From 40153505259d8dc0e4ea6889fca5e567c42b76a9 Mon Sep 17 00:00:00 2001 From: "Borislav Petkov (AMD)" Date: Wed, 31 Jul 2024 18:05:31 +0200 Subject: Documentation/srso: Document a method for checking safe RET operates properly Add a method to quickly verify whether safe RET operates properly on a given system using perf tool. Also, add a selftest which does the same thing. Signed-off-by: Borislav Petkov (AMD) Link: https://lore.kernel.org/r/20240731160531.28640-1-bp@kernel.org --- tools/testing/selftests/x86/Makefile | 2 +- tools/testing/selftests/x86/srso.c | 70 ++++++++++++++++++++++++++++++++++++ 2 files changed, 71 insertions(+), 1 deletion(-) create mode 100644 tools/testing/selftests/x86/srso.c (limited to 'tools/testing') diff --git a/tools/testing/selftests/x86/Makefile b/tools/testing/selftests/x86/Makefile index 5c8757a25998..d51249f14e2f 100644 --- a/tools/testing/selftests/x86/Makefile +++ b/tools/testing/selftests/x86/Makefile @@ -77,7 +77,7 @@ all_32: $(BINARIES_32) all_64: $(BINARIES_64) -EXTRA_CLEAN := $(BINARIES_32) $(BINARIES_64) +EXTRA_CLEAN := $(BINARIES_32) $(BINARIES_64) srso $(BINARIES_32): $(OUTPUT)/%_32: %.c helpers.h $(CC) -m32 -o $@ $(CFLAGS) $(EXTRA_CFLAGS) $< $(EXTRA_FILES) -lrt -ldl -lm diff --git a/tools/testing/selftests/x86/srso.c b/tools/testing/selftests/x86/srso.c new file mode 100644 index 000000000000..394ec8bdeb00 --- /dev/null +++ b/tools/testing/selftests/x86/srso.c @@ -0,0 +1,70 @@ +// SPDX-License-Identifier: GPL-2.0 +#include +#include +#include +#include +#include +#include +#include +#include +#include + +int main(void) +{ + struct perf_event_attr ret_attr, mret_attr; + long long count_rets, count_rets_mispred; + int rrets_fd, mrrets_fd; + unsigned int cpuid1_eax, b, c, d; + + __cpuid(1, cpuid1_eax, b, c, d); + + if (cpuid1_eax < 0x00800f00 || + cpuid1_eax > 0x00afffff) { + fprintf(stderr, "This needs to run on a Zen[1-4] machine (CPUID(1).EAX: 0x%x). Exiting...\n", cpuid1_eax); + exit(EXIT_FAILURE); + } + + memset(&ret_attr, 0, sizeof(struct perf_event_attr)); + memset(&mret_attr, 0, sizeof(struct perf_event_attr)); + + ret_attr.type = mret_attr.type = PERF_TYPE_RAW; + ret_attr.size = mret_attr.size = sizeof(struct perf_event_attr); + ret_attr.config = 0xc8; + mret_attr.config = 0xc9; + ret_attr.disabled = mret_attr.disabled = 1; + ret_attr.exclude_user = mret_attr.exclude_user = 1; + ret_attr.exclude_hv = mret_attr.exclude_hv = 1; + + rrets_fd = syscall(SYS_perf_event_open, &ret_attr, 0, -1, -1, 0); + if (rrets_fd == -1) { + perror("opening retired RETs fd"); + exit(EXIT_FAILURE); + } + + mrrets_fd = syscall(SYS_perf_event_open, &mret_attr, 0, -1, -1, 0); + if (mrrets_fd == -1) { + perror("opening retired mispredicted RETs fd"); + exit(EXIT_FAILURE); + } + + ioctl(rrets_fd, PERF_EVENT_IOC_RESET, 0); + ioctl(mrrets_fd, PERF_EVENT_IOC_RESET, 0); + + ioctl(rrets_fd, PERF_EVENT_IOC_ENABLE, 0); + ioctl(mrrets_fd, PERF_EVENT_IOC_ENABLE, 0); + + printf("Sleeping for 10 seconds\n"); + sleep(10); + + ioctl(rrets_fd, PERF_EVENT_IOC_DISABLE, 0); + ioctl(mrrets_fd, PERF_EVENT_IOC_DISABLE, 0); + + read(rrets_fd, &count_rets, sizeof(long long)); + read(mrrets_fd, &count_rets_mispred, sizeof(long long)); + + printf("RETs: (%lld retired <-> %lld mispredicted)\n", + count_rets, count_rets_mispred); + printf("SRSO Safe-RET mitigation works correctly if both counts are almost equal.\n"); + + return 0; +} -- cgit v1.2.3