From: Michael Ellerman mpe@ellerman.id.au

[ Upstream commit 16391bfc862342f285195013b73c1394fab28b97 ]

This tests that when a process with a mapping above 512TB forks we correctly separate the parent and child address spaces. This exercises the bug in the context id handling fixed in the previous commit.

Signed-off-by: Michael Ellerman mpe@ellerman.id.au Signed-off-by: Sasha Levin sashal@kernel.org --- tools/testing/selftests/powerpc/mm/.gitignore | 3 +- tools/testing/selftests/powerpc/mm/Makefile | 4 +- .../powerpc/mm/large_vm_fork_separation.c | 87 +++++++++++++++++++ 3 files changed, 92 insertions(+), 2 deletions(-) create mode 100644 tools/testing/selftests/powerpc/mm/large_vm_fork_separation.c

diff --git a/tools/testing/selftests/powerpc/mm/.gitignore b/tools/testing/selftests/powerpc/mm/.gitignore index ba919308fe30..d503b8764a8e 100644 --- a/tools/testing/selftests/powerpc/mm/.gitignore +++ b/tools/testing/selftests/powerpc/mm/.gitignore @@ -3,4 +3,5 @@ subpage_prot tempfile prot_sao segv_errors -wild_bctr \ No newline at end of file +wild_bctr +large_vm_fork_separation \ No newline at end of file diff --git a/tools/testing/selftests/powerpc/mm/Makefile b/tools/testing/selftests/powerpc/mm/Makefile index 43d68420e363..f1fbc15800c4 100644 --- a/tools/testing/selftests/powerpc/mm/Makefile +++ b/tools/testing/selftests/powerpc/mm/Makefile @@ -2,7 +2,8 @@ noarg: $(MAKE) -C ../

-TEST_GEN_PROGS := hugetlb_vs_thp_test subpage_prot prot_sao segv_errors wild_bctr +TEST_GEN_PROGS := hugetlb_vs_thp_test subpage_prot prot_sao segv_errors wild_bctr \ + large_vm_fork_separation TEST_GEN_FILES := tempfile

top_srcdir = ../../../../.. @@ -13,6 +14,7 @@ $(TEST_GEN_PROGS): ../harness.c $(OUTPUT)/prot_sao: ../utils.c

$(OUTPUT)/wild_bctr: CFLAGS += -m64 +$(OUTPUT)/large_vm_fork_separation: CFLAGS += -m64

$(OUTPUT)/tempfile: dd if=/dev/zero of=$@ bs=64k count=1 diff --git a/tools/testing/selftests/powerpc/mm/large_vm_fork_separation.c b/tools/testing/selftests/powerpc/mm/large_vm_fork_separation.c new file mode 100644 index 000000000000..2363a7f3ab0d --- /dev/null +++ b/tools/testing/selftests/powerpc/mm/large_vm_fork_separation.c @@ -0,0 +1,87 @@ +// SPDX-License-Identifier: GPL-2.0+ +// +// Copyright 2019, Michael Ellerman, IBM Corp. +// +// Test that allocating memory beyond the memory limit and then forking is +// handled correctly, ie. the child is able to access the mappings beyond the +// memory limit and the child's writes are not visible to the parent. + +#include <stdio.h> +#include <stdlib.h> +#include <sys/mman.h> +#include <sys/types.h> +#include <sys/wait.h> +#include <unistd.h> + +#include "utils.h" + + +#ifndef MAP_FIXED_NOREPLACE +#define MAP_FIXED_NOREPLACE MAP_FIXED // "Should be safe" above 512TB +#endif + + +static int test(void) +{ + int p2c[2], c2p[2], rc, status, c, *p; + unsigned long page_size; + pid_t pid; + + page_size = sysconf(_SC_PAGESIZE); + SKIP_IF(page_size != 65536); + + // Create a mapping at 512TB to allocate an extended_id + p = mmap((void *)(512ul << 40), page_size, PROT_READ | PROT_WRITE, + MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED_NOREPLACE, -1, 0); + if (p == MAP_FAILED) { + perror("mmap"); + printf("Error: couldn't mmap(), confirm kernel has 4TB support?\n"); + return 1; + } + + printf("parent writing %p = 1\n", p); + *p = 1; + + FAIL_IF(pipe(p2c) == -1 || pipe(c2p) == -1); + + pid = fork(); + if (pid == 0) { + FAIL_IF(read(p2c[0], &c, 1) != 1); + + pid = getpid(); + printf("child writing %p = %d\n", p, pid); + *p = pid; + + FAIL_IF(write(c2p[1], &c, 1) != 1); + FAIL_IF(read(p2c[0], &c, 1) != 1); + exit(0); + } + + c = 0; + FAIL_IF(write(p2c[1], &c, 1) != 1); + FAIL_IF(read(c2p[0], &c, 1) != 1); + + // Prevent compiler optimisation + barrier(); + + rc = 0; + printf("parent reading %p = %d\n", p, *p); + if (*p != 1) { + printf("Error: BUG! parent saw child's write! *p = %d\n", *p); + rc = 1; + } + + FAIL_IF(write(p2c[1], &c, 1) != 1); + FAIL_IF(waitpid(pid, &status, 0) == -1); + FAIL_IF(!WIFEXITED(status) || WEXITSTATUS(status)); + + if (rc == 0) + printf("success: test completed OK\n"); + + return rc; +} + +int main(void) +{ + return test_harness(test, "large_vm_fork_separation"); +}