Messages in this thread Patch in this message | | | Date | Thu, 28 Sep 2006 16:30:19 +0100 (BST) | From | Hugh Dickins <> | Subject | Re: [PATCH] Put the BUG __FILE__ and __LINE__ info out of line |
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On Thu, 28 Sep 2006, Andi Kleen wrote: > On Thu, Sep 28, 2006 at 03:30:12AM -0700, Jeremy Fitzhardinge wrote: > > Andi Kleen wrote: > > >But no out of line section. So overall it's smaller, although the cache > > >footprint > > >is 2 bytes larger. But then is 2 bytes larger really an issue? We don't > > >have > > >_that_ many BUGs anyways. > > > > > > > I think the out of line section is a feature; no point in crufting up > > the icache with BUG gunk, especially since a number of them are on > > fairly hot paths. > > It's 10 bytes per BUG.
Or 9 bytes per BUG: I protested about the disassembly problem back when the minimized BUG() first went in, and have been using "ljmp" in my i386 builds ever since:
--- 2.6.18-git9/arch/i386/kernel/traps.c 2006-09-28 12:03:47.000000000 +0100 +++ linux/arch/i386/kernel/traps.c 2006-09-28 16:23:56.000000000 +0100 @@ -422,10 +422,10 @@ static void handle_BUG(struct pt_regs *r char *file; char c; - if (probe_kernel_address((unsigned short __user *)(eip + 2), + if (probe_kernel_address((unsigned short __user *)(eip + 7), line)) break; - if (__get_user(file, (char * __user *)(eip + 4)) || + if (__get_user(file, (char * __user *)(eip + 3)) || (unsigned long)file < PAGE_OFFSET || __get_user(c, file)) file = "<bad filename>"; --- 2.6.18-git9/include/asm-i386/bug.h 2006-09-20 04:42:06.000000000 +0100 +++ linux/include/asm-i386/bug.h 2006-09-28 16:23:56.000000000 +0100 @@ -13,9 +13,11 @@ #ifdef CONFIG_DEBUG_BUGVERBOSE #define BUG() \ __asm__ __volatile__( "ud2\n" \ - "\t.word %c0\n" \ - "\t.long %c1\n" \ - : : "i" (__LINE__), "i" (__FILE__)) + "\t.byte 0xea\n" \ + "\t.long %c0\n" \ + "\t.word %c1\n" \ + : : "i" (__FILE__), "i" (__LINE__)) + /* "ljmp long short" so disassemblers can make sense of it */ #else #define BUG() __asm__ __volatile__("ud2\n") #endif - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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