[PATCH v5sub2 1/8] arm64: add support for module PLTs
Will Deacon
will.deacon at arm.com
Thu Feb 25 10:29:03 PST 2016
On Thu, Feb 25, 2016 at 06:31:04PM +0100, Ard Biesheuvel wrote:
> On 25 February 2016 at 17:56, Will Deacon <will.deacon at arm.com> wrote:
> > the plt will do:
> >
> > get_addr_of_callee_into_x16_and_clobber_x17_or_something
> > br callee
> >
> > then the callee will be compiled with all those weird options, but *not*
> > the ones specifying x16 and x17. That means it can happily use those guys
> > as scratch, because the caller will take care of them.
> >
>
> Yes, that makes sense. But if you don't relax that restriction, you
> only need the alternative __LL_SC_CALL for modules.
Totally untested patch below, but I'll give it a whirl tomorrow.
It looks a bit mental.
Will
--->8
diff --git a/arch/arm64/include/asm/atomic_lse.h b/arch/arm64/include/asm/atomic_lse.h
index 197e06afbf71..5b595b32ab40 100644
--- a/arch/arm64/include/asm/atomic_lse.h
+++ b/arch/arm64/include/asm/atomic_lse.h
@@ -33,6 +33,8 @@ static inline void atomic_andnot(int i, atomic_t *v)
register atomic_t *x1 asm ("x1") = v;
asm volatile(ARM64_LSE_ATOMIC_INSN(__LL_SC_ATOMIC(andnot),
+ " nop\n"
+ " nop\n"
" stclr %w[i], %[v]\n")
: [i] "+r" (w0), [v] "+Q" (v->counter)
: "r" (x1)
@@ -45,6 +47,8 @@ static inline void atomic_or(int i, atomic_t *v)
register atomic_t *x1 asm ("x1") = v;
asm volatile(ARM64_LSE_ATOMIC_INSN(__LL_SC_ATOMIC(or),
+ " nop\n"
+ " nop\n"
" stset %w[i], %[v]\n")
: [i] "+r" (w0), [v] "+Q" (v->counter)
: "r" (x1)
@@ -57,6 +61,8 @@ static inline void atomic_xor(int i, atomic_t *v)
register atomic_t *x1 asm ("x1") = v;
asm volatile(ARM64_LSE_ATOMIC_INSN(__LL_SC_ATOMIC(xor),
+ " nop\n"
+ " nop\n"
" steor %w[i], %[v]\n")
: [i] "+r" (w0), [v] "+Q" (v->counter)
: "r" (x1)
@@ -69,6 +75,8 @@ static inline void atomic_add(int i, atomic_t *v)
register atomic_t *x1 asm ("x1") = v;
asm volatile(ARM64_LSE_ATOMIC_INSN(__LL_SC_ATOMIC(add),
+ " nop\n"
+ " nop\n"
" stadd %w[i], %[v]\n")
: [i] "+r" (w0), [v] "+Q" (v->counter)
: "r" (x1)
@@ -83,9 +91,9 @@ static inline int atomic_add_return##name(int i, atomic_t *v) \
\
asm volatile(ARM64_LSE_ATOMIC_INSN( \
/* LL/SC */ \
- " nop\n" \
__LL_SC_ATOMIC(add_return##name), \
/* LSE atomics */ \
+ " nop\n" \
" ldadd" #mb " %w[i], w30, %[v]\n" \
" add %w[i], %w[i], w30") \
: [i] "+r" (w0), [v] "+Q" (v->counter) \
@@ -109,9 +117,9 @@ static inline void atomic_and(int i, atomic_t *v)
asm volatile(ARM64_LSE_ATOMIC_INSN(
/* LL/SC */
- " nop\n"
__LL_SC_ATOMIC(and),
/* LSE atomics */
+ " nop\n"
" mvn %w[i], %w[i]\n"
" stclr %w[i], %[v]")
: [i] "+r" (w0), [v] "+Q" (v->counter)
@@ -126,9 +134,9 @@ static inline void atomic_sub(int i, atomic_t *v)
asm volatile(ARM64_LSE_ATOMIC_INSN(
/* LL/SC */
- " nop\n"
__LL_SC_ATOMIC(sub),
/* LSE atomics */
+ " nop\n"
" neg %w[i], %w[i]\n"
" stadd %w[i], %[v]")
: [i] "+r" (w0), [v] "+Q" (v->counter)
@@ -144,9 +152,7 @@ static inline int atomic_sub_return##name(int i, atomic_t *v) \
\
asm volatile(ARM64_LSE_ATOMIC_INSN( \
/* LL/SC */ \
- " nop\n" \
- __LL_SC_ATOMIC(sub_return##name) \
- " nop", \
+ __LL_SC_ATOMIC(sub_return##name), \
/* LSE atomics */ \
" neg %w[i], %w[i]\n" \
" ldadd" #mb " %w[i], w30, %[v]\n" \
@@ -174,6 +180,8 @@ static inline void atomic64_andnot(long i, atomic64_t *v)
register atomic64_t *x1 asm ("x1") = v;
asm volatile(ARM64_LSE_ATOMIC_INSN(__LL_SC_ATOMIC64(andnot),
+ " nop\n"
+ " nop\n"
" stclr %[i], %[v]\n")
: [i] "+r" (x0), [v] "+Q" (v->counter)
: "r" (x1)
@@ -186,6 +194,8 @@ static inline void atomic64_or(long i, atomic64_t *v)
register atomic64_t *x1 asm ("x1") = v;
asm volatile(ARM64_LSE_ATOMIC_INSN(__LL_SC_ATOMIC64(or),
+ " nop\n"
+ " nop\n"
" stset %[i], %[v]\n")
: [i] "+r" (x0), [v] "+Q" (v->counter)
: "r" (x1)
@@ -198,6 +208,8 @@ static inline void atomic64_xor(long i, atomic64_t *v)
register atomic64_t *x1 asm ("x1") = v;
asm volatile(ARM64_LSE_ATOMIC_INSN(__LL_SC_ATOMIC64(xor),
+ " nop\n"
+ " nop\n"
" steor %[i], %[v]\n")
: [i] "+r" (x0), [v] "+Q" (v->counter)
: "r" (x1)
@@ -210,6 +222,8 @@ static inline void atomic64_add(long i, atomic64_t *v)
register atomic64_t *x1 asm ("x1") = v;
asm volatile(ARM64_LSE_ATOMIC_INSN(__LL_SC_ATOMIC64(add),
+ " nop\n"
+ " nop\n"
" stadd %[i], %[v]\n")
: [i] "+r" (x0), [v] "+Q" (v->counter)
: "r" (x1)
@@ -224,9 +238,9 @@ static inline long atomic64_add_return##name(long i, atomic64_t *v) \
\
asm volatile(ARM64_LSE_ATOMIC_INSN( \
/* LL/SC */ \
- " nop\n" \
__LL_SC_ATOMIC64(add_return##name), \
/* LSE atomics */ \
+ " nop\n" \
" ldadd" #mb " %[i], x30, %[v]\n" \
" add %[i], %[i], x30") \
: [i] "+r" (x0), [v] "+Q" (v->counter) \
@@ -250,9 +264,9 @@ static inline void atomic64_and(long i, atomic64_t *v)
asm volatile(ARM64_LSE_ATOMIC_INSN(
/* LL/SC */
- " nop\n"
__LL_SC_ATOMIC64(and),
/* LSE atomics */
+ " nop\n"
" mvn %[i], %[i]\n"
" stclr %[i], %[v]")
: [i] "+r" (x0), [v] "+Q" (v->counter)
@@ -267,9 +281,9 @@ static inline void atomic64_sub(long i, atomic64_t *v)
asm volatile(ARM64_LSE_ATOMIC_INSN(
/* LL/SC */
- " nop\n"
__LL_SC_ATOMIC64(sub),
/* LSE atomics */
+ " nop\n"
" neg %[i], %[i]\n"
" stadd %[i], %[v]")
: [i] "+r" (x0), [v] "+Q" (v->counter)
@@ -285,9 +299,7 @@ static inline long atomic64_sub_return##name(long i, atomic64_t *v) \
\
asm volatile(ARM64_LSE_ATOMIC_INSN( \
/* LL/SC */ \
- " nop\n" \
- __LL_SC_ATOMIC64(sub_return##name) \
- " nop", \
+ __LL_SC_ATOMIC64(sub_return##name), \
/* LSE atomics */ \
" neg %[i], %[i]\n" \
" ldadd" #mb " %[i], x30, %[v]\n" \
@@ -312,12 +324,10 @@ static inline long atomic64_dec_if_positive(atomic64_t *v)
asm volatile(ARM64_LSE_ATOMIC_INSN(
/* LL/SC */
- " nop\n"
__LL_SC_ATOMIC64(dec_if_positive)
" nop\n"
" nop\n"
" nop\n"
- " nop\n"
" nop",
/* LSE atomics */
"1: ldr x30, %[v]\n"
@@ -350,9 +360,7 @@ static inline unsigned long __cmpxchg_case_##name(volatile void *ptr, \
\
asm volatile(ARM64_LSE_ATOMIC_INSN( \
/* LL/SC */ \
- " nop\n" \
- __LL_SC_CMPXCHG(name) \
- " nop", \
+ __LL_SC_CMPXCHG(name), \
/* LSE atomics */ \
" mov " #w "30, %" #w "[old]\n" \
" cas" #mb #sz "\t" #w "30, %" #w "[new], %[v]\n" \
@@ -404,8 +412,6 @@ static inline long __cmpxchg_double##name(unsigned long old1, \
asm volatile(ARM64_LSE_ATOMIC_INSN( \
/* LL/SC */ \
" nop\n" \
- " nop\n" \
- " nop\n" \
__LL_SC_CMPXCHG_DBL(name), \
/* LSE atomics */ \
" casp" #mb "\t%[old1], %[old2], %[new1], %[new2], %[v]\n"\
diff --git a/arch/arm64/include/asm/lse.h b/arch/arm64/include/asm/lse.h
index 3de42d68611d..8252dc6b3046 100644
--- a/arch/arm64/include/asm/lse.h
+++ b/arch/arm64/include/asm/lse.h
@@ -25,7 +25,10 @@ __asm__(".arch_extension lse");
#define __LL_SC_EXPORT(x) EXPORT_SYMBOL(__LL_SC_PREFIX(x))
/* Macro for constructing calls to out-of-line ll/sc atomics */
-#define __LL_SC_CALL(op) "bl\t" __stringify(__LL_SC_PREFIX(op)) "\n"
+#define __LL_SC_CALL(op) \
+ "stp x16, x17, [sp, #-16]!\n" \
+ "bl\t" __stringify(__LL_SC_PREFIX(op)) "\n" \
+ "ldp x16, x17, [sp], #16\n"
/* In-line patching at runtime */
#define ARM64_LSE_ATOMIC_INSN(llsc, lse) \
diff --git a/arch/arm64/lib/Makefile b/arch/arm64/lib/Makefile
index 1a811ecf71da..c86b7909ef31 100644
--- a/arch/arm64/lib/Makefile
+++ b/arch/arm64/lib/Makefile
@@ -4,15 +4,16 @@ lib-y := bitops.o clear_user.o delay.o copy_from_user.o \
memcmp.o strcmp.o strncmp.o strlen.o strnlen.o \
strchr.o strrchr.o
-# Tell the compiler to treat all general purpose registers as
-# callee-saved, which allows for efficient runtime patching of the bl
-# instruction in the caller with an atomic instruction when supported by
-# the CPU. Result and argument registers are handled correctly, based on
-# the function prototype.
+# Tell the compiler to treat all general purpose registers (with the
+# exception of the IP registers, which are already handled by the caller
+# in case of a PLT) as callee-saved, which allows for efficient runtime
+# patching of the bl instruction in the caller with an atomic instruction
+# when supported by the CPU. Result and argument registers are handled
+# correctly, based on the function prototype.
lib-$(CONFIG_ARM64_LSE_ATOMICS) += atomic_ll_sc.o
CFLAGS_atomic_ll_sc.o := -fcall-used-x0 -ffixed-x1 -ffixed-x2 \
-ffixed-x3 -ffixed-x4 -ffixed-x5 -ffixed-x6 \
-ffixed-x7 -fcall-saved-x8 -fcall-saved-x9 \
-fcall-saved-x10 -fcall-saved-x11 -fcall-saved-x12 \
-fcall-saved-x13 -fcall-saved-x14 -fcall-saved-x15 \
- -fcall-saved-x16 -fcall-saved-x17 -fcall-saved-x18
+ -fcall-saved-x18
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