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Commit 75e29b18 authored by Jeff Dike's avatar Jeff Dike Committed by Linus Torvalds
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[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: default avatarJeff Dike <jdike@addtoit.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent bf61f50d

arch/um/include/registers.h

+2 −1
Original line number Diff line number Diff line
@@ -7,6 +7,7 @@ 
#define __REGISTERS_H



#include "sysdep/ptrace.h"

#include "sysdep/archsetjmp.h"



extern void init_thread_registers(union uml_pt_regs *to);

extern int save_fp_registers(int pid, unsigned long *fp_regs);
@@ -15,6 +16,6 @@ extern void save_registers(int pid, union uml_pt_regs *regs); 
extern void restore_registers(int pid, union uml_pt_regs *regs);

extern void init_registers(int pid);

extern void get_safe_registers(unsigned long * regs, unsigned long * fp_regs);

extern void get_thread_regs(union uml_pt_regs *uml_regs, void *buffer);

extern unsigned long get_thread_reg(int reg, jmp_buf *buf);



#endif

arch/um/os-Linux/start_up.c

+0 −1
Original line number Diff line number Diff line
@@ -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>

arch/um/os-Linux/sys-i386/registers.c

+9 −6
Original line number Diff line number Diff line
@@ -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;

	}

}

arch/um/os-Linux/sys-x86_64/registers.c

+9 −6
Original line number Diff line number Diff line
@@ -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;

	}

}

include/asm-um/processor-generic.h

+1 −3
Original line number Diff line number Diff line
@@ -138,9 +138,7 @@ extern struct cpuinfo_um cpu_data[]; 


#ifdef CONFIG_MODE_SKAS

#define KSTK_REG(tsk, reg) \

	({ union uml_pt_regs regs; \

	   get_thread_regs(&regs, tsk->thread.mode.skas.switch_buf); \

	   UPT_REG(&regs, reg); })

	get_thread_reg(reg, tsk->thread.mode.skas.switch_buf)

#else

#define KSTK_REG(tsk, reg) (0xbadbabe)

#endif