		pr_debug("no memory for read buffer\n");
 		retval = -ENOMEM;
 		goto out_free;
 	}
@@ -214,25 +206,25 @@ static int decompress_exec(
 
 	/* Check minimum size -- gzip header */
 	if (ret < 10) {
-		DBG_FLT("binfmt_flat: file too small?\n");
+		pr_debug("file too small?\n");
 		goto out_free_buf;
 	}
 
 	/* Check gzip magic number */
 	if ((buf[0] != 037) || ((buf[1] != 0213) && (buf[1] != 0236))) {
-		DBG_FLT("binfmt_flat: unknown compression magic?\n");
+		pr_debug("unknown compression magic?\n");
 		goto out_free_buf;
 	}
 
 	/* Check gzip method */
 	if (buf[2] != 8) {
-		DBG_FLT("binfmt_flat: unknown compression method?\n");
+		pr_debug("unknown compression method?\n");
 		goto out_free_buf;
 	}
 	/* Check gzip flags */
 	if ((buf[3] & ENCRYPTED) || (buf[3] & CONTINUATION) ||
 	    (buf[3] & RESERVED)) {
-		DBG_FLT("binfmt_flat: unknown flags?\n");
+		pr_debug("unknown flags?\n");
 		goto out_free_buf;
 	}
 
@@ -240,7 +232,7 @@ static int decompress_exec(
 	if (buf[3] & EXTRA_FIELD) {
 		ret += 2 + buf[10] + (buf[11] << 8);
 		if (unlikely(ret >= LBUFSIZE)) {
-			DBG_FLT("binfmt_flat: buffer overflow (EXTRA)?\n");
+			pr_debug("buffer overflow (EXTRA)?\n");
 			goto out_free_buf;
 		}
 	}
@@ -248,7 +240,7 @@ static int decompress_exec(
 		while (ret < LBUFSIZE && buf[ret++] != 0)
 			;
 		if (unlikely(ret == LBUFSIZE)) {
-			DBG_FLT("binfmt_flat: buffer overflow (ORIG_NAME)?\n");
+			pr_debug("buffer overflow (ORIG_NAME)?\n");
 			goto out_free_buf;
 		}
 	}
@@ -256,7 +248,7 @@ static int decompress_exec(
 		while (ret < LBUFSIZE && buf[ret++] != 0)
 			;
 		if (unlikely(ret == LBUFSIZE)) {
-			DBG_FLT("binfmt_flat: buffer overflow (COMMENT)?\n");
+			pr_debug("buffer overflow (COMMENT)?\n");
 			goto out_free_buf;
 		}
 	}
@@ -269,7 +261,7 @@ static int decompress_exec(
 	strm.total_out = 0;
 
 	if (zlib_inflateInit2(&strm, -MAX_WBITS) != Z_OK) {
-		DBG_FLT("binfmt_flat: zlib init failed?\n");
+		pr_debug("zlib init failed?\n");
 		goto out_free_buf;
 	}
 
@@ -286,7 +278,7 @@ static int decompress_exec(
 	}
 
 	if (ret < 0) {
-		DBG_FLT("binfmt_flat: decompression failed (%d), %s\n",
+		pr_debug("decompression failed (%d), %s\n",
 			ret, strm.msg);
 		goto out_zlib;
 	}
@@ -323,24 +315,23 @@ calc_reloc(unsigned long r, struct lib_info *p, int curid, int internalp)
 		r &= 0x00ffffff;	/* Trim ID off here */
 	}
 	if (id >= MAX_SHARED_LIBS) {
-		printk("BINFMT_FLAT: reference 0x%lx to shared library %d",
-				r, id);
+		pr_err("reference 0x%lx to shared library %d", r, id);
 		goto failed;
 	}
 	if (curid != id) {
 		if (internalp) {
-			printk("BINFMT_FLAT: reloc address 0x%lx not in same module "
-					"(%d != %d)", r, curid, id);
+			pr_err("reloc address 0x%lx not in same module "
+			       "(%d != %d)", r, curid, id);
 			goto failed;
 		} else if (!p->lib_list[id].loaded &&
 			   load_flat_shared_library(id, p) < 0) {
-			printk("BINFMT_FLAT: failed to load library %d", id);
+			pr_err("failed to load library %d", id);
 			goto failed;
 		}
 		/* Check versioning information (i.e. time stamps) */
 		if (p->lib_list[id].build_date && p->lib_list[curid].build_date &&
 				p->lib_list[curid].build_date < p->lib_list[id].build_date) {
-			printk("BINFMT_FLAT: library %d is younger than %d", id, curid);
+			pr_err("library %d is younger than %d", id, curid);
 			goto failed;
 		}
 	}
@@ -354,7 +345,7 @@ calc_reloc(unsigned long r, struct lib_info *p, int curid, int internalp)
 	text_len = p->lib_list[id].text_len;
 
 	if (!flat_reloc_valid(r, start_brk - start_data + text_len)) {
-		printk("BINFMT_FLAT: reloc outside program 0x%lx (0 - 0x%lx/0x%lx)",
+		pr_err("reloc outside program 0x%lx (0 - 0x%lx/0x%lx)",
 		       r, start_brk-start_data+text_len, text_len);
 		goto failed;
 	}
@@ -368,7 +359,7 @@ calc_reloc(unsigned long r, struct lib_info *p, int curid, int internalp)
 	return addr;
 
 failed:
-	printk(", killing %s!\n", current->comm);
+	pr_cont(", killing %s!\n", current->comm);
 	send_sig(SIGSEGV, current, 0);
 
 	return RELOC_FAILED;
@@ -378,9 +369,7 @@ failed:
 
 static void old_reloc(unsigned long rl)
 {
-#ifdef DEBUG
 	static const char *segment[] = { "TEXT", "DATA", "BSS", "*UNKNOWN*" };
-#endif
 	flat_v2_reloc_t	r;
 	unsigned long *ptr;
 
@@ -391,11 +380,9 @@ static void old_reloc(unsigned long rl)
 	ptr = (unsigned long *) (current->mm->start_data + r.reloc.offset);
 #endif
 
-#ifdef DEBUG
-	printk("Relocation of variable at DATASEG+%x "
-		"(address %p, currently %lx) into segment %s\n",
-		r.reloc.offset, ptr, *ptr, segment[r.reloc.type]);
-#endif
+	pr_debug("Relocation of variable at DATASEG+%x "
+		 "(address %p, currently %lx) into segment %s\n",
+		 r.reloc.offset, ptr, *ptr, segment[r.reloc.type]);
 
 	switch (r.reloc.type) {
 	case OLD_FLAT_RELOC_TYPE_TEXT:
@@ -408,13 +395,11 @@ static void old_reloc(unsigned long rl)
 		*ptr += current->mm->end_data;
 		break;
 	default:
-		printk("BINFMT_FLAT: Unknown relocation type=%x\n", r.reloc.type);
+		pr_err("Unknown relocation type=%x\n", r.reloc.type);
 		break;
 	}
 
-#ifdef DEBUG
-	printk("Relocation became %lx\n", *ptr);
-#endif
+	pr_debug("Relocation became %lx\n", *ptr);
 }
 
 /****************************************************************************/
@@ -463,20 +448,19 @@ static int load_flat_file(struct linux_binprm *bprm,
 	}
 
 	if (flags & FLAT_FLAG_KTRACE)
-		printk("BINFMT_FLAT: Loading file: %s\n", bprm->filename);
+		pr_info("Loading file: %s\n", bprm->filename);
 
 	if (rev != FLAT_VERSION && rev != OLD_FLAT_VERSION) {
-		printk("BINFMT_FLAT: bad flat file version 0x%x (supported "
-			"0x%lx and 0x%lx)\n",
-			rev, FLAT_VERSION, OLD_FLAT_VERSION);
+		pr_err("bad flat file version 0x%x (supported 0x%lx and 0x%lx)\n",
+		       rev, FLAT_VERSION, OLD_FLAT_VERSION);
 		ret = -ENOEXEC;
 		goto err;
 	}
 
 	/* Don't allow old format executables to use shared libraries */
 	if (rev == OLD_FLAT_VERSION && id != 0) {
-		printk("BINFMT_FLAT: shared libraries are not available before rev 0x%lx\n",
-				FLAT_VERSION);
+		pr_err("shared libraries are not available before rev 0x%lx\n",
+		       FLAT_VERSION);
 		ret = -ENOEXEC;
 		goto err;
 	}
@@ -490,7 +474,7 @@ static int load_flat_file(struct linux_binprm *bprm,
 
 #ifndef CONFIG_BINFMT_ZFLAT
 	if (flags & (FLAT_FLAG_GZIP|FLAT_FLAG_GZDATA)) {
-		printk("Support for ZFLAT executables is not enabled.\n");
+		pr_err("Support for ZFLAT executables is not enabled.\n");
 		ret = -ENOEXEC;
 		goto err;
 	}
@@ -536,7 +520,7 @@ static int load_flat_file(struct linux_binprm *bprm,
 		 * this should give us a ROM ptr,  but if it doesn't we don't
 		 * really care
 		 */
-		DBG_FLT("BINFMT_FLAT: ROM mapping of file (we hope)\n");
+		pr_debug("ROM mapping of file (we hope)\n");
 
 		textpos = vm_mmap(bprm->file, 0, text_len, PROT_READ|PROT_EXEC,
 				  MAP_PRIVATE|MAP_EXECUTABLE, 0);
@@ -544,7 +528,7 @@ static int load_flat_file(struct linux_binprm *bprm,
 			ret = textpos;
 			if (!textpos)
 				ret = -ENOMEM;
-			printk("Unable to mmap process text, errno %d\n", ret);
+			pr_err("Unable to mmap process text, errno %d\n", ret);
 			goto err;
 		}
 
@@ -557,7 +541,7 @@ static int load_flat_file(struct linux_binprm *bprm,
 			ret = realdatastart;
 			if (!realdatastart)
 				ret = -ENOMEM;
-			printk("Unable to allocate RAM for process data, "
+			pr_err("Unable to allocate RAM for process data, "
 			       "errno %d\n", ret);
 			vm_munmap(textpos, text_len);
 			goto err;
@@ -566,8 +550,8 @@ static int load_flat_file(struct linux_binprm *bprm,
 				MAX_SHARED_LIBS * sizeof(unsigned long),
 				FLAT_DATA_ALIGN);
 
-		DBG_FLT("BINFMT_FLAT: Allocated data+bss+stack (%ld bytes): %lx\n",
-			data_len + bss_len + stack_len, datapos);
+		pr_debug("Allocated data+bss+stack (%ld bytes): %lx\n",
+			 data_len + bss_len + stack_len, datapos);
 
 		fpos = ntohl(hdr->data_start);
 #ifdef CONFIG_BINFMT_ZFLAT
@@ -582,7 +566,7 @@ static int load_flat_file(struct linux_binprm *bprm,
 		}
 		if (IS_ERR_VALUE(result)) {
 			ret = result;
-			printk("Unable to read data+bss, errno %d\n", ret);
+			pr_err("Unable to read data+bss, errno %d\n", ret);
 			vm_munmap(textpos, text_len);
 			vm_munmap(realdatastart, len);
 			goto err;
@@ -603,7 +587,7 @@ static int load_flat_file(struct linux_binprm *bprm,
 			ret = textpos;
 			if (!textpos)
 				ret = -ENOMEM;
-			printk("Unable to allocate RAM for process text/data, "
+			pr_err("Unable to allocate RAM for process text/data, "
 			       "errno %d\n", ret);
 			goto err;
 		}
@@ -645,7 +629,7 @@ static int load_flat_file(struct linux_binprm *bprm,
 		}
 		if (IS_ERR_VALUE(result)) {
 			ret = result;
-			printk("Unable to read code+data+bss, errno %d\n", ret);
+			pr_err("Unable to read code+data+bss, errno %d\n", ret);
 			vm_munmap(textpos, text_len + data_len + extra +
 				MAX_SHARED_LIBS * sizeof(unsigned long));
 			goto err;
@@ -675,12 +659,12 @@ static int load_flat_file(struct linux_binprm *bprm,
 	}
 
 	if (flags & FLAT_FLAG_KTRACE) {
-		printk("Mapping is %lx, Entry point is %x, data_start is %x\n",
-		       textpos, 0x00ffffff&ntohl(hdr->entry), ntohl(hdr->data_start));
-		printk("%s %s: TEXT=%lx-%lx DATA=%lx-%lx BSS=%lx-%lx\n",
-		       id ? "Lib" : "Load", bprm->filename,
-		       start_code, end_code, datapos, datapos + data_len,
-		       datapos + data_len, (datapos + data_len + bss_len + 3) & ~3);
+		pr_info("Mapping is %lx, Entry point is %x, data_start is %x\n",
+			textpos, 0x00ffffff&ntohl(hdr->entry), ntohl(hdr->data_start));
+		pr_info("%s %s: TEXT=%lx-%lx DATA=%lx-%lx BSS=%lx-%lx\n",
+			id ? "Lib" : "Load", bprm->filename,
+			start_code, end_code, datapos, datapos + data_len,
+			datapos + data_len, (datapos + data_len + bss_len + 3) & ~3);
 	}
 
 	/* Store the current module values into the global library structure */
@@ -890,7 +874,7 @@ static int load_flat_binary(struct linux_binprm *bprm)
 	set_binfmt(&flat_format);
 
 	p = ((current->mm->context.end_brk + stack_len + 3) & ~3) - 4;
-	DBG_FLT("p=%lx\n", p);
+	pr_debug("p=%lx\n", p);
 
 	/* copy the arg pages onto the stack, this could be more efficient :-) */
 	for (i = TOP_OF_ARGS - 1; i >= bprm->p; i--)
@@ -922,8 +906,8 @@ static int load_flat_binary(struct linux_binprm *bprm)
 	FLAT_PLAT_INIT(regs);
 #endif
 
-	DBG_FLT("start_thread(regs=0x%p, entry=0x%lx, start_stack=0x%lx)\n",
-		regs, start_addr, current->mm->start_stack);
+	pr_debug("start_thread(regs=0x%p, entry=0x%lx, start_stack=0x%lx)\n",
+		 regs, start_addr, current->mm->start_stack);
 	start_thread(regs, start_addr, current->mm->start_stack);
 
 	return 0;
-- 
2.7.4

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#1449171 — [PATCH v5 04/15] elf_fdpic_transfer_args_to_stack(): make it generic

From	Nicolas Pitre <nicolas.pitre@linaro.org>
Date	2016-07-24 17:40 +0200
Subject	[PATCH v5 04/15] elf_fdpic_transfer_args_to_stack(): make it generic
Message-ID	<rYtFx-19R-37@gated-at.bofh.it>
In reply to	#1449168

This copying of arguments and environment is common to both NOMMU
binary formats we support. Let's make the elf_fdpic version available
to the flat format as well.

While at it, improve the code a bit not to copy below the actual
data area.

Signed-off-by: Nicolas Pitre <nico@linaro.org>
Reviewed-by: Greg Ungerer <gerg@linux-m68k.org>
---
 fs/binfmt_elf_fdpic.c   | 38 ++------------------------------------
 fs/exec.c               | 33 +++++++++++++++++++++++++++++++++
 include/linux/binfmts.h |  2 ++
 3 files changed, 37 insertions(+), 36 deletions(-)

diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c
index 203589311b..464a972e88 100644
--- a/fs/binfmt_elf_fdpic.c
+++ b/fs/binfmt_elf_fdpic.c
@@ -67,8 +67,6 @@ static int create_elf_fdpic_tables(struct linux_binprm *, struct mm_struct *,
 				   struct elf_fdpic_params *);
 
 #ifndef CONFIG_MMU
-static int elf_fdpic_transfer_args_to_stack(struct linux_binprm *,
-					    unsigned long *);
 static int elf_fdpic_map_file_constdisp_on_uclinux(struct elf_fdpic_params *,
 						   struct file *,
 						   struct mm_struct *);
@@ -515,8 +513,9 @@ static int create_elf_fdpic_tables(struct linux_binprm *bprm,
 	sp = mm->start_stack;
 
 	/* stack the program arguments and environment */
-	if (elf_fdpic_transfer_args_to_stack(bprm, &sp) < 0)
+	if (transfer_args_to_stack(bprm, &sp) < 0)
 		return -EFAULT;
+	sp &= ~15;
 #endif
 
 	/*
@@ -711,39 +710,6 @@ static int create_elf_fdpic_tables(struct linux_binprm *bprm,
 
 /*****************************************************************************/
 /*
- * transfer the program arguments and environment from the holding pages onto
- * the stack
- */
-#ifndef CONFIG_MMU
-static int elf_fdpic_transfer_args_to_stack(struct linux_binprm *bprm,
-					    unsigned long *_sp)
-{
-	unsigned long index, stop, sp;
-	char *src;
-	int ret = 0;
-
-	stop = bprm->p >> PAGE_SHIFT;
-	sp = *_sp;
-
-	for (index = MAX_ARG_PAGES - 1; index >= stop; index--) {
-		src = kmap(bprm->page[index]);
-		sp -= PAGE_SIZE;
-		if (copy_to_user((void *) sp, src, PAGE_SIZE) != 0)
-			ret = -EFAULT;
-		kunmap(bprm->page[index]);
-		if (ret < 0)
-			goto out;
-	}
-
-	*_sp = (*_sp - (MAX_ARG_PAGES * PAGE_SIZE - bprm->p)) & ~15;
-
-out:
-	return ret;
-}
-#endif
-
-/*****************************************************************************/
-/*
  * load the appropriate binary image (executable or interpreter) into memory
  * - we assume no MMU is available
  * - if no other PIC bits are set in params->hdr->e_flags
diff --git a/fs/exec.c b/fs/exec.c
index 887c1c955d..ef0df2f092 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -762,6 +762,39 @@ out_unlock:
 }
 EXPORT_SYMBOL(setup_arg_pages);
 
+#else
+
+/*
+ * Transfer the program arguments and environment from the holding pages
+ * onto the stack. The provided stack pointer is adjusted accordingly.
+ */
+int transfer_args_to_stack(struct linux_binprm *bprm,
+			   unsigned long *sp_location)
+{
+	unsigned long index, stop, sp;
+	int ret = 0;
+
+	stop = bprm->p >> PAGE_SHIFT;
+	sp = *sp_location;
+
+	for (index = MAX_ARG_PAGES - 1; index >= stop; index--) {
+		unsigned int offset = index == stop ? bprm->p & ~PAGE_MASK : 0;
+		char *src = kmap(bprm->page[index]) + offset;
+		sp -= PAGE_SIZE - offset;
+		if (copy_to_user((void *) sp, src, PAGE_SIZE - offset) != 0)
+			ret = -EFAULT;
+		kunmap(bprm->page[index]);
+		if (ret)
+			goto out;
+	}
+
+	*sp_location = sp;
+
+out:
+	return ret;
+}
+EXPORT_SYMBOL(transfer_args_to_stack);
+
 #endif /* CONFIG_MMU */
 
 static struct file *do_open_execat(int fd, struct filename *name, int flags)
diff --git a/include/linux/binfmts.h b/include/linux/binfmts.h
index 314b3caa70..1303b570b1 100644
--- a/include/linux/binfmts.h
+++ b/include/linux/binfmts.h
@@ -113,6 +113,8 @@ extern int suid_dumpable;
 extern int setup_arg_pages(struct linux_binprm * bprm,
 			   unsigned long stack_top,
 			   int executable_stack);
+extern int transfer_args_to_stack(struct linux_binprm *bprm,
+				  unsigned long *sp_location);
 extern int bprm_change_interp(char *interp, struct linux_binprm *bprm);
 extern int copy_strings_kernel(int argc, const char *const *argv,
 			       struct linux_binprm *bprm);
-- 
2.7.4

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#1449172 — [PATCH v5 13/15] m68k: fix bFLT executable running on MMU enabled systems

From	Nicolas Pitre <nicolas.pitre@linaro.org>
Date	2016-07-24 17:40 +0200
Subject	[PATCH v5 13/15] m68k: fix bFLT executable running on MMU enabled systems
Message-ID	<rYtFx-19R-39@gated-at.bofh.it>
In reply to	#1449168

From: Greg Ungerer <gerg@linux-m68k.org>

Even after recent changes to support running flat format executables on
MMU enabled systems (by nicolas.pitre@linaro.org) they still failed to
run on m68k/ColdFire MMU enabled systems. On trying to run a flat format
binary the application would immediately crash with a SIGSEGV.

Code to setup the D5 register with the base of the application data
region was only in the non-MMU code path, so it was not being set for
the MMU enabled case. Flat binaries on m68k/ColdFire use this to support
GOT/PIC flat built application code.

Fix this so that D5 is always setup when loading/running a bFLT executable
on m68k systems.

Signed-off-by: Greg Ungerer <gerg@linux-m68k.org>
Signed-off-by: Nicolas Pitre <nico@linaro.org>
---
 arch/m68k/include/asm/flat.h      | 6 ++++++
 arch/m68k/include/asm/processor.h | 2 --
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/arch/m68k/include/asm/flat.h b/arch/m68k/include/asm/flat.h
index f9454b89a5..f46c2f044f 100644
--- a/arch/m68k/include/asm/flat.h
+++ b/arch/m68k/include/asm/flat.h
@@ -18,4 +18,10 @@ static inline int flat_set_persistent(unsigned long relval,
 	return 0;
 }
 
+#define FLAT_PLAT_INIT(regs) \
+	do { \
+		if (current->mm) \
+			(regs)->d5 = current->mm->start_data; \
+	} while (0)
+
 #endif /* __M68KNOMMU_FLAT_H__ */
diff --git a/arch/m68k/include/asm/processor.h b/arch/m68k/include/asm/processor.h
index a6ce2ec8d6..46672d1f4d 100644
--- a/arch/m68k/include/asm/processor.h
+++ b/arch/m68k/include/asm/processor.h
@@ -131,8 +131,6 @@ extern int handle_kernel_fault(struct pt_regs *regs);
 do {                                                    \
 	(_regs)->pc = (_pc);                            \
 	setframeformat(_regs);                          \
-	if (current->mm)                                \
-		(_regs)->d5 = current->mm->start_data;  \
 	(_regs)->sr &= ~0x2000;                         \
 	wrusp(_usp);                                    \
 } while(0)
-- 
2.7.4

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#1450305

From	Greg Ungerer <gerg@linux-m68k.org>
Date	2016-07-26 03:00 +0200
Message-ID	<rYYT0-3wo-3@gated-at.bofh.it>
In reply to	#1449168

On 25/07/16 01:30, Nicolas Pitre wrote:
> This series provides the necessary changes to allow "flat" executable
> binaries meant for no-MMU systems to actually run on systems with a MMU.
> Also thrown in are various cleanups to binfmt_flat.c.
> 
> This can also be found in the following git repo:
> 
> 	git://git.linaro.org/people/nicolas.pitre/linux binfmt_flat_with_mmu

So everyone is in the loop - I have pulled this into my for-linus branch
at https://git.kernel.org/cgit/linux/kernel/git/gerg/m68knommu.git/ ,
excepting patch 15 (ARM specific changes).

My continued testing hasn't found any issues on m68k platforms.
I can completely boot up with a no-MMU user space and run on an
MMU enabled ColdFire platform).

I'll like to consider pushing this to Linus nearer the end of the
merge window if no-one has any objections.

Regards
Greg


> *Why?*
> 
> Because developing and testing natively on a large system with lots of
> RAM makes it so much more convenient to use all the existing profiling
> tools and debugging facilities that a kernel with lots of RAM can give.
> And incidentally, those systems with lots of RAM all have a MMU.
> 
> *Why not use elf_fdpic?*
> 
> The flat executable format is simple with very small footprint
> overhead, either in the executables themselves or kernel support.
> This makes the flat format more suitable than elf_fdpic for very small
> single user-app embedded systems.
> 
> And while elf_fdpic binaries can run on MMU systems, flat binaries still
> couldn't, which just felt wrong.
> 
> So here it is. The no-MMU support should remain unaffected, confirmed by
> Greg Ungerer. Tested with MMU on ARM and M68K.
> 
> Changes since v4:
> 
> - Isolated architecture specific changes in their own patches for easier
>   review through their own path to mainline.
> 
> - Added needed m68k register fixup from Greg Ungerer.
> 
> Changes since v3:
> 
> - Small cosmetic changes to pr_*().
> 
> - Addressed most important checkpatch complaints on the whole source file
>   and patches in this seris.
> 
> Changes since  v2:
> 
> - Added protection against a corrupted header that could have caused nasty
>   overflows etc. Suggested by Alan Cox.
> 
> - printk() modernization. Suggested by Greg Ungerer / Geert Uytterhoeven.
> 
> - Added Greg Ungerer's reviewed-by tag.
> 
> Changes since v1:
> 
> - Removed SuperH and Xtensa from the Kconfig rule as they fail to build
>   due to lack of get/put_unaligned_user().
> 
> - Clarified some commit logs a bit.
> 
> diffstat:
> 
>  arch/arm/include/asm/flat.h       |   5 +-
>  arch/m68k/include/asm/flat.h      |  11 +-
>  arch/m68k/include/asm/processor.h |   2 -
>  fs/Kconfig.binfmt                 |   3 +-
>  fs/binfmt_elf_fdpic.c             |  38 +--
>  fs/binfmt_flat.c                  | 525 ++++++++++++++++++--------------
>  fs/exec.c                         |  33 ++
>  include/linux/binfmts.h           |   2 +
>  8 files changed, 345 insertions(+), 274 deletions(-)
>

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csiph-web

[PATCH v5 00/15] allow BFLT executables on systems with a MMU

Contents

#1449168 — [PATCH v5 00/15] allow BFLT executables on systems with a MMU

#1449169 — [PATCH v5 09/15] binfmt_flat: use clear_user() rather than memset() to clear .bss

#1449170 — [PATCH v5 02/15] binfmt_flat: convert printk invocations to their modern form

#1449171 — [PATCH v5 04/15] elf_fdpic_transfer_args_to_stack(): make it generic

#1449172 — [PATCH v5 13/15] m68k: fix bFLT executable running on MMU enabled systems

#1450305