Teach DDB how to unwind across a kernel stack overflow.
Kernel stack overflows in MIPS call panic() directly from an assembly handler after storing the interrupted context's registers in a trapframe. Rather than inferring the location of ra, sp, and pc from the instruction stream, recognize the pc of a kernel stack overflow and pull the registers from the trapframe. Sponsored by: DARPA / AFRL
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svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=310445
@ -111,6 +111,7 @@ void trapDump(char *msg);
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void MipsFPTrap(u_int, u_int, u_int);
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void MipsKernGenException(void);
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void MipsKernIntr(void);
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void MipsKStackOverflow(void);
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void MipsTLBInvalidException(void);
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void MipsTLBMissException(void);
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void MipsUserGenException(void);
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@ -36,6 +36,7 @@ __FBSDID("$FreeBSD$");
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#include <sys/stack.h>
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#include <sys/sysent.h>
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#include <machine/asm.h>
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#include <machine/db_machdep.h>
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#include <machine/md_var.h>
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#include <machine/mips_opcode.h>
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@ -157,7 +158,6 @@ stacktrace_subr(register_t pc, register_t sp, register_t ra,
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valid_args[2] = 0;
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valid_args[3] = 0;
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next_ra = 0;
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/* Jump here after a nonstandard (interrupt handler) frame */
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stksize = 0;
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subr = 0;
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if (frames++ > 100) {
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@ -213,6 +213,15 @@ stacktrace_subr(register_t pc, register_t sp, register_t ra,
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ra = 0;
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goto done;
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}
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/*
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* For a kernel stack overflow, skip to the output and
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* afterwards pull the previous registers out of the trapframe
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* instead of decoding the function prologue.
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*/
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if (pc == (uintptr_t)MipsKStackOverflow)
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goto done;
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/*
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* Find the beginning of the current subroutine by scanning
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* backwards from the current PC for the end of the previous
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@ -389,7 +398,21 @@ stacktrace_subr(register_t pc, register_t sp, register_t ra,
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(uintmax_t)(u_register_t) sp,
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stksize);
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if (ra) {
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if (pc == (uintptr_t)MipsKStackOverflow) {
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#define TF_REG(base, reg) ((base) + CALLFRAME_SIZ + ((reg) * SZREG))
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#if defined(__mips_n64) || defined(__mips_n32)
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pc = kdbpeekd((int *)TF_REG(sp, PC));
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ra = kdbpeekd((int *)TF_REG(sp, RA));
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sp = kdbpeekd((int *)TF_REG(sp, SP));
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#else
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pc = kdbpeek((int *)TF_REG(sp, PC));
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ra = kdbpeek((int *)TF_REG(sp, RA));
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sp = kdbpeek((int *)TF_REG(sp, SP));
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#endif
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#undef TF_REG
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(*printfn) ("--- Kernel Stack Overflow ---\n");
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goto loop;
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} else if (ra) {
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if (pc == ra && stksize == 0)
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(*printfn) ("stacktrace: loop!\n");
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else {
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@ -1019,6 +1019,8 @@ tlb_insert_random:
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* of this handler. Otherwise the ddb backtrace code will think that
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* the panic() was called from MipsTLBMissException.
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*/
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.globl MipsKStackOverflow
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MipsKStackOverflow:
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nop
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.set pop
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