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commit f3a5305947077a65aea8091b05cdb542cea0d61a
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Author: Dave Anderson <anderson@redhat.com>
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Date: Wed Oct 24 16:25:43 2018 -0400
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Modify the x86_64 "bt" behavior when a legitimate exception RIP value
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cannot be referenced symbolically, such as when the exception occurs
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while running in seccomp BPF filter code. Without the patch, the
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exception frame register dump is preceded by "[exception RIP: unknown
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or invalid address]", and then followed by "bt: WARNING: possibly
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bogus exception frame". With the patch applied, the translation of
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the exception RIP will show "[exception RIP: no symbolic reference]",
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and there will be no warning message.
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(anderson@redhat.com)
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diff --git a/x86_64.c b/x86_64.c
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index 345122c..d145f96 100644
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--- a/x86_64.c
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+++ b/x86_64.c
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@@ -3259,6 +3259,18 @@ x86_64_in_alternate_stack(int cpu, ulong
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return FALSE;
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}
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+static char *
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+x86_64_exception_RIP_message(struct bt_info *bt, ulong rip)
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+{
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+ physaddr_t phys;
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+
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+ if (IS_VMALLOC_ADDR(rip) &&
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+ machdep->kvtop(bt->tc, rip, &phys, 0))
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+ return ("no symbolic reference");
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+
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+ return ("unknown or invalid address");
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+}
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+
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#define STACK_TRANSITION_ERRMSG_E_I_P \
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"cannot transition from exception stack to IRQ stack to current process stack:\n exception stack pointer: %lx\n IRQ stack pointer: %lx\n process stack pointer: %lx\n current stack base: %lx\n"
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#define STACK_TRANSITION_ERRMSG_E_P \
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@@ -3370,7 +3382,7 @@ x86_64_low_budget_back_trace_cmd(struct
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fprintf(ofp, (*gdb_output_radix == 16) ?
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"+0x%lx" : "+%ld", offset);
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} else
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- fprintf(ofp, "unknown or invalid address");
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+ fprintf(ofp, "%s", x86_64_exception_RIP_message(bt, bt->instptr));
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fprintf(ofp, "]\n");
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if (KVMDUMP_DUMPFILE())
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kvmdump_display_regs(bt->tc->processor, ofp);
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@@ -4458,9 +4470,9 @@ x86_64_exception_frame(ulong flags, ulon
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(*gdb_output_radix == 16) ?
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"+0x%lx" : "+%ld",
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offset);
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- } else
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- fprintf(ofp,
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- "unknown or invalid address");
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+ } else
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+ fprintf(ofp, "%s",
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+ x86_64_exception_RIP_message(bt, rip));
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fprintf(ofp, "]\n");
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}
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} else if (!(cs & 3)) {
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@@ -4472,7 +4484,7 @@ x86_64_exception_frame(ulong flags, ulon
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"+0x%lx" : "+%ld", offset);
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bt->eframe_ip = rip;
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} else
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- fprintf(ofp, "unknown or invalid address");
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+ fprintf(ofp, "%s", x86_64_exception_RIP_message(bt, rip));
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fprintf(ofp, "]\n");
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}
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fprintf(ofp, " RIP: %016lx RSP: %016lx RFLAGS: %08lx\n",
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@@ -4616,6 +4628,7 @@ x86_64_eframe_verify(struct bt_info *bt,
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int estack;
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struct syment *sp;
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ulong offset, exception;
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+ physaddr_t phys;
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if ((rflags & RAZ_MASK) || !(rflags & 0x2))
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return FALSE;
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@@ -4682,6 +4695,12 @@ x86_64_eframe_verify(struct bt_info *bt,
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return TRUE;
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}
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+ if ((cs == 0x10) && kvaddr) {
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+ if (IS_KVADDR(rsp) && IS_VMALLOC_ADDR(rip) &&
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+ machdep->kvtop(bt->tc, rip, &phys, 0))
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+ return TRUE;
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+ }
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+
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if ((cs == 0x33) && (ss == 0x2b)) {
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if (IS_UVADDR(rip, bt->tc) && IS_UVADDR(rsp, bt->tc))
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return TRUE;
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