> The strace problem is a compiler flaw. > > This is the problem: > * Strace examines the applications syscall. > * Strace extracts, via PTRACE, application addresses, addresses that > don't exist in the strace address space (and should not exist). > * Strace compares extracted address to a constant SIG_ERR. > * Compiler generates a call to __c_f_f_c, which dereference the > extracted address and strace faults. > > Strace and the application have completely different address spaces, > and __c_f_f_c can't assume that an address is in the current address > space. Unfortunately, this is necessary to canonicalize function pointers. > The solution is to detect that a comparison between two pointers is a > comparison between pointer and small constant, and avoid calling > __c_f_f_c for both. __c_f_f_c would have to be passed both pointers to detect comparisons with small constants, or the GCC middle-end would have to detect comparisons with constants and avoid canonicalization in that case. > The workaround is to cast both long. I tested this and it works. I'll > submit this to debian as the fix. This is simplest fix. Dave -- J. David Anglin dave.anglin@xxxxxxxxxxxxxx National Research Council of Canada (613) 990-0752 (FAX: 952-6602) -- To unsubscribe from this list: send the line "unsubscribe linux-parisc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
