The biggest difficulty for user mode is MMU support. Otherwise it is a simple matter of setting and clearing MSR[PR] with rfid and sc respectively. Some common harness operations will fail in usermode, so some workarounds are reqiured (e.g., puts() can't be used directly). A usermode privileged instruction interrupt test is added. Signed-off-by: Nicholas Piggin <npiggin@xxxxxxxxx> --- lib/powerpc/asm/processor.h | 9 +++++++++ lib/powerpc/asm/reg.h | 1 + lib/powerpc/asm/smp.h | 1 + lib/powerpc/io.c | 7 +++++++ lib/powerpc/processor.c | 38 +++++++++++++++++++++++++++++++++++++ lib/powerpc/rtas.c | 3 +++ lib/powerpc/setup.c | 8 ++++++-- lib/powerpc/spinlock.c | 4 ++++ lib/ppc64/mmu.c | 2 ++ powerpc/interrupts.c | 28 +++++++++++++++++++++++++++ 10 files changed, 99 insertions(+), 2 deletions(-) diff --git a/lib/powerpc/asm/processor.h b/lib/powerpc/asm/processor.h index d348239c5..749155696 100644 --- a/lib/powerpc/asm/processor.h +++ b/lib/powerpc/asm/processor.h @@ -19,6 +19,8 @@ extern bool cpu_has_prefix; extern bool cpu_has_sc_lev; extern bool cpu_has_pause_short; +bool in_usermode(void); + static inline uint64_t mfspr(int nr) { uint64_t ret; @@ -51,6 +53,8 @@ static inline void local_irq_enable(void) { unsigned long msr; + assert(!in_usermode()); + asm volatile( " mfmsr %0 \n \ ori %0,%0,%1 \n \ @@ -62,6 +66,8 @@ static inline void local_irq_disable(void) { unsigned long msr; + assert(!in_usermode()); + asm volatile( " mfmsr %0 \n \ andc %0,%0,%1 \n \ @@ -90,4 +96,7 @@ static inline bool machine_is_pseries(void) void enable_mcheck(void); void disable_mcheck(void); +void enter_usermode(void); +void exit_usermode(void); + #endif /* _ASMPOWERPC_PROCESSOR_H_ */ diff --git a/lib/powerpc/asm/reg.h b/lib/powerpc/asm/reg.h index b2fab4313..69ef21adb 100644 --- a/lib/powerpc/asm/reg.h +++ b/lib/powerpc/asm/reg.h @@ -58,5 +58,6 @@ #define MSR_SE UL(0x0400) /* Single Step Enable */ #define MSR_EE UL(0x8000) #define MSR_ME UL(0x1000) +#define MSR_PR UL(0x4000) #endif diff --git a/lib/powerpc/asm/smp.h b/lib/powerpc/asm/smp.h index 3d7d3d08f..e591f6ab0 100644 --- a/lib/powerpc/asm/smp.h +++ b/lib/powerpc/asm/smp.h @@ -11,6 +11,7 @@ struct cpu { unsigned long server_no; unsigned long stack; unsigned long exception_stack; + bool in_user; secondary_entry_fn entry; pgd_t *pgtable; }; diff --git a/lib/powerpc/io.c b/lib/powerpc/io.c index cb7f2f050..5c2810884 100644 --- a/lib/powerpc/io.c +++ b/lib/powerpc/io.c @@ -11,6 +11,7 @@ #include <asm/setup.h> #include <asm/processor.h> #include <asm/atomic.h> +#include <asm/smp.h> #include "io.h" static struct spinlock print_lock; @@ -41,10 +42,16 @@ void io_init(void) void puts(const char *s) { + bool user = in_usermode(); + + if (user) + exit_usermode(); spin_lock(&print_lock); while (*s) putchar(*s++); spin_unlock(&print_lock); + if (user) + enter_usermode(); } /* diff --git a/lib/powerpc/processor.c b/lib/powerpc/processor.c index 09f6bb9d8..6c3000d5c 100644 --- a/lib/powerpc/processor.c +++ b/lib/powerpc/processor.c @@ -47,6 +47,8 @@ void do_handle_exception(struct pt_regs *regs) unsigned char v; __current_cpu = (struct cpu *)mfspr(SPR_SPRG0); + if (in_usermode()) + current_cpu()->in_user = false; /* * We run with AIL=0, so interrupts taken with MMU disabled. @@ -60,6 +62,8 @@ void do_handle_exception(struct pt_regs *regs) if (v < 128 && handlers[v].func) { handlers[v].func(regs, handlers[v].data); + if (regs->msr & MSR_PR) + current_cpu()->in_user = true; return; } @@ -169,3 +173,37 @@ void disable_mcheck(void) { rfid_msr(mfmsr() & ~MSR_ME); } + +bool in_usermode(void) +{ + return current_cpu()->in_user; +} + +static void usermode_sc_handler(struct pt_regs *regs, void *data) +{ + regs->msr &= ~(MSR_PR|MSR_EE); + /* Interrupt return handler will keep in_user clear */ +} + +void enter_usermode(void) +{ + assert_msg(!in_usermode(), "enter_usermode called with in_usermode"); + /* mfmsr would fault in usermode anyway */ + assert_msg(!(mfmsr() & MSR_PR), "enter_usermode called from user mode"); + assert_msg(!(mfmsr() & MSR_EE), "enter_usermode called with interrupts enabled"); + assert_msg((mfmsr() & (MSR_IR|MSR_DR)) == (MSR_IR|MSR_DR), + "enter_usermode called with virtual memory disabled"); + + handle_exception(0xc00, usermode_sc_handler, NULL); + rfid_msr(mfmsr() | (MSR_PR|MSR_IR|MSR_DR|MSR_EE)); + current_cpu()->in_user = true; +} + +void exit_usermode(void) +{ + assert_msg(in_usermode(), "enter_usermode called with !in_usermode"); + asm volatile("sc 0" ::: "memory"); + handle_exception(0xc00, NULL, NULL); + assert(!in_usermode()); + assert(!(mfmsr() & MSR_PR)); +} diff --git a/lib/powerpc/rtas.c b/lib/powerpc/rtas.c index b477a38e0..9c1e0affc 100644 --- a/lib/powerpc/rtas.c +++ b/lib/powerpc/rtas.c @@ -9,6 +9,7 @@ #include <libfdt/libfdt.h> #include <devicetree.h> #include <asm/spinlock.h> +#include <asm/smp.h> #include <asm/hcall.h> #include <asm/io.h> #include <asm/rtas.h> @@ -137,6 +138,8 @@ int rtas_call(int token, int nargs, int nret, int *outputs, ...) va_list list; int ret; + assert_msg(!in_usermode(), "May not make RTAS call from user mode\n"); + spin_lock(&rtas_lock); va_start(list, outputs); diff --git a/lib/powerpc/setup.c b/lib/powerpc/setup.c index 53ecbb830..a4ff678ce 100644 --- a/lib/powerpc/setup.c +++ b/lib/powerpc/setup.c @@ -209,8 +209,11 @@ void cpu_init(struct cpu *cpu, int cpu_id) cpu->exception_stack = (unsigned long)memalign_pages(SZ_4K, SZ_64K); cpu->exception_stack += SZ_64K - 64; cpu->pgtable = NULL; + cpu->in_user = false; } +bool is_hvmode; + void setup(const void *fdt) { void *freemem = &stacktop; @@ -219,8 +222,6 @@ void setup(const void *fdt) u32 fdt_size; int ret; - cpu_has_hv = !!(mfmsr() & (1ULL << MSR_HV_BIT)); - memset(cpus, 0xff, sizeof(cpus)); cpu = &cpus[0]; @@ -228,10 +229,13 @@ void setup(const void *fdt) cpu->exception_stack = (unsigned long)boot_exception_stack; cpu->exception_stack += EXCEPTION_STACK_SIZE - 64; cpu->pgtable = NULL; + cpu->in_user = false; mtspr(SPR_SPRG0, (unsigned long)cpu); __current_cpu = cpu; + cpu_has_hv = !!(mfmsr() & (1ULL << MSR_HV_BIT)); + enable_mcheck(); /* diff --git a/lib/powerpc/spinlock.c b/lib/powerpc/spinlock.c index 623a1f2c1..2c4904a33 100644 --- a/lib/powerpc/spinlock.c +++ b/lib/powerpc/spinlock.c @@ -9,6 +9,8 @@ */ void spin_lock(struct spinlock *lock) { + assert(!in_usermode()); + if (!multithreaded) { assert(lock->v == 0); lock->v = 1; @@ -20,7 +22,9 @@ void spin_lock(struct spinlock *lock) void spin_unlock(struct spinlock *lock) { + assert(!in_usermode()); assert(lock->v == 1); + if (!multithreaded) { lock->v = 0; } else { diff --git a/lib/ppc64/mmu.c b/lib/ppc64/mmu.c index 84be31752..bdc5e4637 100644 --- a/lib/ppc64/mmu.c +++ b/lib/ppc64/mmu.c @@ -42,6 +42,7 @@ void mmu_enable(pgd_t *pgtable) cpu->pgtable = pgtable; + assert(!in_usermode()); mtmsr(mfmsr() | (MSR_IR|MSR_DR)); } @@ -51,6 +52,7 @@ void mmu_disable(void) cpu->pgtable = NULL; + assert(!in_usermode()); mtmsr(mfmsr() & ~(MSR_IR|MSR_DR)); } diff --git a/powerpc/interrupts.c b/powerpc/interrupts.c index 6bed26e41..ba965ff76 100644 --- a/powerpc/interrupts.c +++ b/powerpc/interrupts.c @@ -326,6 +326,33 @@ static void test_illegal(void) report_prefix_pop(); } +static void dec_ignore_handler(struct pt_regs *regs, void *data) +{ + mtspr(SPR_DEC, 0x7fffffff); +} + +static void test_privileged(void) +{ + unsigned long msr; + + if (!mmu_enabled()) + return; + + report_prefix_push("privileged instruction"); + + handle_exception(0x700, &program_handler, NULL); + handle_exception(0x900, &dec_ignore_handler, NULL); + enter_usermode(); + asm volatile("mfmsr %0" : "=r"(msr) :: "memory"); + exit_usermode(); + report(got_interrupt, "interrupt on privileged instruction"); + got_interrupt = false; + handle_exception(0x900, NULL, NULL); + handle_exception(0x700, NULL, NULL); + + report_prefix_pop(); +} + static void sc_handler(struct pt_regs *regs, void *data) { got_interrupt = true; @@ -478,6 +505,7 @@ int main(int argc, char **argv) test_mce(); test_mmu(); test_illegal(); + test_privileged(); test_dec(); test_sc(); test_trace(); -- 2.43.0