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powerpc: Punch a hole in /dev/mem for librtas

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With CONFIG_STRICT_DEVMEM=y, user space cannot read any part of /dev/mem.
Since this breaks librtas, punch a hole in /dev/mem to allow access to the
rmo_buffer that librtas needs.

Anton Blanchard reported the problem and helped with the fix.

A quick test for this patch:

       # cat /proc/rtas/rmo_buffer
       000000000f190000 10000

       # python -c "print 0x000000000f190000 / 0x10000"
       3865

       # dd if=/dev/mem of=/tmp/foo count=1 bs=64k skip=3865
       1+0 records in
       1+0 records out
       65536 bytes (66 kB) copied, 0.000205235 s, 319 MB/s

       # dd if=/dev/mem of=/tmp/foo
       dd: reading `/dev/mem': Operation not permitted
       0+0 records in
       0+0 records out
       0 bytes (0 B) copied, 0.00022519 s, 0.0 kB/s

Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This commit is contained in:
sukadev@linux.vnet.ibm.com
2011-12-02 12:26:23 +00:00
committed by Benjamin Herrenschmidt
parent 11eab297f5
commit 8a3e3d31d1
2 changed files with 15 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files

12
arch/powerpc/include/asm/rtas.h
View File

@@ -313,5 +313,17 @@ static inline u32 rtas_config_addr(int busno, int devfn, int reg)
extern void __cpuinit rtas_give_timebase(void);
extern void __cpuinit rtas_take_timebase(void);
#ifdef CONFIG_PPC_RTAS
static inline int page_is_rtas_user_buf(unsigned long pfn)
{
unsigned long paddr = (pfn << PAGE_SHIFT);
if (paddr >= rtas_rmo_buf && paddr < (rtas_rmo_buf + RTAS_RMOBUF_MAX))
return 1;
return 0;
}
#else
static inline int page_is_rtas_user_buf(unsigned long pfn) { return 0;}
#endif
#endif /* __KERNEL__ */
#endif /* _POWERPC_RTAS_H */

3
arch/powerpc/mm/mem.c
View File

@@ -51,6 +51,7 @@
#include <asm/vdso.h>
#include <asm/fixmap.h>
#include <asm/swiotlb.h>
#include <asm/rtas.h>
#include "mmu_decl.h"
@@ -600,6 +601,8 @@ int devmem_is_allowed(unsigned long pfn)
return 0;
if (!page_is_ram(pfn))
return 1;
if (page_is_rtas_user_buf(pfn))
return 1;
return 0;
}
#endif /* CONFIG_STRICT_DEVMEM */