If the parent process has the trap bit set (i.e. a debugger had single
stepped the process to the system call), we need to clear the trap flag from the new frame unless the debugger had set PF_FORK on the parent. Otherwise, the child will receive a (likely unexpected) SIGTRAP when it executes the first instruction after returning to userland. Reviewed by: bde MFC after: 3 days
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parent
6f831b072a
commit
5ad5504c14
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=138592
@ -62,6 +62,7 @@ __FBSDID("$FreeBSD$");
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#include <sys/malloc.h>
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#include <sys/mbuf.h>
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#include <sys/mutex.h>
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#include <sys/pioctl.h>
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#include <sys/proc.h>
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#include <sys/sf_buf.h>
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#include <sys/smp.h>
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@ -194,6 +195,17 @@ cpu_fork(td1, p2, td2, flags)
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td2->td_frame->tf_eflags &= ~PSL_C; /* success */
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td2->td_frame->tf_edx = 1;
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/*
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* If the parent process has the trap bit set (i.e. a debugger had
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* single stepped the process to the system call), we need to clear
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* the trap flag from the new frame unless the debugger had set PF_FORK
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* on the parent. Otherwise, the child will receive a (likely
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* unexpected) SIGTRAP when it executes the first instruction after
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* returning to userland.
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*/
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if ((p1->p_pfsflags & PF_FORK) == 0)
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td2->td_frame->tf_eflags &= ~PSL_T;
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/*
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* Set registers for trampoline to user mode. Leave space for the
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* return address on stack. These are the kernel mode register values.
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