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The kernel CONFIG_UNWINDER_ORC option enables the ORC unwinder, which is
similar in concept to a DWARF unwinder. The difference is that the format
of the ORC data is much simpler than DWARF, which in turn allows the ORC
unwinder to be much simpler and faster.
The ORC data consists of unwind tables which are generated by objtool.
After analyzing all the code paths of a .o file, it determines information
about the stack state at each instruction address in the file and outputs
that information to the .orc_unwind and .orc_unwind_ip sections.
The per-object ORC sections are combined at link time and are sorted and
post-processed at boot time. The unwinder uses the resulting data to
correlate instruction addresses with their stack states at run time.
Most of the logic are similar with x86, in order to get ra info before ra
is saved into stack, add ra_reg and ra_offset into orc_entry. At the same
time, modify some arch-specific code to silence the objtool warnings.
Co-developed-by: Jinyang He <hejinyang@loongson.cn>
Signed-off-by: Jinyang He <hejinyang@loongson.cn>
Co-developed-by: Youling Tang <tangyouling@loongson.cn>
Signed-off-by: Youling Tang <tangyouling@loongson.cn>
Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
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There is no EXPORT_SYMBOL() line there, hence #include <asm/export.h>
is unneeded.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
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The previous patch ("function_graph: Support recording and printing
the return value of function") has laid the groundwork for the for
the funcgraph-retval, and this modification makes it available on
the LoongArch platform.
We introduce a new structure called fgraph_ret_regs for the LoongArch
platform to hold return registers and the frame pointer. We then fill
its content in the return_to_handler and pass its address to the
function ftrace_return_to_handler to record the return value.
Link: https://lkml.kernel.org/r/c5462255e435fab363895c2d7433bc0f5a140411.1680954589.git.pengdonglin@sangfor.com.cn
Reviewed-by: Huacai Chen <chenhuacai@loongson.cn>
Signed-off-by: Donglin Peng <pengdonglin@sangfor.com.cn>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
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Select the HAVE_DYNAMIC_FTRACE_WITH_DIRECT_CALLS to provide the
register_ftrace_direct[_multi] interfaces allowing users to register
the customed trampoline (direct_caller) as the mcount for one or more
target functions. And modify_ftrace_direct[_multi] are also provided
for modifying direct_caller.
There are a few cases to distinguish:
- If a direct call ops is the only one tracing a function AND the direct
called trampoline is within the reach of a 'bl' instruction
-> the ftrace patchsite jumps to the trampoline
- Else
-> the ftrace patchsite jumps to the ftrace_regs_caller trampoline points
to ftrace_list_ops so it iterates over all registered ftrace ops,
including the direct call ops and calls its call_direct_funcs handler
which stores the direct called trampoline's address in the ftrace_regs
and the ftrace_regs_caller trampoline will return to that address
instead of returning to the traced function
Signed-off-by: Qing Zhang <zhangqing@loongson.cn>
Signed-off-by: Youling Tang <tangyouling@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
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This patch implements CONFIG_DYNAMIC_FTRACE_WITH_REGS on LoongArch,
which allows a traced function's arguments (and some other registers)
to be captured into a struct pt_regs, allowing these to be inspected
and modified.
Co-developed-by: Jinyang He <hejinyang@loongson.cn>
Signed-off-by: Jinyang He <hejinyang@loongson.cn>
Signed-off-by: Qing Zhang <zhangqing@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
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Once the function_graph tracer is enabled, a filtered function has the
following call sequence:
1) ftracer_caller ==> on/off by ftrace_make_call/ftrace_make_nop
2) ftrace_graph_caller
3) ftrace_graph_call ==> on/off by ftrace_en/disable_ftrace_graph_caller
4) prepare_ftrace_return
Considering the following DYNAMIC_FTRACE_WITH_REGS feature, it would be
more extendable to have a ftrace_graph_caller function, instead of
calling prepare_ftrace_return directly in ftrace_caller.
Co-developed-by: Jinyang He <hejinyang@loongson.cn>
Signed-off-by: Jinyang He <hejinyang@loongson.cn>
Signed-off-by: Qing Zhang <zhangqing@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
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The compiler has inserted 2 NOPs before the regular function prologue.
T series registers are available and safe because of LoongArch's psABI.
At runtime, we can replace nop with bl to enable ftrace call and replace
bl with nop to disable ftrace call. The bl instruction requires us to
save the original RA value, so it saves RA at t0 here.
Details are:
| Compiled | Disabled | Enabled |
+------------+------------------------+------------------------+
| nop | move t0, ra | move t0, ra |
| nop | nop | bl ftrace_caller |
| func_body | func_body | func_body |
The RA value will be recovered by ftrace_regs_entry, and restored into
RA before returning to the regular function prologue. When a function is
not being traced, the "move t0, ra" is not harmful.
1) ftrace_make_call, ftrace_make_nop (in kernel/ftrace.c)
The two functions turn each recorded call site of filtered functions
into a call to ftrace_caller or nops.
2) ftracce_update_ftrace_func (in kernel/ftrace.c)
turns the nops at ftrace_call into a call to a generic entry for
function tracers.
3) ftrace_caller (in kernel/mcount_dyn.S)
The entry where each _mcount call sites calls to once they are
filtered to be traced.
Co-developed-by: Jinyang He <hejinyang@loongson.cn>
Signed-off-by: Jinyang He <hejinyang@loongson.cn>
Signed-off-by: Qing Zhang <zhangqing@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
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