From d63f4b5269e93759d3036932890c96d7a8639e5b Mon Sep 17 00:00:00 2001 From: Andy Lutomirski Date: Tue, 26 Apr 2016 12:23:31 -0700 Subject: [PATCH] selftests/x86/ldt_gdt: Test set_thread_area() deletion of an active segment Now that set_thread_area() is supposed to give deterministic behavior when it modifies in-use segments, test it. Signed-off-by: Andy Lutomirski Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/f2bc11af1ee1a0f815ed910840cbdba06b640a20.1461698311.git.luto@kernel.org Signed-off-by: Ingo Molnar --- tools/testing/selftests/x86/ldt_gdt.c | 250 ++++++++++++++++++++++++++ 1 file changed, 250 insertions(+) diff --git a/tools/testing/selftests/x86/ldt_gdt.c b/tools/testing/selftests/x86/ldt_gdt.c index 31a3035cd4eb..4af47079cf04 100644 --- a/tools/testing/selftests/x86/ldt_gdt.c +++ b/tools/testing/selftests/x86/ldt_gdt.c @@ -21,6 +21,9 @@ #include #include #include +#include +#include +#include #define AR_ACCESSED (1<<8) @@ -44,6 +47,12 @@ static int nerrs; +/* Points to an array of 1024 ints, each holding its own index. */ +static const unsigned int *counter_page; +static struct user_desc *low_user_desc; +static struct user_desc *low_user_desc_clear; /* Use to delete GDT entry */ +static int gdt_entry_num; + static void check_invalid_segment(uint16_t index, int ldt) { uint32_t has_limit = 0, has_ar = 0, limit, ar; @@ -561,16 +570,257 @@ static void do_exec_test(void) } } +static void setup_counter_page(void) +{ + unsigned int *page = mmap(NULL, 4096, PROT_READ | PROT_WRITE, + MAP_ANONYMOUS | MAP_PRIVATE | MAP_32BIT, -1, 0); + if (page == MAP_FAILED) + err(1, "mmap"); + + for (int i = 0; i < 1024; i++) + page[i] = i; + counter_page = page; +} + +static int invoke_set_thread_area(void) +{ + int ret; + asm volatile ("int $0x80" + : "=a" (ret), "+m" (low_user_desc) : + "a" (243), "b" (low_user_desc) + : "flags"); + return ret; +} + +static void setup_low_user_desc(void) +{ + low_user_desc = mmap(NULL, 2 * sizeof(struct user_desc), + PROT_READ | PROT_WRITE, + MAP_ANONYMOUS | MAP_PRIVATE | MAP_32BIT, -1, 0); + if (low_user_desc == MAP_FAILED) + err(1, "mmap"); + + low_user_desc->entry_number = -1; + low_user_desc->base_addr = (unsigned long)&counter_page[1]; + low_user_desc->limit = 0xfffff; + low_user_desc->seg_32bit = 1; + low_user_desc->contents = 0; /* Data, grow-up*/ + low_user_desc->read_exec_only = 0; + low_user_desc->limit_in_pages = 1; + low_user_desc->seg_not_present = 0; + low_user_desc->useable = 0; + + if (invoke_set_thread_area() == 0) { + gdt_entry_num = low_user_desc->entry_number; + printf("[NOTE]\tset_thread_area is available; will use GDT index %d\n", gdt_entry_num); + } else { + printf("[NOTE]\tset_thread_area is unavailable\n"); + } + + low_user_desc_clear = low_user_desc + 1; + low_user_desc_clear->entry_number = gdt_entry_num; + low_user_desc_clear->read_exec_only = 1; + low_user_desc_clear->seg_not_present = 1; +} + +static void test_gdt_invalidation(void) +{ + if (!gdt_entry_num) + return; /* 64-bit only system -- we can't use set_thread_area */ + + unsigned short prev_sel; + unsigned short sel; + unsigned int eax; + const char *result; +#ifdef __x86_64__ + unsigned long saved_base; + unsigned long new_base; +#endif + + /* Test DS */ + invoke_set_thread_area(); + eax = 243; + sel = (gdt_entry_num << 3) | 3; + asm volatile ("movw %%ds, %[prev_sel]\n\t" + "movw %[sel], %%ds\n\t" +#ifdef __i386__ + "pushl %%ebx\n\t" +#endif + "movl %[arg1], %%ebx\n\t" + "int $0x80\n\t" /* Should invalidate ds */ +#ifdef __i386__ + "popl %%ebx\n\t" +#endif + "movw %%ds, %[sel]\n\t" + "movw %[prev_sel], %%ds" + : [prev_sel] "=&r" (prev_sel), [sel] "+r" (sel), + "+a" (eax) + : "m" (low_user_desc_clear), + [arg1] "r" ((unsigned int)(unsigned long)low_user_desc_clear) + : "flags"); + + if (sel != 0) { + result = "FAIL"; + nerrs++; + } else { + result = "OK"; + } + printf("[%s]\tInvalidate DS with set_thread_area: new DS = 0x%hx\n", + result, sel); + + /* Test ES */ + invoke_set_thread_area(); + eax = 243; + sel = (gdt_entry_num << 3) | 3; + asm volatile ("movw %%es, %[prev_sel]\n\t" + "movw %[sel], %%es\n\t" +#ifdef __i386__ + "pushl %%ebx\n\t" +#endif + "movl %[arg1], %%ebx\n\t" + "int $0x80\n\t" /* Should invalidate es */ +#ifdef __i386__ + "popl %%ebx\n\t" +#endif + "movw %%es, %[sel]\n\t" + "movw %[prev_sel], %%es" + : [prev_sel] "=&r" (prev_sel), [sel] "+r" (sel), + "+a" (eax) + : "m" (low_user_desc_clear), + [arg1] "r" ((unsigned int)(unsigned long)low_user_desc_clear) + : "flags"); + + if (sel != 0) { + result = "FAIL"; + nerrs++; + } else { + result = "OK"; + } + printf("[%s]\tInvalidate ES with set_thread_area: new ES = 0x%hx\n", + result, sel); + + /* Test FS */ + invoke_set_thread_area(); + eax = 243; + sel = (gdt_entry_num << 3) | 3; +#ifdef __x86_64__ + syscall(SYS_arch_prctl, ARCH_GET_FS, &saved_base); +#endif + asm volatile ("movw %%fs, %[prev_sel]\n\t" + "movw %[sel], %%fs\n\t" +#ifdef __i386__ + "pushl %%ebx\n\t" +#endif + "movl %[arg1], %%ebx\n\t" + "int $0x80\n\t" /* Should invalidate fs */ +#ifdef __i386__ + "popl %%ebx\n\t" +#endif + "movw %%fs, %[sel]\n\t" + : [prev_sel] "=&r" (prev_sel), [sel] "+r" (sel), + "+a" (eax) + : "m" (low_user_desc_clear), + [arg1] "r" ((unsigned int)(unsigned long)low_user_desc_clear) + : "flags"); + +#ifdef __x86_64__ + syscall(SYS_arch_prctl, ARCH_GET_FS, &new_base); +#endif + + /* Restore FS/BASE for glibc */ + asm volatile ("movw %[prev_sel], %%fs" : : [prev_sel] "rm" (prev_sel)); +#ifdef __x86_64__ + if (saved_base) + syscall(SYS_arch_prctl, ARCH_SET_FS, saved_base); +#endif + + if (sel != 0) { + result = "FAIL"; + nerrs++; + } else { + result = "OK"; + } + printf("[%s]\tInvalidate FS with set_thread_area: new FS = 0x%hx\n", + result, sel); + +#ifdef __x86_64__ + if (sel == 0 && new_base != 0) { + nerrs++; + printf("[FAIL]\tNew FSBASE was 0x%lx\n", new_base); + } else { + printf("[OK]\tNew FSBASE was zero\n"); + } +#endif + + /* Test GS */ + invoke_set_thread_area(); + eax = 243; + sel = (gdt_entry_num << 3) | 3; +#ifdef __x86_64__ + syscall(SYS_arch_prctl, ARCH_GET_GS, &saved_base); +#endif + asm volatile ("movw %%gs, %[prev_sel]\n\t" + "movw %[sel], %%gs\n\t" +#ifdef __i386__ + "pushl %%ebx\n\t" +#endif + "movl %[arg1], %%ebx\n\t" + "int $0x80\n\t" /* Should invalidate gs */ +#ifdef __i386__ + "popl %%ebx\n\t" +#endif + "movw %%gs, %[sel]\n\t" + : [prev_sel] "=&r" (prev_sel), [sel] "+r" (sel), + "+a" (eax) + : "m" (low_user_desc_clear), + [arg1] "r" ((unsigned int)(unsigned long)low_user_desc_clear) + : "flags"); + +#ifdef __x86_64__ + syscall(SYS_arch_prctl, ARCH_GET_GS, &new_base); +#endif + + /* Restore GS/BASE for glibc */ + asm volatile ("movw %[prev_sel], %%gs" : : [prev_sel] "rm" (prev_sel)); +#ifdef __x86_64__ + if (saved_base) + syscall(SYS_arch_prctl, ARCH_SET_GS, saved_base); +#endif + + if (sel != 0) { + result = "FAIL"; + nerrs++; + } else { + result = "OK"; + } + printf("[%s]\tInvalidate GS with set_thread_area: new GS = 0x%hx\n", + result, sel); + +#ifdef __x86_64__ + if (sel == 0 && new_base != 0) { + nerrs++; + printf("[FAIL]\tNew GSBASE was 0x%lx\n", new_base); + } else { + printf("[OK]\tNew GSBASE was zero\n"); + } +#endif +} + int main(int argc, char **argv) { if (argc == 1 && !strcmp(argv[0], "ldt_gdt_test_exec")) return finish_exec_test(); + setup_counter_page(); + setup_low_user_desc(); + do_simple_tests(); do_multicpu_tests(); do_exec_test(); + test_gdt_invalidation(); + return nerrs ? 1 : 0; } -- 2.30.2