diff options
| author | H. Peter Anvin <hpa@zytor.com> | 2012-04-20 17:12:48 -0700 |
|---|---|---|
| committer | H. Peter Anvin <hpa@zytor.com> | 2012-04-20 17:22:34 -0700 |
| commit | 706276543b699d80f546e45f8b12574e7b18d952 (patch) | |
| tree | fc0fd24bf22517086685aa470a0fb596a71026ab /arch/x86/include/asm/asm.h | |
| parent | fa574a48a1e9706bba38188d3bf61ecb66546a77 (diff) | |
x86, extable: Switch to relative exception table entries
Switch to using relative exception table entries on x86. On i386,
this has the advantage that the exception table entries don't need to
be relocated; on x86-64 this means the exception table entries take up
only half the space.
In either case, a 32-bit delta is sufficient, as the range of kernel
code addresses is limited.
Since part of the goal is to avoid needing to adjust the entries when
the kernel is relocated, the old trick of using addresses in the NULL
pointer range to indicate uaccess_err no longer works (and unlike RISC
architectures we can't use a flag bit); instead use an delta just
below +2G to indicate these special entries. The reach is still
limited to a single instruction.
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Cc: David Daney <david.daney@cavium.com>
Link: http://lkml.kernel.org/r/CA%2B55aFyijf43qSu3N9nWHEBwaGbb7T2Oq9A=9EyR=Jtyqfq_cQ@mail.gmail.com
Diffstat (limited to 'arch/x86/include/asm/asm.h')
| -rw-r--r-- | arch/x86/include/asm/asm.h | 20 |
1 files changed, 12 insertions, 8 deletions
diff --git a/arch/x86/include/asm/asm.h b/arch/x86/include/asm/asm.h index 0f15e8a4f56..1c2d247f65c 100644 --- a/arch/x86/include/asm/asm.h +++ b/arch/x86/include/asm/asm.h @@ -42,26 +42,30 @@ #ifdef __ASSEMBLY__ # define _ASM_EXTABLE(from,to) \ .pushsection "__ex_table","a" ; \ - _ASM_ALIGN ; \ - _ASM_PTR from , to ; \ + .balign 8 ; \ + .long (from) - . ; \ + .long (to) - . ; \ .popsection # define _ASM_EXTABLE_EX(from,to) \ .pushsection "__ex_table","a" ; \ - _ASM_ALIGN ; \ - _ASM_PTR from , (to) - (from) ; \ + .balign 8 ; \ + .long (from) - . ; \ + .long (to) - . + 0x7ffffff0 ; \ .popsection #else # define _ASM_EXTABLE(from,to) \ " .pushsection \"__ex_table\",\"a\"\n" \ - _ASM_ALIGN "\n" \ - _ASM_PTR #from "," #to "\n" \ + " .balign 8\n" \ + " .long (" #from ") - .\n" \ + " .long (" #to ") - .\n" \ " .popsection\n" # define _ASM_EXTABLE_EX(from,to) \ " .pushsection \"__ex_table\",\"a\"\n" \ - _ASM_ALIGN "\n" \ - _ASM_PTR #from ",(" #to ")-(" #from ")\n" \ + " .balign 8\n" \ + " .long (" #from ") - .\n" \ + " .long (" #to ") - . + 0x7ffffff0\n" \ " .popsection\n" #endif |