Re: [RFC:PATCH 02/06] mm: Allow architectures to define additional protection bits
From: Andrew Morton <akpm@linux-foundation.org>
Date: 2008-06-10 22:14:23
Also in:
linux-mm
On Tue, 10 Jun 2008 18:01:07 -0400 Dave Kleikamp [off-list ref] wrote:
mm: Allow architectures to define additional protection bits This patch allows architectures to define functions to deal with additional protections bits for mmap() and mprotect(). arch_calc_vm_prot_bits() maps additonal protection bits to vm_flags arch_vm_get_page_prot() maps additional vm_flags to the vma's vm_page_prot arch_validate_prot() checks for valid values of the protection bits Note: vm_get_page_prot() is now pretty ugly. Suggestions?
It didn't get any better, no ;) I wonder if we can do the ORing after doing the protection_map[] lookup. I guess that's illogical even if it happens to work.
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Signed-off-by: Dave Kleikamp <redacted> --- include/linux/mman.h | 23 ++++++++++++++++++++++- mm/mmap.c | 5 +++-- mm/mprotect.c | 2 +- 3 files changed, 26 insertions(+), 4 deletions(-) diff -Nurp linux001/include/linux/mman.h linux002/include/linux/mman.h--- linux001/include/linux/mman.h 2008-06-05 10:08:01.000000000 -0500 +++ linux002/include/linux/mman.h 2008-06-10 16:48:59.000000000 -0500@@ -34,6 +34,26 @@ static inline void vm_unacct_memory(long } /* + * Allow architectures to handle additional protection bits + */ + +#ifndef HAVE_ARCH_PROT_BITS +#define arch_calc_vm_prot_bits(prot) 0 +#define arch_vm_get_page_prot(vm_flags) __pgprot(0) + +/* + * This is called from mprotect(). PROT_GROWSDOWN and PROT_GROWSUP have + * already been masked out. + * + * Returns true if the prot flags are valid + */ +static inline int arch_validate_prot(unsigned long prot) +{ + return (prot & ~(PROT_READ | PROT_WRITE | PROT_EXEC | PROT_SEM)) == 0; +} +#endif /* HAVE_ARCH_PROT_BITS */
argh, another HAVE_ARCH_foo. A good (but verbose) way of doing this is to nuke the ifdefs and just go and define these three things for each architecture. That can be done via copy-n-paste into include/asm-*/mman.h or #include <asm-generic/arch-mman.h>(?) within each asm/mman.h. Another way would be #ifndef arch_calc_vm_prot_bits #define arch_calc_vm_prot_bits(prot) ...
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+/* * Optimisation macro. It is equivalent to: * (x & bit1) ? bit2 : 0 * but this version is faster.@@ -51,7 +71,8 @@ calc_vm_prot_bits(unsigned long prot) { return _calc_vm_trans(prot, PROT_READ, VM_READ ) | _calc_vm_trans(prot, PROT_WRITE, VM_WRITE) | - _calc_vm_trans(prot, PROT_EXEC, VM_EXEC ); + _calc_vm_trans(prot, PROT_EXEC, VM_EXEC) | + arch_calc_vm_prot_bits(prot); } /*diff -Nurp linux001/mm/mmap.c linux002/mm/mmap.c--- linux001/mm/mmap.c 2008-06-05 10:08:03.000000000 -0500 +++ linux002/mm/mmap.c 2008-06-10 16:48:59.000000000 -0500@@ -72,8 +72,9 @@ pgprot_t protection_map[16] = { pgprot_t vm_get_page_prot(unsigned long vm_flags) { - return protection_map[vm_flags & - (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)]; + return __pgprot(pgprot_val(protection_map[vm_flags & + (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)]) | + pgprot_val(arch_vm_get_page_prot(vm_flags))); } EXPORT_SYMBOL(vm_get_page_prot);diff -Nurp linux001/mm/mprotect.c linux002/mm/mprotect.c--- linux001/mm/mprotect.c 2008-06-05 10:08:03.000000000 -0500 +++ linux002/mm/mprotect.c 2008-06-10 16:48:59.000000000 -0500@@ -239,7 +239,7 @@ sys_mprotect(unsigned long start, size_t end = start + len; if (end <= start) return -ENOMEM; - if (prot & ~(PROT_READ | PROT_WRITE | PROT_EXEC | PROT_SEM)) + if (!arch_validate_prot(prot)) return -EINVAL; reqprot = prot;