The patch titled i386: fix regression, endless loop in ptrace singlestep over an int80 has been added to the -mm tree. Its filename is i386-fix-regression-endless-loop-in-ptrace-singlestep.patch *** Remember to use Documentation/SubmitChecklist when testing your code *** See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find out what to do about this ------------------------------------------------------ Subject: i386: fix regression, endless loop in ptrace singlestep over an int80 From: Jason Wessel <jason.wessel@xxxxxxxxxxxxx> The commit 635cf99a80f4ebee59d70eb64bb85ce829e4591f introduced a regression. Executing a ptrace single step after certain int80 accesses will infinitely loop and never advance the PC. The TIF_SINGLESTEP check should be done on the return from the syscall and not before it. The new test case is below: /* Test whether singlestep through an int80 syscall works. */ #define _GNU_SOURCE #include <stdio.h> #include <unistd.h> #include <fcntl.h> #include <sys/ptrace.h> #include <sys/wait.h> #include <sys/mman.h> #include <asm/user.h> #include <string.h> static int child, status; static struct user_regs_struct regs; static void do_child() { char str[80] = "child: int80 test\n"; ptrace(PTRACE_TRACEME, 0, 0, 0); kill(getpid(), SIGUSR1); write(fileno(stdout),str,strlen(str)); asm ("int $0x80" : : "a" (20)); /* getpid */ } static void do_parent() { unsigned long eip, expected = 0; again: waitpid(child, &status, 0); if (WIFEXITED(status) || WIFSIGNALED(status)) return; if (WIFSTOPPED(status)) { ptrace(PTRACE_GETREGS, child, 0, ®s); eip = regs.eip; if (expected) fprintf(stderr, "child stop @ %08lx, expected %08lx %s\n", eip, expected, eip == expected ? "" : " <== ERROR"); if (*(unsigned short *)eip == 0x80cd) { fprintf(stderr, "int 0x80 at %08x\n", (unsigned int)eip); expected = eip + 2; } else expected = 0; ptrace(PTRACE_SINGLESTEP, child, NULL, NULL); } goto again; } int main(int argc, char * const argv[]) { child = fork(); if (child) do_parent(); else do_child(); return 0; } Signed-off-by: Jason Wessel <jason.wessel@xxxxxxxxxxxxx> Cc: Jeremy Fitzhardinge <jeremy@xxxxxxxx> Cc: <stable@xxxxxxxxxx> Cc: Chuck Ebbert <76306.1226@xxxxxxxxxxxxxx> Cc: Andi Kleen <ak@xxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- arch/i386/kernel/entry.S | 8 ++++---- 1 files changed, 4 insertions(+), 4 deletions(-) diff -puN arch/i386/kernel/entry.S~i386-fix-regression-endless-loop-in-ptrace-singlestep arch/i386/kernel/entry.S --- a/arch/i386/kernel/entry.S~i386-fix-regression-endless-loop-in-ptrace-singlestep +++ a/arch/i386/kernel/entry.S @@ -367,10 +367,6 @@ ENTRY(system_call) CFI_ADJUST_CFA_OFFSET 4 SAVE_ALL GET_THREAD_INFO(%ebp) - testl $TF_MASK,PT_EFLAGS(%esp) - jz no_singlestep - orl $_TIF_SINGLESTEP,TI_flags(%ebp) -no_singlestep: # system call tracing in operation / emulation /* Note, _TIF_SECCOMP is bit number 8, and so it needs testw and not testb */ testw $(_TIF_SYSCALL_EMU|_TIF_SYSCALL_TRACE|_TIF_SECCOMP|_TIF_SYSCALL_AUDIT),TI_flags(%ebp) @@ -385,6 +381,10 @@ syscall_exit: # setting need_resched or sigpending # between sampling and the iret TRACE_IRQS_OFF + testl $TF_MASK,PT_EFLAGS(%esp) # If tracing set singlestep flag on exit + jz no_singlestep + orl $_TIF_SINGLESTEP,TI_flags(%ebp) +no_singlestep: movl TI_flags(%ebp), %ecx testw $_TIF_ALLWORK_MASK, %cx # current->work jne syscall_exit_work _ Patches currently in -mm which might be from jason.wessel@xxxxxxxxxxxxx are i386-fix-regression-endless-loop-in-ptrace-singlestep.patch git-kgdb.patch kgdb-warning-fix.patch kgdb-kconfig-fix.patch kgdb-use-new-style-interrupt-flags.patch kgdb-section-fix.patch kgdb_skipexception-warning-fix.patch kgdb-ia64-fixes.patch kgdb-bust-on-ia64.patch - To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html