diff options
Diffstat (limited to 'sysdeps/unix/sysv/linux/aarch64/makecontext.c')
-rw-r--r-- | sysdeps/unix/sysv/linux/aarch64/makecontext.c | 61 |
1 files changed, 59 insertions, 2 deletions
diff --git a/sysdeps/unix/sysv/linux/aarch64/makecontext.c b/sysdeps/unix/sysv/linux/aarch64/makecontext.c index 5aec182013..9e66b6761c 100644 --- a/sysdeps/unix/sysv/linux/aarch64/makecontext.c +++ b/sysdeps/unix/sysv/linux/aarch64/makecontext.c @@ -22,6 +22,52 @@ #include <stdint.h> #include <ucontext.h> +#define GCS_MAGIC 0x47435300 + +static struct _aarch64_ctx *extension (void *p) +{ + return p; +} + +#ifndef __NR_map_shadow_stack +# define __NR_map_shadow_stack 453 +#endif +#ifndef SHADOW_STACK_SET_TOKEN +# define SHADOW_STACK_SET_TOKEN (1UL << 0) +# define SHADOW_STACK_SET_MARKER (1UL << 1) +#endif + +static void * +map_shadow_stack (void *addr, size_t size, unsigned long flags) +{ + return (void *) INLINE_SYSCALL_CALL (map_shadow_stack, addr, size, flags); +} + +#define GCS_MAX_SIZE (1UL << 31) +#define GCS_ALTSTACK_RESERVE 160 + +static void * +alloc_makecontext_gcs (size_t stack_size) +{ + size_t size = (stack_size / 2 + GCS_ALTSTACK_RESERVE) & -8UL; + if (size > GCS_MAX_SIZE) + size = GCS_MAX_SIZE; + + unsigned long flags = SHADOW_STACK_SET_MARKER | SHADOW_STACK_SET_TOKEN; + void *base = map_shadow_stack (NULL, size, flags); + if (base == (void *) -1) + /* ENOSYS, bad size or OOM. */ + abort (); + uint64_t *gcsp = (uint64_t *) ((char *) base + size); + /* Skip end of GCS token. */ + gcsp--; + /* Verify GCS cap token. */ + gcsp--; + if (((uint64_t)gcsp & 0xfffffffffffff000) + 1 != *gcsp) + abort (); + /* Return the target GCS pointer for context switch. */ + return gcsp + 1; +} /* makecontext sets up a stack and the registers for the user context. The stack looks like this: @@ -56,10 +102,21 @@ __makecontext (ucontext_t *ucp, void (*func) (void), int argc, ...) sp = (uint64_t *) (((uintptr_t) sp) & -16L); ucp->uc_mcontext.regs[19] = (uintptr_t) ucp->uc_link; + ucp->uc_mcontext.regs[20] = (uintptr_t) func; ucp->uc_mcontext.sp = (uintptr_t) sp; - ucp->uc_mcontext.pc = (uintptr_t) func; + ucp->uc_mcontext.pc = (uintptr_t) __startcontext; ucp->uc_mcontext.regs[29] = (uintptr_t) 0; - ucp->uc_mcontext.regs[30] = (uintptr_t) &__startcontext; + ucp->uc_mcontext.regs[30] = (uintptr_t) 0; + + void *p = ucp->uc_mcontext.__reserved; + if (extension (p)->magic == FPSIMD_MAGIC) + p = (char *)p + extension (p)->size; + if (extension (p)->magic == GCS_MAGIC) + { + /* Using the kernel struct gcs_context layout. */ + struct { uint64_t x, gcspr, y, z; } *q = p; + q->gcspr = (uint64_t) alloc_makecontext_gcs (ucp->uc_stack.ss_size); + } va_start (ap, argc); for (i = 0; i < argc; ++i) |