From: Jeff Dike 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 in start_up.c. shouldn't be used anywhere any more since UML uses the klibc setjmp/longjmp. Signed-off-by: Jeff Dike Signed-off-by: Andrew Morton --- arch/um/include/registers.h | 3 ++- arch/um/os-Linux/start_up.c | 1 - arch/um/os-Linux/sys-i386/registers.c | 15 +++++++++------ arch/um/os-Linux/sys-x86_64/registers.c | 15 +++++++++------ include/asm-um/processor-generic.h | 4 +--- 5 files changed, 21 insertions(+), 17 deletions(-) diff -puN arch/um/include/registers.h~uml-stack-usage-reduction arch/um/include/registers.h --- a/arch/um/include/registers.h~uml-stack-usage-reduction +++ a/arch/um/include/registers.h @@ -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, unio 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 diff -puN arch/um/os-Linux/start_up.c~uml-stack-usage-reduction arch/um/os-Linux/start_up.c --- a/arch/um/os-Linux/start_up.c~uml-stack-usage-reduction +++ a/arch/um/os-Linux/start_up.c @@ -14,7 +14,6 @@ #include #include #include -#include #include #include #include diff -puN arch/um/os-Linux/sys-i386/registers.c~uml-stack-usage-reduction arch/um/os-Linux/sys-i386/registers.c --- a/arch/um/os-Linux/sys-i386/registers.c~uml-stack-usage-reduction +++ a/arch/um/os-Linux/sys-i386/registers.c @@ -130,11 +130,14 @@ void get_safe_registers(unsigned long *r 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 -puN arch/um/os-Linux/sys-x86_64/registers.c~uml-stack-usage-reduction arch/um/os-Linux/sys-x86_64/registers.c --- a/arch/um/os-Linux/sys-x86_64/registers.c~uml-stack-usage-reduction +++ a/arch/um/os-Linux/sys-x86_64/registers.c @@ -78,11 +78,14 @@ void get_safe_registers(unsigned long *r 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; + } } diff -puN include/asm-um/processor-generic.h~uml-stack-usage-reduction include/asm-um/processor-generic.h --- a/include/asm-um/processor-generic.h~uml-stack-usage-reduction +++ a/include/asm-um/processor-generic.h @@ -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(®s, tsk->thread.mode.skas.switch_buf); \ - UPT_REG(®s, reg); }) + get_thread_reg(reg, tsk->thread.mode.skas.switch_buf) #else #define KSTK_REG(tsk, reg) (0xbadbabe) #endif _