[Patch mach-o/bfd] improve build command routine robustness.
Iain Sandoe
developer@sandoe-acoustics.co.uk
Wed Jan 11 10:31:00 GMT 2012
Hi Tristan,
On 10 Jan 2012, at 12:52, Tristan Gingold wrote:
>>
>> + cmd->len = 6 * 4;
>
> Please, use:
> sizeof (struct mach_o_symtab_command_external) + sizeof (struct
> mach_o_load_command_external)
> or the ..._SIZE constants.
OK (done). Note that these are not my introductions - and I was erring
on the "don't make unrelated changes" side.
mach-o.c has quite a bit of this (and inconsistent use of the external/
raw stuff) - just a symptom of the growing phase of the
implementation, I expect.
If the general policy is "fix as we go along" then I'm happy to do
that - or perhaps you have a local version already amended?
>>
>> }
>
> Good idea to harden this!
well, we would soon break with real-world examples as I found writing
tests :)
amended version below, (ChangeLog same).
OK?
Iain
bfd/mach-o.c | 126 ++++++++++++++++++++++++++++++++++
+-----------------------
1 files changed, 76 insertions(+), 50 deletions(-)
diff --git a/bfd/mach-o.c b/bfd/mach-o.c
index 1234899..307a8eb 100644
--- a/bfd/mach-o.c
+++ b/bfd/mach-o.c
@@ -2153,11 +2153,11 @@ bfd_boolean
bfd_mach_o_build_commands (bfd *abfd)
{
bfd_mach_o_data_struct *mdata = bfd_mach_o_get_data (abfd);
- unsigned int wide = mach_o_wide_p (&mdata->header);
- bfd_mach_o_segment_command *seg = NULL;
- bfd_mach_o_load_command *cmd;
- bfd_mach_o_load_command *symtab_cmd;
- unsigned symcind;
+ unsigned wide = mach_o_wide_p (&mdata->header);
+ int segcmd_idx = -1;
+ int symtab_idx = -1;
+ int dysymtab_idx = -1;
+ unsigned long base_offset = 0;
/* Return now if commands are already present. */
if (mdata->header.ncmds)
@@ -2187,31 +2187,48 @@ bfd_mach_o_build_commands (bfd *abfd)
if (!bfd_mach_o_mangle_symbols (abfd))
return FALSE;
- /* It's valid to have a file with only absolute symbols... */
+ /* Very simple command set (only really applicable to MH_OBJECTs):
+ All the commands are optional - present only when there is
suitable data.
+ (i.e. it is valid to have an empty file)
+
+ a command (segment) to contain all the sections,
+ command for the symbol table,
+ a command for the dysymtab.
+
+ ??? maybe we should assert that this is an MH_OBJECT? */
+
if (mdata->nsects > 0)
{
+ segcmd_idx = 0;
mdata->header.ncmds = 1;
- symcind = 1;
}
- else
- symcind = 0;
- /* It's OK to have a file with only section statements. */
if (bfd_get_symcount (abfd) > 0)
- mdata->header.ncmds += 1;
+ {
+ mdata->header.ncmds++;
+ symtab_idx = segcmd_idx + 1; /* 0 if the seg command is
absent. */
+ }
- /* Very simple version (only really applicable to MH_OBJECTs):
- a command (segment) to contain all the sections,
- a command for the symbol table
- a n (optional) command for the dysymtab.
+ /* FIXME:
+ This is a rather crude test for whether we should build a
dysymtab. */
+ if (bfd_mach_o_should_emit_dysymtab ()
+ && bfd_get_symcount (abfd))
+ {
+ mdata->header.ncmds++;
+ /* If there should be a case where a dysymtab could be emitted
without
+ a symtab (seems improbable), this would need amending. */
+ dysymtab_idx = symtab_idx + 1;
+ }
- ??? maybe we should assert that this is an MH_OBJECT? */
+ if (wide)
+ base_offset = BFD_MACH_O_HEADER_64_SIZE;
+ else
+ base_offset = BFD_MACH_O_HEADER_SIZE;
- if (bfd_mach_o_should_emit_dysymtab ()
- && bfd_get_symcount (abfd) > 0)
- mdata->header.ncmds += 1;
+ /* Well, we must have a header, at least. */
+ mdata->filelen = base_offset;
- /* A bit weird, but looks like no content;
+ /* A bit unusual, but no content is valid;
as -n empty.s -o empty.o */
if (mdata->header.ncmds == 0)
return TRUE;
@@ -2221,10 +2238,10 @@ bfd_mach_o_build_commands (bfd *abfd)
if (mdata->commands == NULL)
return FALSE;
- if (mdata->nsects > 0)
+ if (segcmd_idx >= 0)
{
- cmd = &mdata->commands[0];
- seg = &cmd->command.segment;
+ bfd_mach_o_load_command *cmd = &mdata->commands[segcmd_idx];
+ bfd_mach_o_segment_command *seg = &cmd->command.segment;
/* Count the segctions in the special blank segment used for
MH_OBJECT. */
seg->nsects = bfd_mach_o_count_sections_for_seg (NULL, mdata);
@@ -2232,52 +2249,61 @@ bfd_mach_o_build_commands (bfd *abfd)
return FALSE;
/* Init segment command. */
+ cmd->offset = base_offset;
if (wide)
{
cmd->type = BFD_MACH_O_LC_SEGMENT_64;
- cmd->offset = BFD_MACH_O_HEADER_64_SIZE;
cmd->len = BFD_MACH_O_LC_SEGMENT_64_SIZE
+ BFD_MACH_O_SECTION_64_SIZE * seg->nsects;
}
else
{
cmd->type = BFD_MACH_O_LC_SEGMENT;
- cmd->offset = BFD_MACH_O_HEADER_SIZE;
cmd->len = BFD_MACH_O_LC_SEGMENT_SIZE
+ BFD_MACH_O_SECTION_SIZE * seg->nsects;
}
+
cmd->type_required = FALSE;
mdata->header.sizeofcmds = cmd->len;
- mdata->filelen = cmd->offset + cmd->len;
+ mdata->filelen += cmd->len;
}
- if (bfd_get_symcount (abfd) > 0)
+ if (symtab_idx >= 0)
{
/* Init symtab command. */
- symtab_cmd = &mdata->commands[symcind];
-
- symtab_cmd->type = BFD_MACH_O_LC_SYMTAB;
- if (symcind > 0)
- symtab_cmd->offset = mdata->commands[0].offset
- + mdata->commands[0].len;
- else
- symtab_cmd->offset = 0;
- symtab_cmd->len = 6 * 4;
- symtab_cmd->type_required = FALSE;
+ bfd_mach_o_load_command *cmd = &mdata->commands[symtab_idx];
- mdata->header.sizeofcmds += symtab_cmd->len;
- mdata->filelen += symtab_cmd->len;
+ cmd->type = BFD_MACH_O_LC_SYMTAB;
+ cmd->offset = base_offset;
+ if (segcmd_idx >= 0)
+ cmd->offset += mdata->commands[segcmd_idx].len;
+
+ cmd->len = sizeof (struct mach_o_symtab_command_external)
+ + BFD_MACH_O_LC_SIZE;
+ cmd->type_required = FALSE;
+ mdata->header.sizeofcmds += cmd->len;
+ mdata->filelen += cmd->len;
}
- /* If required, setup symtab command. */
- if (bfd_mach_o_should_emit_dysymtab ()
- && bfd_get_symcount (abfd) > 0)
+ /* If required, setup symtab command, see comment above about the
quality
+ of the test. */
+ if (dysymtab_idx >= 0)
{
- cmd = &mdata->commands[symcind+1];
+ bfd_mach_o_load_command *cmd = &mdata->commands[dysymtab_idx];
+
cmd->type = BFD_MACH_O_LC_DYSYMTAB;
- cmd->offset = symtab_cmd->offset + symtab_cmd->len;
+ if (symtab_idx >= 0)
+ cmd->offset = mdata->commands[symtab_idx].offset
+ + mdata->commands[symtab_idx].len;
+ else if (segcmd_idx >= 0)
+ cmd->offset = mdata->commands[segcmd_idx].offset
+ + mdata->commands[segcmd_idx].len;
+ else
+ cmd->offset = base_offset;
+
cmd->type_required = FALSE;
- cmd->len = 18 * 4 + BFD_MACH_O_LC_SIZE;
+ cmd->len = sizeof (struct mach_o_dysymtab_command_external)
+ + BFD_MACH_O_LC_SIZE;
mdata->header.sizeofcmds += cmd->len;
mdata->filelen += cmd->len;
@@ -2285,15 +2311,15 @@ bfd_mach_o_build_commands (bfd *abfd)
/* So, now we have sized the commands and the filelen set to that.
Now we can build the segment command and set the section file
offsets. */
- if (mdata->nsects > 0
- && ! bfd_mach_o_build_seg_command (NULL, mdata, seg))
+ if (segcmd_idx >= 0
+ && ! bfd_mach_o_build_seg_command
+ (NULL, mdata, &mdata->commands[segcmd_idx].command.segment))
return FALSE;
/* If we're doing a dysymtab, cmd points to its load command. */
- if (bfd_mach_o_should_emit_dysymtab ()
- && bfd_get_symcount (abfd) > 0
+ if (dysymtab_idx >= 0
&& ! bfd_mach_o_build_dysymtab_command (abfd, mdata,
- &mdata->commands[symcind+1]))
+ &mdata->commands[dysymtab_idx]))
return FALSE;
/* The symtab command is filled in when the symtab is written. */
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