[PATCH v2 5/6] powerpc/32s: prepare prevent_user_access() for user_access_end()
From: Christophe Leroy <hidden>
Date: 2020-01-22 17:53:08
Also in:
linux-fsdevel, linux-mm, lkml
Subsystem:
linux for powerpc (32-bit and 64-bit), the rest · Maintainers:
Madhavan Srinivasan, Michael Ellerman, Linus Torvalds
In preparation of implementing user_access_begin and friends on powerpc, the book3s/32 version of prevent_user_access() need to be prepared for user_access_end(). user_access_end() doesn't provide the address and size which were passed to user_access_begin(), required by prevent_user_access() to know which segment to modify. The list of segments which where unprotected by allow_user_access() are available in current->kuap. But we don't want prevent_user_access() to read this all the time, especially everytime it is 0 (for instance because the access was not a write access). Implement a special direction case named KUAP_SELF. In this case only, the addr and end are retrieved from current->kuap. Signed-off-by: Christophe Leroy <redacted> --- v2: no change --- arch/powerpc/include/asm/book3s/32/kup.h | 25 ++++++++++++++++++------ arch/powerpc/include/asm/kup.h | 1 + 2 files changed, 20 insertions(+), 6 deletions(-)
diff --git a/arch/powerpc/include/asm/book3s/32/kup.h b/arch/powerpc/include/asm/book3s/32/kup.h
index 3c1798e56b55..a99fc3428ac9 100644
--- a/arch/powerpc/include/asm/book3s/32/kup.h
+++ b/arch/powerpc/include/asm/book3s/32/kup.h@@ -117,6 +117,7 @@ static __always_inline void allow_user_access(void __user *to, const void __user return; end = min(addr + size, TASK_SIZE); + current->thread.kuap = (addr & 0xf0000000) | ((((end - 1) >> 28) + 1) & 0xf); kuap_update_sr(mfsrin(addr) & ~SR_KS, addr, end); /* Clear Ks */ }
@@ -127,15 +128,27 @@ static __always_inline void prevent_user_access(void __user *to, const void __us u32 addr, end; BUILD_BUG_ON(!__builtin_constant_p(dir)); - if (!(dir & KUAP_W)) - return; - addr = (__force u32)to; + if (dir == KUAP_SELF) { + u32 kuap = current->thread.kuap; - if (unlikely(addr >= TASK_SIZE || !size)) - return; + if (unlikely(!kuap)) + return; + + addr = kuap & 0xf0000000; + end = kuap << 28; + } else { + if (!(dir & KUAP_W)) + return; + + addr = (__force u32)to; + + if (unlikely(addr >= TASK_SIZE || !size)) + return; + + end = min(addr + size, TASK_SIZE); + } - end = min(addr + size, TASK_SIZE); current->thread.kuap = 0; kuap_update_sr(mfsrin(addr) | SR_KS, addr, end); /* set Ks */ }
diff --git a/arch/powerpc/include/asm/kup.h b/arch/powerpc/include/asm/kup.h
index ff57bfcb88f7..4229e749dcf4 100644
--- a/arch/powerpc/include/asm/kup.h
+++ b/arch/powerpc/include/asm/kup.h@@ -5,6 +5,7 @@ #define KUAP_R 1 #define KUAP_W 2 #define KUAP_RW (KUAP_R | KUAP_W) +#define KUAP_SELF 4 #ifdef CONFIG_PPC64 #include <asm/book3s/64/kup-radix.h>
--
2.25.0