From 2f79d2fc391e4ba64df908b8c07dda6c3a907056 Mon Sep 17 00:00:00 2001 From: Peter Collingbourne Date: Thu, 18 Mar 2021 20:10:52 -0700 Subject: arm64: mte: make the per-task SCTLR_EL1 field usable elsewhere In an upcoming change we are going to introduce per-task SCTLR_EL1 bits for PAC. Move the existing per-task SCTLR_EL1 field out of the MTE-specific code so that we will be able to use it from both the PAC and MTE code paths and make the task switching code more efficient. Signed-off-by: Peter Collingbourne Link: https://linux-review.googlesource.com/id/Ic65fac78a7926168fa68f9e8da591c9e04ff7278 Link: https://lore.kernel.org/r/13d725cb8e741950fb9d6e64b2cd9bd54ff7c3f9.1616123271.git.pcc@google.com Signed-off-by: Catalin Marinas --- arch/arm64/include/asm/processor.h | 6 ++++- arch/arm64/kernel/mte.c | 49 ++++++++------------------------------ arch/arm64/kernel/process.c | 24 +++++++++++++++++++ 3 files changed, 39 insertions(+), 40 deletions(-) (limited to 'arch/arm64') diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h index ca2cd75d3286..80895bb30490 100644 --- a/arch/arm64/include/asm/processor.h +++ b/arch/arm64/include/asm/processor.h @@ -151,11 +151,13 @@ struct thread_struct { struct ptrauth_keys_kernel keys_kernel; #endif #ifdef CONFIG_ARM64_MTE - u64 sctlr_tcf0; u64 gcr_user_excl; #endif + u64 sctlr_user; }; +#define SCTLR_USER_MASK SCTLR_EL1_TCF0_MASK + static inline void arch_thread_struct_whitelist(unsigned long *offset, unsigned long *size) { @@ -247,6 +249,8 @@ extern void release_thread(struct task_struct *); unsigned long get_wchan(struct task_struct *p); +void set_task_sctlr_el1(u64 sctlr); + /* Thread switching */ extern struct task_struct *cpu_switch_to(struct task_struct *prev, struct task_struct *next); diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c index 820bad94870e..8da597e41795 100644 --- a/arch/arm64/kernel/mte.c +++ b/arch/arm64/kernel/mte.c @@ -185,26 +185,6 @@ void mte_check_tfsr_el1(void) } #endif -static void update_sctlr_el1_tcf0(u64 tcf0) -{ - /* ISB required for the kernel uaccess routines */ - sysreg_clear_set(sctlr_el1, SCTLR_EL1_TCF0_MASK, tcf0); - isb(); -} - -static void set_sctlr_el1_tcf0(u64 tcf0) -{ - /* - * mte_thread_switch() checks current->thread.sctlr_tcf0 as an - * optimisation. Disable preemption so that it does not see - * the variable update before the SCTLR_EL1.TCF0 one. - */ - preempt_disable(); - current->thread.sctlr_tcf0 = tcf0; - update_sctlr_el1_tcf0(tcf0); - preempt_enable(); -} - static void update_gcr_el1_excl(u64 excl) { @@ -237,31 +217,22 @@ void flush_mte_state(void) write_sysreg_s(0, SYS_TFSRE0_EL1); clear_thread_flag(TIF_MTE_ASYNC_FAULT); /* disable tag checking */ - set_sctlr_el1_tcf0(SCTLR_EL1_TCF0_NONE); + set_task_sctlr_el1((current->thread.sctlr_user & ~SCTLR_EL1_TCF0_MASK) | + SCTLR_EL1_TCF0_NONE); /* reset tag generation mask */ set_gcr_el1_excl(SYS_GCR_EL1_EXCL_MASK); } void mte_thread_switch(struct task_struct *next) { - if (!system_supports_mte()) - return; - - /* avoid expensive SCTLR_EL1 accesses if no change */ - if (current->thread.sctlr_tcf0 != next->thread.sctlr_tcf0) - update_sctlr_el1_tcf0(next->thread.sctlr_tcf0); - else - isb(); - /* * Check if an async tag exception occurred at EL1. * * Note: On the context switch path we rely on the dsb() present * in __switch_to() to guarantee that the indirect writes to TFSR_EL1 * are synchronized before this point. - * isb() above is required for the same reason. - * */ + isb(); mte_check_tfsr_el1(); } @@ -291,7 +262,7 @@ void mte_suspend_exit(void) long set_mte_ctrl(struct task_struct *task, unsigned long arg) { - u64 tcf0; + u64 sctlr = task->thread.sctlr_user & ~SCTLR_EL1_TCF0_MASK; u64 gcr_excl = ~((arg & PR_MTE_TAG_MASK) >> PR_MTE_TAG_SHIFT) & SYS_GCR_EL1_EXCL_MASK; @@ -300,23 +271,23 @@ long set_mte_ctrl(struct task_struct *task, unsigned long arg) switch (arg & PR_MTE_TCF_MASK) { case PR_MTE_TCF_NONE: - tcf0 = SCTLR_EL1_TCF0_NONE; + sctlr |= SCTLR_EL1_TCF0_NONE; break; case PR_MTE_TCF_SYNC: - tcf0 = SCTLR_EL1_TCF0_SYNC; + sctlr |= SCTLR_EL1_TCF0_SYNC; break; case PR_MTE_TCF_ASYNC: - tcf0 = SCTLR_EL1_TCF0_ASYNC; + sctlr |= SCTLR_EL1_TCF0_ASYNC; break; default: return -EINVAL; } if (task != current) { - task->thread.sctlr_tcf0 = tcf0; + task->thread.sctlr_user = sctlr; task->thread.gcr_user_excl = gcr_excl; } else { - set_sctlr_el1_tcf0(tcf0); + set_task_sctlr_el1(sctlr); set_gcr_el1_excl(gcr_excl); } @@ -333,7 +304,7 @@ long get_mte_ctrl(struct task_struct *task) ret = incl << PR_MTE_TAG_SHIFT; - switch (task->thread.sctlr_tcf0) { + switch (task->thread.sctlr_user & SCTLR_EL1_TCF0_MASK) { case SCTLR_EL1_TCF0_NONE: ret |= PR_MTE_TCF_NONE; break; diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c index 325c83b1a24d..de0ab08cb260 100644 --- a/arch/arm64/kernel/process.c +++ b/arch/arm64/kernel/process.c @@ -529,6 +529,27 @@ static void erratum_1418040_thread_switch(struct task_struct *prev, write_sysreg(val, cntkctl_el1); } +static void update_sctlr_el1(u64 sctlr) +{ + sysreg_clear_set(sctlr_el1, SCTLR_USER_MASK, sctlr); + + /* ISB required for the kernel uaccess routines when setting TCF0. */ + isb(); +} + +void set_task_sctlr_el1(u64 sctlr) +{ + /* + * __switch_to() checks current->thread.sctlr as an + * optimisation. Disable preemption so that it does not see + * the variable update before the SCTLR_EL1 one. + */ + preempt_disable(); + current->thread.sctlr_user = sctlr; + update_sctlr_el1(sctlr); + preempt_enable(); +} + /* * Thread switching. */ @@ -559,6 +580,9 @@ __notrace_funcgraph struct task_struct *__switch_to(struct task_struct *prev, * registers. */ mte_thread_switch(next); + /* avoid expensive SCTLR_EL1 accesses if no change */ + if (prev->thread.sctlr_user != next->thread.sctlr_user) + update_sctlr_el1(next->thread.sctlr_user); /* the actual thread switch */ last = cpu_switch_to(prev, next); -- cgit v1.2.3 From 201698626fbca1cf1a3b686ba14cf2a056500716 Mon Sep 17 00:00:00 2001 From: Peter Collingbourne Date: Thu, 18 Mar 2021 20:10:53 -0700 Subject: arm64: Introduce prctl(PR_PAC_{SET,GET}_ENABLED_KEYS) This change introduces a prctl that allows the user program to control which PAC keys are enabled in a particular task. The main reason why this is useful is to enable a userspace ABI that uses PAC to sign and authenticate function pointers and other pointers exposed outside of the function, while still allowing binaries conforming to the ABI to interoperate with legacy binaries that do not sign or authenticate pointers. The idea is that a dynamic loader or early startup code would issue this prctl very early after establishing that a process may load legacy binaries, but before executing any PAC instructions. This change adds a small amount of overhead to kernel entry and exit due to additional required instruction sequences. On a DragonBoard 845c (Cortex-A75) with the powersave governor, the overhead of similar instruction sequences was measured as 4.9ns when simulating the common case where IA is left enabled, or 43.7ns when simulating the uncommon case where IA is disabled. These numbers can be seen as the worst case scenario, since in more realistic scenarios a better performing governor would be used and a newer chip would be used that would support PAC unlike Cortex-A75 and would be expected to be faster than Cortex-A75. On an Apple M1 under a hypervisor, the overhead of the entry/exit instruction sequences introduced by this patch was measured as 0.3ns in the case where IA is left enabled, and 33.0ns in the case where IA is disabled. Signed-off-by: Peter Collingbourne Reviewed-by: Dave Martin Link: https://linux-review.googlesource.com/id/Ibc41a5e6a76b275efbaa126b31119dc197b927a5 Link: https://lore.kernel.org/r/d6609065f8f40397a4124654eb68c9f490b4d477.1616123271.git.pcc@google.com Signed-off-by: Catalin Marinas --- Documentation/arm64/pointer-authentication.rst | 34 ++++++++++++++ arch/arm64/include/asm/mte.h | 4 +- arch/arm64/include/asm/pointer_auth.h | 25 +++++++++-- arch/arm64/include/asm/processor.h | 9 +++- arch/arm64/include/asm/sysreg.h | 4 +- arch/arm64/kernel/asm-offsets.c | 1 + arch/arm64/kernel/entry.S | 39 +++++++++++++++- arch/arm64/kernel/mte.c | 2 +- arch/arm64/kernel/pointer_auth.c | 62 ++++++++++++++++++++++++++ arch/arm64/kernel/process.c | 10 +++-- arch/arm64/kernel/ptrace.c | 41 +++++++++++++++++ include/uapi/linux/elf.h | 1 + include/uapi/linux/prctl.h | 4 ++ kernel/sys.c | 16 +++++++ 14 files changed, 239 insertions(+), 13 deletions(-) (limited to 'arch/arm64') diff --git a/Documentation/arm64/pointer-authentication.rst b/Documentation/arm64/pointer-authentication.rst index 30b2ab06526b..f127666ea3a8 100644 --- a/Documentation/arm64/pointer-authentication.rst +++ b/Documentation/arm64/pointer-authentication.rst @@ -107,3 +107,37 @@ filter out the Pointer Authentication system key registers from KVM_GET/SET_REG_* ioctls and mask those features from cpufeature ID register. Any attempt to use the Pointer Authentication instructions will result in an UNDEFINED exception being injected into the guest. + + +Enabling and disabling keys +--------------------------- + +The prctl PR_PAC_SET_ENABLED_KEYS allows the user program to control which +PAC keys are enabled in a particular task. It takes two arguments, the +first being a bitmask of PR_PAC_APIAKEY, PR_PAC_APIBKEY, PR_PAC_APDAKEY +and PR_PAC_APDBKEY specifying which keys shall be affected by this prctl, +and the second being a bitmask of the same bits specifying whether the key +should be enabled or disabled. For example:: + + prctl(PR_PAC_SET_ENABLED_KEYS, + PR_PAC_APIAKEY | PR_PAC_APIBKEY | PR_PAC_APDAKEY | PR_PAC_APDBKEY, + PR_PAC_APIBKEY, 0, 0); + +disables all keys except the IB key. + +The main reason why this is useful is to enable a userspace ABI that uses PAC +instructions to sign and authenticate function pointers and other pointers +exposed outside of the function, while still allowing binaries conforming to +the ABI to interoperate with legacy binaries that do not sign or authenticate +pointers. + +The idea is that a dynamic loader or early startup code would issue this +prctl very early after establishing that a process may load legacy binaries, +but before executing any PAC instructions. + +For compatibility with previous kernel versions, processes start up with IA, +IB, DA and DB enabled, and are reset to this state on exec(). Processes created +via fork() and clone() inherit the key enabled state from the calling process. + +It is recommended to avoid disabling the IA key, as this has higher performance +overhead than disabling any of the other keys. diff --git a/arch/arm64/include/asm/mte.h b/arch/arm64/include/asm/mte.h index a38abc15186c..5d6a53cca5d5 100644 --- a/arch/arm64/include/asm/mte.h +++ b/arch/arm64/include/asm/mte.h @@ -39,7 +39,7 @@ void mte_free_tag_storage(char *storage); void mte_sync_tags(pte_t *ptep, pte_t pte); void mte_copy_page_tags(void *kto, const void *kfrom); -void flush_mte_state(void); +void mte_thread_init_user(void); void mte_thread_switch(struct task_struct *next); void mte_suspend_enter(void); void mte_suspend_exit(void); @@ -61,7 +61,7 @@ static inline void mte_sync_tags(pte_t *ptep, pte_t pte) static inline void mte_copy_page_tags(void *kto, const void *kfrom) { } -static inline void flush_mte_state(void) +static inline void mte_thread_init_user(void) { } static inline void mte_thread_switch(struct task_struct *next) diff --git a/arch/arm64/include/asm/pointer_auth.h b/arch/arm64/include/asm/pointer_auth.h index b112a11e9302..cefe7e9b6fa9 100644 --- a/arch/arm64/include/asm/pointer_auth.h +++ b/arch/arm64/include/asm/pointer_auth.h @@ -3,6 +3,7 @@ #define __ASM_POINTER_AUTH_H #include +#include #include #include @@ -71,6 +72,10 @@ static __always_inline void ptrauth_keys_switch_kernel(struct ptrauth_keys_kerne extern int ptrauth_prctl_reset_keys(struct task_struct *tsk, unsigned long arg); +extern int ptrauth_set_enabled_keys(struct task_struct *tsk, unsigned long keys, + unsigned long enabled); +extern int ptrauth_get_enabled_keys(struct task_struct *tsk); + static inline unsigned long ptrauth_strip_insn_pac(unsigned long ptr) { return ptrauth_clear_pac(ptr); @@ -85,8 +90,17 @@ static __always_inline void ptrauth_enable(void) isb(); } -#define ptrauth_thread_init_user(tsk) \ - ptrauth_keys_init_user(&(tsk)->thread.keys_user) +#define ptrauth_thread_init_user() \ + do { \ + ptrauth_keys_init_user(¤t->thread.keys_user); \ + \ + /* enable all keys */ \ + if (system_supports_address_auth()) \ + set_task_sctlr_el1(current->thread.sctlr_user | \ + SCTLR_ELx_ENIA | SCTLR_ELx_ENIB | \ + SCTLR_ELx_ENDA | SCTLR_ELx_ENDB); \ + } while (0) + #define ptrauth_thread_init_kernel(tsk) \ ptrauth_keys_init_kernel(&(tsk)->thread.keys_kernel) #define ptrauth_thread_switch_kernel(tsk) \ @@ -95,10 +109,15 @@ static __always_inline void ptrauth_enable(void) #else /* CONFIG_ARM64_PTR_AUTH */ #define ptrauth_enable() #define ptrauth_prctl_reset_keys(tsk, arg) (-EINVAL) +#define ptrauth_set_enabled_keys(tsk, keys, enabled) (-EINVAL) +#define ptrauth_get_enabled_keys(tsk) (-EINVAL) #define ptrauth_strip_insn_pac(lr) (lr) -#define ptrauth_thread_init_user(tsk) +#define ptrauth_thread_init_user() #define ptrauth_thread_init_kernel(tsk) #define ptrauth_thread_switch_kernel(tsk) #endif /* CONFIG_ARM64_PTR_AUTH */ +#define PR_PAC_ENABLED_KEYS_MASK \ + (PR_PAC_APIAKEY | PR_PAC_APIBKEY | PR_PAC_APDAKEY | PR_PAC_APDBKEY) + #endif /* __ASM_POINTER_AUTH_H */ diff --git a/arch/arm64/include/asm/processor.h b/arch/arm64/include/asm/processor.h index 80895bb30490..2f21c76324bb 100644 --- a/arch/arm64/include/asm/processor.h +++ b/arch/arm64/include/asm/processor.h @@ -156,7 +156,9 @@ struct thread_struct { u64 sctlr_user; }; -#define SCTLR_USER_MASK SCTLR_EL1_TCF0_MASK +#define SCTLR_USER_MASK \ + (SCTLR_ELx_ENIA | SCTLR_ELx_ENIB | SCTLR_ELx_ENDA | SCTLR_ELx_ENDB | \ + SCTLR_EL1_TCF0_MASK) static inline void arch_thread_struct_whitelist(unsigned long *offset, unsigned long *size) @@ -305,6 +307,11 @@ extern void __init minsigstksz_setup(void); /* PR_PAC_RESET_KEYS prctl */ #define PAC_RESET_KEYS(tsk, arg) ptrauth_prctl_reset_keys(tsk, arg) +/* PR_PAC_{SET,GET}_ENABLED_KEYS prctl */ +#define PAC_SET_ENABLED_KEYS(tsk, keys, enabled) \ + ptrauth_set_enabled_keys(tsk, keys, enabled) +#define PAC_GET_ENABLED_KEYS(tsk) ptrauth_get_enabled_keys(tsk) + #ifdef CONFIG_ARM64_TAGGED_ADDR_ABI /* PR_{SET,GET}_TAGGED_ADDR_CTRL prctl */ long set_tagged_addr_ctrl(struct task_struct *task, unsigned long arg); diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h index d4a5fca984c3..9dc2e88b10c6 100644 --- a/arch/arm64/include/asm/sysreg.h +++ b/arch/arm64/include/asm/sysreg.h @@ -565,8 +565,10 @@ #define SCTLR_ELx_TCF_ASYNC (UL(0x2) << SCTLR_ELx_TCF_SHIFT) #define SCTLR_ELx_TCF_MASK (UL(0x3) << SCTLR_ELx_TCF_SHIFT) +#define SCTLR_ELx_ENIA_SHIFT 31 + #define SCTLR_ELx_ITFSB (BIT(37)) -#define SCTLR_ELx_ENIA (BIT(31)) +#define SCTLR_ELx_ENIA (BIT(SCTLR_ELx_ENIA_SHIFT)) #define SCTLR_ELx_ENIB (BIT(30)) #define SCTLR_ELx_ENDA (BIT(27)) #define SCTLR_ELx_EE (BIT(25)) diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c index a36e2fc330d4..8b4fbad427b3 100644 --- a/arch/arm64/kernel/asm-offsets.c +++ b/arch/arm64/kernel/asm-offsets.c @@ -43,6 +43,7 @@ int main(void) #endif BLANK(); DEFINE(THREAD_CPU_CONTEXT, offsetof(struct task_struct, thread.cpu_context)); + DEFINE(THREAD_SCTLR_USER, offsetof(struct task_struct, thread.sctlr_user)); #ifdef CONFIG_ARM64_PTR_AUTH DEFINE(THREAD_KEYS_USER, offsetof(struct task_struct, thread.keys_user)); DEFINE(THREAD_KEYS_KERNEL, offsetof(struct task_struct, thread.keys_kernel)); diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index a31a0a713c85..36ae1cdfaeb6 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -247,7 +247,24 @@ alternative_else_nop_endif check_mte_async_tcf x19, x22 apply_ssbd 1, x22, x23 - ptrauth_keys_install_kernel tsk, x20, x22, x23 + ptrauth_keys_install_kernel_nosync tsk, x20, x22, x23 + +#ifdef CONFIG_ARM64_PTR_AUTH +alternative_if ARM64_HAS_ADDRESS_AUTH + /* + * Enable IA for in-kernel PAC if the task had it disabled. Although + * this could be implemented with an unconditional MRS which would avoid + * a load, this was measured to be slower on Cortex-A75 and Cortex-A76. + */ + ldr x0, [tsk, THREAD_SCTLR_USER] + tbnz x0, SCTLR_ELx_ENIA_SHIFT, 1f + mrs x0, sctlr_el1 + orr x0, x0, SCTLR_ELx_ENIA + msr sctlr_el1, x0 +1: + isb +alternative_else_nop_endif +#endif mte_set_kernel_gcr x22, x23 @@ -351,9 +368,27 @@ alternative_else_nop_endif 3: scs_save tsk, x0 - /* No kernel C function calls after this as user keys are set. */ + /* + * No kernel C function calls after this as user keys are set and IA may + * be disabled. + */ ptrauth_keys_install_user tsk, x0, x1, x2 +#ifdef CONFIG_ARM64_PTR_AUTH +alternative_if ARM64_HAS_ADDRESS_AUTH + /* + * IA was enabled for in-kernel PAC. Disable it now if needed. + * All other per-task SCTLR bits were updated on task switch. + */ + ldr x0, [tsk, THREAD_SCTLR_USER] + tbnz x0, SCTLR_ELx_ENIA_SHIFT, 1f + mrs x0, sctlr_el1 + bic x0, x0, SCTLR_ELx_ENIA + msr sctlr_el1, x0 +1: +alternative_else_nop_endif +#endif + mte_set_user_gcr tsk, x0, x1 apply_ssbd 0, x0, x1 diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c index 8da597e41795..125a10e413e9 100644 --- a/arch/arm64/kernel/mte.c +++ b/arch/arm64/kernel/mte.c @@ -207,7 +207,7 @@ static void set_gcr_el1_excl(u64 excl) */ } -void flush_mte_state(void) +void mte_thread_init_user(void) { if (!system_supports_mte()) return; diff --git a/arch/arm64/kernel/pointer_auth.c b/arch/arm64/kernel/pointer_auth.c index adb955fd9bdd..f03e5bfe4490 100644 --- a/arch/arm64/kernel/pointer_auth.c +++ b/arch/arm64/kernel/pointer_auth.c @@ -46,3 +46,65 @@ int ptrauth_prctl_reset_keys(struct task_struct *tsk, unsigned long arg) return 0; } + +static u64 arg_to_enxx_mask(unsigned long arg) +{ + u64 sctlr_enxx_mask = 0; + + WARN_ON(arg & ~PR_PAC_ENABLED_KEYS_MASK); + if (arg & PR_PAC_APIAKEY) + sctlr_enxx_mask |= SCTLR_ELx_ENIA; + if (arg & PR_PAC_APIBKEY) + sctlr_enxx_mask |= SCTLR_ELx_ENIB; + if (arg & PR_PAC_APDAKEY) + sctlr_enxx_mask |= SCTLR_ELx_ENDA; + if (arg & PR_PAC_APDBKEY) + sctlr_enxx_mask |= SCTLR_ELx_ENDB; + return sctlr_enxx_mask; +} + +int ptrauth_set_enabled_keys(struct task_struct *tsk, unsigned long keys, + unsigned long enabled) +{ + u64 sctlr = tsk->thread.sctlr_user; + + if (!system_supports_address_auth()) + return -EINVAL; + + if (is_compat_thread(task_thread_info(tsk))) + return -EINVAL; + + if ((keys & ~PR_PAC_ENABLED_KEYS_MASK) || (enabled & ~keys)) + return -EINVAL; + + sctlr &= ~arg_to_enxx_mask(keys); + sctlr |= arg_to_enxx_mask(enabled); + if (tsk == current) + set_task_sctlr_el1(sctlr); + else + tsk->thread.sctlr_user = sctlr; + + return 0; +} + +int ptrauth_get_enabled_keys(struct task_struct *tsk) +{ + int retval = 0; + + if (!system_supports_address_auth()) + return -EINVAL; + + if (is_compat_thread(task_thread_info(tsk))) + return -EINVAL; + + if (tsk->thread.sctlr_user & SCTLR_ELx_ENIA) + retval |= PR_PAC_APIAKEY; + if (tsk->thread.sctlr_user & SCTLR_ELx_ENIB) + retval |= PR_PAC_APIBKEY; + if (tsk->thread.sctlr_user & SCTLR_ELx_ENDA) + retval |= PR_PAC_APDAKEY; + if (tsk->thread.sctlr_user & SCTLR_ELx_ENDB) + retval |= PR_PAC_APDBKEY; + + return retval; +} diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c index de0ab08cb260..d583cbae32f6 100644 --- a/arch/arm64/kernel/process.c +++ b/arch/arm64/kernel/process.c @@ -339,7 +339,6 @@ void flush_thread(void) tls_thread_flush(); flush_ptrace_hw_breakpoint(current); flush_tagged_addr_state(); - flush_mte_state(); } void release_thread(struct task_struct *dead_task) @@ -531,7 +530,11 @@ static void erratum_1418040_thread_switch(struct task_struct *prev, static void update_sctlr_el1(u64 sctlr) { - sysreg_clear_set(sctlr_el1, SCTLR_USER_MASK, sctlr); + /* + * EnIA must not be cleared while in the kernel as this is necessary for + * in-kernel PAC. It will be cleared on kernel exit if needed. + */ + sysreg_clear_set(sctlr_el1, SCTLR_USER_MASK & ~SCTLR_ELx_ENIA, sctlr); /* ISB required for the kernel uaccess routines when setting TCF0. */ isb(); @@ -632,7 +635,8 @@ void arch_setup_new_exec(void) { current->mm->context.flags = is_compat_task() ? MMCF_AARCH32 : 0; - ptrauth_thread_init_user(current); + ptrauth_thread_init_user(); + mte_thread_init_user(); if (task_spec_ssb_noexec(current)) { arch_prctl_spec_ctrl_set(current, PR_SPEC_STORE_BYPASS, diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c index 170f42fd6101..eb2f73939b7b 100644 --- a/arch/arm64/kernel/ptrace.c +++ b/arch/arm64/kernel/ptrace.c @@ -909,6 +909,38 @@ static int pac_mask_get(struct task_struct *target, return membuf_write(&to, &uregs, sizeof(uregs)); } +static int pac_enabled_keys_get(struct task_struct *target, + const struct user_regset *regset, + struct membuf to) +{ + long enabled_keys = ptrauth_get_enabled_keys(target); + + if (IS_ERR_VALUE(enabled_keys)) + return enabled_keys; + + return membuf_write(&to, &enabled_keys, sizeof(enabled_keys)); +} + +static int pac_enabled_keys_set(struct task_struct *target, + const struct user_regset *regset, + unsigned int pos, unsigned int count, + const void *kbuf, const void __user *ubuf) +{ + int ret; + long enabled_keys = ptrauth_get_enabled_keys(target); + + if (IS_ERR_VALUE(enabled_keys)) + return enabled_keys; + + ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &enabled_keys, 0, + sizeof(long)); + if (ret) + return ret; + + return ptrauth_set_enabled_keys(target, PR_PAC_ENABLED_KEYS_MASK, + enabled_keys); +} + #ifdef CONFIG_CHECKPOINT_RESTORE static __uint128_t pac_key_to_user(const struct ptrauth_key *key) { @@ -1074,6 +1106,7 @@ enum aarch64_regset { #endif #ifdef CONFIG_ARM64_PTR_AUTH REGSET_PAC_MASK, + REGSET_PAC_ENABLED_KEYS, #ifdef CONFIG_CHECKPOINT_RESTORE REGSET_PACA_KEYS, REGSET_PACG_KEYS, @@ -1160,6 +1193,14 @@ static const struct user_regset aarch64_regsets[] = { .regset_get = pac_mask_get, /* this cannot be set dynamically */ }, + [REGSET_PAC_ENABLED_KEYS] = { + .core_note_type = NT_ARM_PAC_ENABLED_KEYS, + .n = 1, + .size = sizeof(long), + .align = sizeof(long), + .regset_get = pac_enabled_keys_get, + .set = pac_enabled_keys_set, + }, #ifdef CONFIG_CHECKPOINT_RESTORE [REGSET_PACA_KEYS] = { .core_note_type = NT_ARM_PACA_KEYS, diff --git a/include/uapi/linux/elf.h b/include/uapi/linux/elf.h index 30f68b42eeb5..61bf4774b8f2 100644 --- a/include/uapi/linux/elf.h +++ b/include/uapi/linux/elf.h @@ -426,6 +426,7 @@ typedef struct elf64_shdr { #define NT_ARM_PACA_KEYS 0x407 /* ARM pointer authentication address keys */ #define NT_ARM_PACG_KEYS 0x408 /* ARM pointer authentication generic key */ #define NT_ARM_TAGGED_ADDR_CTRL 0x409 /* arm64 tagged address control (prctl()) */ +#define NT_ARM_PAC_ENABLED_KEYS 0x40a /* arm64 ptr auth enabled keys (prctl()) */ #define NT_ARC_V2 0x600 /* ARCv2 accumulator/extra registers */ #define NT_VMCOREDD 0x700 /* Vmcore Device Dump Note */ #define NT_MIPS_DSP 0x800 /* MIPS DSP ASE registers */ diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h index 667f1aed091c..18a9f59dc067 100644 --- a/include/uapi/linux/prctl.h +++ b/include/uapi/linux/prctl.h @@ -255,4 +255,8 @@ struct prctl_mm_map { # define SYSCALL_DISPATCH_FILTER_ALLOW 0 # define SYSCALL_DISPATCH_FILTER_BLOCK 1 +/* Set/get enabled arm64 pointer authentication keys */ +#define PR_PAC_SET_ENABLED_KEYS 60 +#define PR_PAC_GET_ENABLED_KEYS 61 + #endif /* _LINUX_PRCTL_H */ diff --git a/kernel/sys.c b/kernel/sys.c index 2e2e3f378d97..3d62c9599dc0 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -119,6 +119,12 @@ #ifndef PAC_RESET_KEYS # define PAC_RESET_KEYS(a, b) (-EINVAL) #endif +#ifndef PAC_SET_ENABLED_KEYS +# define PAC_SET_ENABLED_KEYS(a, b, c) (-EINVAL) +#endif +#ifndef PAC_GET_ENABLED_KEYS +# define PAC_GET_ENABLED_KEYS(a) (-EINVAL) +#endif #ifndef SET_TAGGED_ADDR_CTRL # define SET_TAGGED_ADDR_CTRL(a) (-EINVAL) #endif @@ -2497,6 +2503,16 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3, return -EINVAL; error = PAC_RESET_KEYS(me, arg2); break; + case PR_PAC_SET_ENABLED_KEYS: + if (arg4 || arg5) + return -EINVAL; + error = PAC_SET_ENABLED_KEYS(me, arg2, arg3); + break; + case PR_PAC_GET_ENABLED_KEYS: + if (arg2 || arg3 || arg4 || arg5) + return -EINVAL; + error = PAC_GET_ENABLED_KEYS(me); + break; case PR_SET_TAGGED_ADDR_CTRL: if (arg3 || arg4 || arg5) return -EINVAL; -- cgit v1.2.3 From b90e483938ce387c256e03fb144f82f64551847b Mon Sep 17 00:00:00 2001 From: Peter Collingbourne Date: Thu, 18 Mar 2021 20:10:54 -0700 Subject: arm64: pac: Optimize kernel entry/exit key installation code paths The kernel does not use any keys besides IA so we don't need to install IB/DA/DB/GA on kernel exit if we arrange to install them on task switch instead, which we can expect to happen an order of magnitude less often. Furthermore we can avoid installing the user IA in the case where the user task has IA disabled and just leave the kernel IA installed. This also lets us avoid needing to install IA on kernel entry. On an Apple M1 under a hypervisor, the overhead of kernel entry/exit has been measured to be reduced by 15.6ns in the case where IA is enabled, and 31.9ns in the case where IA is disabled. Signed-off-by: Peter Collingbourne Link: https://linux-review.googlesource.com/id/Ieddf6b580d23c9e0bed45a822dabe72d2ffc9a8e Link: https://lore.kernel.org/r/2d653d055f38f779937f2b92f8ddd5cf9e4af4f4.1616123271.git.pcc@google.com Signed-off-by: Catalin Marinas --- arch/arm64/include/asm/asm_pointer_auth.h | 20 +---------------- arch/arm64/include/asm/pointer_auth.h | 36 +++++++++++++++++++++++++------ arch/arm64/kernel/asm-offsets.c | 4 ---- arch/arm64/kernel/entry.S | 33 ++++++++++++++++------------ arch/arm64/kernel/pointer_auth.c | 1 + arch/arm64/kernel/process.c | 1 + arch/arm64/kernel/suspend.c | 3 ++- 7 files changed, 53 insertions(+), 45 deletions(-) (limited to 'arch/arm64') diff --git a/arch/arm64/include/asm/asm_pointer_auth.h b/arch/arm64/include/asm/asm_pointer_auth.h index 52dead2a8640..8ca2dc0661ee 100644 --- a/arch/arm64/include/asm/asm_pointer_auth.h +++ b/arch/arm64/include/asm/asm_pointer_auth.h @@ -13,30 +13,12 @@ * so use the base value of ldp as thread.keys_user and offset as * thread.keys_user.ap*. */ - .macro ptrauth_keys_install_user tsk, tmp1, tmp2, tmp3 + .macro __ptrauth_keys_install_user tsk, tmp1, tmp2, tmp3 mov \tmp1, #THREAD_KEYS_USER add \tmp1, \tsk, \tmp1 -alternative_if_not ARM64_HAS_ADDRESS_AUTH - b .Laddr_auth_skip_\@ -alternative_else_nop_endif ldp \tmp2, \tmp3, [\tmp1, #PTRAUTH_USER_KEY_APIA] msr_s SYS_APIAKEYLO_EL1, \tmp2 msr_s SYS_APIAKEYHI_EL1, \tmp3 - ldp \tmp2, \tmp3, [\tmp1, #PTRAUTH_USER_KEY_APIB] - msr_s SYS_APIBKEYLO_EL1, \tmp2 - msr_s SYS_APIBKEYHI_EL1, \tmp3 - ldp \tmp2, \tmp3, [\tmp1, #PTRAUTH_USER_KEY_APDA] - msr_s SYS_APDAKEYLO_EL1, \tmp2 - msr_s SYS_APDAKEYHI_EL1, \tmp3 - ldp \tmp2, \tmp3, [\tmp1, #PTRAUTH_USER_KEY_APDB] - msr_s SYS_APDBKEYLO_EL1, \tmp2 - msr_s SYS_APDBKEYHI_EL1, \tmp3 -.Laddr_auth_skip_\@: -alternative_if ARM64_HAS_GENERIC_AUTH - ldp \tmp2, \tmp3, [\tmp1, #PTRAUTH_USER_KEY_APGA] - msr_s SYS_APGAKEYLO_EL1, \tmp2 - msr_s SYS_APGAKEYHI_EL1, \tmp3 -alternative_else_nop_endif .endm .macro __ptrauth_keys_install_kernel_nosync tsk, tmp1, tmp2, tmp3 diff --git a/arch/arm64/include/asm/pointer_auth.h b/arch/arm64/include/asm/pointer_auth.h index cefe7e9b6fa9..d50416be99be 100644 --- a/arch/arm64/include/asm/pointer_auth.h +++ b/arch/arm64/include/asm/pointer_auth.h @@ -35,6 +35,25 @@ struct ptrauth_keys_kernel { struct ptrauth_key apia; }; +#define __ptrauth_key_install_nosync(k, v) \ +do { \ + struct ptrauth_key __pki_v = (v); \ + write_sysreg_s(__pki_v.lo, SYS_ ## k ## KEYLO_EL1); \ + write_sysreg_s(__pki_v.hi, SYS_ ## k ## KEYHI_EL1); \ +} while (0) + +static inline void ptrauth_keys_install_user(struct ptrauth_keys_user *keys) +{ + if (system_supports_address_auth()) { + __ptrauth_key_install_nosync(APIB, keys->apib); + __ptrauth_key_install_nosync(APDA, keys->apda); + __ptrauth_key_install_nosync(APDB, keys->apdb); + } + + if (system_supports_generic_auth()) + __ptrauth_key_install_nosync(APGA, keys->apga); +} + static inline void ptrauth_keys_init_user(struct ptrauth_keys_user *keys) { if (system_supports_address_auth()) { @@ -46,14 +65,9 @@ static inline void ptrauth_keys_init_user(struct ptrauth_keys_user *keys) if (system_supports_generic_auth()) get_random_bytes(&keys->apga, sizeof(keys->apga)); -} -#define __ptrauth_key_install_nosync(k, v) \ -do { \ - struct ptrauth_key __pki_v = (v); \ - write_sysreg_s(__pki_v.lo, SYS_ ## k ## KEYLO_EL1); \ - write_sysreg_s(__pki_v.hi, SYS_ ## k ## KEYHI_EL1); \ -} while (0) + ptrauth_keys_install_user(keys); +} static __always_inline void ptrauth_keys_init_kernel(struct ptrauth_keys_kernel *keys) { @@ -90,6 +104,9 @@ static __always_inline void ptrauth_enable(void) isb(); } +#define ptrauth_suspend_exit() \ + ptrauth_keys_install_user(¤t->thread.keys_user) + #define ptrauth_thread_init_user() \ do { \ ptrauth_keys_init_user(¤t->thread.keys_user); \ @@ -101,6 +118,9 @@ static __always_inline void ptrauth_enable(void) SCTLR_ELx_ENDA | SCTLR_ELx_ENDB); \ } while (0) +#define ptrauth_thread_switch_user(tsk) \ + ptrauth_keys_install_user(&(tsk)->thread.keys_user) + #define ptrauth_thread_init_kernel(tsk) \ ptrauth_keys_init_kernel(&(tsk)->thread.keys_kernel) #define ptrauth_thread_switch_kernel(tsk) \ @@ -112,8 +132,10 @@ static __always_inline void ptrauth_enable(void) #define ptrauth_set_enabled_keys(tsk, keys, enabled) (-EINVAL) #define ptrauth_get_enabled_keys(tsk) (-EINVAL) #define ptrauth_strip_insn_pac(lr) (lr) +#define ptrauth_suspend_exit() #define ptrauth_thread_init_user() #define ptrauth_thread_init_kernel(tsk) +#define ptrauth_thread_switch_user(tsk) #define ptrauth_thread_switch_kernel(tsk) #endif /* CONFIG_ARM64_PTR_AUTH */ diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c index 8b4fbad427b3..a02573c32f79 100644 --- a/arch/arm64/kernel/asm-offsets.c +++ b/arch/arm64/kernel/asm-offsets.c @@ -148,10 +148,6 @@ int main(void) #endif #ifdef CONFIG_ARM64_PTR_AUTH DEFINE(PTRAUTH_USER_KEY_APIA, offsetof(struct ptrauth_keys_user, apia)); - DEFINE(PTRAUTH_USER_KEY_APIB, offsetof(struct ptrauth_keys_user, apib)); - DEFINE(PTRAUTH_USER_KEY_APDA, offsetof(struct ptrauth_keys_user, apda)); - DEFINE(PTRAUTH_USER_KEY_APDB, offsetof(struct ptrauth_keys_user, apdb)); - DEFINE(PTRAUTH_USER_KEY_APGA, offsetof(struct ptrauth_keys_user, apga)); DEFINE(PTRAUTH_KERNEL_KEY_APIA, offsetof(struct ptrauth_keys_kernel, apia)); BLANK(); #endif diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 36ae1cdfaeb6..2e46c75a5b48 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -247,21 +247,26 @@ alternative_else_nop_endif check_mte_async_tcf x19, x22 apply_ssbd 1, x22, x23 - ptrauth_keys_install_kernel_nosync tsk, x20, x22, x23 - #ifdef CONFIG_ARM64_PTR_AUTH alternative_if ARM64_HAS_ADDRESS_AUTH /* * Enable IA for in-kernel PAC if the task had it disabled. Although * this could be implemented with an unconditional MRS which would avoid * a load, this was measured to be slower on Cortex-A75 and Cortex-A76. + * + * Install the kernel IA key only if IA was enabled in the task. If IA + * was disabled on kernel exit then we would have left the kernel IA + * installed so there is no need to install it again. */ ldr x0, [tsk, THREAD_SCTLR_USER] - tbnz x0, SCTLR_ELx_ENIA_SHIFT, 1f + tbz x0, SCTLR_ELx_ENIA_SHIFT, 1f + __ptrauth_keys_install_kernel_nosync tsk, x20, x22, x23 + b 2f +1: mrs x0, sctlr_el1 orr x0, x0, SCTLR_ELx_ENIA msr sctlr_el1, x0 -1: +2: isb alternative_else_nop_endif #endif @@ -368,24 +373,24 @@ alternative_else_nop_endif 3: scs_save tsk, x0 - /* - * No kernel C function calls after this as user keys are set and IA may - * be disabled. - */ - ptrauth_keys_install_user tsk, x0, x1, x2 - #ifdef CONFIG_ARM64_PTR_AUTH alternative_if ARM64_HAS_ADDRESS_AUTH /* - * IA was enabled for in-kernel PAC. Disable it now if needed. - * All other per-task SCTLR bits were updated on task switch. + * IA was enabled for in-kernel PAC. Disable it now if needed, or + * alternatively install the user's IA. All other per-task keys and + * SCTLR bits were updated on task switch. + * + * No kernel C function calls after this. */ ldr x0, [tsk, THREAD_SCTLR_USER] - tbnz x0, SCTLR_ELx_ENIA_SHIFT, 1f + tbz x0, SCTLR_ELx_ENIA_SHIFT, 1f + __ptrauth_keys_install_user tsk, x0, x1, x2 + b 2f +1: mrs x0, sctlr_el1 bic x0, x0, SCTLR_ELx_ENIA msr sctlr_el1, x0 -1: +2: alternative_else_nop_endif #endif diff --git a/arch/arm64/kernel/pointer_auth.c b/arch/arm64/kernel/pointer_auth.c index f03e5bfe4490..60901ab0a7fe 100644 --- a/arch/arm64/kernel/pointer_auth.c +++ b/arch/arm64/kernel/pointer_auth.c @@ -43,6 +43,7 @@ int ptrauth_prctl_reset_keys(struct task_struct *tsk, unsigned long arg) get_random_bytes(&keys->apdb, sizeof(keys->apdb)); if (arg & PR_PAC_APGAKEY) get_random_bytes(&keys->apga, sizeof(keys->apga)); + ptrauth_keys_install_user(keys); return 0; } diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c index d583cbae32f6..449b94584f9a 100644 --- a/arch/arm64/kernel/process.c +++ b/arch/arm64/kernel/process.c @@ -568,6 +568,7 @@ __notrace_funcgraph struct task_struct *__switch_to(struct task_struct *prev, entry_task_switch(next); ssbs_thread_switch(next); erratum_1418040_thread_switch(prev, next); + ptrauth_thread_switch_user(next); /* * Complete any pending TLB or cache maintenance on this CPU in case diff --git a/arch/arm64/kernel/suspend.c b/arch/arm64/kernel/suspend.c index 6fdc8292b4f5..e3f72df9509d 100644 --- a/arch/arm64/kernel/suspend.c +++ b/arch/arm64/kernel/suspend.c @@ -74,8 +74,9 @@ void notrace __cpu_suspend_exit(void) */ spectre_v4_enable_mitigation(NULL); - /* Restore additional MTE-specific configuration */ + /* Restore additional feature-specific configuration */ mte_suspend_exit(); + ptrauth_suspend_exit(); } /* -- cgit v1.2.3