[PATCH, V5 1/9] gas: scfi: make scfi_state_restore_reg function more precise

[Jan Beulich]

On 13.07.2024 09:38, Indu Bhagat wrote:
> [No changes in V3, V4, V5]
> 
> [New in V2]
>  - This patch is orthogonal to aarch64 support.  It is included here
>    because the testcase added for it is aarch64 specific.  It is a
>    bugfix really.
> [End of New in V2]
> 
> When the SCFI machinery detects that a register has been restored from
> stack, it makes some state changes in the SCFI state object.
> 
> Prior to the patch, scfi_state_restore_reg () was setting a value of
> (reg, CFI_IN_REG) for (base, state) respectively.  This was causing
> issues in the cmp_scfi_state () function:
>   - The default state of all (callee-saved) regs at the beginning of
>     function is set to (0, CFI_UNDEFINED).
>   - If a register is saved and restored on some control path, the state
>     of reg is (reg, CFI_IN_REG) on that path.
>   - On another control path where the register was perhaps not
>     used (or saved/restored on stack) remains (0, CFI_UNDEFINED).
>   - The two states should be treated equal, however, at the point in
>     program after the register has been restored.
> 
> Fix this by resetting the state to (0, CFI_UNDEFINED) in
> scfi_state_restore_reg ().
> 
> A testcase (scfi-cfg-4.s) for this is added in a subsequent commit.
> 
> gas/
>         * scfi.c (scfi_state_restore_reg): Reset to 0, CFI_UNDEFINED
> 	for base, state.

Okay (just in case none was given so far).

Jan