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Christina Schimpe 27e82ad68b LAM: Enable tagged pointer support for watchpoints.
The Intel (R) linear address masking (LAM) feature modifies the checking
applied to 64-bit linear addresses.  With this so-called "modified
canonicality check" the processor masks the metadata bits in a pointer
before using it as a linear address.  LAM supports two different modes that
differ regarding which pointer bits are masked and can be used for
metadata: LAM 48 resulting in a LAM width of 15 and LAM 57 resulting in a
LAM width of 6.

This patch adjusts watchpoint addresses based on the currently enabled
LAM mode using the untag mask provided in the /proc/<pid>/status file.
As LAM can be enabled at runtime or as the configuration may change
when entering an enclave, GDB checks enablement state each time a watchpoint
is updated.

In contrast to the patch implemented for ARM's Top Byte Ignore "Clear
non-significant bits of address on memory access", it is not necessary to
adjust addresses before they are passed to the target layer cache, as
for LAM tagged pointers are supported by the system call to read memory.
Additionally, LAM applies only to addresses used for data accesses.
Thus, it is sufficient to mask addresses used for watchpoints.

The following examples are based on a LAM57 enabled program.
Before this patch tagged pointers were not supported for watchpoints:
~~~
(gdb) print pi_tagged
$2 = (int *) 0x10007ffffffffe004
(gdb) watch *pi_tagged
Hardware watchpoint 2: *pi_tagged
(gdb) c
Continuing.
Couldn't write debug register: Invalid argument.
~~~~

Once LAM 48 or LAM 57 is enabled for the current program, GDB can now
specify watchpoints for tagged addresses with LAM width 15 or 6,
respectively.

Approved-By: Felix Willgerodt <felix.willgerodt@intel.com>
2024-11-18 13:36:16 +00:00
bfd ELF: SHF_STRINGS isn't really tied to SHF_MERGE 2024-11-18 11:36:57 +01:00
binutils gas/ELF: also reject merge entity size being zero 2024-11-18 11:35:57 +01:00
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gas x86: rename SPACE_{,E}VEX_MAP<N> 2024-11-18 11:46:28 +01:00
gdb LAM: Enable tagged pointer support for watchpoints. 2024-11-18 13:36:16 +00:00
gdbserver gdbserver: pass osabi to GDB in more target descriptions 2024-11-12 12:51:36 +00:00
gdbsupport [gdb] Fix some typos 2024-11-18 09:46:31 +01:00
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include aarch64: improve debuggability on array of enum 2024-11-08 11:35:46 +00:00
ld ld: Support percent-encoded JSON in --package-metadata 2024-11-18 11:38:25 +01:00
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configure Deprecate the ARM simulator. 2024-11-07 14:53:26 +00:00
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src-release.sh Add a target to src-release.sh to crate a binutils release without Gold 2024-10-29 11:50:04 +00:00
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