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gdbserver: Add optional runtime register set type.

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Some register sets can be activated and deactivated by the OS during the runtime of
a process.  One example register is the Intel CET shadow stack pointer.  This patch
adds a new type of register set to handle such cases.  We shouldn't deactivate these
regsets and should not show a warning if the register set is not active but supported
by the kernel.  However, it is safe to deactivate them, if they are unsupported by the
kernel.  To differentiate those scenarios we can use the errno returned by the ptrace
call.

Reviewed-by: Thiago Jung Bauermann <thiago.bauermann@linaro.org>
Approved-By: Luis Machado <luis.machado@arm.com>
This commit is contained in:
Christina Schimpe
2023-12-18 18:47:09 +01:00
parent 364e3c2ec7
commit 81d4480fe9
2 changed files with 42 additions and 15 deletions
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50
gdbserver/linux-low.cc
View File

@@ -5006,23 +5006,31 @@ regsets_fetch_inferior_registers (struct regsets_info *regsets_info,
if (res < 0)
{
if (errno == EIO
|| (errno == EINVAL && regset->type == OPTIONAL_REGS))
|| (errno == EINVAL
&& (regset->type == OPTIONAL_REGS
|| regset->type == OPTIONAL_RUNTIME_REGS)))
{
/* If we get EIO on a regset, or an EINVAL and the regset is
optional, do not try it again for this process mode. */
optional, do not try it again for this process mode.
Even if the regset can be enabled at runtime it is safe
to deactivate the regset in case of EINVAL, as we know
the regset itself was the invalid argument of the ptrace
call which means that it's unsupported by the kernel. */
disable_regset (regsets_info, regset);
}
else if (errno == ENODATA)
else if (errno == ENODATA
|| (errno == ENODEV
&& regset->type == OPTIONAL_RUNTIME_REGS)
|| errno == ESRCH)
{
/* ENODATA may be returned if the regset is currently
not "active". This can happen in normal operation,
so suppress the warning in this case. */
}
else if (errno == ESRCH)
{
/* At this point, ESRCH should mean the process is
already gone, in which case we simply ignore attempts
to read its registers. */
/* ENODATA or ENODEV may be returned if the regset is
currently not "active". For ENODEV we additionally check
if the register set is of type OPTIONAL_RUNTIME_REGS.
This can happen in normal operation, so suppress the
warning in this case.
ESRCH should mean the process is already gone at this
point, in which case we simply ignore attempts to read
its registers. */
}
else
{
@@ -5104,12 +5112,26 @@ regsets_store_inferior_registers (struct regsets_info *regsets_info,
if (res < 0)
{
if (errno == EIO
|| (errno == EINVAL && regset->type == OPTIONAL_REGS))
|| (errno == EINVAL
&& (regset->type == OPTIONAL_REGS
|| regset->type == OPTIONAL_RUNTIME_REGS)))
{
/* If we get EIO on a regset, or an EINVAL and the regset is
optional, do not try it again for this process mode. */
optional, do not try it again for this process mode.
Even if the regset can be enabled at runtime it is safe
to deactivate the regset in case of EINVAL, as we know
the regset itself was the invalid argument of the ptrace
call which means that it's unsupported by the kernel. */
disable_regset (regsets_info, regset);
}
else if (errno == ENODEV
&& regset->type == OPTIONAL_RUNTIME_REGS)
{
/* If we get ENODEV on a regset and the regset can be
enabled at runtime try it again for this process mode.
This can happen in normal operation, so suppress the
warning in this case. */
}
else if (errno == ESRCH)
{
/* At this point, ESRCH should mean the process is

7
gdbserver/linux-low.h
View File

@@ -42,7 +42,12 @@ enum regset_type {
GENERAL_REGS,
FP_REGS,
EXTENDED_REGS,
OPTIONAL_REGS, /* Do not error if the regset cannot be accessed. */
OPTIONAL_REGS, /* Do not error if the regset cannot be accessed.
Disable the regset instead. */
OPTIONAL_RUNTIME_REGS, /* Some optional regsets can only be accessed
dependent on the execution flow. For such
access errors don't show a warning and don't
disable the regset. */
};
/* The arch's regsets array initializer must be terminated with a NULL