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target/riscv: warn about truncating register values 

When reading a register via Program Buffer the actual value is read from
a GPR. The GPR size (XLEN) can be greater than the length of the target
register (e.g. `dcsr` is always 32-bit wide). Due to some HW issue GPR
read may return a value that needs to be truncated to fit into the
target register. Warn the user about it.

Moreover, the value in cache was and is truncated, but the `riscv_reg_t`
that is filled by `riscv_reg_get()` didn't use to be. This may lead to
an assertion failure in `abstract_data_write_fill_batch()`:
Link: fa7e2351c8/src/target/riscv/riscv-013.c (L757)

Change-Id: I4d8a5ba2451fc5a60f51b9143b6b140dfe3b73b8
Signed-off-by: Evgeniy Naydanov <evgeniy.naydanov@syntacore.com>
This commit is contained in:
Evgeniy Naydanov 2025-02-26 15:53:06 +03:00
parent fa7e2351c8
commit 96b7d46c45
1 changed files with 24 additions and 7 deletions
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31
src/target/riscv/riscv-013.c
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@ -1370,14 +1370,31 @@ static int register_read_progbuf(struct target *target, uint64_t *value,
{
assert(target->state == TARGET_HALTED);
if (number >= GDB_REGNO_FPR0 && number <= GDB_REGNO_FPR31)
return fpr_read_progbuf(target, value, number);
else if (number >= GDB_REGNO_CSR0 && number <= GDB_REGNO_CSR4095)
return csr_read_progbuf(target, value, number);
int res;
if (number >= GDB_REGNO_FPR0 && number <= GDB_REGNO_FPR31) {
res = fpr_read_progbuf(target, value, number);
} else if (number >= GDB_REGNO_CSR0 && number <= GDB_REGNO_CSR4095) {
res = csr_read_progbuf(target, value, number);
} else {
LOG_TARGET_ERROR(target, "Unexpected read of %s via program buffer.",
riscv_reg_gdb_regno_name(target, number));
return ERROR_FAIL;
}
if (res != ERROR_OK)
return res;
LOG_TARGET_ERROR(target, "Unexpected read of %s via program buffer.",
riscv_reg_gdb_regno_name(target, number));
return ERROR_FAIL;
unsigned int size_bits = register_size(target, number);
unsigned int value_bits = sizeof(*value) * CHAR_BIT;
assert(size_bits <= value_bits);
if (size_bits == value_bits || *value >> size_bits == 0)
return ERROR_OK;
LOG_TARGET_WARNING(target, "Value read for register %s of %" PRIx64
" does not fit into the size of the register (%u bits)."
" This is a HW bug. Truncating the value to fit into the register.",
riscv_reg_gdb_regno_name(target, number), *value, size_bits);
*value &= GENMASK_ULL(size_bits - 1U, 0U);
return ERROR_OK;
}
/**