91 lines
3.3 KiB
Diff
91 lines
3.3 KiB
Diff
From 51f21b0d1c91a4ae02ebf0d8c81460ec8b6c1283 Mon Sep 17 00:00:00 2001
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From: Tao Liu <ltao@redhat.com>
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Date: Thu, 15 Jul 2021 17:34:29 +0800
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Subject: [PATCH 22/27] x86_64_irq_eframe_link_init: Fix wrong instruction
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searching range calculation
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In function x86_64_irq_eframe_link_init, instruction "push xxx" is searched in
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addresses range from "common_interrupt" to the next nearby symbol, in order to
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calculate the value of irq_eframe_link. The searching distance is given by
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max_instructions, which is calculated by end ranging address minus start ranging
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address. Then crash asks gdb to disassemble max_instructions quantity of instructions.
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Taking max_instructions as the quantity of disassemble instructions is inappropriate,
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because most x86_64 instructions have a length longer than 1, as a consequence, much
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more than the actual needed instructions get disassembled.
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In gdb-7.6 crash, the extra instructions are skipped by "if (!strstr(buf, sp->name))",
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which breaks if one instruction doesn't belongs to a symbol:
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0xffffffff8005d5b4 <common_interrupt+0>: cld
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0xffffffff8005d5b5 <common_interrupt+1>: sub $0x48,%rsp
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...
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0xffffffff8005d61e <common_interrupt+106>: leaveq
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0xffffffff8005d61f <exit_intr>: mov %gs:0x10,%rcx <--- searching stops here
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...
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In gdb-10.2 crash, "exit_intr" doesn't show, however it really exist. As a result,
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searching for "push xxx" will go to a wrong place.
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0xffffffff8005d5b4 <common_interrupt+0>: cld
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0xffffffff8005d5b5 <common_interrupt+1>: sub $0x48,%rsp
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...
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0xffffffff8005d61e <common_interrupt+106>: leave
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0xffffffff8005d61f <common_interrupt+107>: mov %gs:0x10,%rcx <--- searching continues
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...
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(gdb) p exit_intr
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$1 = {<text variable, no debug info>} 0xffffffff8005d61f <common_interrupt+107>
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(gdb) info symbol exit_intr
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common_interrupt + 107 in section .text
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The previous way to determine start and end searching range is not stable, otherwise we may
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encounter regression that cmd "bt" prints wrong IRQ stack. This patch fix the bug by removing
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max_instructions calculation, and directly ask gdb to disassemble addresses range from
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"common_interrupt" to the next nearby symbol.
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Signed-off-by: Tao Liu <ltao@redhat.com>
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---
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x86_64.c | 9 ++++-----
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1 file changed, 4 insertions(+), 5 deletions(-)
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diff --git a/x86_64.c b/x86_64.c
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index d0565ba26a0c..552d6194930b 100644
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--- a/x86_64.c
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+++ b/x86_64.c
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@@ -6472,7 +6472,6 @@ x86_64_irq_eframe_link_init(void)
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char buf[BUFSIZE];
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char link_register[BUFSIZE];
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char *arglist[MAXARGS];
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- ulong max_instructions;
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if (machdep->machspec->irq_eframe_link == UNINITIALIZED)
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machdep->machspec->irq_eframe_link = 0;
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@@ -6487,12 +6486,10 @@ x86_64_irq_eframe_link_init(void)
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return;
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}
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- max_instructions = spn->value - sp->value;
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-
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open_tmpfile();
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- sprintf(buf, "x/%ldi 0x%lx",
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- max_instructions, sp->value);
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+ sprintf(buf, "disassemble 0x%lx, 0x%lx",
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+ sp->value, spn->value);
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if (!gdb_pass_through(buf, pc->tmpfile, GNU_RETURN_ON_ERROR))
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return;
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@@ -6501,6 +6498,8 @@ x86_64_irq_eframe_link_init(void)
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rewind(pc->tmpfile);
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while (fgets(buf, BUFSIZE, pc->tmpfile)) {
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+ if (STRNEQ(buf, "Dump of assembler code"))
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+ continue;
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if (!strstr(buf, sp->name))
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break;
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if ((c = parse_line(buf, arglist)) < 4)
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--
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2.30.2
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