linux-kernel - Re: linux-next: Tree for Feb 7 (objtool warning)

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Message-ID: <20200210102951.GD14879@hirez.programming.kicks-ass.net>
Date:   Mon, 10 Feb 2020 11:29:51 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Randy Dunlap <rdunlap@...radead.org>
Cc:     Stephen Rothwell <sfr@...b.auug.org.au>,
        Linux Next Mailing List <linux-next@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>
Subject: Re: linux-next: Tree for Feb 7 (objtool warning)

On Fri, Feb 07, 2020 at 08:17:25AM -0800, Randy Dunlap wrote:
> on x86_64:
> 
> drivers/gpu/drm/i915/gem/i915_gem_execbuffer.o: warning: objtool: i915_gem_execbuffer2_ioctl()+0x6c7: call to gen8_canonical_addr() with UACCESS enabled

> CONFIG_CC_OPTIMIZE_FOR_SIZE=y
> CONFIG_64BIT=y

That's just really sad, stupid compiler.

Something like so I suppose...

diff --git a/drivers/gpu/drm/i915/gt/intel_gpu_commands.h b/drivers/gpu/drm/i915/gt/intel_gpu_commands.h
index 51b8718513bc..db6b75d4572f 100644
--- a/drivers/gpu/drm/i915/gt/intel_gpu_commands.h
+++ b/drivers/gpu/drm/i915/gt/intel_gpu_commands.h
@@ -330,12 +330,12 @@
  * canonical form [63:48] == [47]."
  */
 #define GEN8_HIGH_ADDRESS_BIT 47
-static inline u64 gen8_canonical_addr(u64 address)
+static __always_inline u64 gen8_canonical_addr(u64 address)
 {
 	return sign_extend64(address, GEN8_HIGH_ADDRESS_BIT);
 }
 
-static inline u64 gen8_noncanonical_addr(u64 address)
+static __always_inline u64 gen8_noncanonical_addr(u64 address)
 {
 	return address & GENMASK_ULL(GEN8_HIGH_ADDRESS_BIT, 0);
 }
diff --git a/include/linux/bitops.h b/include/linux/bitops.h
index 47f54b459c26..9acf654f0b19 100644
--- a/include/linux/bitops.h
+++ b/include/linux/bitops.h
@@ -162,7 +162,7 @@ static inline __u8 ror8(__u8 word, unsigned int shift)
  *
  * This is safe to use for 16- and 8-bit types as well.
  */
-static inline __s32 sign_extend32(__u32 value, int index)
+static __always_inline __s32 sign_extend32(__u32 value, int index)
 {
 	__u8 shift = 31 - index;
 	return (__s32)(value << shift) >> shift;
@@ -173,7 +173,7 @@ static inline __s32 sign_extend32(__u32 value, int index)
  * @value: value to sign extend
  * @index: 0 based bit index (0<=index<64) to sign bit
  */
-static inline __s64 sign_extend64(__u64 value, int index)
+static __always_inline __s64 sign_extend64(__u64 value, int index)
 {
 	__u8 shift = 63 - index;
 	return (__s64)(value << shift) >> shift;