Re: [PATCH v3 5/5] LoongArch: Add generic ex-handler unwind in prologue unwinder
From: Qing Zhang
Date: Tue Jan 17 2023 - 02:48:06 EST
On 2023/1/17 下午2:25, Huacai Chen wrote:
On Thu, Jan 12, 2023 at 8:41 AM Jinyang He <hejinyang@xxxxxxxxxxx> wrote:
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 unwind to handler_\exception it cannot go on prologue
analysis. It is asynchronous code flow, we should get the next frame
PC from regs->csr_era but not from regs->regs[1]. And we copy the
handler codes to eentry in the early time and copy the handler codes
to NUMA-relative memory named pcpu_handlers if NUMA is enabled. Thus,
unwinder cannot unwind normally. Therefore, try to give some hint in
handler_\exception and fixup it in unwind_next_frame.
Reported-by: Qing Zhang <zhangqing@xxxxxxxxxxx>
Signed-off-by: Jinyang He <hejinyang@xxxxxxxxxxx>
---
arch/loongarch/include/asm/unwind.h | 2 +-
arch/loongarch/kernel/genex.S | 3 +
arch/loongarch/kernel/unwind_prologue.c | 100 +++++++++++++++++++++---
arch/loongarch/mm/tlb.c | 2 +-
4 files changed, 92 insertions(+), 15 deletions(-)
diff --git a/arch/loongarch/include/asm/unwind.h b/arch/loongarch/include/asm/unwind.h
index cb428e1b19af..a38eb152aefb 100644
--- 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;
Hi, Qing,
Do you think is_reset is better than reset here?
int graph_idx;
unsigned long sp, pc, ra;
};
diff --git a/arch/loongarch/kernel/genex.S b/arch/loongarch/kernel/genex.S
index 75e5be807a0d..7e5c293ed89f 100644
--- 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
I think the 668 label should be after RESTORE_ALL_AND_RET, right?
This means that the value of ra after do_\handler is called, the 668
label should come after jirl.
Thanks
-Qing
Huacai
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 e6c3f2ee507c..e52c18c2b604 100644
--- a/arch/loongarch/kernel/unwind_prologue.c
+++ b/arch/loongarch/kernel/unwind_prologue.c
@@ -2,21 +2,100 @@
/*
* 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_handler(unsigned long entry_offset)
{
-#ifdef CONFIG_DYNAMIC_FTRACE
- static unsigned long ftrace = (unsigned long)ftrace_call + 4;
+ int idx, offset;
- if (state->pc == ftrace)
- state->is_ftrace = true;
+ 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_exceptions(unsigned long pc)
+{
+#ifdef CONFIG_NUMA
+ int cpu;
+
+ for_each_possible_cpu(cpu) {
+ if (!pcpu_handlers[cpu])
+ continue;
+ if (scan_handler(pc - pcpu_handlers[cpu]))
+ return true;
+ }
#endif
+ return scan_handler(pc - eentry);
+}
+
+/*
+ * 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_exceptions(state->pc) && !fix_ftrace(state->pc))
+ return false;
+ state->reset = true;
+ return true;
}
/*
@@ -39,14 +118,10 @@ 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];
@@ -111,8 +186,7 @@ static bool unwind_by_prologue(struct unwind_state *state)
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 da3681f131c8..8bad6b0cff59 100644
--- 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)];
--
2.34.3