[PATCH] uml: stack usage reduction

The KSTK_* macros used an inordinate amount of stack.  In order to overcome
an impedance mismatch between their interface, which just returns a single
register value, and the interface of get_thread_regs, which took a full
pt_regs, the implementation created an on-stack pt_regs, filled it in, and
returned one field.  do_task_stat calls KSTK_* twice, resulting in two
local pt_regs, blowing out the stack.

This patch changes the interface (and name) of get_thread_regs to just
return a single register from a jmp_buf.

The include of archsetjmp.h" in registers.h to get the definition of
jmp_buf exposed a bogus include of <setjmp.h> in start_up.c.  <setjmp.h>
shouldn't be used anywhere any more since UML uses the klibc
setjmp/longjmp.

Signed-off-by: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 9 insertions, 6 deletions

diff --git a/arch/um/os-Linux/sys-x86_64/registers.c b/arch/um/os-Linux/sys-x86_64/registers.c
index e730447d6c02..cb8e8a263280 100644
--- a/arch/um/os-Linux/sys-x86_64/registers.c
+++ b/arch/um/os-Linux/sys-x86_64/registers.c
@@ -78,11 +78,14 @@ void get_safe_registers(unsigned long *regs, unsigned long *fp_regs)
                        HOST_FP_SIZE * sizeof(unsigned long));
 }
 
-void get_thread_regs(union uml_pt_regs *uml_regs, void *buffer)
+unsigned long get_thread_reg(int reg, jmp_buf *buf)
 {
-        struct __jmp_buf *jmpbuf = buffer;
-
-        UPT_SET(uml_regs, RIP, jmpbuf->__rip);
-        UPT_SET(uml_regs, RSP, jmpbuf->__rsp);
-        UPT_SET(uml_regs, RBP, jmpbuf->__rbp);
+        switch(reg){
+        case RIP: return buf[0]->__rip;
+        case RSP: return buf[0]->__rsp;
+        case RBP: return buf[0]->__rbp;
+        default:
+                printk("get_thread_regs - unknown register %d\n", reg);
+                return 0;
+        }
 }