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perf annotate-data: Handle global variable access with const register

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When a register holds a constant value (TSR_KIND_CONST) and is used with
a negative offset, treat it as a potential global variable access
instead of falling through to CFA (frame) handling.

This fixes cases like array indexing with computed offsets:

    movzbl -0x7d72725a(%rax), %eax   # array[%rax]

Where %rax contains a computed index and the negative offset points to a
global array. Previously this fell through to the CFA path which doesn't
handle global variables, resulting in "no type information".

The fix redirects such accesses to check_kernel which calls
get_global_var_type() to resolve the type from the global variable
cache. This is only done for kernel DSOs since the pattern relies on
kernel-specific global variable resolution. We could also treat
registers with integer types to the global variable path, but this
requires more changes.

Signed-off-by: Zecheng Li <zli94@ncsu.edu>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
This commit is contained in:
Zecheng Li 2026-03-09 13:55:20 -04:00 committed by Namhyung Kim
parent 752e662ae0
commit 1b8db0c963
1 changed files with 5 additions and 0 deletions
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5
tools/perf/util/annotate-data.c
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@ -1229,6 +1229,11 @@ static enum type_match_result check_matching_type(struct type_state *state,
return PERF_TMR_BAIL_OUT;
}
if (state->regs[reg].kind == TSR_KIND_CONST &&
dso__kernel(map__dso(dloc->ms->map))) {
if (dloc->op->offset < 0 && reg != state->stack_reg && reg != dloc->fbreg)
goto check_kernel;
}
check_non_register:
if (reg == dloc->fbreg || reg == state->stack_reg) {
struct type_state_stack *stack;