ee9f8fce99
Add the new ORC unwinder which is enabled by CONFIG_ORC_UNWINDER=y. It plugs into the existing x86 unwinder framework. It relies on objtool to generate the needed .orc_unwind and .orc_unwind_ip sections. For more details on why ORC is used instead of DWARF, see Documentation/x86/orc-unwinder.txt - but the short version is that it's a simplified, fundamentally more robust debugninfo data structure, which also allows up to two orders of magnitude faster lookups than the DWARF unwinder - which matters to profiling workloads like perf. Thanks to Andy Lutomirski for the performance improvement ideas: splitting the ORC unwind table into two parallel arrays and creating a fast lookup table to search a subset of the unwind table. Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Jiri Slaby <jslaby@suse.cz> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mike Galbraith <efault@gmx.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: live-patching@vger.kernel.org Link: http://lkml.kernel.org/r/0a6cbfb40f8da99b7a45a1a8302dc6aef16ec812.1500938583.git.jpoimboe@redhat.com [ Extended the changelog. ] Signed-off-by: Ingo Molnar <mingo@kernel.org>
73 lines
1.8 KiB
C
73 lines
1.8 KiB
C
#include <linux/sched.h>
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#include <linux/ftrace.h>
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#include <asm/ptrace.h>
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#include <asm/bitops.h>
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#include <asm/stacktrace.h>
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#include <asm/unwind.h>
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unsigned long unwind_get_return_address(struct unwind_state *state)
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{
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unsigned long addr;
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if (unwind_done(state))
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return 0;
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addr = READ_ONCE_NOCHECK(*state->sp);
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return ftrace_graph_ret_addr(state->task, &state->graph_idx,
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addr, state->sp);
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}
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EXPORT_SYMBOL_GPL(unwind_get_return_address);
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unsigned long *unwind_get_return_address_ptr(struct unwind_state *state)
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{
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return NULL;
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}
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bool unwind_next_frame(struct unwind_state *state)
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{
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struct stack_info *info = &state->stack_info;
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if (unwind_done(state))
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return false;
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do {
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for (state->sp++; state->sp < info->end; state->sp++) {
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unsigned long addr = READ_ONCE_NOCHECK(*state->sp);
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if (__kernel_text_address(addr))
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return true;
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}
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state->sp = PTR_ALIGN(info->next_sp, sizeof(long));
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} while (!get_stack_info(state->sp, state->task, info,
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&state->stack_mask));
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return false;
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}
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EXPORT_SYMBOL_GPL(unwind_next_frame);
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void __unwind_start(struct unwind_state *state, struct task_struct *task,
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struct pt_regs *regs, unsigned long *first_frame)
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{
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memset(state, 0, sizeof(*state));
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state->task = task;
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state->sp = PTR_ALIGN(first_frame, sizeof(long));
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get_stack_info(first_frame, state->task, &state->stack_info,
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&state->stack_mask);
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/*
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* The caller can provide the address of the first frame directly
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* (first_frame) or indirectly (regs->sp) to indicate which stack frame
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* to start unwinding at. Skip ahead until we reach it.
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*/
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if (!unwind_done(state) &&
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(!on_stack(&state->stack_info, first_frame, sizeof(long)) ||
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!__kernel_text_address(*first_frame)))
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unwind_next_frame(state);
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}
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EXPORT_SYMBOL_GPL(__unwind_start);
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