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Update comments about output offsets and merged input sections.

This commit is contained in:
Ian Lance Taylor 2007-12-20 16:27:34 +00:00
parent 63c2c2877b
commit 1e9836570f
4 changed files with 49 additions and 22 deletions
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39
gold/merge.cc
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@ -49,7 +49,8 @@ class Object_merge_map
// Add a mapping for MERGE_MAP, for the bytes from OFFSET to OFFSET
// + LENGTH in the input section SHNDX to OUTPUT_OFFSET in the
// output section. An OUTPUT_OFFSET of -1 means that the bytes are
// discarded.
// discarded. OUTPUT_OFFSET is relative to the start of the merged
// data in the output section.
void
add_mapping(const Merge_map*, unsigned int shndx, section_offset_type offset,
section_size_type length, section_offset_type output_offset);
@ -58,7 +59,8 @@ class Object_merge_map
// input address is at offset OFFSET in section SHNDX. This sets
// *OUTPUT_OFFSET to the offset in the output section; this will be
// -1 if the bytes are not being copied to the output. This returns
// true if the mapping is known, false otherwise.
// true if the mapping is known, false otherwise. *OUTPUT_OFFSET is
// relative to the start of the merged data in the output section.
bool
get_output_offset(const Merge_map*, unsigned int shndx,
section_offset_type offset,
@ -86,10 +88,28 @@ class Object_merge_map
{ return i1.input_offset < i2.input_offset; }
};
// A list of entries for a particular section.
// A list of entries for a particular input section.
struct Input_merge_map
{
// The Merge_map for this section.
// We store these with the Relobj, and we look them up by input
// section. It is possible to have two different merge maps
// associated with a single output section. For example, this
// happens routinely with .rodata, when merged string constants
// and merged fixed size constants are both put into .rodata. The
// output offset that we store is not the offset from the start of
// the output section; it is the offset from the start of the
// merged data in the output section. That means that the caller
// is going to add the offset of the merged data within the output
// section, which means that the caller needs to know which set of
// merged data it found the entry in. So it's not enough to find
// this data based on the input section and the output section; we
// also have to find it based on a set of merged data in the
// output section. In order to verify that we are looking at the
// right data, we store a pointer to the Merge_map here, and we
// pass in a pointer when looking at the data. If we are asked to
// look up information for a different Merge_map, we report that
// we don't have it, rather than trying a lookup and returning an
// answer which will receive the wrong offset.
const Merge_map* merge_map;
// The list of mappings.
std::vector<Input_merge_entry> entries;
@ -162,7 +182,7 @@ Object_merge_map::get_or_make_input_merge_map(const Merge_map* merge_map,
if (map != NULL)
{
// For a given input section in a given object, every mapping
// must be donw with the same Merge_map.
// must be done with the same Merge_map.
gold_assert(map->merge_map == merge_map);
return map;
}
@ -277,8 +297,8 @@ Object_merge_map::get_output_offset(const Merge_map* merge_map,
// Class Merge_map.
// Add a mapping for the bytes from OFFSET to OFFSET + LENGTH in input
// section SHNDX in object OBJECT to an OUTPUT_OFFSET in a merged
// output section.
// section SHNDX in object OBJECT to an OUTPUT_OFFSET in merged data
// in an output section.
void
Merge_map::add_mapping(Relobj* object, unsigned int shndx,
@ -297,8 +317,9 @@ Merge_map::add_mapping(Relobj* object, unsigned int shndx,
// Return the output offset for an input address. The input address
// is at offset OFFSET in section SHNDX in OBJECT. This sets
// *OUTPUT_OFFSET to the offset in the output section. This returns
// true if the mapping is known, false otherwise.
// *OUTPUT_OFFSET to the offset in the merged data in the output
// section. This returns true if the mapping is known, false
// otherwise.
bool
Merge_map::get_output_offset(const Relobj* object, unsigned int shndx,

12
gold/merge.h
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@ -44,7 +44,9 @@ class Merge_map
// Add a mapping for the bytes from OFFSET to OFFSET + LENGTH in the
// input section SHNDX in object OBJECT to OUTPUT_OFFSET in the
// output section. An OUTPUT_OFFSET of -1 means that the bytes are
// discarded.
// discarded. OUTPUT_OFFSET is not the offset from the start of the
// output section, it is the offset from the start of the merged
// data within the output section.
void
add_mapping(Relobj* object, unsigned int shndx,
section_offset_type offset, section_size_type length,
@ -54,7 +56,9 @@ class Merge_map
// is at offset OFFSET in section SHNDX in OBJECT. This sets
// *OUTPUT_OFFSET to the offset in the output section; this will be
// -1 if the bytes are not being copied to the output. This returns
// true if the mapping is known, false otherwise.
// true if the mapping is known, false otherwise. This returns the
// value stored by add_mapping, namely the offset from the start of
// the merged data within the output section.
bool
get_output_offset(const Relobj* object, unsigned int shndx,
section_offset_type offset,
@ -84,7 +88,9 @@ class Output_merge_base : public Output_section_data
{ return this->entsize_; }
// Add a mapping from an OFFSET in input section SHNDX in object
// OBJECT to an OUTPUT_OFFSET in the output section.
// OBJECT to an OUTPUT_OFFSET in the output section. OUTPUT_OFFSET
// is the offset from the start of the merged data in the output
// section.
void
add_mapping(Relobj* object, unsigned int shndx, section_offset_type offset,
section_size_type length, section_offset_type output_offset)

14
gold/output.cc
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@ -1347,7 +1347,9 @@ Output_section::Input_section::finalize_data_size()
this->u2_.posd->finalize_data_size();
}
// Try to turn an input offset into an output offset.
// Try to turn an input offset into an output offset. We want to
// return the output offset relative to the start of this
// Input_section in the output section.
inline bool
Output_section::Input_section::output_offset(
@ -1362,11 +1364,7 @@ Output_section::Input_section::output_offset(
{
if (this->shndx_ != shndx || this->u2_.object != object)
return false;
section_offset_type output_offset;
Output_section* os = object->output_section(shndx, &output_offset);
gold_assert(os != NULL);
gold_assert(output_offset != -1);
*poutput = output_offset + offset;
*poutput = offset;
return true;
}
}
@ -1655,8 +1653,8 @@ Output_section::is_input_address_mapped(const Relobj* object,
// Given an address OFFSET relative to the start of input section
// SHNDX in object OBJECT, return the output offset relative to the
// start of the section. This should only be called if SHNDX in
// OBJECT has a special mapping.
// start of the input section in the output section. This should only
// be called if SHNDX in OBJECT has a special mapping.
section_offset_type
Output_section::output_offset(const Relobj* object, unsigned int shndx,

6
gold/output.h
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@ -1895,8 +1895,10 @@ class Output_section : public Output_data
// Given an input OBJECT, an input section index SHNDX within that
// object, and an OFFSET relative to the start of that input
// section, return whether or not the output offset is known. If
// this function returns true, it sets *POUTPUT to the output
// offset.
// this function returns true, it sets *POUTPUT to the offset in
// the output section, relative to the start of the input section
// in the output section. *POUTPUT may be different from OFFSET
// for a merged section.
bool
output_offset(const Relobj* object, unsigned int shndx,
section_offset_type offset,