From 77f5e65ecfb669ea1d2fd74b74fbbf0d0c20daf8 Mon Sep 17 00:00:00 2001 From: Andrew Burgess Date: Tue, 17 Jan 2017 19:12:54 +0000 Subject: [PATCH] ld: better handling of lma region for orphan sections When picking an lma_region for an orphan section we currently create a new lang_output_section_statement_type and then populate this with the orphan section. The problem is that the lang_output_section_statement_type has a prev pointer that links back to the previous output section. For non-orphan output sections, that are created in linker script order, the prev pointer will point to the output section that appears previous in linker script order, as you'd probably expect. The problem is that orphan sections are placed after processing the linker script, and so, in the case of an output section created for an orphan input section, the prev pointer actually points to the last output section created. This causes some unexpected behaviour when the orphan section is not placed after the last non-orphan section that was created. For example, consider this linker script: MEMORY { TEXT : ORIGIN = 0x200, LENGTH = 0x10 RODATA : ORIGIN = 0x400, LENGTH = 0x10 } SECTIONS { .text : {*(.text) } AT>TEXT .data : AT(0x300) { *(.data) } .rodata : { *(.rodata) } AT>RODATA } If we are processing an orphan section '.data.1' and decide to place this after '.data', then the output section created will have a prev pointer that references the '.rodata' output section. The result of this is that '.data.1' will actually be assigned to the RODATA lma region, which is probably not the expected behaviour. The reason why '.data.1' is placed into the lma region of the '.rodata' section is that lma region propagation is done at the time we create the output section, based on the previous output section pointer, which is really just a last-output-section-created pointer at that point in time, though the prev point is fixed up later to reflect the true order of the output sections. The solution I propose in this commit is to move the propagation of lma regions into a separate pass of the linker, rather than performing this as part of the enter/exit of output sections during linker script parsing. During this later phase we have all of the output sections to hand, and the prev/next points have been fixed up by this point to reflect the actual placement ordering. There's a new test to cover this issue that passes on a range of targets, however, some targets generate additional sections, or have stricter memory region size requirements that make it harder to come up with a generic pass pattern, that still tests the required features. For now I've set the test to ignore these targets. ld/ChangeLog: * ldlang.c (lang_leave_output_section_statement): Move lma_region logic to... (lang_propagate_lma_regions): ...this new function. (lang_process): Call new function. * testsuite/ld-elf/orphan-9.d: New file. * testsuite/ld-elf/orphan-9.ld: New file. * testsuite/ld-elf/orphan-9.s: New file. * NEWS: Mention change in behaviour. --- ld/ChangeLog | 11 +++++++++++ ld/NEWS | 3 +++ ld/ldlang.c | 34 +++++++++++++++++++++++---------- ld/testsuite/ld-elf/orphan-9.d | 12 ++++++++++++ ld/testsuite/ld-elf/orphan-9.ld | 28 +++++++++++++++++++++++++++ ld/testsuite/ld-elf/orphan-9.s | 11 +++++++++++ 6 files changed, 89 insertions(+), 10 deletions(-) create mode 100644 ld/testsuite/ld-elf/orphan-9.d create mode 100644 ld/testsuite/ld-elf/orphan-9.ld create mode 100644 ld/testsuite/ld-elf/orphan-9.s diff --git a/ld/ChangeLog b/ld/ChangeLog index 3883bcbd4d..c1c977ac3b 100644 --- a/ld/ChangeLog +++ b/ld/ChangeLog @@ -1,3 +1,14 @@ +2017-03-09 Andrew Burgess + + * ldlang.c (lang_leave_output_section_statement): Move lma_region + logic to... + (lang_propagate_lma_regions): ...this new function. + (lang_process): Call new function. + * testsuite/ld-elf/orphan-9.d: New file. + * testsuite/ld-elf/orphan-9.ld: New file. + * testsuite/ld-elf/orphan-9.s: New file. + * NEWS: Mention change in behaviour. + 2017-03-07 Alan Modra * ldlang.c (open_input_bfds): Check that lang_assignment_statement diff --git a/ld/NEWS b/ld/NEWS index 23ca25a4f1..86e9073617 100644 --- a/ld/NEWS +++ b/ld/NEWS @@ -5,6 +5,9 @@ * When configuring for arc*-*-linux* targets the default linker emulation will change if --with-cpu=nps400 is used at configure time. +* Improve assignment of LMAs to orphan sections in some edge cases where a + mixture of both AT>LMA_REGION and AT(LMA) are used. + Changes in 2.28: * The EXCLUDE_FILE linker script construct can now be applied outside of the diff --git a/ld/ldlang.c b/ld/ldlang.c index ff6ef395b5..89b896f51d 100644 --- a/ld/ldlang.c +++ b/ld/ldlang.c @@ -6844,6 +6844,27 @@ lang_check_relocs (void) } } +/* Look through all output sections looking for places where we can + propagate forward the lma region. */ + +static void +lang_propagate_lma_regions (void) +{ + lang_output_section_statement_type *os; + + for (os = &lang_output_section_statement.head->output_section_statement; + os != NULL; + os = os->next) + { + if (os->prev != NULL + && os->lma_region == NULL + && os->load_base == NULL + && os->addr_tree == NULL + && os->region == os->prev->region) + os->lma_region = os->prev->lma_region; + } +} + void lang_process (void) { @@ -7022,6 +7043,9 @@ lang_process (void) } } + /* Copy forward lma regions for output sections in same lma region. */ + lang_propagate_lma_regions (); + /* Do anything special before sizing sections. This is where ELF and other back-ends size dynamic sections. */ ldemul_before_allocation (); @@ -7302,16 +7326,6 @@ lang_leave_output_section_statement (fill_type *fill, const char *memspec, current_section->load_base != NULL, current_section->addr_tree != NULL); - /* If this section has no load region or base, but uses the same - region as the previous section, then propagate the previous - section's load region. */ - - if (current_section->lma_region == NULL - && current_section->load_base == NULL - && current_section->addr_tree == NULL - && current_section->region == current_section->prev->region) - current_section->lma_region = current_section->prev->lma_region; - current_section->fill = fill; current_section->phdrs = phdrs; pop_stat_ptr (); diff --git a/ld/testsuite/ld-elf/orphan-9.d b/ld/testsuite/ld-elf/orphan-9.d new file mode 100644 index 0000000000..637e8c5d37 --- /dev/null +++ b/ld/testsuite/ld-elf/orphan-9.d @@ -0,0 +1,12 @@ +#source: orphan-9.s +#ld: -N -T orphan-9.ld +#objdump: -h +#notarget: d30v-* dlx-* fr30-* frv-* ft32-* iq2000-* mn10200-* moxie-* ms1-* msp430-* mt-* pj-* + +#... + . \.text 0+(08|10) [0-9a-f]+ 0+200 .* +#... + . \.data 0+(08|10) [0-9a-f]+ 0+300 .* +#... + . \.data\.1 0+8 [0-9a-f]+ 0+3(0|1)[0-9a-f] .* +#pass diff --git a/ld/testsuite/ld-elf/orphan-9.ld b/ld/testsuite/ld-elf/orphan-9.ld new file mode 100644 index 0000000000..1a6773de18 --- /dev/null +++ b/ld/testsuite/ld-elf/orphan-9.ld @@ -0,0 +1,28 @@ +/* This linker script is used for orphan-9 test. + + We have a single byte in .data, and an orphan .data.1 + section. We are checking that the .data.1 orphan is assigned an + LMA after .data rather than picking up the lma region of .rodata. */ + +MEMORY +{ + MEM : ORIGIN = 0x1000, LENGTH = 0x100 + TEXT : ORIGIN = 0x200, LENGTH = 0x50 + DATA : ORIGIN = 0x300, LENGTH = 0x50 + RODATA : ORIGIN = 0x400, LENGTH = 0x50 +} + +SECTIONS +{ + .text : { + *(.text) + } >MEM AT>TEXT + + .data : AT(0x300) { + *(.data) + } >MEM + + .rodata : { + *(.rodata) + } >MEM AT>RODATA +} diff --git a/ld/testsuite/ld-elf/orphan-9.s b/ld/testsuite/ld-elf/orphan-9.s new file mode 100644 index 0000000000..27efad8c2d --- /dev/null +++ b/ld/testsuite/ld-elf/orphan-9.s @@ -0,0 +1,11 @@ + .text + .byte 0, 0, 0, 0, 0, 0, 0, 0 + + .data + .byte 0, 0, 0, 0, 0, 0, 0, 0 + + .section ".data.1", "aw" + .byte 0, 0, 0, 0, 0, 0, 0, 0 + + .section ".rodata", "a" + .byte 0, 0, 0, 0, 0, 0, 0, 0 -- 2.34.1