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arm64: Disable PAC when booting on a Windows Dev Kit 2023

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It appears that PAC registers are configured to trap upon access, but
since the kernel starts in EL1 on this platform it has no ability to
inspect or modify this configuration.  Simply disable PAC on this
platform for now, since the kernel otherwise hangs during boot.

PR:		270472
Reviewed by:	andrew, emaste
MFC after:	2 weeks
Differential Revision:	https://reviews.freebsd.org/D39748
This commit is contained in:
Mark Johnston 2023-04-23 13:32:45 -04:00
parent ff13b92475
commit 4b39a12830
1 changed files with 30 additions and 1 deletions
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31
sys/arm64/arm64/ptrauth.c
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@ -59,6 +59,31 @@ struct thread *ptrauth_switch(struct thread *);
void ptrauth_exit_el0(struct thread *);
void ptrauth_enter_el0(struct thread *);
static bool
ptrauth_disable(void)
{
const char *family, *maker, *product;
family = kern_getenv("smbios.system.family");
maker = kern_getenv("smbios.system.maker");
product = kern_getenv("smbios.system.product");
if (family == NULL || maker == NULL || product == NULL)
return (false);
/*
* The Dev Kit appears to be configured to trap upon access to PAC
* registers, but the kernel boots at EL1 and so we have no way to
* inspect or change this configuration. As a workaround, simply
* disable PAC on this platform.
*/
if (strcmp(maker, "Microsoft Corporation") == 0 &&
strcmp(family, "Surface") == 0 &&
strcmp(product, "Windows Dev Kit 2023") == 0)
return (true);
return (false);
}
void
ptrauth_init(void)
{
@ -77,7 +102,11 @@ ptrauth_init(void)
return;
}
get_kernel_reg(ID_AA64ISAR1_EL1, &isar1);
if (!get_kernel_reg(ID_AA64ISAR1_EL1, &isar1))
return;
if (ptrauth_disable())
return;
/*
* This assumes if there is pointer authentication on the boot CPU