Subject: [PATCH 1/1] Punch a hole in /dev/mem for librtas 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 Changelog[v3]: [Ben Harrenschmidt]: Incremental patch for the punched hole, since CONFIG_STRICT_DEVMEM was merged into the -next branch. [Ben Harrenschmidt]: Rename interface to page_is_rtas_user_buf() move declaration to a header file and ensure it doesn't break CONFIG_PPC_RTAS=n. Signed-off-by: Sukadev Bhattiprolu <suka...@linux.vnet.ibm.com> --- arch/powerpc/include/asm/rtas.h | 12 ++++++++++++ arch/powerpc/mm/mem.c | 3 +++ 2 files changed, 15 insertions(+), 0 deletions(-) diff --git a/arch/powerpc/include/asm/rtas.h b/arch/powerpc/include/asm/rtas.h index 58625d1..c2d3c9f 100644 --- a/arch/powerpc/include/asm/rtas.h +++ b/arch/powerpc/include/asm/rtas.h @@ -305,5 +305,17 @@ 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 */ diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c index 553fb41..05abd49 100644 --- a/arch/powerpc/mm/mem.c +++ b/arch/powerpc/mm/mem.c @@ -50,6 +50,7 @@ #include <asm/vdso.h> #include <asm/fixmap.h> #include <asm/swiotlb.h> +#include <asm/rtas.h> #include "mmu_decl.h" @@ -564,6 +565,8 @@ 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 */ -- 1.7.0.4 _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev