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Handle B-unit break instructions. The break.b is unique in that the

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immediate is not saved by the architecture. Any of the break.{mifx}
instructions have their immediate saved in cr.iim on interruption.
Consequently, when we handle the break interrupt, we end up with a
break value of 0 when it was a break.b. The immediate is important
because it distinguishes between different uses of the break and
which are defined by the runtime specification.
The bottomline is that when the GNU debugger replaces a B-unit
instruction with a break instruction in the inferior, we would not
send the process a SIGTRAP when we encounter it, because the value
is not one we recognize as a debugger breakpoint.

This change adds logic to decode the bundle in which the break
instruction lives whenever the break value is 0. The assumption
being that it's a break.b and we fetch the immediate directly out
of the instruction. If the break instruction was not a break.b,
but any of break.{mifx} with an immediate of 0, we would be doing
unnecessary work. But since a break 0 is invalid, this is not a
problem and it will still result in a SIGILL being sent to the
process.

Approved by: re (scottl)
This commit is contained in:
Marcel Moolenaar 2005-06-27 23:51:38 +00:00
parent fc37111e5d
commit c31450b00d
1 changed files with 50 additions and 1 deletions
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51
sys/ia64/ia64/trap.c
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@ -72,6 +72,8 @@ __FBSDID("$FreeBSD$");
#include <sys/ktrace.h>
#endif
#include <ia64/disasm/disasm.h>
static int print_usertrap = 0;
SYSCTL_INT(_machdep, OID_AUTO, print_usertrap,
CTLFLAG_RW, &print_usertrap, 0, "");
@ -281,6 +283,39 @@ printtrap(int vector, struct trapframe *tf, int isfatal, int user)
printf("\n");
}
/*
* We got a trap caused by a break instruction and the immediate was 0.
* This indicates that we may have a break.b with some non-zero immediate.
* The break.b doesn't cause the immediate to be put in cr.iim. Hence,
* we need to disassemble the bundle and return the immediate found there.
* This may be a 0 value anyway. Return 0 for any error condition. This
* will result in a SIGILL, which is pretty much the best thing to do.
*/
static uint64_t
trap_decode_break(struct trapframe *tf)
{
struct asm_bundle bundle;
struct asm_inst *inst;
int slot;
if (!asm_decode(tf->tf_special.iip, &bundle))
return (0);
slot = ((tf->tf_special.psr & IA64_PSR_RI) == IA64_PSR_RI_0) ? 0 :
((tf->tf_special.psr & IA64_PSR_RI) == IA64_PSR_RI_1) ? 1 : 2;
inst = bundle.b_inst + slot;
/*
* Sanity checking: It must be a break instruction and the operand
* that has the break value must be an immediate.
*/
if (inst->i_op != ASM_OP_BREAK ||
inst->i_oper[1].o_type != ASM_OPER_IMM)
return (0);
return (inst->i_oper[1].o_value);
}
void
trap_panic(int vector, struct trapframe *tf)
{
@ -414,8 +449,22 @@ trap(int vector, struct trapframe *tf)
case IA64_VEC_BREAK:
if (user) {
/* XXX we don't decode break.b */
ucode = (int)tf->tf_special.ifa & 0x1FFFFF;
if (ucode == 0) {
/*
* A break.b doesn't cause the immediate to be
* stored in cr.iim (and saved in the TF in
* tf_special.ifa). We need to decode the
* instruction to find out what the immediate
* was. Note that if the break instruction
* didn't happen to be a break.b, but any
* other break with an immediate of 0, we
* will do unnecessary work to get the value
* we already had. Not an issue, because a
* break 0 is invalid.
*/
ucode = trap_decode_break(tf);
}
if (ucode < 0x80000) {
/* Software interrupts. */
switch (ucode) {