| Message ID | c9553c3a4850d43c8af0c00e97850d70428b7de7.1553093421.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 03:51:25PM +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. > > seq_print_user_ip() uses provided user pointers for vma lookups, which > can only by done with untagged pointers. > > Untag user pointers in this function. > > Signed-off-by: Andrey Konovalov <andreyknvl@google.com> > --- > kernel/trace/trace_output.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c > index 54373d93e251..6376bee93c84 100644 > --- a/kernel/trace/trace_output.c > +++ b/kernel/trace/trace_output.c > @@ -370,6 +370,7 @@ static int seq_print_user_ip(struct trace_seq *s, struct mm_struct *mm, > { > struct file *file = NULL; > unsigned long vmstart = 0; > + unsigned long untagged_ip = untagged_addr(ip); > int ret = 1; > > if (s->full) > @@ -379,7 +380,7 @@ static int seq_print_user_ip(struct trace_seq *s, struct mm_struct *mm, > const struct vm_area_struct *vma; > > down_read(&mm->mmap_sem); > - vma = find_vma(mm, ip); > + vma = find_vma(mm, untagged_ip); > if (vma) { > file = vma->vm_file; > vmstart = vma->vm_start; > @@ -388,7 +389,7 @@ static int seq_print_user_ip(struct trace_seq *s, struct mm_struct *mm, > ret = trace_seq_path(s, &file->f_path); > if (ret) > trace_seq_printf(s, "[+0x%lx]", > - ip - vmstart); > + untagged_ip - vmstart); > } > up_read(&mm->mmap_sem); > } How would we end up with a tagged address here? Does "ip" here imply instruction pointer, which we wouldn't tag?
On Fri, Mar 22, 2019 at 4:45 PM Catalin Marinas <catalin.marinas@arm.com> wrote: > > On Wed, Mar 20, 2019 at 03:51:25PM +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. > > > > seq_print_user_ip() uses provided user pointers for vma lookups, which > > can only by done with untagged pointers. > > > > Untag user pointers in this function. > > > > Signed-off-by: Andrey Konovalov <andreyknvl@google.com> > > --- > > kernel/trace/trace_output.c | 5 +++-- > > 1 file changed, 3 insertions(+), 2 deletions(-) > > > > diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c > > index 54373d93e251..6376bee93c84 100644 > > --- a/kernel/trace/trace_output.c > > +++ b/kernel/trace/trace_output.c > > @@ -370,6 +370,7 @@ static int seq_print_user_ip(struct trace_seq *s, struct mm_struct *mm, > > { > > struct file *file = NULL; > > unsigned long vmstart = 0; > > + unsigned long untagged_ip = untagged_addr(ip); > > int ret = 1; > > > > if (s->full) > > @@ -379,7 +380,7 @@ static int seq_print_user_ip(struct trace_seq *s, struct mm_struct *mm, > > const struct vm_area_struct *vma; > > > > down_read(&mm->mmap_sem); > > - vma = find_vma(mm, ip); > > + vma = find_vma(mm, untagged_ip); > > if (vma) { > > file = vma->vm_file; > > vmstart = vma->vm_start; > > @@ -388,7 +389,7 @@ static int seq_print_user_ip(struct trace_seq *s, struct mm_struct *mm, > > ret = trace_seq_path(s, &file->f_path); > > if (ret) > > trace_seq_printf(s, "[+0x%lx]", > > - ip - vmstart); > > + untagged_ip - vmstart); > > } > > up_read(&mm->mmap_sem); > > } > > How would we end up with a tagged address here? Does "ip" here imply > instruction pointer, which we wouldn't tag? Yes, it's the instruction pointer. I think I got confused and decided that it's OK to have instruction pointer tagged, but I guess it's not a part of this ABI relaxation. I'll drop the patches that untag instruction pointers.
diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c index 54373d93e251..6376bee93c84 100644 --- a/kernel/trace/trace_output.c +++ b/kernel/trace/trace_output.c @@ -370,6 +370,7 @@ static int seq_print_user_ip(struct trace_seq *s, struct mm_struct *mm, { struct file *file = NULL; unsigned long vmstart = 0; + unsigned long untagged_ip = untagged_addr(ip); int ret = 1; if (s->full) @@ -379,7 +380,7 @@ static int seq_print_user_ip(struct trace_seq *s, struct mm_struct *mm, const struct vm_area_struct *vma; down_read(&mm->mmap_sem); - vma = find_vma(mm, ip); + vma = find_vma(mm, untagged_ip); if (vma) { file = vma->vm_file; vmstart = vma->vm_start; @@ -388,7 +389,7 @@ static int seq_print_user_ip(struct trace_seq *s, struct mm_struct *mm, ret = trace_seq_path(s, &file->f_path); if (ret) trace_seq_printf(s, "[+0x%lx]", - ip - vmstart); + untagged_ip - vmstart); } up_read(&mm->mmap_sem); }
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. seq_print_user_ip() uses provided user pointers for vma lookups, which can only by done with untagged pointers. Untag user pointers in this function. Signed-off-by: Andrey Konovalov <andreyknvl@google.com> --- kernel/trace/trace_output.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)