match_var_offset compares address offsets to determine if an access
falls within a variable's bounds. The offsets involved for those
relative to base registers from DW_OP_breg can be negative.
The current implementation uses unsigned types (u64) for these offsets,
which rejects almost all negative values.
This commit changes the local variables within match_var_offset to
signed types (s64) before performing comparisons. This ensures correct
behavior when addr_offset_ or addr_type_ are negative.
Signed-off-by: Zecheng Li <zecheng@google.com>
---
tools/perf/util/dwarf-aux.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/tools/perf/util/dwarf-aux.c b/tools/perf/util/dwarf-aux.c
index 559c953ca172..bf906dff9ef0 100644
--- a/tools/perf/util/dwarf-aux.c
+++ b/tools/perf/util/dwarf-aux.c
@@ -1388,10 +1388,12 @@ struct find_var_data {
#define DWARF_OP_DIRECT_REGS 32
static bool match_var_offset(Dwarf_Die *die_mem, struct find_var_data *data,
- u64 addr_offset, u64 addr_type, bool is_pointer)
+ u64 addr_offset_, u64 addr_type_, bool is_pointer)
{
Dwarf_Die type_die;
Dwarf_Word size;
+ s64 addr_offset = (s64)addr_offset_;
+ s64 addr_type = (s64)addr_type_;
if (addr_offset == addr_type) {
/* Update offset relative to the start of the variable */
@@ -1414,7 +1416,7 @@ static bool match_var_offset(Dwarf_Die *die_mem, struct find_var_data *data,
if (dwarf_aggregate_size(&type_die, &size) < 0)
return false;
- if (addr_offset >= addr_type + size)
+ if (addr_offset_ - addr_type_ >= size)
return false;
/* Update offset relative to the start of the variable */
--
2.50.1.470.g6ba607880d-googOn Fri, Jul 25, 2025 at 1:28 PM Zecheng Li <zecheng@google.com> wrote:
>
> match_var_offset compares address offsets to determine if an access
> falls within a variable's bounds. The offsets involved for those
> relative to base registers from DW_OP_breg can be negative.
>
> The current implementation uses unsigned types (u64) for these offsets,
> which rejects almost all negative values.
>
> This commit changes the local variables within match_var_offset to
> signed types (s64) before performing comparisons. This ensures correct
> behavior when addr_offset_ or addr_type_ are negative.
>
> Signed-off-by: Zecheng Li <zecheng@google.com>
> ---
> tools/perf/util/dwarf-aux.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/tools/perf/util/dwarf-aux.c b/tools/perf/util/dwarf-aux.c
> index 559c953ca172..bf906dff9ef0 100644
> --- a/tools/perf/util/dwarf-aux.c
> +++ b/tools/perf/util/dwarf-aux.c
> @@ -1388,10 +1388,12 @@ struct find_var_data {
> #define DWARF_OP_DIRECT_REGS 32
>
> static bool match_var_offset(Dwarf_Die *die_mem, struct find_var_data *data,
> - u64 addr_offset, u64 addr_type, bool is_pointer)
> + u64 addr_offset_, u64 addr_type_, bool is_pointer)
> {
> Dwarf_Die type_die;
> Dwarf_Word size;
> + s64 addr_offset = (s64)addr_offset_;
> + s64 addr_type = (s64)addr_type_;
Would it be better to make the function take signed types? I'm
thinking if a 32-bit int is passed, with the signature as-is it is
unclear if sign-extension will happen.
Thanks,
Ian
>
> if (addr_offset == addr_type) {
> /* Update offset relative to the start of the variable */
> @@ -1414,7 +1416,7 @@ static bool match_var_offset(Dwarf_Die *die_mem, struct find_var_data *data,
> if (dwarf_aggregate_size(&type_die, &size) < 0)
> return false;
>
> - if (addr_offset >= addr_type + size)
> + if (addr_offset_ - addr_type_ >= size)
> return false;
>
> /* Update offset relative to the start of the variable */
> --
> 2.50.1.470.g6ba607880d-goog
>
On Fri, Jul 25, 2025 at 05:58:05PM -0700, Ian Rogers wrote:
> On Fri, Jul 25, 2025 at 1:28 PM Zecheng Li <zecheng@google.com> wrote:
> >
> > match_var_offset compares address offsets to determine if an access
> > falls within a variable's bounds. The offsets involved for those
> > relative to base registers from DW_OP_breg can be negative.
> >
> > The current implementation uses unsigned types (u64) for these offsets,
> > which rejects almost all negative values.
> >
> > This commit changes the local variables within match_var_offset to
> > signed types (s64) before performing comparisons. This ensures correct
> > behavior when addr_offset_ or addr_type_ are negative.
> >
> > Signed-off-by: Zecheng Li <zecheng@google.com>
> > ---
> > tools/perf/util/dwarf-aux.c | 6 ++++--
> > 1 file changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/tools/perf/util/dwarf-aux.c b/tools/perf/util/dwarf-aux.c
> > index 559c953ca172..bf906dff9ef0 100644
> > --- a/tools/perf/util/dwarf-aux.c
> > +++ b/tools/perf/util/dwarf-aux.c
> > @@ -1388,10 +1388,12 @@ struct find_var_data {
> > #define DWARF_OP_DIRECT_REGS 32
> >
> > static bool match_var_offset(Dwarf_Die *die_mem, struct find_var_data *data,
> > - u64 addr_offset, u64 addr_type, bool is_pointer)
> > + u64 addr_offset_, u64 addr_type_, bool is_pointer)
> > {
> > Dwarf_Die type_die;
> > Dwarf_Word size;
> > + s64 addr_offset = (s64)addr_offset_;
> > + s64 addr_type = (s64)addr_type_;
>
> Would it be better to make the function take signed types? I'm
> thinking if a 32-bit int is passed, with the signature as-is it is
> unclear if sign-extension will happen.
Hmm.. right. The addr_offset often from 'int' type so negative value
can have the sign-extension problem.
Zecheng, can you please update the function signature to s64 and check
if the final offset is negative or bigger than the size?
Thanks,
Namhyung
> >
> > if (addr_offset == addr_type) {
> > /* Update offset relative to the start of the variable */
> > @@ -1414,7 +1416,7 @@ static bool match_var_offset(Dwarf_Die *die_mem, struct find_var_data *data,
> > if (dwarf_aggregate_size(&type_die, &size) < 0)
> > return false;
> >
> > - if (addr_offset >= addr_type + size)
> > + if (addr_offset_ - addr_type_ >= size)
> > return false;
> >
> > /* Update offset relative to the start of the variable */
> > --
> > 2.50.1.470.g6ba607880d-goog
> >
© 2016 - 2025 Red Hat, Inc.