[PATCH 0/14] Pass MAP_FIXED down to get_unmapped_area

[PATCH 0/14] Pass MAP_FIXED down to get_unmapped_area

[Benjamin Herrenschmidt]

This is a "first step" as there are still cleanups to be done in various
areas touched by that code but I think it's probably good to go as is and
at least enables me to implement what I need for PowerPC.

The current get_unmapped_area code calls the f_ops->get_unmapped_area or
the arch one (via the mm) only when MAP_FIXED is not passed. That makes
it impossible for archs to impose proper constraints on regions of the
virtual address space. To work around that, get_unmapped_area() then
calls some hugetlbfs specific hacks.

This cause several problems, among others:

 - It makes it impossible for a driver or filesystem to do the same thing
that hugetlbfs does (for example, to allow a driver to use larger page
sizes to map external hardware) if that requires applying a constraint
on the addresses (constraining that mapping in certain regions and other
mappings out of those regions).

 - Some archs like arm, mips, sparc, sparc64, sh and sh64 already want
MAP_FIXED to be passed down in order to deal with aliasing issues.
The code is there to handle it... but is never called.

This serie of patches moves the logic to handle MAP_FIXED down to the
various arch/driver get_unmapped_area() implementations, and then changes
the generic code to always call them. The hugetlbfs hacks then disappear
from the generic code.

Since I need to do some special 64K pages mappings for SPEs on cell, I need
to work around the first problem at least. I have further patches thus
implementing a "slices" layer that handles multiple page sizes through
slices of the address space for use by hugetlbfs, the SPE code, and possibly
others, but it requires that serie of patches first/

There is still a potential (but not practical) issue due to the fact that
filesystems/drivers implemeting g_u_a will effectively bypass all arch
checks. This is not an issue in practice as the only filesystems/drivers
using that hook are doing so for arch specific purposes in the first place.

There is also a problem with mremap that will completely bypass all arch
checks. I'll try to address that separately, I'm not 100% certain yet how,
possibly by making it not work when the vma has a file whose f_ops has a
get_unmapped_area callback, and by making it use is_hugepage_only_range()
before expanding into a new area.

Also, I want to turn is_hugepage_only_range() into a more generic
is_normal_page_range() as that's really what it will end up meaning
when used in stack grow, brk grow and mremap.

None of the above "issues" however are introduced by this patch, they are
already there, so I think the patch can go in after review of the individual
bits by respective maintainers I suppose.

Cheers,
Ben.

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[PATCH 1/14] get_unmapped_area handles MAP_FIXED on powerpc

[Benjamin Herrenschmidt]

---

 arch/powerpc/mm/hugetlbpage.c |   21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

Index: linux-cell/arch/powerpc/mm/hugetlbpage.c
===================================================================
--- linux-cell.orig/arch/powerpc/mm/hugetlbpage.c	2007-03-22 14:52:07.000000000 +1100
+++ linux-cell/arch/powerpc/mm/hugetlbpage.c	2007-03-22 14:57:40.000000000 +1100
@@ -572,6 +572,13 @@ unsigned long arch_get_unmapped_area(str
 	if (len > TASK_SIZE)
 		return -ENOMEM;
 
+	/* handle fixed mapping: prevent overlap with huge pages */
+	if (flags & MAP_FIXED) {
+		if (is_hugepage_only_range(mm, addr, len))
+			return -EINVAL;
+		return addr;
+	}
+
 	if (addr) {
 		addr = PAGE_ALIGN(addr);
 		vma = find_vma(mm, addr);
@@ -647,6 +654,13 @@ arch_get_unmapped_area_topdown(struct fi
 	if (len > TASK_SIZE)
 		return -ENOMEM;
 
+	/* handle fixed mapping: prevent overlap with huge pages */
+	if (flags & MAP_FIXED) {
+		if (is_hugepage_only_range(mm, addr, len))
+			return -EINVAL;
+		return addr;
+	}
+
 	/* dont allow allocations above current base */
 	if (mm->free_area_cache > base)
 		mm->free_area_cache = base;
@@ -829,6 +843,13 @@ unsigned long hugetlb_get_unmapped_area(
 	/* Paranoia, caller should have dealt with this */
 	BUG_ON((addr + len)  < addr);
 
+	/* Handle MAP_FIXED */
+	if (flags & MAP_FIXED) {
+		if (prepare_hugepage_range(addr, len, pgoff))
+			return -EINVAL;
+		return addr;
+	}
+
 	if (test_thread_flag(TIF_32BIT)) {
 		curareas = current->mm->context.low_htlb_areas;
 

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[PATCH 2/14] get_unmapped_area handles MAP_FIXED on alpha

[Benjamin Herrenschmidt]

---

 arch/alpha/kernel/osf_sys.c |    3 +++
 1 file changed, 3 insertions(+)

Index: linux-cell/arch/alpha/kernel/osf_sys.c
===================================================================
--- linux-cell.orig/arch/alpha/kernel/osf_sys.c	2007-03-22 14:58:33.000000000 +1100
+++ linux-cell/arch/alpha/kernel/osf_sys.c	2007-03-22 14:58:44.000000000 +1100
@@ -1267,6 +1267,9 @@ arch_get_unmapped_area(struct file *filp
 	if (len > limit)
 		return -ENOMEM;
 
+	if (flags & MAP_FIXED)
+		return addr;
+
 	/* First, see if the given suggestion fits.
 
 	   The OSF/1 loader (/sbin/loader) relies on us returning an

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[PATCH 3/14] get_unmapped_area handles MAP_FIXED on arm

[Benjamin Herrenschmidt]

---

 arch/arm/mm/mmap.c |    3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

Index: linux-cell/arch/arm/mm/mmap.c
===================================================================
--- linux-cell.orig/arch/arm/mm/mmap.c	2007-03-22 14:59:51.000000000 +1100
+++ linux-cell/arch/arm/mm/mmap.c	2007-03-22 15:00:01.000000000 +1100
@@ -49,8 +49,7 @@ arch_get_unmapped_area(struct file *filp
 #endif
 
 	/*
-	 * We should enforce the MAP_FIXED case.  However, currently
-	 * the generic kernel code doesn't allow us to handle this.
+	 * We enforce the MAP_FIXED case.
 	 */
 	if (flags & MAP_FIXED) {
 		if (aliasing && flags & MAP_SHARED && addr & (SHMLBA - 1))

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[PATCH 5/14] get_unmapped_area handles MAP_FIXED on i386

[Benjamin Herrenschmidt]

---

 arch/i386/mm/hugetlbpage.c |    6 ++++++
 1 file changed, 6 insertions(+)

Index: linux-cell/arch/i386/mm/hugetlbpage.c
===================================================================
--- linux-cell.orig/arch/i386/mm/hugetlbpage.c	2007-03-22 16:08:12.000000000 +1100
+++ linux-cell/arch/i386/mm/hugetlbpage.c	2007-03-22 16:14:19.000000000 +1100
@@ -367,6 +367,12 @@ hugetlb_get_unmapped_area(struct file *f
 	if (len > TASK_SIZE)
 		return -ENOMEM;
 
+	if (flags & MAP_FIXED) {
+		if (prepare_hugepage_range(addr, len, pgoff))
+			return -EINVAL;
+		return addr;
+	}
+
 	if (addr) {
 		addr = ALIGN(addr, HPAGE_SIZE);
 		vma = find_vma(mm, addr);

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[PATCH 4/14] get_unmapped_area handles MAP_FIXED on frv

[Benjamin Herrenschmidt]

---

 arch/frv/mm/elf-fdpic.c |    4 ++++
 1 file changed, 4 insertions(+)

Index: linux-cell/arch/frv/mm/elf-fdpic.c
===================================================================
--- linux-cell.orig/arch/frv/mm/elf-fdpic.c	2007-03-22 15:00:50.000000000 +1100
+++ linux-cell/arch/frv/mm/elf-fdpic.c	2007-03-22 15:01:06.000000000 +1100
@@ -64,6 +64,10 @@ unsigned long arch_get_unmapped_area(str
 	if (len > TASK_SIZE)
 		return -ENOMEM;
 
+	/* handle MAP_FIXED */
+	if (flags & MAP_FIXED)
+		return addr;
+
 	/* only honour a hint if we're not going to clobber something doing so */
 	if (addr) {
 		addr = PAGE_ALIGN(addr);

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[PATCH 6/14] get_unmapped_area handles MAP_FIXED on ia64

[Benjamin Herrenschmidt]

---

 arch/ia64/kernel/sys_ia64.c |    7 +++++++
 arch/ia64/mm/hugetlbpage.c  |    8 ++++++++
 2 files changed, 15 insertions(+)

Index: linux-cell/arch/ia64/kernel/sys_ia64.c
===================================================================
--- linux-cell.orig/arch/ia64/kernel/sys_ia64.c	2007-03-22 15:10:45.000000000 +1100
+++ linux-cell/arch/ia64/kernel/sys_ia64.c	2007-03-22 15:10:47.000000000 +1100
@@ -33,6 +33,13 @@ arch_get_unmapped_area (struct file *fil
 	if (len > RGN_MAP_LIMIT)
 		return -ENOMEM;
 
+	/* handle fixed mapping: prevent overlap with huge pages */
+	if (flags & MAP_FIXED) {
+		if (is_hugepage_only_range(mm, addr, len))
+			return -EINVAL;
+		return addr;
+	}
+
 #ifdef CONFIG_HUGETLB_PAGE
 	if (REGION_NUMBER(addr) == RGN_HPAGE)
 		addr = 0;
Index: linux-cell/arch/ia64/mm/hugetlbpage.c
===================================================================
--- linux-cell.orig/arch/ia64/mm/hugetlbpage.c	2007-03-22 15:12:32.000000000 +1100
+++ linux-cell/arch/ia64/mm/hugetlbpage.c	2007-03-22 15:12:39.000000000 +1100
@@ -148,6 +148,14 @@ unsigned long hugetlb_get_unmapped_area(
 		return -ENOMEM;
 	if (len & ~HPAGE_MASK)
 		return -EINVAL;
+
+	/* Handle MAP_FIXED */
+	if (flags & MAP_FIXED) {
+		if (prepare_hugepage_range(addr, len, pgoff))
+			return -EINVAL;
+		return addr;
+	}
+
 	/* This code assumes that RGN_HPAGE != 0. */
 	if ((REGION_NUMBER(addr) != RGN_HPAGE) || (addr & (HPAGE_SIZE - 1)))
 		addr = HPAGE_REGION_BASE;
 

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[PATCH 7/14] get_unmapped_area handles MAP_FIXED on parisc

[Benjamin Herrenschmidt]

---

 arch/parisc/kernel/sys_parisc.c |    5 +++++
 1 file changed, 5 insertions(+)

Index: linux-cell/arch/parisc/kernel/sys_parisc.c
===================================================================
--- linux-cell.orig/arch/parisc/kernel/sys_parisc.c	2007-03-22 15:28:05.000000000 +1100
+++ linux-cell/arch/parisc/kernel/sys_parisc.c	2007-03-22 15:29:08.000000000 +1100
@@ -106,6 +106,11 @@ unsigned long arch_get_unmapped_area(str
 {
 	if (len > TASK_SIZE)
 		return -ENOMEM;
+	/* Might want to check for cache aliasing issues for MAP_FIXED case
+	 * like ARM or MIPS ??? --BenH.
+	 */
+	if (flags & MAP_FIXED)
+		return addr;
 	if (!addr)
 		addr = TASK_UNMAPPED_BASE;
 

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[PATCH 8/14] get_unmapped_area handles MAP_FIXED on sparc64

[Benjamin Herrenschmidt]

---

 arch/sparc64/mm/hugetlbpage.c |    6 ++++++
 1 file changed, 6 insertions(+)

Index: linux-cell/arch/sparc64/mm/hugetlbpage.c
===================================================================
--- linux-cell.orig/arch/sparc64/mm/hugetlbpage.c	2007-03-22 16:12:57.000000000 +1100
+++ linux-cell/arch/sparc64/mm/hugetlbpage.c	2007-03-22 16:15:33.000000000 +1100
@@ -175,6 +175,12 @@ hugetlb_get_unmapped_area(struct file *f
 	if (len > task_size)
 		return -ENOMEM;
 
+	if (flags & MAP_FIXED) {
+		if (prepare_hugepage_range(addr, len, pgoff))
+			return -EINVAL;
+		return addr;
+	}
+
 	if (addr) {
 		addr = ALIGN(addr, HPAGE_SIZE);
 		vma = find_vma(mm, addr);

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[PATCH 9/14] get_unmapped_area handles MAP_FIXED on x86_64

[Benjamin Herrenschmidt]

---

 arch/x86_64/kernel/sys_x86_64.c |    3 +++
 1 file changed, 3 insertions(+)

Index: linux-cell/arch/x86_64/kernel/sys_x86_64.c
===================================================================
--- linux-cell.orig/arch/x86_64/kernel/sys_x86_64.c	2007-03-22 16:10:10.000000000 +1100
+++ linux-cell/arch/x86_64/kernel/sys_x86_64.c	2007-03-22 16:11:06.000000000 +1100
@@ -93,6 +93,9 @@ arch_get_unmapped_area(struct file *filp
 	unsigned long start_addr;
 	unsigned long begin, end;
 	
+	if (flags & MAP_FIXED)
+		return addr;
+
 	find_start_end(flags, &begin, &end); 
 
 	if (len > end)

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[PATCH 10/14] get_unmapped_area handles MAP_FIXED in hugetlbfs

[Benjamin Herrenschmidt]

---

 fs/hugetlbfs/inode.c |    6 ++++++
 1 file changed, 6 insertions(+)

Index: linux-cell/fs/hugetlbfs/inode.c
===================================================================
--- linux-cell.orig/fs/hugetlbfs/inode.c	2007-03-22 16:12:56.000000000 +1100
+++ linux-cell/fs/hugetlbfs/inode.c	2007-03-22 16:16:02.000000000 +1100
@@ -115,6 +115,12 @@ hugetlb_get_unmapped_area(struct file *f
 	if (len > TASK_SIZE)
 		return -ENOMEM;
 
+	if (flags & MAP_FIXED) {
+		if (prepare_hugepage_range(addr, len, pgoff))
+			return -EINVAL;
+		return addr;
+	}
+
 	if (addr) {
 		addr = ALIGN(addr, HPAGE_SIZE);
 		vma = find_vma(mm, addr);

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[PATCH 11/14] get_unmapped_area handles MAP_FIXED on ramfs (nommu)

[Benjamin Herrenschmidt]

---

 fs/ramfs/file-nommu.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

Index: linux-cell/fs/ramfs/file-nommu.c
===================================================================
--- linux-cell.orig/fs/ramfs/file-nommu.c	2007-03-22 16:18:27.000000000 +1100
+++ linux-cell/fs/ramfs/file-nommu.c	2007-03-22 16:20:14.000000000 +1100
@@ -238,7 +238,10 @@ unsigned long ramfs_nommu_get_unmapped_a
 	struct page **pages = NULL, **ptr, *page;
 	loff_t isize;
 
-	if (!(flags & MAP_SHARED))
+	/* Deal with MAP_FIXED differently ? Forbid it ? Need help from some nommu
+	 * folks there... --BenH.
+	 */
+	if ((flags & MAP_FIXED) || !(flags & MAP_SHARED))
 		return addr;
 
 	/* the mapping mustn't extend beyond the EOF */

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[PATCH 12/14] get_unmapped_area handles MAP_FIXED in /dev/mem (nommu)

[Benjamin Herrenschmidt]

This also fixes a bug, I think, it used to return a pgoff (pfn)
instead of an address. (To split ?)

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
---

 drivers/char/mem.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

Index: linux-cell/drivers/char/mem.c
===================================================================
--- linux-cell.orig/drivers/char/mem.c	2007-03-22 16:24:04.000000000 +1100
+++ linux-cell/drivers/char/mem.c	2007-03-22 16:26:30.000000000 +1100
@@ -246,9 +246,12 @@ static unsigned long get_unmapped_area_m
 					   unsigned long pgoff,
 					   unsigned long flags)
 {
+	if (flags & MAP_FIXED)
+		if ((addr >> PAGE_SHIFT) != pgoff)
+			return (unsigned long) -EINVAL;
 	if (!valid_mmap_phys_addr_range(pgoff, len))
 		return (unsigned long) -EINVAL;
-	return pgoff;
+	return pgoff << PAGE_SHIFT;
 }
 
 /* can't do an in-place private mapping if there's no MMU */

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Re: [PATCH 0/14] Pass MAP_FIXED down to get_unmapped_area

[Benjamin Herrenschmidt]

On Wed, 2007-04-04 at 14:01 +1000, Benjamin Herrenschmidt wrote:
> This is a "first step" as there are still cleanups to be done in various
> areas touched by that code but I think it's probably good to go as is and
> at least enables me to implement what I need for PowerPC.


 .../...

And sorry for the double-send of some of the patches, a script hickup on
my side.

Cheers,
Ben.


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[PATCH 7/14] get_unmapped_area handles MAP_FIXED on parisc

[Benjamin Herrenschmidt]

---

 arch/parisc/kernel/sys_parisc.c |    5 +++++
 1 file changed, 5 insertions(+)

Index: linux-cell/arch/parisc/kernel/sys_parisc.c
===================================================================
--- linux-cell.orig/arch/parisc/kernel/sys_parisc.c	2007-03-22 15:28:05.000000000 +1100
+++ linux-cell/arch/parisc/kernel/sys_parisc.c	2007-03-22 15:29:08.000000000 +1100
@@ -106,6 +106,11 @@ unsigned long arch_get_unmapped_area(str
 {
 	if (len > TASK_SIZE)
 		return -ENOMEM;
+	/* Might want to check for cache aliasing issues for MAP_FIXED case
+	 * like ARM or MIPS ??? --BenH.
+	 */
+	if (flags & MAP_FIXED)
+		return addr;
 	if (!addr)
 		addr = TASK_UNMAPPED_BASE;
 

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