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potential gcc bug causes kvm-userspace build break

PATCH Jochen Roth 3 participants 5 messages Mar 11, 2009 KVM

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Jochen Roth

author
#0 lore raw

FYI

I just discovered a potential gcc bug which causes kvm-userspace builds to break. I looks like it happens only with the latest fedora rawhide gcc 4.4
https://bugzilla.redhat.com/show_bug.cgi?id=489753

The following patch circumvents this problem by just renaming R to REG. People facing the same problem might find this patch useful.

user/test/x86/apic.c +18 -18
index 9c6205b..ec3777c 100644
@@ -35,9 +35,9 @@ typedef struct {
 } isr_regs_t;
 
 #ifdef __x86_64__
-#  define R "r"
+#  define REG "r"
 #else
-#  define R "e"
+#  define REG "e"
 #endif
 
 extern char isr_entry_point[];

@@ -54,14 +54,14 @@ asm (
     "push %r9  \n\t"
     "push %r8  \n\t"
 #endif
-    "push %"R"di \n\t"
-    "push %"R"si \n\t"
-    "push %"R"bp \n\t"
-    "push %"R"sp \n\t"
-    "push %"R"bx \n\t"
-    "push %"R"dx \n\t"
-    "push %"R"cx \n\t"
-    "push %"R"ax \n\t"
+    "push %"REG"di \n\t"
+    "push %"REG"si \n\t"
+    "push %"REG"bp \n\t"
+    "push %"REG"sp \n\t"
+    "push %"REG"bx \n\t"
+    "push %"REG"dx \n\t"
+    "push %"REG"cx \n\t"
+    "push %"REG"ax \n\t"
 #ifdef __x86_64__
     "mov %rsp, %rdi \n\t"
     "callq *8*16(%rsp) \n\t"

@@ -70,14 +70,14 @@ asm (
     "calll *4+4*8(%esp) \n\t"
     "add $4, %esp \n\t"
 #endif
-    "pop %"R"ax \n\t"
-    "pop %"R"cx \n\t"
-    "pop %"R"dx \n\t"
-    "pop %"R"bx \n\t"
-    "pop %"R"bp \n\t"
-    "pop %"R"bp \n\t"
-    "pop %"R"si \n\t"
-    "pop %"R"di \n\t"
+    "pop %"REG"ax \n\t"
+    "pop %"REG"cx \n\t"
+    "pop %"REG"dx \n\t"
+    "pop %"REG"bx \n\t"
+    "pop %"REG"bp \n\t"
+    "pop %"REG"bp \n\t"
+    "pop %"REG"si \n\t"
+    "pop %"REG"di \n\t"
 #ifdef __x86_64__
     "pop %r8  \n\t"
     "pop %r9  \n\t"
user/test/x86/vmexit.c +3 -3
index bd57bfa..bc81be9 100644
@@ -19,9 +19,9 @@ static inline unsigned long long rdtsc()
 #define N (1 << 22)
 
 #ifdef __x86_64__
-#  define R "r"
+#  define REG "r"
 #else
-#  define R "e"
+#  define REG "e"
 #endif
 
 int main()

@@ -31,7 +31,7 @@ int main()
 
 	t1 = rdtsc();
 	for (i = 0; i < N; ++i)
-		asm volatile ("push %%"R"bx; cpuid; pop %%"R"bx"
+		asm volatile ("push %%"REG"bx; cpuid; pop %%"REG"bx"
 			      : : : "eax", "ecx", "edx");
 	t2 = rdtsc();
 	printf("vmexit latency: %d\n", (int)((t2 - t1) / N));
#1 lore raw
Quoted 10 lines · Jochen Roth

FYI

I just discovered a potential gcc bug which causes kvm-userspace builds to break.
I looks like it happens only with the latest fedora rawhide gcc 4.4
https://bugzilla.redhat.com/show_bug.cgi?id=489753

The following patch circumvents this problem by just renaming R to REG. People facing the same problem might find this patch useful.

Adding a space between the R is a much better fix, since nothing guarantees gcc won't use "REG" in the future too.

Eduardo sent a fix for this a while ago, but it was not applied.

Signature · 5 lines
Glauber  Costa.
"Free as in Freedom"
http://glommer.net

"The less confident you are, the more serious you have to act."
author
#2 lore raw
Quoted 8 lines · Glauber Costa
Quoted 7 lines · Jochen Roth

FYI

I just discovered a potential gcc bug which causes kvm-userspace builds to break.
I looks like it happens only with the latest fedora rawhide gcc 4.4
https://bugzilla.redhat.com/show_bug.cgi?id=489753

Quoted 8 lines
Quoted 3 lines

The following patch circumvents this problem by just renaming R to REG. People facing the same problem might find this patch useful.

Adding a space between the R is a much better fix, since nothing guarantees gcc won't use "REG" in the future too.

Eduardo sent a fix for this a while ago, but it was not applied.

Jakub just closed the bug. It works as designed:
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2442.htm

Shall I send another patch with spaces or do you plan to apply Eduardo's patch?

Signature · 1 line
Jochen
#3 lore raw
Quoted 20 lines · Jochen Roth
Quoted 19 lines · Glauber Costa
Quoted 12 lines · Jochen Roth

FYI

I just discovered a potential gcc bug which causes kvm-userspace builds to
break.
I looks like it happens only with the latest fedora rawhide gcc 4.4
https://bugzilla.redhat.com/show_bug.cgi?id=489753

The following patch circumvents this problem by just renaming R to REG. People facing the same problem might find this patch useful.

Adding a space between the R is a much better fix, since nothing guarantees
gcc won't use "REG" in the future too.

Quoted 8 lines
Quoted 2 lines

Eduardo sent a fix for this a while ago, but it was not applied.

Jakub just closed the bug. It works as designed:
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2442.htm

Shall I send another patch with spaces or do you plan to apply Eduardo's patch?

anthony?

Signature · 5 lines
Glauber  Costa.
"Free as in Freedom"
http://glommer.net

"The less confident you are, the more serious you have to act."
#4 lore raw
Quoted 26 lines · Glauber Costa
Quoted 24 lines · Jochen Roth
Quoted 22 lines · Glauber Costa
Quoted 12 lines · Jochen Roth

FYI

I just discovered a potential gcc bug which causes kvm-userspace builds to
break.
I looks like it happens only with the latest fedora rawhide gcc 4.4
https://bugzilla.redhat.com/show_bug.cgi?id=489753

The following patch circumvents this problem by just renaming R to REG. People facing the same problem might find this patch useful.

Adding a space between the R is a much better fix, since nothing guarantees
gcc won't use "REG" in the future too.

Eduardo sent a fix for this a while ago, but it was not applied.

Quoted 9 lines
Quoted 6 lines

Jakub just closed the bug. It works as designed:
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2442.htm

Shall I send another patch with spaces or do you plan to apply Eduardo's patch?

anthony?

I haven't seen a patch against QEMU... Was it sent to qemu-devel?

Regards,

Anthony Liguori