Messages in this thread Patch in this message | | | From | Benjamin Gray <> | Subject | [RFC PATCH 06/13] powerpc/dexcr: Add prctl implementation | Date | Mon, 28 Nov 2022 13:44:51 +1100 |
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Adds an initial prctl interface implementation. Unprivileged processes can query the current prctl setting, including whether an aspect is implemented by the hardware or is permitted to be modified by a setter prctl. Editable aspects can be changed by a CAP_SYS_ADMIN privileged process.
The prctl setting represents what the process itself has requested, and does not account for any overrides. Either the kernel or a hypervisor may enforce a different setting for an aspect.
Userspace can access a readonly view of the current DEXCR via SPR 812, and a readonly view of the aspects enforced by the hypervisor via SPR 455. A bitwise OR of these two SPRs will give the effective DEXCR aspect state of the process.
Signed-off-by: Benjamin Gray <bgray@linux.ibm.com> --- arch/powerpc/include/asm/processor.h | 13 +++ arch/powerpc/kernel/dexcr.c | 133 ++++++++++++++++++++++++++- arch/powerpc/kernel/process.c | 6 ++ 3 files changed, 151 insertions(+), 1 deletion(-)
diff --git a/arch/powerpc/include/asm/processor.h b/arch/powerpc/include/asm/processor.h index 2381217c95dc..4c995258f668 100644 --- a/arch/powerpc/include/asm/processor.h +++ b/arch/powerpc/include/asm/processor.h @@ -265,6 +265,9 @@ struct thread_struct { unsigned long sier2; unsigned long sier3; unsigned long hashkeyr; + unsigned int dexcr_override; + unsigned int dexcr_mask; + unsigned int dexcr_forced; #endif }; @@ -338,6 +341,16 @@ extern int set_endian(struct task_struct *tsk, unsigned int val); extern int get_unalign_ctl(struct task_struct *tsk, unsigned long adr); extern int set_unalign_ctl(struct task_struct *tsk, unsigned int val); +#ifdef CONFIG_PPC_BOOK3S_64 + +#define PPC_GET_DEXCR_ASPECT(tsk, asp) dexcr_prctl_get((tsk), (asp)) +#define PPC_SET_DEXCR_ASPECT(tsk, asp, val) dexcr_prctl_set((tsk), (asp), (val)) + +int dexcr_prctl_get(struct task_struct *tsk, unsigned long asp); +int dexcr_prctl_set(struct task_struct *tsk, unsigned long asp, unsigned long val); + +#endif + extern void load_fp_state(struct thread_fp_state *fp); extern void store_fp_state(struct thread_fp_state *fp); extern void load_vr_state(struct thread_vr_state *vr); diff --git a/arch/powerpc/kernel/dexcr.c b/arch/powerpc/kernel/dexcr.c index 11515e67afac..9290beed722a 100644 --- a/arch/powerpc/kernel/dexcr.c +++ b/arch/powerpc/kernel/dexcr.c @@ -1,5 +1,8 @@ #include <linux/cache.h> +#include <linux/capability.h> #include <linux/init.h> +#include <linux/prctl.h> +#include <linux/sched.h> #include <asm/cpu_has_feature.h> #include <asm/cputable.h> @@ -11,6 +14,10 @@ #define DEFAULT_DEXCR 0 +/* Allow process configuration of these by default */ +#define DEXCR_PRCTL_EDITABLE (DEXCR_PRO_SBHE | DEXCR_PRO_IBRTPD | \ + DEXCR_PRO_SRAPD | DEXCR_PRO_NPHIE) + static int __init dexcr_init(void) { if (!early_cpu_has_feature(CPU_FTR_ARCH_31)) @@ -43,5 +50,129 @@ bool is_hashchk_trap(struct pt_regs const *regs) unsigned long get_thread_dexcr(struct thread_struct const *t) { - return DEFAULT_DEXCR; + unsigned long dexcr = DEFAULT_DEXCR; + + /* Apply prctl overrides */ + dexcr = (dexcr & ~t->dexcr_mask) | t->dexcr_override; + + return dexcr; +} + +static void update_dexcr_on_cpu(void *info) +{ + mtspr(SPRN_DEXCR, get_thread_dexcr(¤t->thread)); +} + +static int dexcr_aspect_get(struct task_struct *task, unsigned int aspect) +{ + int ret = 0; + + if (aspect & DEXCR_PRCTL_EDITABLE) + ret |= PR_PPC_DEXCR_PRCTL; + + if (aspect & task->thread.dexcr_mask) { + if (aspect & task->thread.dexcr_override) { + if (aspect & task->thread.dexcr_forced) + ret |= PR_PPC_DEXCR_FORCE_SET_ASPECT; + else + ret |= PR_PPC_DEXCR_SET_ASPECT; + } else { + ret |= PR_PPC_DEXCR_CLEAR_ASPECT; + } + } + + return ret; +} + +int dexcr_prctl_get(struct task_struct *task, unsigned long which) +{ + switch (which) { + case PR_PPC_DEXCR_SBHE: + if (!cpu_has_feature(CPU_FTR_DEXCR_SBHE)) + return -ENODEV; + return dexcr_aspect_get(task, DEXCR_PRO_SBHE); + case PR_PPC_DEXCR_IBRTPD: + if (!cpu_has_feature(CPU_FTR_DEXCR_IBRTPD)) + return -ENODEV; + return dexcr_aspect_get(task, DEXCR_PRO_IBRTPD); + case PR_PPC_DEXCR_SRAPD: + if (!cpu_has_feature(CPU_FTR_DEXCR_SRAPD)) + return -ENODEV; + return dexcr_aspect_get(task, DEXCR_PRO_SRAPD); + case PR_PPC_DEXCR_NPHIE: + if (!cpu_has_feature(CPU_FTR_DEXCR_NPHIE)) + return -ENODEV; + return dexcr_aspect_get(task, DEXCR_PRO_NPHIE); + default: + return -ENODEV; + } +} + +static int dexcr_aspect_set(struct task_struct *task, unsigned int aspect, unsigned long ctrl) +{ + if (!(aspect & DEXCR_PRCTL_EDITABLE)) + return -ENXIO; /* Aspect is not allowed to be changed by prctl */ + + if (aspect & task->thread.dexcr_forced) + return -EPERM; /* Aspect has been forced to current state */ + + switch (ctrl) { + case PR_PPC_DEXCR_SET_ASPECT: + task->thread.dexcr_mask |= aspect; + task->thread.dexcr_override |= aspect; + break; + case PR_PPC_DEXCR_FORCE_SET_ASPECT: + task->thread.dexcr_mask |= aspect; + task->thread.dexcr_override |= aspect; + task->thread.dexcr_forced |= aspect; + break; + case PR_PPC_DEXCR_CLEAR_ASPECT: + task->thread.dexcr_mask |= aspect; + task->thread.dexcr_override &= ~aspect; + break; + default: + return -ERANGE; + } + + return 0; +} + +int dexcr_prctl_set(struct task_struct *task, unsigned long which, unsigned long ctrl) +{ + int err = 0; + + if (!capable(CAP_SYS_ADMIN)) + return -EPERM; + + switch (which) { + case PR_PPC_DEXCR_SBHE: + if (!cpu_has_feature(CPU_FTR_DEXCR_SBHE)) + return -ENODEV; + err = dexcr_aspect_set(task, DEXCR_PRO_SBHE, ctrl); + break; + case PR_PPC_DEXCR_IBRTPD: + if (!cpu_has_feature(CPU_FTR_DEXCR_IBRTPD)) + return -ENODEV; + err = dexcr_aspect_set(task, DEXCR_PRO_IBRTPD, ctrl); + break; + case PR_PPC_DEXCR_SRAPD: + if (!cpu_has_feature(CPU_FTR_DEXCR_SRAPD)) + return -ENODEV; + err = dexcr_aspect_set(task, DEXCR_PRO_SRAPD, ctrl); + break; + case PR_PPC_DEXCR_NPHIE: + if (!cpu_has_feature(CPU_FTR_DEXCR_NPHIE)) + return -ENODEV; + err = dexcr_aspect_set(task, DEXCR_PRO_NPHIE, ctrl); + break; + default: + return -ENODEV; + } + + if (err) + return err; + + update_dexcr_on_cpu(NULL); + + return 0; } diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c index 4d7b0c7641d0..a280842750f9 100644 --- a/arch/powerpc/kernel/process.c +++ b/arch/powerpc/kernel/process.c @@ -1825,6 +1825,12 @@ int copy_thread(struct task_struct *p, const struct kernel_clone_args *args) #ifdef CONFIG_PPC_BOOK3S_64 if (cpu_has_feature(CPU_FTR_DEXCR_NPHIE)) p->thread.hashkeyr = current->thread.hashkeyr; + + if (cpu_has_feature(CPU_FTR_ARCH_31)) { + p->thread.dexcr_override = current->thread.dexcr_override; + p->thread.dexcr_mask = current->thread.dexcr_mask; + p->thread.dexcr_forced = current->thread.dexcr_forced; + } #endif /* * Run with the current AMR value of the kernel -- 2.38.1
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