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authorAndy Lutomirski <luto@MIT.EDU>2011-06-05 21:50:24 +0400
committerIngo Molnar <mingo@elte.hu>2011-06-07 12:02:35 +0400
commit5cec93c216db77c45f7ce970d46283bcb1933884 (patch)
tree1dffa866471cd3f4ad1a342e389d3a14cb87d05f /arch/x86/include/asm/irq_vectors.h
parent5dfcea629a08b4684a019cd0cb59d0c9129a6c02 (diff)
downloadlinux-5cec93c216db77c45f7ce970d46283bcb1933884.tar.xz
x86-64: Emulate legacy vsyscalls
There's a fair amount of code in the vsyscall page. It contains a syscall instruction (in the gettimeofday fallback) and who knows what will happen if an exploit jumps into the middle of some other code. Reduce the risk by replacing the vsyscalls with short magic incantations that cause the kernel to emulate the real vsyscalls. These incantations are useless if entered in the middle. This causes vsyscalls to be a little more expensive than real syscalls. Fortunately sensible programs don't use them. The only exception is time() which is still called by glibc through the vsyscall - but calling time() millions of times per second is not sensible. glibc has this fixed in the development tree. This patch is not perfect: the vread_tsc and vread_hpet functions are still at a fixed address. Fixing that might involve making alternative patching work in the vDSO. Signed-off-by: Andy Lutomirski <luto@mit.edu> Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Cc: Jesper Juhl <jj@chaosbits.net> Cc: Borislav Petkov <bp@alien8.de> Cc: Arjan van de Ven <arjan@infradead.org> Cc: Jan Beulich <JBeulich@novell.com> Cc: richard -rw- weinberger <richard.weinberger@gmail.com> Cc: Mikael Pettersson <mikpe@it.uu.se> Cc: Andi Kleen <andi@firstfloor.org> Cc: Brian Gerst <brgerst@gmail.com> Cc: Louis Rilling <Louis.Rilling@kerlabs.com> Cc: Valdis.Kletnieks@vt.edu Cc: pageexec@freemail.hu Link: http://lkml.kernel.org/r/e64e1b3c64858820d12c48fa739efbd1485e79d5.1307292171.git.luto@mit.edu [ Removed the CONFIG option - it's simpler to just do it unconditionally. Tidied up the code as well. ] Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'arch/x86/include/asm/irq_vectors.h')
-rw-r--r--arch/x86/include/asm/irq_vectors.h6
1 files changed, 5 insertions, 1 deletions
diff --git a/arch/x86/include/asm/irq_vectors.h b/arch/x86/include/asm/irq_vectors.h
index 6e976ee3b3ef..a563c509edcb 100644
--- a/arch/x86/include/asm/irq_vectors.h
+++ b/arch/x86/include/asm/irq_vectors.h
@@ -17,7 +17,8 @@
* Vectors 0 ... 31 : system traps and exceptions - hardcoded events
* Vectors 32 ... 127 : device interrupts
* Vector 128 : legacy int80 syscall interface
- * Vectors 129 ... INVALIDATE_TLB_VECTOR_START-1 : device interrupts
+ * Vector 204 : legacy x86_64 vsyscall emulation
+ * Vectors 129 ... INVALIDATE_TLB_VECTOR_START-1 except 204 : device interrupts
* Vectors INVALIDATE_TLB_VECTOR_START ... 255 : special interrupts
*
* 64-bit x86 has per CPU IDT tables, 32-bit has one shared IDT table.
@@ -50,6 +51,9 @@
#ifdef CONFIG_X86_32
# define SYSCALL_VECTOR 0x80
#endif
+#ifdef CONFIG_X86_64
+# define VSYSCALL_EMU_VECTOR 0xcc
+#endif
/*
* Vectors 0x30-0x3f are used for ISA interrupts.