diff options
| -rw-r--r-- | tools/testing/selftests/x86/sigreturn.c | 46 |
1 files changed, 29 insertions, 17 deletions
diff --git a/tools/testing/selftests/x86/sigreturn.c b/tools/testing/selftests/x86/sigreturn.c index 246145b84a12..2559e2c01793 100644 --- a/tools/testing/selftests/x86/sigreturn.c +++ b/tools/testing/selftests/x86/sigreturn.c @@ -612,19 +612,38 @@ static int test_valid_sigreturn(int cs_bits, bool use_16bit_ss, int force_ss) greg_t req = requested_regs[i], res = resulting_regs[i]; if (i == REG_TRAPNO || i == REG_IP) continue; /* don't care */ - if (i == REG_SP) { - printf("\tSP: %llx -> %llx\n", (unsigned long long)req, - (unsigned long long)res); + if (i == REG_SP) { /* - * In many circumstances, the high 32 bits of rsp - * are zeroed. For example, we could be a real - * 32-bit program, or we could hit any of a number - * of poorly-documented IRET or segmented ESP - * oddities. If this happens, it's okay. + * If we were using a 16-bit stack segment, then + * the kernel is a bit stuck: IRET only restores + * the low 16 bits of ESP/RSP if SS is 16-bit. + * The kernel uses a hack to restore bits 31:16, + * but that hack doesn't help with bits 63:32. + * On Intel CPUs, bits 63:32 end up zeroed, and, on + * AMD CPUs, they leak the high bits of the kernel + * espfix64 stack pointer. There's very little that + * the kernel can do about it. + * + * Similarly, if we are returning to a 32-bit context, + * the CPU will often lose the high 32 bits of RSP. */ - if (res == (req & 0xFFFFFFFF)) - continue; /* OK; not expected to work */ + + if (res == req) + continue; + + if (cs_bits != 64 && ((res ^ req) & 0xFFFFFFFF) == 0) { + printf("[NOTE]\tSP: %llx -> %llx\n", + (unsigned long long)req, + (unsigned long long)res); + continue; + } + + printf("[FAIL]\tSP mismatch: requested 0x%llx; got 0x%llx\n", + (unsigned long long)requested_regs[i], + (unsigned long long)resulting_regs[i]); + nerrs++; + continue; } bool ignore_reg = false; @@ -663,13 +682,6 @@ static int test_valid_sigreturn(int cs_bits, bool use_16bit_ss, int force_ss) } if (requested_regs[i] != resulting_regs[i] && !ignore_reg) { - /* - * SP is particularly interesting here. The - * usual cause of failures is that we hit the - * nasty IRET case of returning to a 16-bit SS, - * in which case bits 16:31 of the *kernel* - * stack pointer persist in ESP. - */ printf("[FAIL]\tReg %d mismatch: requested 0x%llx; got 0x%llx\n", i, (unsigned long long)requested_regs[i], (unsigned long long)resulting_regs[i]); |