Merge branch 'x86/asm' into x86/apic, to resolve a conflict

Conflicts:
	arch/x86/kernel/apic/io_apic.c
	arch/x86/kernel/apic/vector.c

Signed-off-by: Ingo Molnar <mingo@kernel.org>

19 files changed, 269 insertions, 53 deletions

diff --git a/tools/hv/Makefile b/tools/hv/Makefile
index 99ffe61051a7..a8ab79556926 100644
--- a/tools/hv/Makefile
+++ b/tools/hv/Makefile
@@ -3,7 +3,7 @@
 CC = $(CROSS_COMPILE)gcc
 PTHREAD_LIBS = -lpthread
 WARNINGS = -Wall -Wextra
-CFLAGS = $(WARNINGS) -g $(PTHREAD_LIBS)
+CFLAGS = $(WARNINGS) -g $(PTHREAD_LIBS) $(shell getconf LFS_CFLAGS)
 
 all: hv_kvp_daemon hv_vss_daemon hv_fcopy_daemon
 %: %.c
diff --git a/tools/hv/hv_vss_daemon.c b/tools/hv/hv_vss_daemon.c
index 5e63f70bd956..506dd0148828 100644
--- a/tools/hv/hv_vss_daemon.c
+++ b/tools/hv/hv_vss_daemon.c
@@ -81,6 +81,7 @@ static int vss_operate(int operation)
         char match[] = "/dev/";
         FILE *mounts;
         struct mntent *ent;
+        char errdir[1024] = {0};
         unsigned int cmd;
         int error = 0, root_seen = 0, save_errno = 0;
 
@@ -115,6 +116,8 @@ static int vss_operate(int operation)
                         goto err;
         }
 
+        endmntent(mounts);
+
         if (root_seen) {
                 error |= vss_do_freeze("/", cmd);
                 if (error && operation == VSS_OP_FREEZE)
@@ -124,16 +127,19 @@ static int vss_operate(int operation)
         goto out;
 err:
         save_errno = errno;
+        if (ent) {
+                strncpy(errdir, ent->mnt_dir, sizeof(errdir)-1);
+                endmntent(mounts);
+        }
         vss_operate(VSS_OP_THAW);
         /* Call syslog after we thaw all filesystems */
         if (ent)
                 syslog(LOG_ERR, "FREEZE of %s failed; error:%d %s",
-                       ent->mnt_dir, save_errno, strerror(save_errno));
+                       errdir, save_errno, strerror(save_errno));
         else
                 syslog(LOG_ERR, "FREEZE of / failed; error:%d %s", save_errno,
                        strerror(save_errno));
 out:
-        endmntent(mounts);
         return error;
 }
 
diff --git a/tools/lib/api/Makefile b/tools/lib/api/Makefile
index d8fe29fc19a4..8bd960658463 100644
--- a/tools/lib/api/Makefile
+++ b/tools/lib/api/Makefile
@@ -16,7 +16,7 @@ MAKEFLAGS += --no-print-directory
 LIBFILE = $(OUTPUT)libapi.a
 
 CFLAGS := $(EXTRA_WARNINGS) $(EXTRA_CFLAGS)
-CFLAGS += -ggdb3 -Wall -Wextra -std=gnu99 -Werror -O6 -D_FORTIFY_SOURCE=2 -fPIC
+CFLAGS += -ggdb3 -Wall -Wextra -std=gnu99 -Werror -O6 -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=2 -fPIC
 CFLAGS += -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64
 
 RM = rm -f
diff --git a/tools/lib/traceevent/event-parse.c b/tools/lib/traceevent/event-parse.c
index e0917c0f5d9f..29f94f6f0d9e 100644
--- a/tools/lib/traceevent/event-parse.c
+++ b/tools/lib/traceevent/event-parse.c
@@ -3865,7 +3865,7 @@ static void print_str_arg(struct trace_seq *s, void *data, int size,
                         } else if (el_size == 4) {
                                 trace_seq_printf(s, "%u", *(uint32_t *)num);
                         } else if (el_size == 8) {
-                                trace_seq_printf(s, "%lu", *(uint64_t *)num);
+                                trace_seq_printf(s, "%"PRIu64, *(uint64_t *)num);
                         } else {
                                 trace_seq_printf(s, "BAD SIZE:%d 0x%x",
                                                  el_size, *(uint8_t *)num);
diff --git a/tools/perf/bench/futex-requeue.c b/tools/perf/bench/futex-requeue.c
index bedff6b5b3cf..ad0d9b5342fb 100644
--- a/tools/perf/bench/futex-requeue.c
+++ b/tools/perf/bench/futex-requeue.c
@@ -132,6 +132,9 @@ int bench_futex_requeue(int argc, const char **argv,
         if (!fshared)
                 futex_flag = FUTEX_PRIVATE_FLAG;
 
+        if (nrequeue > nthreads)
+                nrequeue = nthreads;
+
         printf("Run summary [PID %d]: Requeuing %d threads (from [%s] %p to %p), "
                "%d at a time.\n\n",  getpid(), nthreads,
                fshared ? "shared":"private", &futex1, &futex2, nrequeue);
@@ -161,20 +164,18 @@ int bench_futex_requeue(int argc, const char **argv,
 
                 /* Ok, all threads are patiently blocked, start requeueing */
                 gettimeofday(&start, NULL);
-                for (nrequeued = 0; nrequeued < nthreads; nrequeued += nrequeue) {
+                while (nrequeued < nthreads) {
                         /*
                          * Do not wakeup any tasks blocked on futex1, allowing
                          * us to really measure futex_wait functionality.
                          */
-                        futex_cmp_requeue(&futex1, 0, &futex2, 0,
-                                          nrequeue, futex_flag);
+                        nrequeued += futex_cmp_requeue(&futex1, 0, &futex2, 0,
+                                                       nrequeue, futex_flag);
                 }
+
                 gettimeofday(&end, NULL);
                 timersub(&end, &start, &runtime);
 
-                if (nrequeued > nthreads)
-                        nrequeued = nthreads;
-
                 update_stats(&requeued_stats, nrequeued);
                 update_stats(&requeuetime_stats, runtime.tv_usec);
 
@@ -184,7 +185,7 @@ int bench_futex_requeue(int argc, const char **argv,
                 }
 
                 /* everybody should be blocked on futex2, wake'em up */
-                nrequeued = futex_wake(&futex2, nthreads, futex_flag);
+                nrequeued = futex_wake(&futex2, nrequeued, futex_flag);
                 if (nthreads != nrequeued)
                         warnx("couldn't wakeup all tasks (%d/%d)", nrequeued, nthreads);
 
diff --git a/tools/perf/bench/numa.c b/tools/perf/bench/numa.c
index ebfa163b80b5..ba5efa4710b5 100644
--- a/tools/perf/bench/numa.c
+++ b/tools/perf/bench/numa.c
@@ -180,7 +180,7 @@ static const struct option options[] = {
         OPT_INTEGER('H', "thp"          , &p0.thp,              "MADV_NOHUGEPAGE < 0 < MADV_HUGEPAGE"),
         OPT_BOOLEAN('c', "show_convergence", &p0.show_convergence, "show convergence details"),
         OPT_BOOLEAN('m', "measure_convergence", &p0.measure_convergence, "measure convergence latency"),
-        OPT_BOOLEAN('q', "quiet"        , &p0.show_quiet,       "bzero the initial allocations"),
+        OPT_BOOLEAN('q', "quiet"        , &p0.show_quiet,       "quiet mode"),
         OPT_BOOLEAN('S', "serialize-startup", &p0.serialize_startup,"serialize thread startup"),
 
         /* Special option string parsing callbacks: */
@@ -828,6 +828,9 @@ static int count_process_nodes(int process_nr)
                 td = g->threads + task_nr;
 
                 node = numa_node_of_cpu(td->curr_cpu);
+                if (node < 0) /* curr_cpu was likely still -1 */
+                        return 0;
+
                 node_present[node] = 1;
         }
 
@@ -882,6 +885,11 @@ static void calc_convergence_compression(int *strong)
         for (p = 0; p < g->p.nr_proc; p++) {
                 unsigned int nodes = count_process_nodes(p);
 
+                if (!nodes) {
+                        *strong = 0;
+                        return;
+                }
+
                 nodes_min = min(nodes, nodes_min);
                 nodes_max = max(nodes, nodes_max);
         }
@@ -1395,7 +1403,7 @@ static void print_res(const char *name, double val,
         if (!name)
                 name = "main,";
 
-        if (g->p.show_quiet)
+        if (!g->p.show_quiet)
                 printf(" %-30s %15.3f, %-15s %s\n", name, val, txt_unit, txt_short);
         else
                 printf(" %14.3f %s\n", val, txt_long);
diff --git a/tools/perf/builtin-kmem.c b/tools/perf/builtin-kmem.c
index 63ea01349b6e..1634186d537c 100644
--- a/tools/perf/builtin-kmem.c
+++ b/tools/perf/builtin-kmem.c
@@ -319,7 +319,7 @@ static int page_stat_cmp(struct page_stat *a, struct page_stat *b)
         return 0;
 }
 
-static struct page_stat *search_page_alloc_stat(struct page_stat *stat, bool create)
+static struct page_stat *search_page_alloc_stat(struct page_stat *pstat, bool create)
 {
         struct rb_node **node = &page_alloc_tree.rb_node;
         struct rb_node *parent = NULL;
@@ -331,7 +331,7 @@ static struct page_stat *search_page_alloc_stat(struct page_stat *stat, bool cre
                 parent = *node;
                 data = rb_entry(*node, struct page_stat, node);
 
-                cmp = page_stat_cmp(data, stat);
+                cmp = page_stat_cmp(data, pstat);
                 if (cmp < 0)
                         node = &parent->rb_left;
                 else if (cmp > 0)
@@ -345,10 +345,10 @@ static struct page_stat *search_page_alloc_stat(struct page_stat *stat, bool cre
 
         data = zalloc(sizeof(*data));
         if (data != NULL) {
-                data->page = stat->page;
-                data->order = stat->order;
-                data->gfp_flags = stat->gfp_flags;
-                data->migrate_type = stat->migrate_type;
+                data->page = pstat->page;
+                data->order = pstat->order;
+                data->gfp_flags = pstat->gfp_flags;
+                data->migrate_type = pstat->migrate_type;
 
                 rb_link_node(&data->node, parent, node);
                 rb_insert_color(&data->node, &page_alloc_tree);
@@ -375,7 +375,7 @@ static int perf_evsel__process_page_alloc_event(struct perf_evsel *evsel,
         unsigned int migrate_type = perf_evsel__intval(evsel, sample,
                                                        "migratetype");
         u64 bytes = kmem_page_size << order;
-        struct page_stat *stat;
+        struct page_stat *pstat;
         struct page_stat this = {
                 .order = order,
                 .gfp_flags = gfp_flags,
@@ -401,21 +401,21 @@ static int perf_evsel__process_page_alloc_event(struct perf_evsel *evsel,
          * This is to find the current page (with correct gfp flags and
          * migrate type) at free event.
          */
-        stat = search_page(page, true);
-        if (stat == NULL)
+        pstat = search_page(page, true);
+        if (pstat == NULL)
                 return -ENOMEM;
 
-        stat->order = order;
-        stat->gfp_flags = gfp_flags;
-        stat->migrate_type = migrate_type;
+        pstat->order = order;
+        pstat->gfp_flags = gfp_flags;
+        pstat->migrate_type = migrate_type;
 
         this.page = page;
-        stat = search_page_alloc_stat(&this, true);
-        if (stat == NULL)
+        pstat = search_page_alloc_stat(&this, true);
+        if (pstat == NULL)
                 return -ENOMEM;
 
-        stat->nr_alloc++;
-        stat->alloc_bytes += bytes;
+        pstat->nr_alloc++;
+        pstat->alloc_bytes += bytes;
 
         order_stats[order][migrate_type]++;
 
@@ -428,7 +428,7 @@ static int perf_evsel__process_page_free_event(struct perf_evsel *evsel,
         u64 page;
         unsigned int order = perf_evsel__intval(evsel, sample, "order");
         u64 bytes = kmem_page_size << order;
-        struct page_stat *stat;
+        struct page_stat *pstat;
         struct page_stat this = {
                 .order = order,
         };
@@ -441,8 +441,8 @@ static int perf_evsel__process_page_free_event(struct perf_evsel *evsel,
         nr_page_frees++;
         total_page_free_bytes += bytes;
 
-        stat = search_page(page, false);
-        if (stat == NULL) {
+        pstat = search_page(page, false);
+        if (pstat == NULL) {
                 pr_debug2("missing free at page %"PRIx64" (order: %d)\n",
                           page, order);
 
@@ -453,18 +453,18 @@ static int perf_evsel__process_page_free_event(struct perf_evsel *evsel,
         }
 
         this.page = page;
-        this.gfp_flags = stat->gfp_flags;
-        this.migrate_type = stat->migrate_type;
+        this.gfp_flags = pstat->gfp_flags;
+        this.migrate_type = pstat->migrate_type;
 
-        rb_erase(&stat->node, &page_tree);
-        free(stat);
+        rb_erase(&pstat->node, &page_tree);
+        free(pstat);
 
-        stat = search_page_alloc_stat(&this, false);
-        if (stat == NULL)
+        pstat = search_page_alloc_stat(&this, false);
+        if (pstat == NULL)
                 return -ENOENT;
 
-        stat->nr_free++;
-        stat->free_bytes += bytes;
+        pstat->nr_free++;
+        pstat->free_bytes += bytes;
 
         return 0;
 }
@@ -640,9 +640,9 @@ static void print_page_summary(void)
                nr_page_frees, total_page_free_bytes / 1024);
         printf("\n");
 
-        printf("%-30s: %'16lu   [ %'16"PRIu64" KB ]\n", "Total alloc+freed requests",
+        printf("%-30s: %'16"PRIu64"   [ %'16"PRIu64" KB ]\n", "Total alloc+freed requests",
                nr_alloc_freed, (total_alloc_freed_bytes) / 1024);
-        printf("%-30s: %'16lu   [ %'16"PRIu64" KB ]\n", "Total alloc-only requests",
+        printf("%-30s: %'16"PRIu64"   [ %'16"PRIu64" KB ]\n", "Total alloc-only requests",
                nr_page_allocs - nr_alloc_freed,
                (total_page_alloc_bytes - total_alloc_freed_bytes) / 1024);
         printf("%-30s: %'16lu   [ %'16"PRIu64" KB ]\n", "Total free-only requests",
diff --git a/tools/perf/builtin-report.c b/tools/perf/builtin-report.c
index 476cdf7afcca..b63aeda719be 100644
--- a/tools/perf/builtin-report.c
+++ b/tools/perf/builtin-report.c
@@ -329,7 +329,7 @@ static int perf_evlist__tty_browse_hists(struct perf_evlist *evlist,
                 fprintf(stdout, "\n\n");
         }
 
-        if (sort_order == default_sort_order &&
+        if (sort_order == NULL &&
             parent_pattern == default_parent_pattern) {
                 fprintf(stdout, "#\n# (%s)\n#\n", help);
 
diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index 1cb3436276d1..6a4d5d41c671 100644
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -733,7 +733,7 @@ static void perf_event__process_sample(struct perf_tool *tool,
 "Kernel address maps (/proc/{kallsyms,modules}) are restricted.\n\n"
 "Check /proc/sys/kernel/kptr_restrict.\n\n"
 "Kernel%s samples will not be resolved.\n",
-                          !RB_EMPTY_ROOT(&al.map->dso->symbols[MAP__FUNCTION]) ?
+                          al.map && !RB_EMPTY_ROOT(&al.map->dso->symbols[MAP__FUNCTION]) ?
                           " modules" : "");
                 if (use_browser <= 0)
                         sleep(5);
diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index e124741be187..e122970361f2 100644
--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -2241,10 +2241,11 @@ static int trace__run(struct trace *trace, int argc, const char **argv)
         if (err < 0)
                 goto out_error_mmap;
 
+        if (!target__none(&trace->opts.target))
+                perf_evlist__enable(evlist);
+
         if (forks)
                 perf_evlist__start_workload(evlist);
-        else
-                perf_evlist__enable(evlist);
 
         trace->multiple_threads = evlist->threads->map[0] == -1 ||
                                   evlist->threads->nr > 1 ||
@@ -2272,6 +2273,11 @@ next_event:
 
                         if (interrupted)
                                 goto out_disable;
+
+                        if (done && !draining) {
+                                perf_evlist__disable(evlist);
+                                draining = true;
+                        }
                 }
         }
 
diff --git a/tools/perf/util/probe-event.c b/tools/perf/util/probe-event.c
index d8bb616ff57c..d05b77cf35f7 100644
--- a/tools/perf/util/probe-event.c
+++ b/tools/perf/util/probe-event.c
@@ -1084,6 +1084,8 @@ static int parse_perf_probe_point(char *arg, struct perf_probe_event *pev)
          *
          * TODO:Group name support
          */
+        if (!arg)
+                return -EINVAL;
 
         ptr = strpbrk(arg, ";=@+%");
         if (ptr && *ptr == '=') {       /* Event name */
diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c
index b5bf9d5efeaf..2a76e14db732 100644
--- a/tools/perf/util/probe-finder.c
+++ b/tools/perf/util/probe-finder.c
@@ -578,10 +578,12 @@ static int find_variable(Dwarf_Die *sc_die, struct probe_finder *pf)
         /* Search child die for local variables and parameters. */
         if (!die_find_variable_at(sc_die, pf->pvar->var, pf->addr, &vr_die)) {
                 /* Search again in global variables */
-                if (!die_find_variable_at(&pf->cu_die, pf->pvar->var, 0, &vr_die))
+                if (!die_find_variable_at(&pf->cu_die, pf->pvar->var,
+                                                0, &vr_die)) {
                         pr_warning("Failed to find '%s' in this function.\n",
                                    pf->pvar->var);
                         ret = -ENOENT;
+                }
         }
         if (ret >= 0)
                 ret = convert_variable(&vr_die, pf);
diff --git a/tools/power/cpupower/utils/helpers/pci.c b/tools/power/cpupower/utils/helpers/pci.c
index 9690798e6446..8b278983cfc5 100644
--- a/tools/power/cpupower/utils/helpers/pci.c
+++ b/tools/power/cpupower/utils/helpers/pci.c
@@ -25,14 +25,21 @@
 struct pci_dev *pci_acc_init(struct pci_access **pacc, int domain, int bus,
                              int slot, int func, int vendor, int dev)
 {
-        struct pci_filter filter_nb_link = { domain, bus, slot, func,
-                                             vendor, dev };
+        struct pci_filter filter_nb_link;
         struct pci_dev *device;
 
         *pacc = pci_alloc();
         if (*pacc == NULL)
                 return NULL;
 
+        pci_filter_init(*pacc, &filter_nb_link);
+        filter_nb_link.domain   = domain;
+        filter_nb_link.bus      = bus;
+        filter_nb_link.slot     = slot;
+        filter_nb_link.func     = func;
+        filter_nb_link.vendor   = vendor;
+        filter_nb_link.device   = dev;
+
         pci_init(*pacc);
         pci_scan_bus(*pacc);
 
diff --git a/tools/testing/selftests/powerpc/pmu/Makefile b/tools/testing/selftests/powerpc/pmu/Makefile
index 5a161175bbd4..a9099d9f8f39 100644
--- a/tools/testing/selftests/powerpc/pmu/Makefile
+++ b/tools/testing/selftests/powerpc/pmu/Makefile
@@ -26,7 +26,7 @@ override define EMIT_TESTS
         $(MAKE) -s -C ebb emit_tests
 endef
 
-DEFAULT_INSTALL := $(INSTALL_RULE)
+DEFAULT_INSTALL_RULE := $(INSTALL_RULE)
 override define INSTALL_RULE
         $(DEFAULT_INSTALL_RULE)
         $(MAKE) -C ebb install
diff --git a/tools/testing/selftests/powerpc/tm/Makefile b/tools/testing/selftests/powerpc/tm/Makefile
index 1b616fa79e93..6bff955e1d55 100644
--- a/tools/testing/selftests/powerpc/tm/Makefile
+++ b/tools/testing/selftests/powerpc/tm/Makefile
@@ -1,4 +1,4 @@
-TEST_PROGS := tm-resched-dscr tm-syscall
+TEST_PROGS := tm-resched-dscr
 
 all: $(TEST_PROGS)
 
diff --git a/tools/testing/selftests/x86/Makefile b/tools/testing/selftests/x86/Makefile
index ddf63569df5a..9309097f58e8 100644
--- a/tools/testing/selftests/x86/Makefile
+++ b/tools/testing/selftests/x86/Makefile
@@ -1,6 +1,6 @@
 .PHONY: all all_32 all_64 check_build32 clean run_tests
 
-TARGETS_C_BOTHBITS := sigreturn single_step_syscall
+TARGETS_C_BOTHBITS := sigreturn single_step_syscall sysret_ss_attrs
 
 BINARIES_32 := $(TARGETS_C_BOTHBITS:%=%_32)
 BINARIES_64 := $(TARGETS_C_BOTHBITS:%=%_64)
@@ -46,3 +46,6 @@ check_build32:
           echo "  yum install glibc-devel.*i686";                       \
           exit 1;                                                       \
         fi
+
+# Some tests have additional dependencies.
+sysret_ss_attrs_64: thunks.S
diff --git a/tools/testing/selftests/x86/run_x86_tests.sh b/tools/testing/selftests/x86/run_x86_tests.sh
index 3fc19b376812..d25034280dd5 100644
--- a/tools/testing/selftests/x86/run_x86_tests.sh
+++ b/tools/testing/selftests/x86/run_x86_tests.sh
@@ -4,10 +4,12 @@
 # script here.
 ./sigreturn_32 || exit 1
 ./single_step_syscall_32 || exit 1
+./sysret_ss_attrs_32 || exit 1
 
 if [[ "$uname -p" -eq "x86_64" ]]; then
     ./sigreturn_64 || exit 1
     ./single_step_syscall_64 || exit 1
+    ./sysret_ss_attrs_64 || exit 1
 fi
 
 exit 0
diff --git a/tools/testing/selftests/x86/sysret_ss_attrs.c b/tools/testing/selftests/x86/sysret_ss_attrs.c
new file mode 100644
index 000000000000..ce42d5a64009
--- /dev/null
+++ b/tools/testing/selftests/x86/sysret_ss_attrs.c
@@ -0,0 +1,112 @@
+/*
+ * sysret_ss_attrs.c - test that syscalls return valid hidden SS attributes
+ * Copyright (c) 2015 Andrew Lutomirski
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * On AMD CPUs, SYSRET can return with a valid SS descriptor with with
+ * the hidden attributes set to an unusable state.  Make sure the kernel
+ * doesn't let this happen.
+ */
+
+#define _GNU_SOURCE
+
+#include <stdlib.h>
+#include <unistd.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <err.h>
+#include <stddef.h>
+#include <stdbool.h>
+#include <pthread.h>
+
+static void *threadproc(void *ctx)
+{
+        /*
+         * Do our best to cause sleeps on this CPU to exit the kernel and
+         * re-enter with SS = 0.
+         */
+        while (true)
+                ;
+
+        return NULL;
+}
+
+#ifdef __x86_64__
+extern unsigned long call32_from_64(void *stack, void (*function)(void));
+
+asm (".pushsection .text\n\t"
+     ".code32\n\t"
+     "test_ss:\n\t"
+     "pushl $0\n\t"
+     "popl %eax\n\t"
+     "ret\n\t"
+     ".code64");
+extern void test_ss(void);
+#endif
+
+int main()
+{
+        /*
+         * Start a busy-looping thread on the same CPU we're on.
+         * For simplicity, just stick everything to CPU 0.  This will
+         * fail in some containers, but that's probably okay.
+         */
+        cpu_set_t cpuset;
+        CPU_ZERO(&cpuset);
+        CPU_SET(0, &cpuset);
+        if (sched_setaffinity(0, sizeof(cpuset), &cpuset) != 0)
+                printf("[WARN]\tsched_setaffinity failed\n");
+
+        pthread_t thread;
+        if (pthread_create(&thread, 0, threadproc, 0) != 0)
+                err(1, "pthread_create");
+
+#ifdef __x86_64__
+        unsigned char *stack32 = mmap(NULL, 4096, PROT_READ | PROT_WRITE,
+                                      MAP_32BIT | MAP_ANONYMOUS | MAP_PRIVATE,
+                                      -1, 0);
+        if (stack32 == MAP_FAILED)
+                err(1, "mmap");
+#endif
+
+        printf("[RUN]\tSyscalls followed by SS validation\n");
+
+        for (int i = 0; i < 1000; i++) {
+                /*
+                 * Go to sleep and return using sysret (if we're 64-bit
+                 * or we're 32-bit on AMD on a 64-bit kernel).  On AMD CPUs,
+                 * SYSRET doesn't fix up the cached SS descriptor, so the
+                 * kernel needs some kind of workaround to make sure that we
+                 * end the system call with a valid stack segment.  This
+                 * can be a confusing failure because the SS *selector*
+                 * is the same regardless.
+                 */
+                usleep(2);
+
+#ifdef __x86_64__
+                /*
+                 * On 32-bit, just doing a syscall through glibc is enough
+                 * to cause a crash if our cached SS descriptor is invalid.
+                 * On 64-bit, it's not, so try extra hard.
+                 */
+                call32_from_64(stack32 + 4088, test_ss);
+#endif
+        }
+
+        printf("[OK]\tWe survived\n");
+
+#ifdef __x86_64__
+        munmap(stack32, 4096);
+#endif
+
+        return 0;
+}
diff --git a/tools/testing/selftests/x86/thunks.S b/tools/testing/selftests/x86/thunks.S
new file mode 100644
index 000000000000..ce8a995bbb17
--- /dev/null
+++ b/tools/testing/selftests/x86/thunks.S
@@ -0,0 +1,67 @@
+/*
+ * thunks.S - assembly helpers for mixed-bitness code
+ * Copyright (c) 2015 Andrew Lutomirski
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * These are little helpers that make it easier to switch bitness on
+ * the fly.
+ */
+
+        .text
+
+        .global call32_from_64
+        .type call32_from_64, @function
+call32_from_64:
+        // rdi: stack to use
+        // esi: function to call
+
+        // Save registers
+        pushq %rbx
+        pushq %rbp
+        pushq %r12
+        pushq %r13
+        pushq %r14
+        pushq %r15
+        pushfq
+
+        // Switch stacks
+        mov %rsp,(%rdi)
+        mov %rdi,%rsp
+
+        // Switch to compatibility mode
+        pushq $0x23  /* USER32_CS */
+        pushq $1f
+        lretq
+
+1:
+        .code32
+        // Call the function
+        call *%esi
+        // Switch back to long mode
+        jmp $0x33,$1f
+        .code64
+
+1:
+        // Restore the stack
+        mov (%rsp),%rsp
+
+        // Restore registers
+        popfq
+        popq %r15
+        popq %r14
+        popq %r13
+        popq %r12
+        popq %rbp
+        popq %rbx
+
+        ret
+
+.size call32_from_64, .-call32_from_64