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Fix off-by-one error in stack delta lookup #185

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Fix off-by-one error in stack delta lookup #185

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1 change: 1 addition & 0 deletions support/ebpf/interpreter_dispatcher.ebpf.c
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Original file line number Diff line number Diff line change
Expand Up @@ -763,6 +763,7 @@ static EBPF_INLINE int unwind_stop(struct pt_regs *ctx)
increment_metric(metricID_NumUnknownPC);
}
// Fallthrough to report the error
[[fallthrough]];
default: increment_metric(state->error_metric);
}

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9 changes: 6 additions & 3 deletions support/ebpf/native_stack_trace.ebpf.c
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Original file line number Diff line number Diff line change
Expand Up @@ -137,16 +137,19 @@ static EBPF_INLINE void *get_stack_delta_map(int mapID)
// Get the stack offset of the given instruction.
static EBPF_INLINE ErrorCode get_stack_delta(UnwindState *state, int *addrDiff, u32 *unwindInfo)
{
u64 text_section_offset = state->text_section_offset;
if (state->return_address)
--text_section_offset;
u64 exe_id = state->text_section_id;

// Look up the stack delta page information for this address.
StackDeltaPageKey key = {};
key.fileID = state->text_section_id;
key.page = state->text_section_offset & ~STACK_DELTA_PAGE_MASK;
key.page = text_section_offset & ~STACK_DELTA_PAGE_MASK;
DEBUG_PRINT(
"Look up stack delta for %lx:%lx",
(unsigned long)state->text_section_id,
(unsigned long)state->text_section_offset);
(unsigned long)text_section_offset);
StackDeltaPageInfo *info = bpf_map_lookup_elem(&stack_delta_page_to_info, &key);
if (!info) {
DEBUG_PRINT(
Expand Down Expand Up @@ -176,7 +179,7 @@ static EBPF_INLINE ErrorCode get_stack_delta(UnwindState *state, int *addrDiff,

// Preinitialize the idx for the index to use for page without any deltas.
u32 idx = info->firstDelta;
u16 page_offset = state->text_section_offset & STACK_DELTA_PAGE_MASK;
u16 page_offset = text_section_offset & STACK_DELTA_PAGE_MASK;
if (info->numDeltas) {
// Page has deltas, so find the correct one to use using binary search.
u32 lo = info->firstDelta;
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Binary file modified support/ebpf/tracer.ebpf.amd64
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Binary file modified support/ebpf/tracer.ebpf.arm64
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30 changes: 30 additions & 0 deletions tools/coredump/testdata/arm64/rust-debug-offbyone.json
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Original file line number Diff line number Diff line change
@@ -0,0 +1,30 @@
{
"coredump-ref": "517028a6d45241ed202e81083d836a47469e68a1345d7be7860f8127b5823d90",
"threads": [
{
"lwp": 3428,
"frames": [
"test_rust+0x12f60",
"test_rust+0x12f83",
"test_rust+0x12fa7",
"test_rust+0x1317f",
"test_rust+0x1303f",
"test_rust+0x1312b",
"test_rust+0x2be73",
"test_rust+0x13103",
"test_rust+0x1301f",
"<unwinding aborted due to error native_no_pid_page_mapping>"
]
}
],
"modules": [
{
"ref": "36d6ee161f7831c61ecad24a80fc26d8a7221db3907639c6f078d59bbadc2549",
"local-path": "/home/brennan/test_rust/target/debug/test_rust"
},
{
"ref": "a5945db37288c7ccf89169b911fa7ac634e7d2434a0b8287e485cf5ea98d5646",
"local-path": "/gnu/store/50jqiigxwa1s9xljqrl1wh85yncqnybr-glibc-2.41/lib/ld-linux-aarch64.so.1"
}
]
}
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