[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>

3 files changed, 18 insertions, 13 deletions

diff --git a/arch/um/os-Linux/start_up.c b/arch/um/os-Linux/start_up.c
index 503148504009..7fe92680c7dd 100644
--- a/arch/um/os-Linux/start_up.c
+++ b/arch/um/os-Linux/start_up.c
@@ -14,7 +14,6 @@
 #include <sched.h>
 #include <fcntl.h>
 #include <errno.h>
-#include <setjmp.h>
 #include <sys/time.h>
 #include <sys/wait.h>
 #include <sys/mman.h>
diff --git a/arch/um/os-Linux/sys-i386/registers.c b/arch/um/os-Linux/sys-i386/registers.c
index 1f90a2d71386..7cd0369e02b3 100644
--- a/arch/um/os-Linux/sys-i386/registers.c
+++ b/arch/um/os-Linux/sys-i386/registers.c
@@ -130,11 +130,14 @@ 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, EIP, jmpbuf->__eip);
-	UPT_SET(uml_regs, UESP, jmpbuf->__esp);
-	UPT_SET(uml_regs, EBP, jmpbuf->__ebp);
+	switch(reg){
+	case EIP: return buf[0]->__eip;
+	case UESP: return buf[0]->__esp;
+	case EBP: return buf[0]->__ebp;
+	default:
+		printk("get_thread_regs - unknown register %d\n", reg);
+		return 0;
+	}
 }
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;
+	}
 }