DWARF_GET_FDE_INFO_FOR_REG3(3) | Library Functions Manual | DWARF_GET_FDE_INFO_FOR_REG3(3)

# NAME

`dwarf_get_fde_info_for_reg3` —
retrieve register rule

# LIBRARY

DWARF Access Library (libdwarf, -ldwarf)

# SYNOPSIS

`#include <libdwarf.h>`

int
`dwarf_get_fde_info_for_reg3`(Dwarf_Fde fde, Dwarf_Half table_column, Dwarf_Addr pc, Dwarf_Small *type, Dwarf_Signed *offset_relevant, Dwarf_Signed *register_num, Dwarf_Signed *offset_or_block_len, Dwarf_Ptr *block_ptr, Dwarf_Addr *row_pc, Dwarf_Error *error);

# DESCRIPTION

Function `dwarf_get_fde_info_for_reg3`() retrieves a register rule from the register rule table associated with a given FDE descriptor, given a program counter address and rule column number.

Argument fde should reference a valid DWARF FDE descriptor.

Arugment table_column should hold the column number of the register rule desired.

Argument pc should hold the program counter address to be used to locate the desired register rule row.

On successful execution, `dwarf_get_fde_info_for_reg3`() stores information about the register rule found into the locations pointed to by the arguments type, offset_relevant, register_num, offset_or_block_len, block_ptr and row_pc.

Argument type should point to a location which will hold the type code of the register rule found. The returned value is one of the `DW_EXPR_*` contants defined in the header file `<libdwarf.h>`.

If there is an offset value associated with the register rule, the location pointed to by argument offset_relevant will be set to 1.

Argument register_num should point to a location which will hold the register number associated with the register rule.

If the register rule is of type `DW_EXPR_OFFSET` or `DW_EXPR_VAL_OFFSET`, the location pointed to by argument offset_or_block_len will be set to the offset value associated with the register rule, or to 0 if the register rule does not have an offset value. If the type code is `DW_EXPR_EXPRESSION` or `DW_EXPR_VAL_EXPRESSION`, the location pointed to by argument offset_or_block_len will be set to the length in bytes of the DWARF expression block associated with the register rule.

Argument block_ptr should point to a location which will be set to a pointer to the content of the DWARF expression block associated with the register rule.

Argument row_pc should point to a location which will be set to the lowest program counter address associated with the register rule found.

If argument err is not NULL, it will be used to return an error descriptor in case of an error.

# RETURN VALUES

Function `dwarf_get_fde_info_for_reg3`() returns `DW_DLV_OK` when it succeeds. In case of an error, it returns `DW_DLV_ERROR` and sets the argument err.

# ERRORS

Function `dwarf_get_fde_info_for_reg3`() can fail with:

[`DW_DLE_ARGUMENT`]
  One of the arguments block_ptr, fde, offset_or_block_len, offset_relevant, register_num, row_pc, or type was NULL.
[`DW_DLE_FRAME_TABLE_COL_BAD`]
  The column number provided in argument table_column was too large.
[`DW_DLE_PC_NOT_IN_FDE_RANGE`]
  The program counter value provided in argument pc did not fall in the range covered by argument fde.

# EXAMPLE

To retrieve the register rules at column 3 from a rule table associated with a FDE descriptor:

    Dwarf_Fde fde;
    Dwarf_Off fde_offset, cie_offset;
    Dwarf_Unsigned func_len, fde_length;
    Dwarf_Signed cie_index, offset_relevant, register_num;
    Dwarf_Signed offset_or_block_len;
    Dwarf_Addr low_pc, row_pc;
    Dwarf_Ptr fde_addr, block_ptr;
    Dwarf_Small type;
    Dwarf_Error de;

    /* ... assuming `fde` references a valid FDE descriptor... */
    if (dwarf_get_fde_range(fde, &low_pc, &func_len, &fde_addr,
        &fde_length, &cie_offset, &cie_index, &fde_offset,
        &de) != DW_DLV_OK)
    	errx(EXIT_FAILURE, "dwarf_get_fde_range failed: %s",
    	    dwarf_errmsg(de));

    /* Iterate all the table rows. */
    for (pc = low_pc; pc < low_pc + func_len; pc++) {
    	if (dwarf_get_fde_info_for_reg3(fde, 3, pc, &type,
    	    &offset_relevant, &register_num, &offset_or_block_len,
    	    &block_ptr, &row_pc, &de) != DW_DLV_OK) {
    		warnx("dwarf_get_fde_info_for_reg3 failed: %s",
    		    dwarf_errmsg(de));
    		continue;
    	}
    	/* ... use the retrieved register rule ... */
    }

# SEE ALSO

dwarf(3), dwarf_get_fde_at_pc(3), dwarf_get_fde_info_for_all_regs(3), dwarf_get_fde_info_for_all_regs3(3), dwarf_get_fde_info_for_cfa_reg3(3), dwarf_get_fde_info_for_reg(3), dwarf_get_fde_n(3), dwarf_set_frame_cfa_value(3), dwarf_set_frame_rule_table_size(3), dwarf_set_frame_rule_initial_value(3), dwarf_set_frame_same_value(3), dwarf_set_frame_undefined_value(3)

November 9, 2011 | NetBSD 9.4