| Message ID | 20250110-virtual_address_range-tests-v2-2-262a2bf3c3d0@linutronix.de (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | selftests/mm: virtual_address_range: Reduce memory usage and avoid VVAR access | expand |
On 10.01.25 14:05, Thomas Weißschuh wrote: > For each accessed chunk a PTE is created. > More than 1GiB of PTEs is used in this way. > Remove each PTE after validating a chunk to reduce peak memory usage. > > It is important to only unmap memory that previously mmap()ed, > as unmapping other mappings like the stack, heap or executable mappings > will crash the process. > The mappings read from /proc/self/maps and the return values from mmap() > don't allow a simple correlation due to merging and no guaranteed order. > To correlate the pointers and mappings use prctl(PR_SET_VMA_ANON_NAME). > While it introduces a test dependency, other alternatives would > introduce runtime or development overhead. > > Fixes: 010409649885 ("selftests/mm: confirm VA exhaustion without reliance on correctness of mmap()") > Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de> > --- > tools/testing/selftests/mm/config | 1 + > tools/testing/selftests/mm/virtual_address_range.c | 26 ++++++++++++++++++++-- > 2 files changed, 25 insertions(+), 2 deletions(-) > > diff --git a/tools/testing/selftests/mm/config b/tools/testing/selftests/mm/config > index 4309916f629e36498efb07eb606b2f0c49ee6211..a28baa536332f3fcfb1b83759b5fbb432ae80178 100644 > --- a/tools/testing/selftests/mm/config > +++ b/tools/testing/selftests/mm/config > @@ -7,3 +7,4 @@ CONFIG_TEST_HMM=m > CONFIG_GUP_TEST=y > CONFIG_TRANSPARENT_HUGEPAGE=y > CONFIG_MEM_SOFT_DIRTY=y > +CONFIG_ANON_VMA_NAME=y I'm afraid, nobody uses these :) People run these tests against arbitrary kernels (i.e., distro kernels). In addition to that, we should handle it like uffd-unit-tests.c and sense support for CONFIG_ANON_VMA_NAME in the current kernel. If not around skip the test, like uffd-unit-tests.c does. > diff --git a/tools/testing/selftests/mm/virtual_address_range.c b/tools/testing/selftests/mm/virtual_address_range.c > index ea6ccf49ef4c552f26317c2a40b09bca1a677f8f..4fc1c21a5e218eaec4d059b75c31a21dd4e8a215 100644 > --- a/tools/testing/selftests/mm/virtual_address_range.c > +++ b/tools/testing/selftests/mm/virtual_address_range.c > @@ -10,6 +10,7 @@ > #include <string.h> > #include <unistd.h> > #include <errno.h> > +#include <sys/prctl.h> > #include <sys/mman.h> > #include <sys/time.h> > #include <fcntl.h> > @@ -82,6 +83,17 @@ static void validate_addr(char *ptr, int high_addr) > ksft_exit_fail_msg("Bad address %lx\n", addr); > } > > +static void mark_addr(char *ptr) I would call this "mark_range" and pass the size (MAP_CHUNK_SIZE) as well. > +{ > + if (prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, ptr, MAP_CHUNK_SIZE, "virtual_address_range")) > + ksft_exit_fail_msg("prctl(PR_SET_VMA_ANON_NAME) failed: %s\n", strerror(errno)); > +} > + > +static int is_marked_addr(const char *vma_name) "is_marked_vma" / "is_marked_mapping" ? Because you are not passing an address ... Apart from that LGTM.
diff --git a/tools/testing/selftests/mm/config b/tools/testing/selftests/mm/config index 4309916f629e36498efb07eb606b2f0c49ee6211..a28baa536332f3fcfb1b83759b5fbb432ae80178 100644 --- a/tools/testing/selftests/mm/config +++ b/tools/testing/selftests/mm/config @@ -7,3 +7,4 @@ CONFIG_TEST_HMM=m CONFIG_GUP_TEST=y CONFIG_TRANSPARENT_HUGEPAGE=y CONFIG_MEM_SOFT_DIRTY=y +CONFIG_ANON_VMA_NAME=y diff --git a/tools/testing/selftests/mm/virtual_address_range.c b/tools/testing/selftests/mm/virtual_address_range.c index ea6ccf49ef4c552f26317c2a40b09bca1a677f8f..4fc1c21a5e218eaec4d059b75c31a21dd4e8a215 100644 --- a/tools/testing/selftests/mm/virtual_address_range.c +++ b/tools/testing/selftests/mm/virtual_address_range.c @@ -10,6 +10,7 @@ #include <string.h> #include <unistd.h> #include <errno.h> +#include <sys/prctl.h> #include <sys/mman.h> #include <sys/time.h> #include <fcntl.h> @@ -82,6 +83,17 @@ static void validate_addr(char *ptr, int high_addr) ksft_exit_fail_msg("Bad address %lx\n", addr); } +static void mark_addr(char *ptr) +{ + if (prctl(PR_SET_VMA, PR_SET_VMA_ANON_NAME, ptr, MAP_CHUNK_SIZE, "virtual_address_range")) + ksft_exit_fail_msg("prctl(PR_SET_VMA_ANON_NAME) failed: %s\n", strerror(errno)); +} + +static int is_marked_addr(const char *vma_name) +{ + return vma_name && !strcmp(vma_name, "[anon:virtual_address_range]\n"); +} + static int validate_lower_address_hint(void) { char *ptr; @@ -116,12 +128,17 @@ static int validate_complete_va_space(void) prev_end_addr = 0; while (fgets(line, sizeof(line), file)) { + const char *vma_name = NULL; + int vma_name_start = 0; unsigned long hop; - if (sscanf(line, "%lx-%lx %s[rwxp-]", - &start_addr, &end_addr, prot) != 3) + if (sscanf(line, "%lx-%lx %4s %*s %*s %*s %n", + &start_addr, &end_addr, prot, &vma_name_start) != 3) ksft_exit_fail_msg("cannot parse /proc/self/maps\n"); + if (vma_name_start) + vma_name = line + vma_name_start; + /* end of userspace mappings; ignore vsyscall mapping */ if (start_addr & (1UL << 63)) return 0; @@ -149,6 +166,9 @@ static int validate_complete_va_space(void) return 1; lseek(fd, 0, SEEK_SET); + if (is_marked_addr(vma_name)) + munmap((char *)(start_addr + hop), MAP_CHUNK_SIZE); + hop += MAP_CHUNK_SIZE; } } @@ -175,6 +195,7 @@ int main(int argc, char *argv[]) break; } + mark_addr(ptr[i]); validate_addr(ptr[i], 0); } lchunks = i; @@ -192,6 +213,7 @@ int main(int argc, char *argv[]) if (hptr[i] == MAP_FAILED) break; + mark_addr(ptr[i]); validate_addr(hptr[i], 1); } hchunks = i;
For each accessed chunk a PTE is created. More than 1GiB of PTEs is used in this way. Remove each PTE after validating a chunk to reduce peak memory usage. It is important to only unmap memory that previously mmap()ed, as unmapping other mappings like the stack, heap or executable mappings will crash the process. The mappings read from /proc/self/maps and the return values from mmap() don't allow a simple correlation due to merging and no guaranteed order. To correlate the pointers and mappings use prctl(PR_SET_VMA_ANON_NAME). While it introduces a test dependency, other alternatives would introduce runtime or development overhead. Fixes: 010409649885 ("selftests/mm: confirm VA exhaustion without reliance on correctness of mmap()") Signed-off-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de> --- tools/testing/selftests/mm/config | 1 + tools/testing/selftests/mm/virtual_address_range.c | 26 ++++++++++++++++++++-- 2 files changed, 25 insertions(+), 2 deletions(-)