[RFC 03/22] x86: Use symbol name in jump table for PIE support
From: Thomas Garnier <hidden>
Date: 2017-07-18 22:33:14
Also in:
kvm, linux-arch, linux-crypto, xen-devel
Subsystem:
static branch/call, the rest, x86 architecture (32-bit and 64-bit) · Maintainers:
Peter Zijlstra, Josh Poimboeuf, Jason Baron, Alice Ryhl, Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen
Replace the %c constraint with %P. The %c is incompatible with PIE because it implies an immediate value whereas %P reference a symbol. Position Independent Executable (PIE) support will allow to extended the KASLR randomization range below the -2G memory limit. Signed-off-by: Thomas Garnier <redacted> --- 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 adc54c12cbd1..6e558e4524dc 100644
--- a/arch/x86/include/asm/jump_label.h
+++ b/arch/x86/include/asm/jump_label.h@@ -36,9 +36,9 @@ static __always_inline bool arch_static_branch(struct static_key *key, bool bran ".byte " __stringify(STATIC_KEY_INIT_NOP) "\n\t" ".pushsection __jump_table, \"aw\" \n\t" _ASM_ALIGN "\n\t" - _ASM_PTR "1b, %l[l_yes], %c0 + %c1 \n\t" + _ASM_PTR "1b, %l[l_yes], %P0 \n\t" ".popsection \n\t" - : : "i" (key), "i" (branch) : : l_yes); + : : "X" (&((char *)key)[branch]) : : l_yes); return false; l_yes:
@@ -52,9 +52,9 @@ static __always_inline bool arch_static_branch_jump(struct static_key *key, bool "2:\n\t" ".pushsection __jump_table, \"aw\" \n\t" _ASM_ALIGN "\n\t" - _ASM_PTR "1b, %l[l_yes], %c0 + %c1 \n\t" + _ASM_PTR "1b, %l[l_yes], %P0 \n\t" ".popsection \n\t" - : : "i" (key), "i" (branch) : : l_yes); + : : "X" (&((char *)key)[branch]) : : l_yes); return false; l_yes:
--
2.13.2.932.g7449e964c-goog
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