Messages in this thread Patch in this message |  | | Subject | [PATCH] C undefined behavior fix | | From | Momchil Velikov <> | | Date | 02 Jan 2002 01:03:25 +0200 |
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[Cc: to gcc list, in case someone wants to argue about standards]
The appended patch fix incorrect code, which interferes badly with optimizations in GCC 3.0.4 and GCC 3.1.
The GCC tries to replace the strcpy from a constant string source with a memcpy, since the length is know at compile time.
Thus strcpy (dst, "abcdef" + 2) gives memcpy (dst, "abcdef" + 2, 5)
However, GCC does not handle the case, when the above offset (2) is not within the bounds of the string, which result in undefined behavior according to ANSI/ISO C99.
The error is that strcpy (namep, "linux,phandle" + 0xc0000000); gets emitted as memcpy (namep, "linux,phandle" + 0xc0000000, 14 - 0xc0000000);
Regards, -velco
--- 1.3/arch/ppc/kernel/prom.c Wed Dec 26 18:27:54 2001 +++ edited/arch/ppc/kernel/prom.c Tue Jan 1 22:53:23 2002 @@ -997,7 +997,7 @@ prev_propp = &pp->next; namep = (char *) (pp + 1); pp->name = PTRUNRELOC(namep); - strcpy(namep, RELOC("linux,phandle")); + memcpy (namep, RELOC("linux,phandle"), sizeof("linux,phandle")); mem_start = ALIGN((unsigned long)namep + strlen(namep) + 1); pp->value = (unsigned char *) PTRUNRELOC(&np->node); pp->length = sizeof(np->node); - 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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