Re: [PATCH v3 dwarves 0/2] Check DW_OP_[GNU_]entry_value for possible parameter matching

[Alan Maguire <alan.maguire@oracle.com>]

On 15/11/2024 11:36, Alan Maguire wrote:
> Currently, pahole relies on DWARF to find whether a particular func
> has its parameter mismatched with standard or optimized away.
> In both these cases, the func will not be put in BTF and this
> will prevent fentry/fexit tracing for these functions.
> 
> The current parameter checking focuses on the first location/expression
> to match intended parameter register. But in some cases, the first
> location/expression does not have expected matching information,
> but further location like DW_OP_[GNU_]entry_value can provide
> information which matches the expected parameter register.
> 
> Patch 1 supports this; patch 2 adds locking around dwarf_getlocation*
> as it is unsafe in a multithreaded environment.
>

apologies, forgot to note

Changes since v2:

- handle multiple DW_OP_entry_value expressions by bailing if the
register matches expected, otherwise save reg in return value (Eduard
Yonghong, Jiri, patch 1)

> Alan Maguire (1):
>   dwarf_loader: use libdw__lock for dwarf_getlocation(s)
> 
> Eduard Zingerman (1):
>   dwarf_loader: Check DW_OP_[GNU_]entry_value for possible parameter
>     matching
> 
>  dwarf_loader.c | 123 +++++++++++++++++++++++++++++++++++++++----------
>  1 file changed, 98 insertions(+), 25 deletions(-)
>