[PATCH 1/3] s390/kernel: add system calls for access PCI memory

Alexey Ishchuk
2014-10-10T09:34:15Z

Add the new __NR_s390_pci_mmio_write and __NR_s390_pci_mmio_read
system calls to allow user space applications to access device PCI I/O
memory pages on s390x platform.

Signed-off-by: Alexey Ishchuk <alexey_ishchuk-JgLE2wv1ufrQT0dZR+AlfA@public.gmane.org>
---
arch/s390/include/uapi/asm/unistd.h | 4 +-
arch/s390/kernel/Makefile | 1 +
arch/s390/kernel/entry.h | 4 +
arch/s390/kernel/pci_mmio.c | 207 ++++++++++++++++++++++++++++++++++++
arch/s390/kernel/syscalls.S | 2 +
5 files changed, 217 insertions(+), 1 deletion(-)
create mode 100644 arch/s390/kernel/pci_mmio.c

diff --git a/arch/s390/include/uapi/asm/unistd.h b/arch/s390/include/uapi/asm/unistd.h
index 3802d2d..ab49d1d 100644
--- a/arch/s390/include/uapi/asm/unistd.h
+++ b/arch/s390/include/uapi/asm/unistd.h
@@ -283,7 +283,9 @@
#define __NR_sched_setattr 345
#define __NR_sched_getattr 346
#define __NR_renameat2 347
-#define NR_syscalls 348
+#define __NR_s390_pci_mmio_write 348
+#define __NR_s390_pci_mmio_read 349
+#define NR_syscalls 350

/*
* There are some system calls that are not present on 64 bit, some
diff --git a/arch/s390/kernel/Makefile b/arch/s390/kernel/Makefile
index 33225e8..3e71b7e 100644
--- a/arch/s390/kernel/Makefile
+++ b/arch/s390/kernel/Makefile
@@ -60,6 +60,7 @@ ifdef CONFIG_64BIT
obj-$(CONFIG_PERF_EVENTS) += perf_event.o perf_cpum_cf.o perf_cpum_sf.o \
perf_cpum_cf_events.o
obj-y += runtime_instr.o cache.o
+obj-y += pci_mmio.o
endif

# vdso
diff --git a/arch/s390/kernel/entry.h b/arch/s390/kernel/entry.h
index 6ac7819..a36b6f9 100644
--- a/arch/s390/kernel/entry.h
+++ b/arch/s390/kernel/entry.h
@@ -70,4 +70,8 @@ struct old_sigaction;
long sys_s390_personality(unsigned int personality);
long sys_s390_runtime_instr(int command, int signum);

+long sys_s390_pci_mmio_write(const unsigned long mmio_addr,
+ const void *user_buffer, const size_t length);
+long sys_s390_pci_mmio_read(const unsigned long mmio_addr,
+ void *user_buffer, const size_t length);
#endif /* _ENTRY_H */
diff --git a/arch/s390/kernel/pci_mmio.c b/arch/s390/kernel/pci_mmio.c
new file mode 100644
index 0000000..f318207
--- /dev/null
+++ b/arch/s390/kernel/pci_mmio.c
@@ -0,0 +1,207 @@
+/*
+ * Access to PCI I/O memory from user space programs.
+ *
+ * Copyright IBM Corp. 2014
+ * Author(s): Alexey Ishchuk <aishchuk-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>
+ */
+#include <linux/kernel.h>
+#include <linux/syscalls.h>
+#include <linux/init.h>
+#include <linux/mm.h>
+#include <linux/errno.h>
+#include <linux/pci.h>
+
+union value_buffer {
+ u8 buf8;
+ u16 buf16;
+ u32 buf32;
+ u64 buf64;
+ u8 buf_large[64];
+};
+
+static long get_pfn(const unsigned long user_addr,
+ const unsigned long access,
+ unsigned long *pfn)
+{
+ struct vm_area_struct *vma = NULL;
+ long ret = 0L;
+
+ if (!pfn)
+ return -EINVAL;
+
+ down_read(&current->mm->mmap_sem);
+ vma = find_vma(current->mm, user_addr);
+ if (vma) {
+ if (!(vma->vm_flags & access))
+ ret = -EACCES;
+ else
+ ret = follow_pfn(vma, user_addr, pfn);
+ } else {
+ ret = -EINVAL;
+ }
+ up_read(&current->mm->mmap_sem);
+
+ return ret;
+}
+
+static inline int verify_page_addr(const unsigned long page_addr)
+{
+ return !(page_addr < ZPCI_IOMAP_ADDR_BASE ||
+ page_addr > (ZPCI_IOMAP_ADDR_BASE | ZPCI_IOMAP_ADDR_IDX_MASK));
+}
+
+static long choose_buffer(const size_t length,
+ union value_buffer *value,
+ void **buf)
+{
+ long ret = 0L;
+
+ if (length > sizeof(value->buf_large)) {
+ *buf = kmalloc(length, GFP_KERNEL);
+ if (!*buf)
+ return -ENOMEM;
+ ret = 1;
+ } else {
+ *buf = value->buf_large;
+ }
+ return ret;
+}
+
+SYSCALL_DEFINE3(s390_pci_mmio_write,
+ const unsigned long, mmio_addr,
+ const void __user *, user_buffer,
+ const size_t, length)
+{
+ long ret = 0L;
+ void *buf = NULL;
+ long buf_allocated = 0;
+ void __iomem *io_addr = NULL;
+ unsigned long pfn = 0UL;
+ unsigned long offset = 0UL;
+ unsigned long page_addr = 0UL;
+ union value_buffer value;
+
+ if (!length)
+ return -EINVAL;
+ if (!zpci_is_enabled())
+ return -ENODEV;
+
+ ret = get_pfn(mmio_addr, VM_WRITE, &pfn);
+ if (ret)
+ return ret;
+
+ page_addr = pfn << PAGE_SHIFT;
+ if (!verify_page_addr(page_addr))
+ return -EFAULT;
+
+ offset = mmio_addr & ~PAGE_MASK;
+ if (offset + length > PAGE_SIZE)
+ return -EINVAL;
+ io_addr = (void *)(page_addr | offset);
+
+ buf_allocated = choose_buffer(length, &value, &buf);
+ if (buf_allocated < 0L)
+ return -ENOMEM;
+
+ switch (length) {
+ case 1:
+ ret = get_user(value.buf8, ((u8 *)user_buffer));
+ break;
+ case 2:
+ ret = get_user(value.buf16, ((u16 *)user_buffer));
+ break;
+ case 4:
+ ret = get_user(value.buf32, ((u32 *)user_buffer));
+ break;
+ case 8:
+ ret = get_user(value.buf64, ((u64 *)user_buffer));
+ break;
+ default:
+ ret = copy_from_user(buf, user_buffer, length);
+ }
+ if (ret)
+ goto out;
+
+ switch (length) {
+ case 1:
+ __raw_writeb(value.buf8, io_addr);
+ break;
+ case 2:
+ __raw_writew(value.buf16, io_addr);
+ break;
+ case 4:
+ __raw_writel(value.buf32, io_addr);
+ break;
+ case 8:
+ __raw_writeq(value.buf64, io_addr);
+ break;
+ default:
+ memcpy_toio(io_addr, buf, length);
+ }
+out:
+ if (buf_allocated > 0L)
+ kfree(buf);
+ return ret;
+}
+
+SYSCALL_DEFINE3(s390_pci_mmio_read,
+ const unsigned long, mmio_addr,
+ void __user *, user_buffer,
+ const size_t, length)
+{
+ long ret = 0L;
+ void *buf = NULL;
+ long buf_allocated = 0L;
+ void __iomem *io_addr = NULL;
+ unsigned long pfn = 0UL;
+ unsigned long offset = 0UL;
+ unsigned long page_addr = 0UL;
+ union value_buffer value;
+
+ if (!length)
+ return -EINVAL;
+ if (!zpci_is_enabled())
+ return -ENODEV;
+
+ ret = get_pfn(mmio_addr, VM_READ, &pfn);
+ if (ret)
+ return ret;
+
+ page_addr = pfn << PAGE_SHIFT;
+ if (!verify_page_addr(page_addr))
+ return -EFAULT;
+
+ offset = mmio_addr & ~PAGE_MASK;
+ if (offset + length > PAGE_SIZE)
+ return -EINVAL;
+ io_addr = (void *)(page_addr | offset);
+
+ buf_allocated = choose_buffer(length, &value, &buf);
+ if (buf_allocated < 0L)
+ return -ENOMEM;
+
+ switch (length) {
+ case 1:
+ value.buf8 = __raw_readb(io_addr);
+ ret = put_user(value.buf8, ((u8 *)user_buffer));
+ break;
+ case 2:
+ value.buf16 = __raw_readw(io_addr);
+ ret = put_user(value.buf16, ((u16 *)user_buffer));
+ break;
+ case 4:
+ value.buf32 = __raw_readl(io_addr);
+ ret = put_user(value.buf32, ((u32 *)user_buffer));
+ break;
+ case 8:
+ value.buf64 = __raw_readq(io_addr);
+ ret = put_user(value.buf64, ((u64 *)user_buffer));
+ break;
+ default:
+ memcpy_fromio(buf, io_addr, length);
+ ret = copy_to_user(user_buffer, buf, length);
+ }
+ if (buf_allocated > 0L)
+ kfree(buf);
+ return ret;
+}
diff --git a/arch/s390/kernel/syscalls.S b/arch/s390/kernel/syscalls.S
index fe5cdf2..1faa942 100644
--- a/arch/s390/kernel/syscalls.S
+++ b/arch/s390/kernel/syscalls.S
@@ -356,3 +356,5 @@ SYSCALL(sys_finit_module,sys_finit_module,compat_sys_finit_module)
SYSCALL(sys_sched_setattr,sys_sched_setattr,compat_sys_sched_setattr) /* 345 */
SYSCALL(sys_sched_getattr,sys_sched_getattr,compat_sys_sched_getattr)
SYSCALL(sys_renameat2,sys_renameat2,compat_sys_renameat2)
+SYSCALL(sys_ni_syscall,sys_s390_pci_mmio_write,sys_ni_syscall)
+SYSCALL(sys_ni_syscall,sys_s390_pci_mmio_read,sys_ni_syscall)
--
1.8.5.5