Re: [Compile Regression in 2.4.25-pre8][PATCH 37/42]

Kronos
2004-02-04T20:24:03Z

Il Tue, Feb 03, 2004 at 11:14:21PM +0000, Philippe Elie ha scritto:
> > diff -Nru -X dontdiff linux-2.4-vanilla/include/asm-i386/page.h linux-2.4/include/asm-i386/page.h
> > --- linux-2.4-vanilla/include/asm-i386/page.h Tue Nov 11 18:05:52 2003
> > +++ linux-2.4/include/asm-i386/page.h Tue Feb 3 07:26:04 2004
> > @@ -10,6 +10,7 @@
> > #ifndef __ASSEMBLY__
> >
> > #include <linux/config.h>
> > +#include <linux/compiler.h>
> >
> > #ifdef CONFIG_X86_USE_3DNOW
> >
> > @@ -94,6 +95,26 @@
> > * The offending file and line are encoded after the "officially
> > * undefined" opcode for parsing in the trap handler.
> > */
> > +#ifdef __bug
> > +#if 1 /* Set to zero for a slightly smaller kernel */
> > +__bug void __bugfn(void) {
> > + while(1) {
> > + __asm__ __volatile__( "ud2\n"
> > + "\t.word %c0\n"
> > + "\t.long %c1\n"
> > + : : "i" (__LINE__), "i" (__FILE__));
> > + }
> > +}
>
> You must pass __LINE__ and __FILE__ as parameter to this function.

Good point. It's not that easy though ;)
BUG() places file name and line number after the invalid opcode (ud2) and
the kernel trap handler decodes these information when printing a BUG().
In order to do that you need immediate values to pass to assembler.

I think that the following patch will work. This is a BUG() from a dummy module
which calls BUG() in the init function:

kernel BUG at /tmp/mod3.c:22!
invalid operand: 0000 [#3]
CPU: 0
EIP: 0060:[<e09ed003>] Tainted: PF
EFLAGS: 00010202
EIP is at modinit+0x3/0x20 [mod3]
eax: e09ed000 ebx: cdf9a000 ecx: c036de78 edx: 00000000
esi: e09ed180 edi: c036de78 ebp: cdf9bfa4 esp: cdf9bfa4
ds: 007b es: 007b ss: 0068
Process insmod (pid: 1960, threadinfo=cdf9a000 task=dd7546b0)
Stack: cdf9bfbc c01345d8 0804b018 080486dd 4009199b c036de5c cdf9a000 c0109067
0804b018 0000055c 0804b008 080486dd 4009199b bffffb28 00000080 0000007b
0000007b 00000080 400fb4ce 00000073 00000246 bffffae0 0000007b
Call Trace:
[<c01345d8>] sys_init_module+0x118/0x240
[<c0109067>] syscall_call+0x7/0xb

Code: 0f 0b 16 00 25 d0 9e e0 90 8d 74 26 00 eb fe 8d b4 26 00 00
Segmentation fault

It seems ok to me (kernel is tainted because I forgot MODULE_LICENSE...).
Comments on the patch?

diff -Nru -X dontdiff linux-2.4-vanilla/include/asm-i386/page.h linux-2.4/include/asm-i386/page.h
--- linux-2.4-vanilla/include/asm-i386/page.h Tue Nov 11 18:05:52 2003
+++ linux-2.4/include/asm-i386/page.h Wed Feb 4 14:43:00 2004
@@ -95,14 +95,28 @@
* undefined" opcode for parsing in the trap handler.
*/

+#ifdef __bug
+static inline void __dummy_noreturn(void) __bug;
+static inline void __dummy_noreturn(void) {
+ while(1) {}
+}
+#else
+#define __dummy_noreturn() do {} while(0)
+#endif
+
#if 1 /* Set to zero for a slightly smaller kernel */
-#define BUG() \
- __asm__ __volatile__( "ud2\n" \
- "\t.word %c0\n" \
- "\t.long %c1\n" \
- : : "i" (__LINE__), "i" (__FILE__))
+#define BUG() do { \
+ __asm__ __volatile__( "ud2\n" \
+ "\t.word %c0\n" \
+ "\t.long %c1\n" \
+ : : "i" (__LINE__), "i" (__FILE__)); \
+ __dummy_noreturn(); \
+ } while(0)
#else
-#define BUG() __asm__ __volatile__("ud2\n")
+#define BUG() do { \
+ __asm__ __volatile__("ud2\n"); \
+ __dummy_noreturn(); \
+ } while(0)
#endif

#define PAGE_BUG(page) do { \
diff -Nru -X dontdiff linux-2.4-vanilla/include/linux/compiler.h linux-2.4/include/linux/compiler.h
--- linux-2.4-vanilla/include/linux/compiler.h Tue Sep 18 23:12:45 2001
+++ linux-2.4/include/linux/compiler.h Tue Feb 3 18:29:56 2004
@@ -13,4 +13,11 @@
#define likely(x) __builtin_expect((x),1)
#define unlikely(x) __builtin_expect((x),0)

+#if __GNUC__ >= 3
+/* __noreturn__ is implemented since gcc 2.5.
+ * __always_inline__ is not present in 2.9x
+ */
+#define __bug __attribute__((__noreturn__, __always_inline__))
+#endif
+
#endif /* __LINUX_COMPILER_H */

Luca
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