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Re: [PATCH] Move nested functions in link_map.c to file scope.
- From: Mark Wielaard <mjw at redhat dot com>
- To: elfutils-devel at lists dot fedorahosted dot org
- Date: Sun, 03 Jan 2016 22:25:46 +0100
- Subject: Re: [PATCH] Move nested functions in link_map.c to file scope.
On Tue, 2015-11-17 at 14:45 -0800, Chih-Hung Hsieh wrote:
> * In libdwfl/link_map.c, nested functions check64, check32,
For check64 and check32 the define plus static function extra args call
trick seems a good fit. I did push this part of the patch.
> release_buffer, read_addrs, and consider_phdr are moved
> to file scope to compile with clang.
But for the rest I feel it makes the code unnecessary messy. So I didn't
apply those. See below for some suggestions how to maybe get something
that doesn't create new functions with lots and lots of arguments (which
I find doesn't improve readability).
> +static inline int
> +do_release_buffer (int result, Dwfl *dwfl,
> + void **pbuffer, size_t *pbuffer_available,
> + void *memory_callback_arg,
> + Dwfl_Memory_Callback *memory_callback)
> +{
> + if (*pbuffer != NULL)
> + (void) (*memory_callback) (dwfl, -1, pbuffer, pbuffer_available, 0, 0,
> + memory_callback_arg);
> + return result;
> +}
> +
> +#define release_buffer(result) \
> + do_release_buffer (result, dwfl, &buffer, &buffer_available, \
> + memory_callback_arg, memory_callback)
This is just 3 lines, and it is either used as "return release_buffer
(result)" to cleanup and return a result or as release_buffer (0) just
to cleanup the buffer (if not NULL). It seems better to make the define
just the function body. Assuming your compiler does know about statement
expressions https://gcc.gnu.org/onlinedocs/gcc/Statement-Exprs.html
Otherwise maybe just split it in two. Don't use an argument, just use it
as "cleanup_buffer()" plus a separate return line.
> +static inline bool
> +do_read_addrs (GElf_Addr vaddr, size_t n, GElf_Addr *addrs,
> + uint_fast8_t elfdata, GElf_Addr *pread_vaddr,
> + int elfclass, Dwfl *dwfl,
> + void **pbuffer, size_t *pbuffer_available,
> + void *memory_callback_arg,
> + Dwfl_Memory_Callback *memory_callback)
> +{
> + size_t nb = n * addrsize (elfclass); /* Address words -> bytes to read. */
> +
> + /* Read a new buffer if the old one doesn't cover these words. */
> + if (*pbuffer == NULL
> + || vaddr < *pread_vaddr
> + || vaddr - *pread_vaddr + nb > *pbuffer_available)
> + {
> + do_release_buffer (0, dwfl, pbuffer, pbuffer_available,
> + memory_callback_arg, memory_callback);
> +
> + *pread_vaddr = vaddr;
> + int segndx = INTUSE(dwfl_addrsegment) (dwfl, vaddr, NULL);
> + if (unlikely (segndx < 0)
> + || unlikely (! (*memory_callback) (dwfl, segndx,
> + pbuffer, pbuffer_available,
> + vaddr, nb, memory_callback_arg)))
> + return true;
> + }
> +
> + Elf32_Addr (*a32)[n] = vaddr - *pread_vaddr + *pbuffer;
> + Elf64_Addr (*a64)[n] = (void *) a32;
> +
> + if (elfclass == ELFCLASS32)
> + {
> + if (elfdata == ELFDATA2MSB)
> + for (size_t i = 0; i < n; ++i)
> + addrs[i] = BE32 (read_4ubyte_unaligned_noncvt (&(*a32)[i]));
> + else
> + for (size_t i = 0; i < n; ++i)
> + addrs[i] = LE32 (read_4ubyte_unaligned_noncvt (&(*a32)[i]));
> + }
> + else
> + {
> + if (elfdata == ELFDATA2MSB)
> + for (size_t i = 0; i < n; ++i)
> + addrs[i] = BE64 (read_8ubyte_unaligned_noncvt (&(*a64)[i]));
> + else
> + for (size_t i = 0; i < n; ++i)
> + addrs[i] = LE64 (read_8ubyte_unaligned_noncvt (&(*a64)[i]));
> + }
> +
> + return false;
> +}
> +
> +#define read_addrs(vaddr, n) \
> + do_read_addrs (vaddr, n, addrs, elfdata, &read_vaddr, elfclass, dwfl, \
> + &buffer, &buffer_available, \
> + memory_callback_arg, memory_callback)
This very generic, but only used twice. Once to read 1 address and once
to read 4 addresses. Can't we make this a little simpler? Maybe just let
it handle reading one address. It might be a bit more hairy than needs
to because of the extra arguments needed to pass to the buffer cleanup.
> +static inline bool
> +do_consider_phdr (GElf_Word type, GElf_Addr vaddr, GElf_Xword filesz,
> + Dwfl *dwfl, GElf_Addr phdr, GElf_Addr *pdyn_bias,
> + GElf_Addr *pdyn_vaddr, GElf_Xword *pdyn_filesz)
> +{
> + switch (type)
> + {
> + case PT_PHDR:
> + if (*pdyn_bias == (GElf_Addr) - 1
> + /* Do a sanity check on the putative address. */
> + && ((vaddr & (dwfl->segment_align - 1))
> + == (phdr & (dwfl->segment_align - 1))))
> + {
> + *pdyn_bias = phdr - vaddr;
> + return *pdyn_vaddr != 0;
> + }
> + break;
> +
> + case PT_DYNAMIC:
> + *pdyn_vaddr = vaddr;
> + *pdyn_filesz = filesz;
> + return *pdyn_bias != (GElf_Addr) - 1;
> + }
> +
> + return false;
> +}
> +
> +#define consider_phdr(type, vaddr, filesz) \
> + do_consider_phdr (type, vaddr, filesz, \
> + dwfl, phdr, &dyn_bias, &dyn_vaddr, &dyn_filesz)
This is just used twice in the function. Might be simpler to just inline
it twice and simplifying the switch by an if type == PT_... check
instead of inventing a new function with 8 arguments.
Thanks,
Mark