An earlier commit 3f107464 defined the SFRAME_FRE_TYPE_*_LIMIT
constants. These constants are used (by gas and libsframe) to pick an
SFrame FRE type based on the function size. Those constants, however,
were buggy, causing the generated SFrame sections to be bloated as
SFRAME_FRE_TYPE_ADDR2/SFRAME_FRE_TYPE_ADDR4 got chosen more often than
necessary.
gas/
* sframe-opt.c (sframe_estimate_size_before_relax): Use
typecast.
(sframe_convert_frag): Likewise.
libsframe/
* sframe.c (sframe_calc_fre_type): Use a more appropriate type
for argument. Adjust the check for SFRAME_FRE_TYPE_ADDR4_LIMIT
to keep it warning-free but meaningful.
include/
* sframe-api.h (sframe_calc_fre_type): Use a more appropriate
type for the argument.
* sframe.h (SFRAME_FRE_TYPE_ADDR1_LIMIT): Correct the constant.
(SFRAME_FRE_TYPE_ADDR2_LIMIT): Likewise.
(SFRAME_FRE_TYPE_ADDR4_LIMIT): Likewise.
The newer update-copyright.py fixes file encoding too, removing cr/lf
on binutils/bfdtest2.c and ld/testsuite/ld-cygwin/exe-export.exp, and
embedded cr in binutils/testsuite/binutils-all/ar.exp string match.
ARM 8.3 provides five separate keys that can be used to authenticate
pointers. There are two key for executable (instruction) pointers. The
enum pointer_auth_key in gas/config/tc-aarch64.h currently holds two keys:
enum pointer_auth_key {
AARCH64_PAUTH_KEY_A,
AARCH64_PAUTH_KEY_B
};
Analogous to the above, in SFrame format V1, a bit is reserved in the SFrame
FDE to indicate which key is used for signing the frame's return addresses:
- SFRAME_AARCH64_PAUTH_KEY_A has a value of 0
- SFRAME_AARCH64_PAUTH_KEY_B has a value of 1
Note that the information in this bit will always be used along with the
mangled_ra_p bit, the latter indicates whether the return addresses are
mangled/contain PAC auth bits.
include/ChangeLog:
* sframe.h (SFRAME_AARCH64_PAUTH_KEY_A): New definition.
(SFRAME_AARCH64_PAUTH_KEY_B): Likewise.
(SFRAME_V1_FUNC_INFO): Adjust to accommodate pauth_key.
(SFRAME_V1_FUNC_PAUTH_KEY): New macro.
(SFRAME_V1_FUNC_INFO_UPDATE_PAUTH_KEY): Likewise.
Use the last remaining bit in the 'SFrame FRE info' word to store whether
the RA is signed/unsigned with PAC authorization code: this bit is named
as the "mangled RA" bit. This bit is still unused for x86-64.
The behaviour of the mangled-RA info bit in SFrame format closely
follows the behaviour of DW_CFA_AARCH64_negate_ra_state in DWARF. During
unwinding, whenever an SFrame FRE with non-zero "mangled RA" bit is
encountered, it means the upper bits of the return address contain Pointer
Authentication code. The unwinder, hence, must use appropriate means to
restore LR correctly in such cases.
include/ChangeLog:
* sframe.h (SFRAME_V1_FRE_INFO_UPDATE_MANGLED_RA_P): New macro.
(SFRAME_V1_FRE_MANGLED_RA_P): Likewise.
Define constants in sframe.h for the various limits associated with the
range of offsets that can be encoded in the start address of an SFrame
FRE. E.g., sframe_frame_row_entry_addr1 is used when start address
offset can be encoded as 1-byte unsigned value.
Update the code in gas to use these defined constants as it checks for
these limits, and remove the usage of magic numbers.
ChangeLog:
* gas/sframe-opt.c (sframe_estimate_size_before_relax):
(sframe_convert_frag): Do not use magic numbers.
* libsframe/sframe.c (sframe_calc_fre_type): Likewise.
include/ChangeLog:
* sframe.h (SFRAME_FRE_TYPE_ADDR1_LIMIT): New constant.
(SFRAME_FRE_TYPE_ADDR2_LIMIT): Likewise.
(SFRAME_FRE_TYPE_ADDR4_LIMIT): Likewise.
The header sframe.h defines the SFrame format.
The SFrame format is the Simple Frame format. It can be used to
represent the minimal necessary unwind information required for
backtracing. The current version supports AMD64 and AARCH64.
More details of the SFrame format are included in the documentation
of the header file in this patch.
include/ChangeLog:
* sframe.h: New file.
