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Subject[PATCH v6 02/27] x86: Use symbol name in jump table for PIE support
Date
Replace the %c constraint with %P. The %c is incompatible with PIE
because it implies an immediate value whereas %P reference a symbol.
Change the _ASM_PTR reference to .long for expected relocation size and
add a long padding to ensure entry alignment.

Position Independent Executable (PIE) support will allow to extend the
KASLR randomization range below 0xffffffff80000000.

Signed-off-by: Thomas Garnier <thgarnie@chromium.org>
---
arch/x86/include/asm/jump_label.h | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/jump_label.h b/arch/x86/include/asm/jump_label.h
index 65191ce8e1cf..e47fad8ee632 100644
--- a/arch/x86/include/asm/jump_label.h
+++ b/arch/x86/include/asm/jump_label.h
@@ -25,9 +25,9 @@ static __always_inline bool arch_static_branch(struct static_key *key, bool bran
".pushsection __jump_table, \"aw\" \n\t"
_ASM_ALIGN "\n\t"
".long 1b - ., %l[l_yes] - . \n\t"
- _ASM_PTR "%c0 + %c1 - .\n\t"
+ _ASM_PTR "%P0 - .\n\t"
".popsection \n\t"
- : : "i" (key), "i" (branch) : : l_yes);
+ : : "X" (&((char *)key)[branch]) : : l_yes);

return false;
l_yes:
@@ -42,9 +42,9 @@ static __always_inline bool arch_static_branch_jump(struct static_key *key, bool
".pushsection __jump_table, \"aw\" \n\t"
_ASM_ALIGN "\n\t"
".long 1b - ., %l[l_yes] - . \n\t"
- _ASM_PTR "%c0 + %c1 - .\n\t"
+ _ASM_PTR "%P0 - .\n\t"
".popsection \n\t"
- : : "i" (key), "i" (branch) : : l_yes);
+ : : "X" (&((char *)key)[branch]) : : l_yes);

return false;
l_yes:
--
2.20.1.495.gaa96b0ce6b-goog
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