Searched hist:"9 bd1190a11c9d2c59d35cb999b8d170ad52aab5f" (Results 1 – 3 of 3) sorted by relevance
| /openbmc/linux/arch/x86/kernel/ |
| H A D | step.c | diff 9bd1190a11c9d2c59d35cb999b8d170ad52aab5f Mon Sep 03 08:24:17 CDT 2012 Oleg Nesterov <oleg@redhat.com> uprobes/x86: Do not (ab)use TIF_SINGLESTEP/user_*_single_step() for single-stepping
user_enable/disable_single_step() was designed for ptrace, it assumes
a single user and does unnecessary and wrong things for uprobes. For
example:
- arch_uprobe_enable_step() can't trust TIF_SINGLESTEP, an
application itself can set X86_EFLAGS_TF which must be
preserved after arch_uprobe_disable_step().
- we do not want to set TIF_SINGLESTEP/TIF_FORCED_TF in
arch_uprobe_enable_step(), this only makes sense for ptrace.
- otoh we leak TIF_SINGLESTEP if arch_uprobe_disable_step()
doesn't do user_disable_single_step(), the application will
be killed after the next syscall.
- arch_uprobe_enable_step() does access_process_vm() we do
not need/want.
Change arch_uprobe_enable/disable_step() to set/clear X86_EFLAGS_TF
directly, this is much simpler and more correct. However, we need to
clear TIF_BLOCKSTEP/DEBUGCTLMSR_BTF before executing the probed insn,
add set_task_blockstep(false).
Note: with or without this patch, there is another (hopefully minor)
problem. A probed "pushf" insn can see the wrong X86_EFLAGS_TF set by
uprobes. Perhaps we should change _disable to update the stack, or
teach arch_uprobe_skip_sstep() to emulate this insn.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
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| H A D | uprobes.c | diff 9bd1190a11c9d2c59d35cb999b8d170ad52aab5f Mon Sep 03 08:24:17 CDT 2012 Oleg Nesterov <oleg@redhat.com> uprobes/x86: Do not (ab)use TIF_SINGLESTEP/user_*_single_step() for single-stepping
user_enable/disable_single_step() was designed for ptrace, it assumes
a single user and does unnecessary and wrong things for uprobes. For
example:
- arch_uprobe_enable_step() can't trust TIF_SINGLESTEP, an
application itself can set X86_EFLAGS_TF which must be
preserved after arch_uprobe_disable_step().
- we do not want to set TIF_SINGLESTEP/TIF_FORCED_TF in
arch_uprobe_enable_step(), this only makes sense for ptrace.
- otoh we leak TIF_SINGLESTEP if arch_uprobe_disable_step()
doesn't do user_disable_single_step(), the application will
be killed after the next syscall.
- arch_uprobe_enable_step() does access_process_vm() we do
not need/want.
Change arch_uprobe_enable/disable_step() to set/clear X86_EFLAGS_TF
directly, this is much simpler and more correct. However, we need to
clear TIF_BLOCKSTEP/DEBUGCTLMSR_BTF before executing the probed insn,
add set_task_blockstep(false).
Note: with or without this patch, there is another (hopefully minor)
problem. A probed "pushf" insn can see the wrong X86_EFLAGS_TF set by
uprobes. Perhaps we should change _disable to update the stack, or
teach arch_uprobe_skip_sstep() to emulate this insn.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
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| /openbmc/linux/arch/x86/include/asm/ |
| H A D | processor.h | diff 9bd1190a11c9d2c59d35cb999b8d170ad52aab5f Mon Sep 03 08:24:17 CDT 2012 Oleg Nesterov <oleg@redhat.com> uprobes/x86: Do not (ab)use TIF_SINGLESTEP/user_*_single_step() for single-stepping
user_enable/disable_single_step() was designed for ptrace, it assumes
a single user and does unnecessary and wrong things for uprobes. For
example:
- arch_uprobe_enable_step() can't trust TIF_SINGLESTEP, an
application itself can set X86_EFLAGS_TF which must be
preserved after arch_uprobe_disable_step().
- we do not want to set TIF_SINGLESTEP/TIF_FORCED_TF in
arch_uprobe_enable_step(), this only makes sense for ptrace.
- otoh we leak TIF_SINGLESTEP if arch_uprobe_disable_step()
doesn't do user_disable_single_step(), the application will
be killed after the next syscall.
- arch_uprobe_enable_step() does access_process_vm() we do
not need/want.
Change arch_uprobe_enable/disable_step() to set/clear X86_EFLAGS_TF
directly, this is much simpler and more correct. However, we need to
clear TIF_BLOCKSTEP/DEBUGCTLMSR_BTF before executing the probed insn,
add set_task_blockstep(false).
Note: with or without this patch, there is another (hopefully minor)
problem. A probed "pushf" insn can see the wrong X86_EFLAGS_TF set by
uprobes. Perhaps we should change _disable to update the stack, or
teach arch_uprobe_skip_sstep() to emulate this insn.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
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