Re: [PATCH 04/18] arm: implement nospec_ptr()

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On 01/05/2018 05:10 PM, Dan Williams wrote:
From: Mark Rutland <mark.rutland@xxxxxxx>

This patch implements nospec_ptr() for arm, following the recommended
architectural sequences for the arm and thumb instruction sets.


Fedora picked up the series and it fails on arm:

In file included from ./include/linux/compiler.h:242:0,
                 from ./include/uapi/linux/swab.h:6,
                 from ./include/linux/swab.h:5,
                 from ./arch/arm/include/asm/opcodes.h:89,
                 from ./arch/arm/include/asm/bug.h:7,
                 from ./include/linux/bug.h:5,
                 from ./include/linux/mmdebug.h:5,
                 from ./include/linux/gfp.h:5,
                 from ./include/linux/slab.h:15,
                 from kernel/fork.c:14:
./include/linux/fdtable.h: In function '__fcheck_files':
./arch/arm/include/asm/barrier.h:112:41: error: expected declaration specifiers or '...' before numeric constant
  __load_no_speculate(&__np_ptr, lo, hi, 0, __np_ptr);  \
                                         ^
./arch/arm/include/asm/barrier.h:68:32: note: in definition of macro '__load_no_speculate_n'
   (typeof(*ptr)(unsigned long)(failval));  \
                                ^~~~~~~
./arch/arm/include/asm/barrier.h:112:2: note: in expansion of macro '__load_no_speculate'
  __load_no_speculate(&__np_ptr, lo, hi, 0, __np_ptr);  \
  ^~~~~~~~~~~~~~~~~~~
./include/asm-generic/barrier.h:122:2: note: in expansion of macro 'nospec_ptr'
  nospec_ptr(__arr + __idx, __arr, __arr + __sz);   \
  ^~~~~~~~~~
./include/linux/fdtable.h:86:13: note: in expansion of macro 'nospec_array_ptr'
  if ((fdp = nospec_array_ptr(fdt->fd, fd, fdt->max_fds)))
             ^~~~~~~~~~~~~~~~
./arch/arm/include/asm/barrier.h:112:41: error: expected declaration specifiers or '...' before numeric constant
  __load_no_speculate(&__np_ptr, lo, hi, 0, __np_ptr);  \
                                         ^
./arch/arm/include/asm/barrier.h:68:32: note: in definition of macro '__load_no_speculate_n'
   (typeof(*ptr)(unsigned long)(failval));  \
                                ^~~~~~~
./arch/arm/include/asm/barrier.h:112:2: note: in expansion of macro '__load_no_speculate'
  __load_no_speculate(&__np_ptr, lo, hi, 0, __np_ptr);  \
  ^~~~~~~~~~~~~~~~~~~
./include/asm-generic/barrier.h:122:2: note: in expansion of macro 'nospec_ptr'
  nospec_ptr(__arr + __idx, __arr, __arr + __sz);   \
  ^~~~~~~~~~
./include/linux/fdtable.h:86:13: note: in expansion of macro 'nospec_array_ptr'
  if ((fdp = nospec_array_ptr(fdt->fd, fd, fdt->max_fds)))
             ^~~~~~~~~~~~~~~~
./arch/arm/include/asm/barrier.h:112:41: error: expected declaration specifiers or '...' before numeric constant
  __load_no_speculate(&__np_ptr, lo, hi, 0, __np_ptr);  \
                                         ^
./arch/arm/include/asm/barrier.h:68:32: note: in definition of macro '__load_no_speculate_n'
   (typeof(*ptr)(unsigned long)(failval));  \
                                ^~~~~~~
./arch/arm/include/asm/barrier.h:112:2: note: in expansion of macro '__load_no_speculate'
  __load_no_speculate(&__np_ptr, lo, hi, 0, __np_ptr);  \
  ^~~~~~~~~~~~~~~~~~~
./include/asm-generic/barrier.h:122:2: note: in expansion of macro 'nospec_ptr'
  nospec_ptr(__arr + __idx, __arr, __arr + __sz);   \
  ^~~~~~~~~~
./include/linux/fdtable.h:86:13: note: in expansion of macro 'nospec_array_ptr'
  if ((fdp = nospec_array_ptr(fdt->fd, fd, fdt->max_fds)))

I can't puzzle out what exactly is the problem here, except that it really
does not seem to like that failval. Does the arm compiler not like doing
the typeof with the __arr + __idx?

Thanks,
Laura

Signed-off-by: Mark Rutland <mark.rutland@xxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
---
  arch/arm/include/asm/barrier.h |   75 ++++++++++++++++++++++++++++++++++++++++
  1 file changed, 75 insertions(+)

diff --git a/arch/arm/include/asm/barrier.h b/arch/arm/include/asm/barrier.h
index 40f5c410fd8c..6384c90e4b72 100644
--- a/arch/arm/include/asm/barrier.h
+++ b/arch/arm/include/asm/barrier.h
@@ -37,6 +37,81 @@
  #define dmb(x) __asm__ __volatile__ ("" : : : "memory")
  #endif
+#ifdef CONFIG_THUMB2_KERNEL
+#define __load_no_speculate_n(ptr, lo, hi, failval, cmpptr, sz)	\
+({								\
+	typeof(*ptr) __nln_val;					\
+	typeof(*ptr) __failval =				\
+		(typeof(*ptr)(unsigned long)(failval));		\
+								\
+	asm volatile (						\
+	"	cmp	%[c], %[l]\n"				\
+	"	it	hs\n"					\
+	"	cmphs	%[h], %[c]\n"				\
+	"	blo	1f\n"					\
+	"	ld" #sz " %[v], %[p]\n"				\
+	"1:	it	lo\n"					\
+	"	movlo	%[v], %[f]\n"				\
+	"	.inst 0xf3af8014 @ CSDB\n"			\
+	: [v] "=&r" (__nln_val)					\
+	: [p] "m" (*(ptr)), [l] "r" (lo), [h] "r" (hi),		\
+	  [f] "r" (__failval), [c] "r" (cmpptr)			\
+	: "cc");						\
+								\
+	__nln_val;						\
+})
+#else
+#define __load_no_speculate_n(ptr, lo, hi, failval, cmpptr, sz)	\
+({								\
+	typeof(*ptr) __nln_val;					\
+	typeof(*ptr) __failval =				\
+		(typeof(*ptr)(unsigned long)(failval));		\
+								\
+	asm volatile (						\
+	"	cmp	%[c], %[l]\n"				\
+	"	cmphs	%[h], %[c]\n"				\
+	"	ldr" #sz "hi %[v], %[p]\n"			\
+	"	movls	%[v], %[f]\n"				\
+	"	.inst 0xe320f014 @ CSDB\n"			\
+	: [v] "=&r" (__nln_val)					\
+	: [p] "m" (*(ptr)), [l] "r" (lo), [h] "r" (hi),		\
+	  [f] "r" (__failval), [c] "r" (cmpptr)			\
+	: "cc");						\
+								\
+	__nln_val;						\
+})
+#endif
+
+#define __load_no_speculate(ptr, lo, hi, failval, cmpptr)		\
+({									\
+	typeof(*(ptr)) __nl_val;					\
+									\
+	switch (sizeof(__nl_val)) {					\
+	case 1:								\
+		__nl_val = __load_no_speculate_n(ptr, lo, hi, failval,	\
+						 cmpptr, b);		\
+		break;							\
+	case 2:								\
+		__nl_val = __load_no_speculate_n(ptr, lo, hi, failval,	\
+						 cmpptr, h);		\
+		break;							\
+	case 4:								\
+		__nl_val = __load_no_speculate_n(ptr, lo, hi, failval,	\
+						 cmpptr, );		\
+		break;							\
+	default:							\
+		BUILD_BUG();						\
+	}								\
+									\
+	__nl_val;							\
+})
+
+#define nospec_ptr(ptr, lo, hi)						\
+({									\
+	typeof(ptr) __np_ptr = (ptr);					\
+	__load_no_speculate(&__np_ptr, lo, hi, 0, __np_ptr);		\
+})
+
  #ifdef CONFIG_ARM_HEAVY_MB
  extern void (*soc_mb)(void);
  extern void arm_heavy_mb(void);





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