diff options
Diffstat (limited to 'arch/parisc/kernel/syscall.S')
| -rw-r--r-- | arch/parisc/kernel/syscall.S | 34 |
1 files changed, 29 insertions, 5 deletions
diff --git a/arch/parisc/kernel/syscall.S b/arch/parisc/kernel/syscall.S index 5e055240f00..e767ab733e3 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 |