| Message ID | 09d6b8e5c8275de85c7aba716578fbcb3cbce924.1553093421.git.andreyknvl@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm64: untag user pointers passed to the kernel | expand |
On Wed, Mar 20, 2019 at 03:51:27PM +0100, Andrey Konovalov wrote: > This patch is a part of a series that extends arm64 kernel ABI to allow to > pass tagged user pointers (with the top byte set to something else other > than 0x00) as syscall arguments. > > stack_map_get_build_id_offset() uses provided user pointers for vma > lookups, which can only by done with untagged pointers. > > Untag user pointers in this function for doing the lookup and > calculating the offset, but save as is in the bpf_stack_build_id > struct. > > Signed-off-by: Andrey Konovalov <andreyknvl@google.com> > --- > kernel/bpf/stackmap.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c > index 950ab2f28922..bb89341d3faf 100644 > --- a/kernel/bpf/stackmap.c > +++ b/kernel/bpf/stackmap.c > @@ -320,7 +320,9 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs, > } > > for (i = 0; i < trace_nr; i++) { > - vma = find_vma(current->mm, ips[i]); > + u64 untagged_ip = untagged_addr(ips[i]); > + > + vma = find_vma(current->mm, untagged_ip); > if (!vma || stack_map_get_build_id(vma, id_offs[i].build_id)) { > /* per entry fall back to ips */ > id_offs[i].status = BPF_STACK_BUILD_ID_IP; > @@ -328,7 +330,7 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs, > memset(id_offs[i].build_id, 0, BPF_BUILD_ID_SIZE); > continue; > } > - id_offs[i].offset = (vma->vm_pgoff << PAGE_SHIFT) + ips[i] > + id_offs[i].offset = (vma->vm_pgoff << PAGE_SHIFT) + untagged_ip > - vma->vm_start; > id_offs[i].status = BPF_STACK_BUILD_ID_VALID; > } Can the ips[*] here ever be tagged?
On Fri, Mar 22, 2019 at 4:52 PM Catalin Marinas <catalin.marinas@arm.com> wrote: > > On Wed, Mar 20, 2019 at 03:51:27PM +0100, Andrey Konovalov wrote: > > This patch is a part of a series that extends arm64 kernel ABI to allow to > > pass tagged user pointers (with the top byte set to something else other > > than 0x00) as syscall arguments. > > > > stack_map_get_build_id_offset() uses provided user pointers for vma > > lookups, which can only by done with untagged pointers. > > > > Untag user pointers in this function for doing the lookup and > > calculating the offset, but save as is in the bpf_stack_build_id > > struct. > > > > Signed-off-by: Andrey Konovalov <andreyknvl@google.com> > > --- > > kernel/bpf/stackmap.c | 6 ++++-- > > 1 file changed, 4 insertions(+), 2 deletions(-) > > > > diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c > > index 950ab2f28922..bb89341d3faf 100644 > > --- a/kernel/bpf/stackmap.c > > +++ b/kernel/bpf/stackmap.c > > @@ -320,7 +320,9 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs, > > } > > > > for (i = 0; i < trace_nr; i++) { > > - vma = find_vma(current->mm, ips[i]); > > + u64 untagged_ip = untagged_addr(ips[i]); > > + > > + vma = find_vma(current->mm, untagged_ip); > > if (!vma || stack_map_get_build_id(vma, id_offs[i].build_id)) { > > /* per entry fall back to ips */ > > id_offs[i].status = BPF_STACK_BUILD_ID_IP; > > @@ -328,7 +330,7 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs, > > memset(id_offs[i].build_id, 0, BPF_BUILD_ID_SIZE); > > continue; > > } > > - id_offs[i].offset = (vma->vm_pgoff << PAGE_SHIFT) + ips[i] > > + id_offs[i].offset = (vma->vm_pgoff << PAGE_SHIFT) + untagged_ip > > - vma->vm_start; > > id_offs[i].status = BPF_STACK_BUILD_ID_VALID; > > } > > Can the ips[*] here ever be tagged? Those are instruction pointers AFAIU, so no, not within the current ABI. I'll drop this patch. Thanks! > > -- > Catalin
diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c index 950ab2f28922..bb89341d3faf 100644 --- a/kernel/bpf/stackmap.c +++ b/kernel/bpf/stackmap.c @@ -320,7 +320,9 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs, } for (i = 0; i < trace_nr; i++) { - vma = find_vma(current->mm, ips[i]); + u64 untagged_ip = untagged_addr(ips[i]); + + vma = find_vma(current->mm, untagged_ip); if (!vma || stack_map_get_build_id(vma, id_offs[i].build_id)) { /* per entry fall back to ips */ id_offs[i].status = BPF_STACK_BUILD_ID_IP; @@ -328,7 +330,7 @@ static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs, memset(id_offs[i].build_id, 0, BPF_BUILD_ID_SIZE); continue; } - id_offs[i].offset = (vma->vm_pgoff << PAGE_SHIFT) + ips[i] + id_offs[i].offset = (vma->vm_pgoff << PAGE_SHIFT) + untagged_ip - vma->vm_start; id_offs[i].status = BPF_STACK_BUILD_ID_VALID; }
This patch is a part of a series that extends arm64 kernel ABI to allow to pass tagged user pointers (with the top byte set to something else other than 0x00) as syscall arguments. stack_map_get_build_id_offset() uses provided user pointers for vma lookups, which can only by done with untagged pointers. Untag user pointers in this function for doing the lookup and calculating the offset, but save as is in the bpf_stack_build_id struct. Signed-off-by: Andrey Konovalov <andreyknvl@google.com> --- kernel/bpf/stackmap.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)