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[S390] Change vmalloc defintions

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Currently the vmalloc area starts at a dynamic address depending on
the memory size. There was also an 8MB security hole after the
physical memory to catch out-of-bounds accesses.
We can simplify the code by putting the vmalloc area explicitely at
the top of the kernel mapping and setting the vmalloc size to a fixed
value of 128MB/128GB for 31bit/64bit systems. Part of the vmalloc
area will be used for the vmem_map. This leaves an area of 96MB/1GB
for normal vmalloc allocations.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Christian Borntraeger
2008-01-26 14:11:00 +01:00
committed by Martin Schwidefsky
parent 8ffd74a092
commit 5fd9c6e214
3 changed files with 26 additions and 46 deletions
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46
include/asm-s390/pgtable.h
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@@ -104,41 +104,27 @@ extern char empty_zero_page[PAGE_SIZE];
#ifndef __ASSEMBLY__
/*
* Just any arbitrary offset to the start of the vmalloc VM area: the
* current 8MB value just means that there will be a 8MB "hole" after the
* physical memory until the kernel virtual memory starts. That means that
* any out-of-bounds memory accesses will hopefully be caught.
* The vmalloc() routines leaves a hole of 4kB between each vmalloced
* area for the same reason. ;)
* vmalloc area starts at 4GB to prevent syscall table entry exchanging
* from modules.
*/
extern unsigned long vmalloc_end;
#ifdef CONFIG_64BIT
#define VMALLOC_ADDR (max(0x100000000UL, (unsigned long) high_memory))
#else
#define VMALLOC_ADDR ((unsigned long) high_memory)
#endif
#define VMALLOC_OFFSET (8*1024*1024)
#define VMALLOC_START ((VMALLOC_ADDR + VMALLOC_OFFSET) & ~(VMALLOC_OFFSET-1))
#define VMALLOC_END vmalloc_end
/*
* We need some free virtual space to be able to do vmalloc.
* VMALLOC_MIN_SIZE defines the minimum size of the vmalloc
* area. On a machine with 2GB memory we make sure that we
* have at least 128MB free space for vmalloc. On a machine
* with 4TB we make sure we have at least 128GB.
* The vmalloc area will always be on the topmost area of the kernel
* mapping. We reserve 96MB (31bit) / 1GB (64bit) for vmalloc,
* which should be enough for any sane case.
* By putting vmalloc at the top, we maximise the gap between physical
* memory and vmalloc to catch misplaced memory accesses. As a side
* effect, this also makes sure that 64 bit module code cannot be used
* as system call address.
*/
#ifndef __s390x__
#define VMALLOC_MIN_SIZE 0x8000000UL
#define VMALLOC_END_INIT 0x80000000UL
#define VMALLOC_START 0x78000000UL
#define VMALLOC_END 0x7e000000UL
#define VMEM_MAP_MAX 0x80000000UL
#else /* __s390x__ */
#define VMALLOC_MIN_SIZE 0x2000000000UL
#define VMALLOC_END_INIT 0x40000000000UL
#define VMALLOC_START 0x3e000000000UL
#define VMALLOC_END 0x3e040000000UL
#define VMEM_MAP_MAX 0x40000000000UL
#endif /* __s390x__ */
#define VMEM_MAP ((struct page *) VMALLOC_END)
#define VMEM_MAP_SIZE ((VMALLOC_START / PAGE_SIZE) * sizeof(struct page))
/*
* A 31 bit pagetable entry of S390 has following format:
* | PFRA | | OS |