On Thu, Oct 22, 2015 at 7:11 AM, Ilya Verbin <iver...@gmail.com> wrote: > On Wed, Oct 21, 2015 at 10:44:56 -0700, H.J. Lu wrote: >> On Wed, Oct 21, 2015 at 10:42 AM, Ilya Verbin <iver...@gmail.com> wrote: >> > On Wed, Oct 21, 2015 at 10:38:10 -0700, H.J. Lu wrote: >> >> On Wed, Oct 21, 2015 at 10:33 AM, Ilya Verbin <iver...@gmail.com> wrote: >> >> > H.J., >> >> > Maybe linker should print some warning about joining writable + >> >> > nonwritable >> >> > sections? Here is a simple testcase: >> >> > >> >> > $ cat t1.s >> >> > .section ".AAA", "a" >> >> > .long 0x12345678 >> >> > $ cat t2.s >> >> > .section ".AAA", "wa" >> >> > .long 0x12345678 >> >> > $ as t1.s -o t1.o >> >> > $ as t2.s -o t2.o >> >> > $ ld -shared t1.o t2.o >> >> > $ ls -lh a.out >> >> > 2.1M a.out >> >> > >> >> >> >> Does linker make AAA writable? If yes, linker does what it >> >> is told. >> > >> > Yes, it makes it writable, but why it also makes this? >> > >> > [Nr] Name Type Address Offset >> > Size EntSize Flags Link Info Align >> > [ 0] NULL 0000000000000000 00000000 >> > 0000000000000000 0000000000000000 0 0 0 >> > [ 1] .hash HASH 00000000000000b0 000000b0 >> > 0000000000000028 0000000000000004 A 2 0 8 >> > [ 2] .dynsym DYNSYM 00000000000000d8 000000d8 >> > 0000000000000078 0000000000000018 A 3 2 8 >> > [ 3] .dynstr STRTAB 0000000000000150 00000150 >> > 0000000000000019 0000000000000000 A 0 0 1 >> > [ 4] .AAA PROGBITS 0000000000000169 00000169 >> > 0000000000000008 0000000000000000 WA 0 0 1 >> > [ 5] .eh_frame PROGBITS 0000000000000178 00000178 >> > 0000000000000000 0000000000000000 A 0 0 8 >> > [ 6] .dynamic DYNAMIC 0000000000200178 00200178 <-- >> > ??? >> > 00000000000000b0 0000000000000010 WA 3 0 8 >> > [ 7] .shstrtab STRTAB 0000000000000000 00200380 >> > 0000000000000049 0000000000000000 0 0 1 >> > [ 8] .symtab SYMTAB 0000000000000000 00200228 >> > 0000000000000120 0000000000000018 9 9 8 >> > [ 9] .strtab STRTAB 0000000000000000 00200348 >> > 0000000000000038 0000000000000000 0 0 1 >> > >> >> Linker groups input sections by section name and ors section >> flags. > > Could you please help figure out how this number 0x200178 is calculated? > ld -verbose doesn't show anything helpful. It seems that something goes wrong > during section-to-segment mapping, because when both .AAA have "wa" flags, we > got small binary with 2 LOAD segments: > Type Offset VirtAddr PhysAddr > FileSiz MemSiz Flags Align > LOAD 0x0000000000000000 0x0000000000000000 0x0000000000000000 > 0x00000000000001a8 0x00000000000001a8 R 200000 > LOAD 0x00000000000001a8 0x00000000002001a8 0x00000000002001a8 > 0x00000000000000b8 0x00000000000000b8 RW 200000 > > But when one .AAA has "a" flag, and another .AAA has "wa" flag, we got huge > binary with only one big LOAD segment: > Type Offset VirtAddr PhysAddr > FileSiz MemSiz Flags Align > LOAD 0x0000000000000000 0x0000000000000000 0x0000000000000000 > 0x0000000000200228 0x0000000000200228 RW 200000 > > BTW, gold produces small binary in both cases. >
Please open a binutils bug with a testcase. -- H.J.
