Messages in this thread | | | Date | Wed, 23 May 2007 08:19:02 -0400 | From | Jeff Dike <> | Subject | Re: Current utrace breaks UML |
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On Tue, May 22, 2007 at 11:46:11PM -0700, Roland McGrath wrote: > Do you have a test case for PTRACE_SYSEMU that does not work right?
UML, obviously. Below is a smaller test. orig_eax is wrong, so you can't read the system call number from the process.
With kernel-2.6.20-1.2948, it prints out a bunch of -1's. On FC5 kernels, you get more reasonable numbers.
Jeff
-- Work email - jdike at linux dot intel dot com
#include <stdlib.h> #include <stdio.h> #include <asm/unistd.h> #include <sys/mman.h> #include <sys/ptrace.h> #include <asm/ptrace.h> #include <sys/wait.h>
#define PTRACE_SYSEMU 31 #define PAGE_SIZE 4096
static inline long stub_syscall0(long syscall) { long ret;
__asm__ volatile ("int $0x80" : "=a" (ret) : "0" (syscall));
return ret; }
static void child(void) { if(ptrace(PTRACE_TRACEME, 0, 0, 0) < 0){ perror("traceme"); exit(1); }
kill(getpid(), SIGUSR1); stub_syscall0(__NR_getpid); }
int main(void) { void *stack; unsigned long sp, regs[FRAME_SIZE]; int pid, n, status;
stack = mmap(NULL, PAGE_SIZE, PROT_READ | PROT_WRITE | PROT_EXEC, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); if(stack == MAP_FAILED){ perror("mmap"); exit(1); }
sp = (unsigned long) stack + PAGE_SIZE - sizeof(void *); pid = fork(); if(pid < 0) perror("fork"); else if(pid == 0){ child(); } else { while(1){ n = waitpid(pid, &status, WUNTRACED); if(n < 0){ perror("waitpid"); exit(1); }
n = ptrace(PTRACE_GETREGS, pid, 0, regs); if(n < 0){ perror("PTRACE_GETREGS"); exit(1); }
printf("Status 0x%x orig_eax 0x%x\n", status, regs[ORIG_EAX]);
if(ptrace(PTRACE_SYSEMU, pid, 0, 0)){ perror("PTRACE_SYSEMU"); exit(1); } } }
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