powerpc: Punch a hole in /dev/mem for librtas (8a3e3d31) · Commits · 戴 / test

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>

arch/powerpc/include/asm/rtas.h

+12 −0

Original line number	Diff line number	Diff line
		@@ -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 */

arch/powerpc/mm/mem.c

+3 −0

Original line number	Diff line number	Diff line
		@@ -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 */

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