On 17.08.2016 08:48, Suraj Jitindar Singh wrote:
> On Power machines if a guest cedes while a tm transaction is in the
> suspended state then the checkpointed state of the vcpu may be lost and we
> lose the cpu in the host.
>
> Add a file for tm tests "powerpc/tm.c" and add a test to check if the fix
> has been applied to the host kernel. If this fix hasn't been applied then
> the test will never complete and the cpu will be lost. Otherwise the test
> should succeed. Since this has the ability to mess things up in the host
> mark this test as don't run by default.
>
> This vulnerability has been assigned the ID CVE-2016-5412.
>
> Based on initial work done by: Cyril Bur <cyril.bur@xxxxxxxxxxx>
>
> Signed-off-by: Suraj Jitindar Singh <sjitindarsingh@xxxxxxxxx>
> Reviewed-by: Andrew Jones <drjones@xxxxxxxxxx>
>
> ---
>
> Change Log:
>
> V2 -> V3:
> - Remove get_dec() and sleep() functions as sleep functionality is
> now provided by a generic implementation in processor.c.
> - Replace TM instructions with raw machine code to support older
> compilers
> V3 -> V4:
> - Style Changes
> ---
> lib/powerpc/asm/hcall.h | 1 +
> powerpc/Makefile.common | 3 +-
> powerpc/tm.c | 120 ++++++++++++++++++++++++++++++++++++++++++++++++
> powerpc/unittests.cfg | 6 +++
> 4 files changed, 129 insertions(+), 1 deletion(-)
> create mode 100644 powerpc/tm.c
>
> diff --git a/lib/powerpc/asm/hcall.h b/lib/powerpc/asm/hcall.h
> index 99bce79..80aa3e3 100644
> --- a/lib/powerpc/asm/hcall.h
> +++ b/lib/powerpc/asm/hcall.h
> @@ -18,6 +18,7 @@
> #define H_SET_SPRG0 0x24
> #define H_SET_DABR 0x28
> #define H_PAGE_INIT 0x2c
> +#define H_CEDE 0xE0
> #define H_PUT_TERM_CHAR 0x58
> #define H_RANDOM 0x300
> #define H_SET_MODE 0x31C
> diff --git a/powerpc/Makefile.common b/powerpc/Makefile.common
> index 677030a..93e4f66 100644
> --- a/powerpc/Makefile.common
> +++ b/powerpc/Makefile.common
> @@ -8,7 +8,8 @@ tests-common = \
> $(TEST_DIR)/selftest.elf \
> $(TEST_DIR)/spapr_hcall.elf \
> $(TEST_DIR)/rtas.elf \
> - $(TEST_DIR)/emulator.elf
> + $(TEST_DIR)/emulator.elf \
> + $(TEST_DIR)/tm.elf
>
> all: $(TEST_DIR)/boot_rom.bin test_cases
>
> diff --git a/powerpc/tm.c b/powerpc/tm.c
> new file mode 100644
> index 0000000..6ce750a
> --- /dev/null
> +++ b/powerpc/tm.c
> @@ -0,0 +1,120 @@
> +/*
> + * Transactional Memory Unit Tests
> + *
> + * Copyright 2016 Suraj Jitindar Singh, IBM.
> + *
> + * This work is licensed under the terms of the GNU LGPL, version 2.
> + */
> +#include <libcflat.h>
> +#include <asm/hcall.h>
> +#include <asm/processor.h>
> +#include <asm/handlers.h>
> +#include <asm/smp.h>
> +
> +static int h_cede(void)
> +{
> + register uint64_t r3 asm("r3") = H_CEDE;
> +
> + asm volatile ("sc 1" : "+r"(r3) :
> + : "r0", "r4", "r5", "r6", "r7", "r8", "r9",
> + "r10", "r11", "r12", "xer", "ctr", "cc");
> +
> + return r3;
> +}
> +
> +/*
> + * Enable transactional memory
> + * Returns: FALSE - Failure
> + * TRUE - Success
> + */
> +static bool enable_tm(void)
> +{
> + uint64_t msr = 0;
> +
> + asm volatile ("mfmsr %[msr]" : [msr] "=r" (msr));
> +
> + msr |= (((uint64_t) 1) << 32);
> +
> + asm volatile ("mtmsrd %[msr]\n\t"
> + "mfmsr %[msr]" : [msr] "+r" (msr));
> +
> + return !!(msr & (((uint64_t) 1) << 32));
> +}
> +
> +/*
> + * Test H_CEDE call while transactional memory transaction is suspended
> + *
> + * WARNING: This tests for a known vulnerability in which the host may go down.
> + * Probably best not to run this if your host going down is going to cause
> + * problems.
> + *
> + * If the test passes then your kernel probably has the necessary patch.
> + * If the test fails then the H_CEDE call was unsuccessful and the
> + * vulnerability wasn't tested.
> + * If the test hits the vulnerability then it will never complete or report and
> + * the qemu process will block indefinitely. RCU stalls will be detected on the
> + * cpu and any process scheduled on the lost cpu will also block indefinitely.
> + */
> +static void test_h_cede_tm(int argc, char **argv)
> +{
> + int i;
> +
> + if (argc > 2)
> + report_abort("Unsupported argument: '%s'", argv[2]);
> +
> + handle_exception(0x900, &dec_except_handler, NULL);
> +
> + if (!start_all_cpus(halt, 0))
> + report_abort("Failed to start secondary cpus");
> +
> + if (!enable_tm())
> + report_abort("Failed to enable tm");
> +
> + /*
> + * Begin a transaction and guarantee we are in the suspend state
> + * before continuing
> + */
> + asm volatile ("1: .long 0x7c00051d\n\t" /* tbegin. */
> + "beq 2f\n\t"
> + ".long 0x7c0005dd\n\t" /* tsuspend. */
> + "2: .long 0x7c00059c\n\t" /* tcheck cr0 */
> + "bf 2,1b" : : : "cr0");
> +
> + for (i = 0; i < 500; i++) {
> + uint64_t rval = h_cede();
> +
> + if (rval != H_SUCCESS)
> + break;
> + mdelay(5);
> + }
> +
> + report("H_CEDE TM", i == 500);
> +}
> +
> +struct {
> + const char *name;
> + void (*func)(int argc, char **argv);
> +} hctests[] = {
> + { "h_cede_tm", test_h_cede_tm },
> + { NULL, NULL }
> +};
> +
> +int main(int argc, char **argv)
> +{
> + bool all;
> + int i;
> +
> + report_prefix_push("tm");
> +
> + all = argc == 1 || !strcmp(argv[1], "all");
> +
> + for (i = 0; hctests[i].name != NULL; i++) {
> + if (all || strcmp(argv[1], hctests[i].name) == 0) {
> + report_prefix_push(hctests[i].name);
> + hctests[i].func(argc, argv);
> + report_prefix_pop();
> + }
> + }
> +
> + return report_summary();
> +}
> diff --git a/powerpc/unittests.cfg b/powerpc/unittests.cfg
> index 0098cb6..20dbde6 100644
> --- a/powerpc/unittests.cfg
> +++ b/powerpc/unittests.cfg
> @@ -53,3 +53,9 @@ groups = rtas
>
> [emulator]
> file = emulator.elf
> +
> +[h_cede_tm]
> +file = tm.elf
> +smp = 2,threads=2
> +extra_params = -append "h_cede_tm"
> +groups = nodefault,h_cede_tm
>
Reviewed-by: Thomas Huth <thuth@xxxxxxxxxx>
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