LoongArch: Add generic ex-handler unwind in prologue unwinder

When exception is triggered, code flow go handle_\exception in some
cases. One of stackframe in this case as follows,

high -> +-------+
        | REGS  |  <- a pt_regs
        |       |
        |       |  <- ex trigger
        | REGS  |  <- ex pt_regs   <-+
        |       |                    |
        |       |                    |
low  -> +-------+           ->unwind-+

When unwinder unwinds to handler_\exception it cannot go on prologue
analysis. Because it is an asynchronous code flow, we should get the
next frame PC from regs->csr_era rather than regs->regs[1]. At init time
we copy the handlers to eentry and also copy them to NUMA-affine memory
named pcpu_handlers if NUMA is enabled. Thus, unwinder cannot unwind
normally. To solve this, we try to give some hints in handler_\exception
and fixup unwinders in unwind_next_frame().

Reported-by: Qing Zhang <zhangqing@loongson.cn>
Signed-off-by: Jinyang He <hejinyang@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>

diff --git a/arch/loongarch/include/asm/unwind.h b/arch/loongarch/include/asm/unwind.h
index 36584b95ef8b672d9d278171e967b6a141eb3058..b9dce87afd2e058a3dd786ccbb513a3bbbff637c 100644 (file)
--- a/arch/loongarch/include/asm/unwind.h
+++ b/arch/loongarch/include/asm/unwind.h
@@ -22,7 +22,7 @@ struct unwind_state {
        char type; /* UNWINDER_XXX */
        struct stack_info stack_info;
        struct task_struct *task;
-       bool first, error, is_ftrace;
+       bool first, error, reset;
        int graph_idx;
        unsigned long sp, pc, ra;
 };

diff --git a/arch/loongarch/kernel/genex.S b/arch/loongarch/kernel/genex.S
index 75e5be807a0d5004feb5f1e6eb42f8bcc9efef5f..7e5c293ed89f70c4872d54dfcad422673dc65112 100644 (file)
--- a/arch/loongarch/kernel/genex.S
+++ b/arch/loongarch/kernel/genex.S
@@ -67,14 +67,17 @@ SYM_FUNC_END(except_vec_cex)
        .macro  BUILD_HANDLER exception handler prep
        .align  5
        SYM_FUNC_START(handle_\exception)
+       666:
        BACKUP_T0T1
        SAVE_ALL
        build_prep_\prep
        move    a0, sp
        la.abs  t0, do_\handler
        jirl    ra, t0, 0
+       668:
        RESTORE_ALL_AND_RET
        SYM_FUNC_END(handle_\exception)
+       SYM_DATA(unwind_hint_\exception, .word 668b - 666b)
        .endm
 
        BUILD_HANDLER ade ade badv

diff --git a/arch/loongarch/kernel/unwind_prologue.c b/arch/loongarch/kernel/unwind_prologue.c
index dfc352dba746599f7f7c84685a424f2662314598..9095fde8e55d5c57177c83ab0548ab888c348f16 100644 (file)
--- a/arch/loongarch/kernel/unwind_prologue.c
+++ b/arch/loongarch/kernel/unwind_prologue.c
@@ -2,23 +2,103 @@
 /*
  * Copyright (C) 2022 Loongson Technology Corporation Limited
  */
+#include <linux/cpumask.h>
 #include <linux/ftrace.h>
 #include <linux/kallsyms.h>
 
 #include <asm/inst.h>
+#include <asm/loongson.h>
 #include <asm/ptrace.h>
+#include <asm/setup.h>
 #include <asm/unwind.h>
 
-static inline void unwind_state_fixup(struct unwind_state *state)
+extern const int unwind_hint_ade;
+extern const int unwind_hint_ale;
+extern const int unwind_hint_bp;
+extern const int unwind_hint_fpe;
+extern const int unwind_hint_fpu;
+extern const int unwind_hint_lsx;
+extern const int unwind_hint_lasx;
+extern const int unwind_hint_lbt;
+extern const int unwind_hint_ri;
+extern const int unwind_hint_watch;
+extern unsigned long eentry;
+#ifdef CONFIG_NUMA
+extern unsigned long pcpu_handlers[NR_CPUS];
+#endif
+
+static inline bool scan_handlers(unsigned long entry_offset)
 {
-#ifdef CONFIG_DYNAMIC_FTRACE
-       static unsigned long ftrace = (unsigned long)ftrace_call + 4;
+       int idx, offset;
+
+       if (entry_offset >= EXCCODE_INT_START * VECSIZE)
+               return false;
+
+       idx = entry_offset / VECSIZE;
+       offset = entry_offset % VECSIZE;
+       switch (idx) {
+       case EXCCODE_ADE:
+               return offset == unwind_hint_ade;
+       case EXCCODE_ALE:
+               return offset == unwind_hint_ale;
+       case EXCCODE_BP:
+               return offset == unwind_hint_bp;
+       case EXCCODE_FPE:
+               return offset == unwind_hint_fpe;
+       case EXCCODE_FPDIS:
+               return offset == unwind_hint_fpu;
+       case EXCCODE_LSXDIS:
+               return offset == unwind_hint_lsx;
+       case EXCCODE_LASXDIS:
+               return offset == unwind_hint_lasx;
+       case EXCCODE_BTDIS:
+               return offset == unwind_hint_lbt;
+       case EXCCODE_INE:
+               return offset == unwind_hint_ri;
+       case EXCCODE_WATCH:
+               return offset == unwind_hint_watch;
+       default:
+               return false;
+       }
+}
+
+static inline bool fix_exception(unsigned long pc)
+{
+#ifdef CONFIG_NUMA
+       int cpu;
+
+       for_each_possible_cpu(cpu) {
+               if (!pcpu_handlers[cpu])
+                       continue;
+               if (scan_handlers(pc - pcpu_handlers[cpu]))
+                       return true;
+       }
+#endif
+       return scan_handlers(pc - eentry);
+}
 
-       if (state->pc == ftrace)
-               state->is_ftrace = true;
+/*
+ * As we meet ftrace_regs_entry, reset first flag like first doing
+ * tracing. Prologue analysis will stop soon because PC is at entry.
+ */
+static inline bool fix_ftrace(unsigned long pc)
+{
+#ifdef CONFIG_DYNAMIC_FTRACE
+       return pc == (unsigned long)ftrace_call + LOONGARCH_INSN_SIZE;
+#else
+       return false;
 #endif
 }
 
+static inline bool unwind_state_fixup(struct unwind_state *state)
+{
+       if (!fix_exception(state->pc) && !fix_ftrace(state->pc))
+               return false;
+
+       state->reset = true;
+       return true;
+}
+
 /*
  * LoongArch function prologue is like follows,
  *     [instructions not use stack var]
@@ -39,14 +119,10 @@ static bool unwind_by_prologue(struct unwind_state *state)
        if (state->sp >= info->end || state->sp < info->begin)
                return false;
 
-       if (state->is_ftrace) {
-               /*
-                * As we meet ftrace_regs_entry, reset first flag like first doing
-                * tracing. Prologue analysis will stop soon because PC is at entry.
-                */
+       if (state->reset) {
                regs = (struct pt_regs *)state->sp;
                state->first = true;
-               state->is_ftrace = false;
+               state->reset = false;
                state->pc = regs->csr_era;
                state->ra = regs->regs[1];
                state->sp = regs->regs[3];
@@ -112,8 +188,7 @@ first:
 
 out:
        state->first = false;
-       unwind_state_fixup(state);
-       return !!__kernel_text_address(state->pc);
+       return unwind_state_fixup(state) || __kernel_text_address(state->pc);
 }
 
 static bool next_frame(struct unwind_state *state)

diff --git a/arch/loongarch/mm/tlb.c b/arch/loongarch/mm/tlb.c
index da3681f131c8d8a722b7f479775f7a48be47fc0a..8bad6b0cff59b96b2ebdda34214fdc1e4758e27e 100644 (file)
--- a/arch/loongarch/mm/tlb.c
+++ b/arch/loongarch/mm/tlb.c
@@ -251,7 +251,7 @@ static void output_pgtable_bits_defines(void)
 }
 
 #ifdef CONFIG_NUMA
-static unsigned long pcpu_handlers[NR_CPUS];
+unsigned long pcpu_handlers[NR_CPUS];
 #endif
 extern long exception_handlers[VECSIZE * 128 / sizeof(long)];