From: Bin Meng <bin.meng@xxxxxxxxxxxxx> This makes up the test case for the following QEMU patch: http://patchwork.ozlabs.org/project/qemu-devel/patch/1605261378-77971-1-git-send-email-bmeng.cn@xxxxxxxxx/ Note the test case only fails on an unpatched QEMU with "accel=tcg". Signed-off-by: Bin Meng <bin.meng@xxxxxxxxxxxxx> --- Sending this as RFC since I am new to kvm-unit-tests x86/emulator.c | 38 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 38 insertions(+) diff --git a/x86/emulator.c b/x86/emulator.c index e46d97e..6100b6d 100644 --- a/x86/emulator.c +++ b/x86/emulator.c @@ -6,10 +6,14 @@ #include "processor.h" #include "vmalloc.h" #include "alloc_page.h" +#include "usermode.h" #define memset __builtin_memset #define TESTDEV_IO_PORT 0xe0 +#define MAGIC_NUM 0xdeadbeefdeadbeefUL +#define GS_BASE 0x400000 + static int exceptions; /* Forced emulation prefix, used to invoke the emulator unconditionally. */ @@ -925,6 +929,39 @@ static void test_sreg(volatile uint16_t *mem) write_ss(ss); } +static uint64_t usr_gs_mov(void) +{ + static uint64_t dummy = MAGIC_NUM; + uint64_t dummy_ptr = (uint64_t)&dummy; + uint64_t ret; + + dummy_ptr -= GS_BASE; + asm volatile("mov %%gs:(%%rcx), %%rax" : "=a"(ret): "c"(dummy_ptr) :); + + return ret; +} + +static void test_iret(void) +{ + uint64_t val; + bool raised_vector; + + /* Update GS base to 4MiB */ + wrmsr(MSR_GS_BASE, GS_BASE); + + /* + * Per the SDM, jumping to user mode via `iret`, which is returning to + * outer privilege level, for segment registers (ES, FS, GS, and DS) + * if the check fails, the segment selector becomes null. + * + * In our test case, GS becomes null. + */ + val = run_in_user((usermode_func)usr_gs_mov, GP_VECTOR, + 0, 0, 0, 0, &raised_vector); + + report(val == MAGIC_NUM, "Test ret/iret with a nullified segment"); +} + /* Broken emulation causes triple fault, which skips the other tests. */ #if 0 static void test_lldt(volatile uint16_t *mem) @@ -1074,6 +1111,7 @@ int main(void) test_shld_shrd(mem); //test_lgdt_lidt(mem); test_sreg(mem); + test_iret(); //test_lldt(mem); test_ltr(mem); test_cmov(mem); -- 2.7.4
