aboutsummaryrefslogtreecommitdiff
path: root/arch/parisc/kernel/syscall.S
diff options
context:
space:
mode:
Diffstat (limited to 'arch/parisc/kernel/syscall.S')
-rw-r--r--arch/parisc/kernel/syscall.S34
1 files changed, 29 insertions, 5 deletions
diff --git a/arch/parisc/kernel/syscall.S b/arch/parisc/kernel/syscall.S
index 5e055240f00b..e767ab733e32 100644
--- a/arch/parisc/kernel/syscall.S
+++ b/arch/parisc/kernel/syscall.S
@@ -1,12 +1,35 @@
/*
* Linux/PA-RISC Project (http://www.parisc-linux.org/)
*
- * System call entry code Copyright (c) Matthew Wilcox 1999 <willy@bofh.ai>
+ * System call entry code / Linux gateway page
+ * Copyright (c) Matthew Wilcox 1999 <willy@bofh.ai>
* Licensed under the GNU GPL.
* thanks to Philipp Rumpf, Mike Shaver and various others
* sorry about the wall, puffin..
*/
+/*
+How does the Linux gateway page on PA-RISC work?
+------------------------------------------------
+The Linux gateway page on PA-RISC is "special".
+It actually has PAGE_GATEWAY bits set (this is linux terminology; in parisc
+terminology it's Execute, promote to PL0) in the page map. So anything
+executing on this page executes with kernel level privilege (there's more to it
+than that: to have this happen, you also have to use a branch with a ,gate
+completer to activate the privilege promotion). The upshot is that everything
+that runs on the gateway page runs at kernel privilege but with the current
+user process address space (although you have access to kernel space via %sr2).
+For the 0x100 syscall entry, we redo the space registers to point to the kernel
+address space (preserving the user address space in %sr3), move to wide mode if
+required, save the user registers and branch into the kernel syscall entry
+point. For all the other functions, we execute at kernel privilege but don't
+flip address spaces. The basic upshot of this is that these code snippets are
+executed atomically (because the kernel can't be pre-empted) and they may
+perform architecturally forbidden (to PL3) operations (like setting control
+registers).
+*/
+
+
#include <asm/asm-offsets.h>
#include <asm/unistd.h>
#include <asm/errno.h>
@@ -15,6 +38,7 @@
#include <asm/thread_info.h>
#include <asm/assembly.h>
#include <asm/processor.h>
+#include <asm/cache.h>
#include <linux/linkage.h>
@@ -643,7 +667,7 @@ ENTRY(end_linux_gateway_page)
.section .rodata,"a"
- .align PAGE_SIZE
+ .align 8
/* Light-weight-syscall table */
/* Start of lws table. */
ENTRY(lws_table)
@@ -652,13 +676,13 @@ ENTRY(lws_table)
END(lws_table)
/* End of lws table */
- .align PAGE_SIZE
+ .align 8
ENTRY(sys_call_table)
#include "syscall_table.S"
END(sys_call_table)
#ifdef CONFIG_64BIT
- .align PAGE_SIZE
+ .align 8
ENTRY(sys_call_table64)
#define SYSCALL_TABLE_64BIT
#include "syscall_table.S"
@@ -674,7 +698,7 @@ END(sys_call_table64)
with ldcw.
*/
.section .data
- .align PAGE_SIZE
+ .align L1_CACHE_BYTES
ENTRY(lws_lock_start)
/* lws locks */
.rept 16