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Support for new CHERI128 trace format from hardware. #3

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Support for new CHERI128 trace format from hardware. #3

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9c75335
Support for new CHERI128 trace format from hardware.
jonwoodruff Mar 31, 2017
8c31650
A small sample binary trace in the updated CHERI128 format to test a …
jonwoodruff Apr 5, 2017
e4826c3
Fix whitespace.
jonwoodruff Apr 5, 2017
90baaf4
A text version of the small trace as interpreted by berictl. Times a…
jonwoodruff Apr 5, 2017
0eca53f
Add detailed comments to CHERI128 assembly routine.
jonwoodruff Apr 6, 2017
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66 changes: 66 additions & 0 deletions streamtrace.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -1695,6 +1695,51 @@ void decode_cap(capability_register &cap, uint64_t val2, uint64_t val3,
cap.length = val5;
cap.offset = val3 - cap.base;
}
/**
* Decode a 128-bit capability register from streamtrace values. `val2` is always
* `val2` from the streamtrace, but `val1` is either `val1` or `pc` depending
* on the trace format. val1/pc is the 1st half of the capability containing the
* pointer and val2 is the 2nd half of the compressed capability containing the
* bounds and permissions.
*/
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The first half of this comment is confusing, as it's talking about where these values come from long before they get to this function.

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Yes. This is brought forward from the older variations of this function. If we want to change the comment, we should change it everywhere.

void decode_cap128(capability_register &cap, uint64_t val2, uint64_t val1)
{
// extract the tag from the reserved bits where it has been stashed for tracing.
cap->valid = extract_bits<47>(val2);
cap->unsealed = extract_bits<40>(val2);
cap->type = 0; // TODO extract type from typed capabilities
cap->permissions = extract_bits<63,49>(val2);
uint64_t exp = extract_bits<46,41>(val2);
uint64_t mask = ((uint64_t) ~0)<<20ULL;
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I think I can figure out what this is doing, but please add a comment explaining it.

mask <<= exp;
uint64_t ptr = val1;
uint64_t botbits = extract_bits<39,20>(val2);//(half2>>20) & 0xFFFFFULL;
uint64_t bot = (ptr&mask)|(botbits<<exp);
uint64_t topbits = (half2) & 0xFFFFFULL;
uint64_t top = (ptr&mask)|(topbits<<exp);
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There's some quite random spacing here...


uint64_t edgbits = (botbits-0x100ULL)&0xFFFFFULL;
uint64_t ptrbits = (ptr>>exp)&0xFFFFFULL;
uint8_t ptrHi = (ptrbits < edgbits);
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Indentation.

uint8_t botHi = (botbits < edgbits);
uint8_t topHi = (topbits < edgbits);

uint64_t bigOne = 1ULL<<(exp+20ULL);
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Indentation.

// Calculate potential upper-bits fixup for the top.
uint64_t topfix = 0;
if (topHi && !ptrHi) topfix = bigOne;
if (!topHi && ptrHi) topfix = -bigOne;
top = top + topfix;
// Calculate potential upper-bits fixup for the bottom.
uint64_t botfix = 0;
if (botHi && !ptrHi) botfix = bigOne;
if (!botHi && ptrHi) botfix = -bigOne;
bot = bot + botfix;
// Fill the full address fields.
cap.offset = ptr - bot;
cap.base = bot;
cap.length = top - bot;
}


/**
Expand Down Expand Up @@ -1728,6 +1773,27 @@ void decode_entry(debug_trace_entry &e, uint8_t version, uint64_t val1, uint64_t
e.memory_address = val1;
break;
}
case 8:
{
decode_cap128(e.reg_value.cap, val2, val1);
break;
}
case 9:
{
e.is_load = true;
e.memory_address = val1;
decode_cap128(e.reg_value.cap, val2, e.pc);
e.pc = 0;
break;
}
case 10:
{
e.is_store = true;
decode_cap128(e.reg_value.cap, val2, e.pc);
e.memory_address = val1;
e.pc = 0;
break;
}
case 11:
{
decode_cap(e.reg_value.cap, val2, val1);
Expand Down