On Fri, Jul 28, 2017 at 05:38:52PM -0700, Matthias Kaehlcke wrote:
> El Thu, Jul 20, 2017 at 03:56:52PM -0500 Josh Poimboeuf ha dit:
>
> > On Thu, Jul 20, 2017 at 06:30:24PM +0300, Andrey Ryabinin wrote:
> > > FWIW bellow is my understanding of what's going on.
> > >
> > > It seems clang treats local named register almost the same as ordinary
> > > local variables.
> > > The only difference is that before reading the register variable clang
> > > puts variable's value into the specified register.
> > >
> > > So clang just assigns stack slot for the variable __sp where it's
> > > going to keep variable's value.
> > > But since __sp is unitialized (we haven't assign anything to it), the
> > > value of the __sp is some garbage from stack.
> > > inline asm specifies __sp as input, so clang assumes that it have to
> > > load __sp into 'rsp' because inline asm is going to use
> > > it. And it just loads garbage from stack into 'rsp'
> > >
> > > In fact, such behavior (I mean storing the value on stack and loading
> > > into reg before the use) is very useful.
> > > Clang's behavior allows to keep the value assigned to the
> > > call-clobbered register across the function calls.
> > >
> > > Unlike clang, gcc assigns value to the register right away and doesn't
> > > store the value anywhere else. So if the reg is
> > > call clobbered register you have to be absolutely sure that there is
> > > no subsequent function call that might clobber the register.
> > >
> > > E.g. see some real examples
> > > https://patchwork.kernel.org/patch/4111971/ or 98d4ded60bda("msm: scm:
> > > Fix improper register assignment").
> > > These bugs shouldn't happen with clang.
> > >
> > > But the global named register works slightly differently in clang. For
> > > the global, the value is just the value of the register itself,
> > > whatever it is. Read/write from global named register is just like
> > > direct read/write to the register
> >
> > Thanks, that clears up a lot of the confusion for me.
> >
> > Still, unfortunately, I don't think that's going to work for GCC.
> > Changing the '__sp' register variable to global in the header file
> > causes it to make a *bunch* of changes across the kernel, even in
> > functions which don't do inline asm. It seems to be disabling some
> > optimizations across the board.
> >
> > I do have another idea, which is to replace all uses of
> >
> > asm(" ... call foo ... " : outputs : inputs : clobbers);
> >
> > with a new ASM_CALL macro:
> >
> > ASM_CALL(" ... call foo ... ", outputs, inputs, clobbers);
> >
> > Then the compiler differences can be abstracted out, with GCC adding
> > "sp" as an output constraint and clang doing nothing (for now).
>
> The idea sounds interesting, however I see two issues with ASM_CALL():
>
> Inline assembly expects the individual elements of outputs, inputs and
> clobbers to be comma separated, and so does the macro for it's
> parameters.
I think this isn't a problem, see the (untested and unfinished) patch
below for an idea of how the arguments can be handled.
> The assembler template can refer to the position of output and input
> operands, adding "sp" as output changes the positions of the inputs
> wrt to the clang version.
True, though I think we could convert all ASM_CALL users to use named
operands instead of the (bug-prone) numbered ones. It would be an
improvement regardless.
> Not sure how to move forward from here. Not even using an ugly #ifdef
> seems to be a halfway reasonable solution, since get_user() isn't the
> only place using this construct and #ifdefs would result in highly
> redundant macros in multiple places.
I still think ASM_CALL might work. The below patch is what I came up
with last week before I got pulled into some other work. I'll be out on
vacation next week but I hope to finish the patch after that.
diff --git a/arch/x86/include/asm/alternative.h
b/arch/x86/include/asm/alternative.h
index 1b020381ab38..5da4bcbeebab 100644
--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -216,14 +216,14 @@ static inline int alternatives_text_reserved(void *start,
void *end)
* Otherwise, old function is used.
*/
#define alternative_call_2(oldfunc, newfunc1, feature1, newfunc2, feature2, \
- output, input...) \
+ output, input, clobbers...) \
{ \
- register void *__sp asm(_ASM_SP); \
- asm volatile (ALTERNATIVE_2("call %P[old]", "call %P[new1]", feature1,\
- "call %P[new2]", feature2) \
- : output, "+r" (__sp) \
- : [old] "i" (oldfunc), [new1] "i" (newfunc1), \
- [new2] "i" (newfunc2), ## input); \
+ ASM_CALL(ALTERNATIVE_2("call %P[old]", "call %P[new1]", feature1, \
+ "call %P[new2]", feature2), \
+ ARGS(output), \
+ ARGS([old] "i" (oldfunc), [new1] "i" (newfunc1), \
+ [new2] "i" (newfunc2), ARGS(input)), \
+ ## clobbers); \
}
/*
diff --git a/arch/x86/include/asm/page_64.h b/arch/x86/include/asm/page_64.h
index b4a0d43248cf..21adcc8e739f 100644
--- a/arch/x86/include/asm/page_64.h
+++ b/arch/x86/include/asm/page_64.h
@@ -45,8 +45,8 @@ static inline void clear_page(void *page)
clear_page_rep, X86_FEATURE_REP_GOOD,
clear_page_erms, X86_FEATURE_ERMS,
"=D" (page),
- "0" (page)
- : "memory", "rax", "rcx");
+ "0" (page),
+ ARGS("memory", "rax", "rcx"));
}
void copy_page(void *to, void *from);
diff --git a/arch/x86/include/asm/paravirt_types.h
b/arch/x86/include/asm/paravirt_types.h
index cb976bab6299..2a585b799a3e 100644
--- a/arch/x86/include/asm/paravirt_types.h
+++ b/arch/x86/include/asm/paravirt_types.h
@@ -471,8 +471,7 @@ int paravirt_disable_iospace(void);
*/
#ifdef CONFIG_X86_32
#define PVOP_VCALL_ARGS
\
- unsigned long __eax = __eax, __edx = __edx, __ecx = __ecx; \
- register void *__sp asm("esp")
+ unsigned long __eax = __eax, __edx = __edx, __ecx = __ecx;
#define PVOP_CALL_ARGS PVOP_VCALL_ARGS
#define PVOP_CALL_ARG1(x) "a" ((unsigned long)(x))
@@ -492,8 +491,7 @@ int paravirt_disable_iospace(void);
/* [re]ax isn't an arg, but the return val */
#define PVOP_VCALL_ARGS \
unsigned long __edi = __edi, __esi = __esi, \
- __edx = __edx, __ecx = __ecx, __eax = __eax; \
- register void *__sp asm("rsp")
+ __edx = __edx, __ecx = __ecx, __eax = __eax;
#define PVOP_CALL_ARGS PVOP_VCALL_ARGS
#define PVOP_CALL_ARG1(x) "D" ((unsigned long)(x))
@@ -541,24 +539,24 @@ int paravirt_disable_iospace(void);
/* This is 32-bit specific, but is okay in 64-bit */ \
/* since this condition will never hold */ \
if (sizeof(rettype) > sizeof(unsigned long)) { \
- asm volatile(pre \
- paravirt_alt(PARAVIRT_CALL) \
- post \
- : call_clbr, "+r" (__sp) \
- : paravirt_type(op), \
- paravirt_clobber(clbr), \
- ##__VA_ARGS__ \
- : "memory", "cc" extra_clbr); \
+ ASM_CALL(pre \
+ paravirt_alt(PARAVIRT_CALL) \
+ post, \
+ ARGS(call_clbr), \
+ ARGS(paravirt_type(op), \
+ paravirt_clobber(clbr), \
+ ##__VA_ARGS__), \
+ ARGS("memory", "cc" extra_clbr)); \
__ret = (rettype)((((u64)__edx) << 32) | __eax); \
} else { \
- asm volatile(pre \
- paravirt_alt(PARAVIRT_CALL) \
- post \
- : call_clbr, "+r" (__sp) \
- : paravirt_type(op), \
- paravirt_clobber(clbr), \
- ##__VA_ARGS__ \
- : "memory", "cc" extra_clbr); \
+ ASM_CALL(pre \
+ paravirt_alt(PARAVIRT_CALL) \
+ post, \
+ ARGS(call_clbr), \
+ ARGS(paravirt_type(op), \
+ paravirt_clobber(clbr), \
+ ##__VA_ARGS__), \
+ ARGS("memory", "cc" extra_clbr)); \
__ret = (rettype)(__eax & PVOP_RETMASK(rettype));
\
} \
__ret; \
@@ -578,14 +576,14 @@ int paravirt_disable_iospace(void);
({ \
PVOP_VCALL_ARGS; \
PVOP_TEST_NULL(op); \
- asm volatile(pre \
- paravirt_alt(PARAVIRT_CALL) \
- post \
- : call_clbr, "+r" (__sp) \
- : paravirt_type(op), \
- paravirt_clobber(clbr), \
- ##__VA_ARGS__ \
- : "memory", "cc" extra_clbr); \
+ ASM_CALL(pre \
+ paravirt_alt(PARAVIRT_CALL) \
+ post, \
+ ARGS(call_clbr), \
+ ARGS(paravirt_type(op), \
+ paravirt_clobber(clbr), \
+ ##__VA_ARGS__), \
+ ARGS("memory", "cc" extra_clbr)); \
})
#define __PVOP_VCALL(op, pre, post, ...) \
diff --git a/arch/x86/include/asm/preempt.h b/arch/x86/include/asm/preempt.h
index ec1f3c651150..19a034cbde37 100644
--- a/arch/x86/include/asm/preempt.h
+++ b/arch/x86/include/asm/preempt.h
@@ -102,16 +102,14 @@ static __always_inline bool should_resched(int
preempt_offset)
extern asmlinkage void ___preempt_schedule(void);
# define __preempt_schedule() \
({ \
- register void *__sp asm(_ASM_SP); \
- asm volatile ("call ___preempt_schedule" : "+r"(__sp)); \
+ ASM_CALL("call ___preempt_schedule",,); \
})
extern asmlinkage void preempt_schedule(void);
extern asmlinkage void ___preempt_schedule_notrace(void);
# define __preempt_schedule_notrace() \
({ \
- register void *__sp asm(_ASM_SP); \
- asm volatile ("call ___preempt_schedule_notrace" : "+r"(__sp)); \
+ ASM_CALL("call ___preempt_schedule_notrace",,); \
})
extern asmlinkage void preempt_schedule_notrace(void);
#endif
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h
index 550bc4ab0df4..2bbfb777c8bb 100644
--- a/arch/x86/include/asm/processor.h
+++ b/arch/x86/include/asm/processor.h
@@ -677,20 +677,19 @@ static inline void sync_core(void)
* Like all of Linux's memory ordering operations, this is a
* compiler barrier as well.
*/
- register void *__sp asm(_ASM_SP);
#ifdef CONFIG_X86_32
- asm volatile (
+ ASM_CALL(
"pushfl\n\t"
"pushl %%cs\n\t"
"pushl $1f\n\t"
"iret\n\t"
- "1:"
- : "+r" (__sp) : : "memory");
+ "1:",
+ , , "memory");
#else
unsigned int tmp;
- asm volatile (
+ ASM_CALL(
UNWIND_HINT_SAVE
"mov %%ss, %0\n\t"
"pushq %q0\n\t"
@@ -702,8 +701,8 @@ static inline void sync_core(void)
"pushq $1f\n\t"
"iretq\n\t"
UNWIND_HINT_RESTORE
- "1:"
- : "=&r" (tmp), "+r" (__sp) : : "cc", "memory");
+ "1:",
+ "=&r" (tmp), , ARGS("cc", "memory"));
#endif
}
diff --git a/arch/x86/include/asm/rwsem.h b/arch/x86/include/asm/rwsem.h
index a34e0d4b957d..9d20f4fb5d7c 100644
--- a/arch/x86/include/asm/rwsem.h
+++ b/arch/x86/include/asm/rwsem.h
@@ -99,25 +99,24 @@ static inline bool __down_read_trylock(struct rw_semaphore
*sem)
/*
* lock for writing
*/
-#define ____down_write(sem, slow_path) \
-({ \
- long tmp; \
- struct rw_semaphore* ret; \
- register void *__sp asm(_ASM_SP); \
- \
- asm volatile("# beginning down_write\n\t" \
- LOCK_PREFIX " xadd %1,(%4)\n\t" \
- /* adds 0xffff0001, returns the old value */ \
- " test " __ASM_SEL(%w1,%k1) "," __ASM_SEL(%w1,%k1) "\n\t"
\
- /* was the active mask 0 before? */\
- " jz 1f\n" \
- " call " slow_path "\n" \
- "1:\n" \
- "# ending down_write" \
- : "+m" (sem->count), "=d" (tmp), "=a" (ret), "+r" (__sp) \
- : "a" (sem), "1" (RWSEM_ACTIVE_WRITE_BIAS) \
- : "memory", "cc"); \
- ret; \
+#define ____down_write(sem, slow_path) \
+({ \
+ long tmp; \
+ struct rw_semaphore* ret; \
+ \
+ ASM_CALL("# beginning down_write\n\t" \
+ LOCK_PREFIX " xadd %1,(%3)\n\t" \
+ /* adds 0xffff0001, returns the old value */ \
+ " test " __ASM_SEL(%w1,%k1) "," __ASM_SEL(%w1,%k1) "\n\t" \
+ /* was the active mask 0 before? */ \
+ " jz 1f\n" \
+ " call " slow_path "\n" \
+ "1:\n" \
+ "# ending down_write", \
+ ARGS("+m" (sem->count), "=d" (tmp), "=a" (ret)), \
+ ARGS("a" (sem), "1" (RWSEM_ACTIVE_WRITE_BIAS)), \
+ ARGS("memory", "cc")); \
+ ret; \
})
static inline void __down_write(struct rw_semaphore *sem)
diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
index 184eb9894dae..c7be076ee703 100644
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -166,12 +166,11 @@ __typeof__(__builtin_choose_expr(sizeof(x) > sizeof(0UL),
0ULL, 0UL))
({ \
int __ret_gu; \
register __inttype(*(ptr)) __val_gu asm("%"_ASM_DX); \
- register void *__sp asm(_ASM_SP); \
__chk_user_ptr(ptr); \
might_fault(); \
- asm volatile("call __get_user_%P4" \
- : "=a" (__ret_gu), "=r" (__val_gu), "+r" (__sp) \
- : "0" (ptr), "i" (sizeof(*(ptr)))); \
+ ASM_CALL("call __get_user_%P3", \
+ ARGS("=a" (__ret_gu), "=r" (__val_gu)), \
+ ARGS("0" (ptr), "i" (sizeof(*(ptr))))); \
(x) = (__force __typeof__(*(ptr))) __val_gu; \
__builtin_expect(__ret_gu, 0); \
})
diff --git a/arch/x86/include/asm/uaccess_64.h
b/arch/x86/include/asm/uaccess_64.h
index b16f6a1d8b26..8b63e2cb1eaf 100644
--- a/arch/x86/include/asm/uaccess_64.h
+++ b/arch/x86/include/asm/uaccess_64.h
@@ -38,10 +38,9 @@ copy_user_generic(void *to, const void *from, unsigned len)
X86_FEATURE_REP_GOOD,
copy_user_enhanced_fast_string,
X86_FEATURE_ERMS,
- ASM_OUTPUT2("=a" (ret), "=D" (to), "=S" (from),
- "=d" (len)),
- "1" (to), "2" (from), "3" (len)
- : "memory", "rcx", "r8", "r9", "r10", "r11");
+ ARGS("=a" (ret), "=D" (to), "=S" (from), "=d" (len)),
+ ARGS("1" (to), "2" (from), "3" (len)),
+ ARGS("memory", "rcx", "r8", "r9", "r10", "r11"));
return ret;
}
diff --git a/arch/x86/include/asm/xen/hypercall.h
b/arch/x86/include/asm/xen/hypercall.h
index 11071fcd630e..2feddeeec1d1 100644
--- a/arch/x86/include/asm/xen/hypercall.h
+++ b/arch/x86/include/asm/xen/hypercall.h
@@ -114,9 +114,8 @@ extern struct { char _entry[32]; } hypercall_page[];
register unsigned long __arg3 asm(__HYPERCALL_ARG3REG) = __arg3; \
register unsigned long __arg4 asm(__HYPERCALL_ARG4REG) = __arg4; \
register unsigned long __arg5 asm(__HYPERCALL_ARG5REG) = __arg5; \
- register void *__sp asm(_ASM_SP);
-#define __HYPERCALL_0PARAM "=r" (__res), "+r" (__sp)
+#define __HYPERCALL_0PARAM "=r" (__res)
#define __HYPERCALL_1PARAM __HYPERCALL_0PARAM, "+r" (__arg1)
#define __HYPERCALL_2PARAM __HYPERCALL_1PARAM, "+r" (__arg2)
#define __HYPERCALL_3PARAM __HYPERCALL_2PARAM, "+r" (__arg3)
@@ -146,10 +145,10 @@ extern struct { char _entry[32]; } hypercall_page[];
({ \
__HYPERCALL_DECLS; \
__HYPERCALL_0ARG(); \
- asm volatile (__HYPERCALL \
- : __HYPERCALL_0PARAM \
- : __HYPERCALL_ENTRY(name) \
- : __HYPERCALL_CLOBBER0); \
+ ASM_CALL(__HYPERCALL, \
+ __HYPERCALL_0PARAM, \
+ __HYPERCALL_ENTRY(name), \
+ __HYPERCALL_CLOBBER0); \
(type)__res; \
})
@@ -157,10 +156,10 @@ extern struct { char _entry[32]; } hypercall_page[];
({ \
__HYPERCALL_DECLS; \
__HYPERCALL_1ARG(a1); \
- asm volatile (__HYPERCALL \
- : __HYPERCALL_1PARAM \
- : __HYPERCALL_ENTRY(name) \
- : __HYPERCALL_CLOBBER1); \
+ ASM_CALL(__HYPERCALL, \
+ __HYPERCALL_1PARAM, \
+ __HYPERCALL_ENTRY(name), \
+ __HYPERCALL_CLOBBER1); \
(type)__res; \
})
@@ -168,10 +167,10 @@ extern struct { char _entry[32]; } hypercall_page[];
({ \
__HYPERCALL_DECLS; \
__HYPERCALL_2ARG(a1, a2); \
- asm volatile (__HYPERCALL \
- : __HYPERCALL_2PARAM \
- : __HYPERCALL_ENTRY(name) \
- : __HYPERCALL_CLOBBER2); \
+ ASM_CALL(__HYPERCALL, \
+ __HYPERCALL_2PARAM, \
+ __HYPERCALL_ENTRY(name), \
+ __HYPERCALL_CLOBBER2); \
(type)__res; \
})
@@ -179,10 +178,10 @@ extern struct { char _entry[32]; } hypercall_page[];
({ \
__HYPERCALL_DECLS; \
__HYPERCALL_3ARG(a1, a2, a3); \
- asm volatile (__HYPERCALL \
- : __HYPERCALL_3PARAM \
- : __HYPERCALL_ENTRY(name) \
- : __HYPERCALL_CLOBBER3); \
+ ASM_CALL(__HYPERCALL, \
+ __HYPERCALL_3PARAM, \
+ __HYPERCALL_ENTRY(name), \
+ __HYPERCALL_CLOBBER3); \
(type)__res; \
})
@@ -190,10 +189,10 @@ extern struct { char _entry[32]; } hypercall_page[];
({ \
__HYPERCALL_DECLS; \
__HYPERCALL_4ARG(a1, a2, a3, a4); \
- asm volatile (__HYPERCALL \
- : __HYPERCALL_4PARAM \
- : __HYPERCALL_ENTRY(name) \
- : __HYPERCALL_CLOBBER4); \
+ ASM_CALL(__HYPERCALL, \
+ __HYPERCALL_4PARAM, \
+ __HYPERCALL_ENTRY(name), \
+ __HYPERCALL_CLOBBER4); \
(type)__res; \
})
@@ -201,10 +200,10 @@ extern struct { char _entry[32]; } hypercall_page[];
({ \
__HYPERCALL_DECLS; \
__HYPERCALL_5ARG(a1, a2, a3, a4, a5); \
- asm volatile (__HYPERCALL \
- : __HYPERCALL_5PARAM \
- : __HYPERCALL_ENTRY(name) \
- : __HYPERCALL_CLOBBER5); \
+ ASM_CALL(__HYPERCALL, \
+ __HYPERCALL_5PARAM, \
+ __HYPERCALL_ENTRY(name), \
+ __HYPERCALL_CLOBBER5); \
(type)__res; \
})
@@ -218,10 +217,10 @@ privcmd_call(unsigned call,
__HYPERCALL_5ARG(a1, a2, a3, a4, a5);
stac();
- asm volatile("call *%[call]"
- : __HYPERCALL_5PARAM
- : [call] "a" (&hypercall_page[call])
- : __HYPERCALL_CLOBBER5);
+ ASM_CALL("call *%[call]",
+ __HYPERCALL_5PARAM,
+ [call] "a" (&hypercall_page[call]),
+ __HYPERCALL_CLOBBER5);
clac();
return (long)__res;
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index fb0055953fbc..4d0d326029a7 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -5284,16 +5284,15 @@ static void fetch_possible_mmx_operand(struct
x86_emulate_ctxt *ctxt,
static int fastop(struct x86_emulate_ctxt *ctxt, void (*fop)(struct fastop *))
{
- register void *__sp asm(_ASM_SP);
ulong flags = (ctxt->eflags & EFLAGS_MASK) | X86_EFLAGS_IF;
if (!(ctxt->d & ByteOp))
fop += __ffs(ctxt->dst.bytes) * FASTOP_SIZE;
- asm("push %[flags]; popf; call *%[fastop]; pushf; pop %[flags]\n"
- : "+a"(ctxt->dst.val), "+d"(ctxt->src.val), [flags]"+D"(flags),
- [fastop]"+S"(fop), "+r"(__sp)
- : "c"(ctxt->src2.val));
+ ASM_CALL("push %[flags]; popf; call *%[fastop]; pushf; pop %[flags]\n",
+ ARGS("+a"(ctxt->dst.val), "+d"(ctxt->src.val),
+ [flags]"+D"(flags), [fastop]"+S"(fop)),
+ ARGS("c"(ctxt->src2.val)));
ctxt->eflags = (ctxt->eflags & ~EFLAGS_MASK) | (flags & EFLAGS_MASK);
if (!fop) /* exception is returned in fop variable */
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index ffd469ecad57..d42806ad3c9c 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -8671,7 +8671,6 @@ static void vmx_complete_atomic_exit(struct vcpu_vmx *vmx)
static void vmx_handle_external_intr(struct kvm_vcpu *vcpu)
{
u32 exit_intr_info = vmcs_read32(VM_EXIT_INTR_INFO);
- register void *__sp asm(_ASM_SP);
if ((exit_intr_info & (INTR_INFO_VALID_MASK | INTR_INFO_INTR_TYPE_MASK))
== (INTR_INFO_VALID_MASK | INTR_TYPE_EXT_INTR)) {
@@ -8686,7 +8685,7 @@ static void vmx_handle_external_intr(struct kvm_vcpu
*vcpu)
vector = exit_intr_info & INTR_INFO_VECTOR_MASK;
desc = (gate_desc *)vmx->host_idt_base + vector;
entry = gate_offset(*desc);
- asm volatile(
+ ASM_CALL(
#ifdef CONFIG_X86_64
"mov %%" _ASM_SP ", %[sp]\n\t"
"and $0xfffffffffffffff0, %%" _ASM_SP "\n\t"
@@ -8695,16 +8694,14 @@ static void vmx_handle_external_intr(struct kvm_vcpu
*vcpu)
#endif
"pushf\n\t"
__ASM_SIZE(push) " $%c[cs]\n\t"
- "call *%[entry]\n\t"
- :
+ "call *%[entry]\n\t",
#ifdef CONFIG_X86_64
- [sp]"=&r"(tmp),
+ [sp]"=&r"(tmp)
#endif
- "+r"(__sp)
- :
- [entry]"r"(entry),
- [ss]"i"(__KERNEL_DS),
- [cs]"i"(__KERNEL_CS)
+ ,
+ ARGS([entry]"r"(entry),
+ [ss]"i"(__KERNEL_DS),
+ [cs]"i"(__KERNEL_CS))
);
}
}
diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 2a1fa10c6a98..ca642ac3a390 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -802,7 +802,6 @@ no_context(struct pt_regs *regs, unsigned long error_code,
if (is_vmalloc_addr((void *)address) &&
(((unsigned long)tsk->stack - 1 - address < PAGE_SIZE) ||
address - ((unsigned long)tsk->stack + THREAD_SIZE) < PAGE_SIZE)) {
- register void *__sp asm("rsp");
unsigned long stack =
this_cpu_read(orig_ist.ist[DOUBLEFAULT_STACK]) - sizeof(void *);
/*
* We're likely to be running with very little stack space
@@ -814,13 +813,12 @@ no_context(struct pt_regs *regs, unsigned long error_code,
* and then double-fault, though, because we're likely to
* break the console driver and lose most of the stack dump.
*/
- asm volatile ("movq %[stack], %%rsp\n\t"
- "call handle_stack_overflow\n\t"
- "1: jmp 1b"
- : "+r" (__sp)
- : "D" ("kernel stack overflow (page fault)"),
- "S" (regs), "d" (address),
- [stack] "rm" (stack));
+ ASM_CALL("movq %[stack], %%rsp\n\t"
+ "call handle_stack_overflow\n\t"
+ "1: jmp 1b",
+ ,
+ ARGS("D" ("kernel stack overflow (page fault)"),
+ "S" (regs), "d" (address), [stack] "rm" (stack)));
unreachable();
}
#endif
diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index 3f8c88e29a46..3a57f32a0bfd 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -589,4 +589,18 @@ static __always_inline void __write_once_size(volatile
void *p, void *res, int s
(_________p1); \
})
+#define ARGS(args...) args
+
+#ifdef CONFIG_FRAME_POINTER
+
+#define ASM_CALL(str, outputs, inputs, clobbers...) \
+ asm volatile(str : outputs : inputs : "sp", ## clobbers)
+
+#else
+
+#define ASM_CALL(str, outputs, inputs, clobbers...) \
+ asm volatile(str : outputs : inputs : clobbers);
+
+#endif
+
#endif /* __LINUX_COMPILER_H */
diff --git a/tools/objtool/Documentation/stack-validation.txt
b/tools/objtool/Documentation/stack-validation.txt
index 6a1af43862df..766a00ebf80c 100644
--- a/tools/objtool/Documentation/stack-validation.txt
+++ b/tools/objtool/Documentation/stack-validation.txt
@@ -193,13 +193,8 @@ they mean, and suggestions for how to fix them.
If it's a GCC-compiled .c file, the error may be because the function
uses an inline asm() statement which has a "call" instruction. An
- asm() statement with a call instruction must declare the use of the
- stack pointer in its output operand. For example, on x86_64:
-
- register void *__sp asm("rsp");
- asm volatile("call func" : "+r" (__sp));
-
- Otherwise the stack frame may not get created before the call.
+ asm() statement with a call instruction must use the ASM_CALL macro,
+ which forces the frame pointer to be saved before the call.
2. file.o: warning: objtool: .text+0x53: unreachable instruction
@@ -221,7 +216,7 @@ they mean, and suggestions for how to fix them.
change ENDPROC to END.
-4. file.o: warning: objtool: func(): can't find starting instruction
+3. file.o: warning: objtool: func(): can't find starting instruction
or
file.o: warning: objtool: func()+0x11dd: can't decode instruction
@@ -230,7 +225,7 @@ they mean, and suggestions for how to fix them.
section like .data or .rodata.
-5. file.o: warning: objtool: func()+0x6: unsupported instruction in callable
function
+4. file.o: warning: objtool: func()+0x6: unsupported instruction in callable
function
This is a kernel entry/exit instruction like sysenter or iret. Such
instructions aren't allowed in a callable function, and are most
@@ -239,7 +234,7 @@ they mean, and suggestions for how to fix them.
annotated with the unwind hint macros in asm/unwind_hints.h.
-6. file.o: warning: objtool: func()+0x26: sibling call from callable
instruction with modified stack frame
+5. file.o: warning: objtool: func()+0x26: sibling call from callable
instruction with modified stack frame
This is a dynamic jump or a jump to an undefined symbol. Objtool
assumed it's a sibling call and detected that the frame pointer
@@ -253,7 +248,7 @@ they mean, and suggestions for how to fix them.
the unwind hint macros in asm/unwind_hints.h.
-7. file: warning: objtool: func()+0x5c: stack state mismatch
+6. file: warning: objtool: func()+0x5c: stack state mismatch
The instruction's frame pointer state is inconsistent, depending on
which execution path was taken to reach the instruction.
@@ -270,7 +265,7 @@ they mean, and suggestions for how to fix them.
asm/unwind_hints.h.
-8. file.o: warning: objtool: funcA() falls through to next function funcB()
+7. file.o: warning: objtool: funcA() falls through to next function funcB()
This means that funcA() doesn't end with a return instruction or an
unconditional jump, and that objtool has determined that the function
