Re: [PATCHv2 bpf-next 5/8] selftests/bpf: Test user memory mmap kfuncs

[Jiri Olsa <olsajiri@gmail.com>]

On Tue, Nov 03, 2026 at 08:05:35AM +0000, sashiko-bot@kernel.org wrote:
> Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:
> - [Medium] selftests/bpf: call to undefined get_procmap_info() in user_mem.c
> - [Medium] selftests/bpf: unresolved kfunc externs in progs/user_mem.c
> --
> 
> commit c7cc5f98b3a4b4d8d168ef0934e6c41fe197849d
> Author: Jiri Olsa <jolsa@kernel.org>
> 
> selftests/bpf: Test user memory mmap kfuncs
> 
> This commit adds BPF selftests for bpf_user_anon_mmap and bpf_user_munmap
> invoked from a sleepable uprobe, verifying mapping permissions and
> unmapping behavior.
> 
> > diff --git a/tools/testing/selftests/bpf/prog_tests/user_mem.c b/tools/testing/selftests/bpf/prog_tests/user_mem.c
> > new file mode 100644
> > index 0000000000000..f301a18437062
> > --- /dev/null
> > +++ b/tools/testing/selftests/bpf/prog_tests/user_mem.c
> > @@ -0,0 +1,112 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +
> > +#include <test_progs.h>
> > +#include <sys/mman.h>
> > +#include <sys/personality.h>
> > +#include <unistd.h>
> > +
> > +#include "user_mem.skel.h"
> > +#include "trace_helpers.h"
> > +
> > +enum {
> > +	USER_MEM_MMAP = 1,
> > +	USER_MEM_UNMAP,
> > +};
> > +
> > +static noinline void user_mem_trigger(void)
> > +{
> > +	asm volatile ("" ::: "memory");
> > +}
> > +
> > +static bool check_user_mem_vma(void *addr, unsigned long size, const char *perms)
> > +{
> > +	size_t start, end;
> > +	char vma_perms[5];
> > +	int err;
> > +
> > +	err = get_procmap_info(addr, &start, &end, vma_perms);
> > +	if (!ASSERT_OK(err, "user_mem_vma"))
> > +		return false;
> > +
> > +	/* VMA can be merged, so ensure it covers at least the requested range. */
> > +	if (!ASSERT_GE(end - (size_t)addr, size, "vma_size"))
> > +		return false;
> > +
> > +	return !perms || ASSERT_STREQ(vma_perms, perms, "vma_perms");
> > +}
> > +
> > +static bool check_user_mem_unmapped(void *addr)
> > +{
> > +	size_t start, end;
> > +	int err;
> > +
> > +	err = get_procmap_info(addr, &start, &end, NULL);
> 
> [Severity: Medium]
> Where is get_procmap_info() defined? Both check_user_mem_vma() and
> check_user_mem_unmapped() call get_procmap_info(), and this file includes
> trace_helpers.h, but neither tools/testing/selftests/bpf/trace_helpers.h nor
> tools/testing/selftests/bpf/trace_helpers.c declares or defines
> get_procmap_info().

in previous patch:
  selftests/bpf: Add get_procmap_info helper

> 
> Because test_progs objects are compiled with -Wall -Werror, won't calling an
> undeclared and undefined get_procmap_info() cause compiling and linking
> tools/testing/selftests/bpf to fail?
> 
> > diff --git a/tools/testing/selftests/bpf/progs/user_mem.c b/tools/testing/selftests/bpf/progs/user_mem.c
> > new file mode 100644
> > index 0000000000000..e3b0689f5f2a5
> > --- /dev/null
> > +++ b/tools/testing/selftests/bpf/progs/user_mem.c
> > @@ -0,0 +1,43 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +
> > +#include <vmlinux.h>
> > +#include <bpf/bpf_helpers.h>
> > +#include <bpf/bpf_tracing.h>
> > +
> > +#include "bpf_misc.h"
> > +
> > +char _license[] SEC("license") = "GPL";
> > +
> > +extern unsigned long bpf_user_anon_mmap(unsigned long len, unsigned long prot) __ksym;
> > +extern int bpf_user_munmap(unsigned long addr, unsigned long len) __ksym;
> 
> [ ... ]
> 
> > +SEC("uprobe.s//proc/self/exe:user_mem_trigger")
> > +int user_mem_test(struct pt_regs *ctx)
> > +{
> > +	if ((bpf_get_current_pid_tgid() >> 32) != monitored_pid)
> > +		return 0;
> > +
> > +	switch (action) {
> > +	case USER_MEM_MMAP:
> > +		user_addr = bpf_user_anon_mmap(map_len, map_prot);
> > +		break;
> > +	case USER_MEM_UNMAP:
> > +		ret = bpf_user_munmap(user_addr, map_len);
> > +		break;
> > +	}
> 
> [Severity: Medium]
> Can user_mem__open_and_load() in test_user_mem() succeed when loading this
> program?
> 
> user_mem_test() calls bpf_user_anon_mmap() and bpf_user_munmap(), which are
> declared as required __ksym externs, but neither symbol is defined or
> registered as a BPF kfunc in the kernel or bpf_testmod. Won't libbpf fail to
> resolve these kfunc BTF IDs during user_mem__open_and_load(), causing
> test_user_mem() to fail unconditionally?

defined in:
  bpf: Add user memory kfuncs

jirka