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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
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d04a4c76f7
The perf tool assumes that kernel symbols are never present at address
zero. In fact it assumes if functions that map symbols to addresses
return zero, that the symbol was not found.
Given that s390's _text symbol historically is located at address zero
this yields at least a couple of false errors and warnings in one of
perf's test cases about not present symbols ("perf test 1").
To fix this simply move the _text symbol to address 0x200, just behind
the initial psw and channel program located at the beginning of the
kernel image. This is now hard coded within the linker script.
I tried a nicer solution which moves the initial psw and channel
program into an own section. However that would move the symbols
within the "real" head.text section to different addresses, since the
".org" statements within head.S are relative to the head.text
section. If there is a new section in front, everything else will be
moved. Alternatively I could have adjusted all ".org" statements. But
this current solution seems to be the easiest one, since nobody really
cares where the _text symbol is actually located.
Reported-by: Zvonko Kosic <zkosic@linux.vnet.ibm.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
126 lines
2.5 KiB
ArmAsm
126 lines
2.5 KiB
ArmAsm
/* ld script to make s390 Linux kernel
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* Written by Martin Schwidefsky (schwidefsky@de.ibm.com)
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*/
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#include <asm/thread_info.h>
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#include <asm/page.h>
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/*
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* Put .bss..swapper_pg_dir as the first thing in .bss. This will
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* make sure it has 16k alignment.
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*/
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#define BSS_FIRST_SECTIONS *(.bss..swapper_pg_dir)
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/* Handle ro_after_init data on our own. */
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#define RO_AFTER_INIT_DATA
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#include <asm-generic/vmlinux.lds.h>
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OUTPUT_FORMAT("elf64-s390", "elf64-s390", "elf64-s390")
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OUTPUT_ARCH(s390:64-bit)
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ENTRY(startup)
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jiffies = jiffies_64;
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PHDRS {
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text PT_LOAD FLAGS(5); /* R_E */
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data PT_LOAD FLAGS(7); /* RWE */
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note PT_NOTE FLAGS(0); /* ___ */
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}
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SECTIONS
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{
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. = 0x00000000;
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.text : {
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/* Text and read-only data */
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HEAD_TEXT
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/*
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* E.g. perf doesn't like symbols starting at address zero,
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* therefore skip the initial PSW and channel program located
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* at address zero and let _text start at 0x200.
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*/
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_text = 0x200;
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TEXT_TEXT
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SCHED_TEXT
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CPUIDLE_TEXT
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LOCK_TEXT
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KPROBES_TEXT
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IRQENTRY_TEXT
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SOFTIRQENTRY_TEXT
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*(.fixup)
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*(.gnu.warning)
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} :text = 0x0700
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. = ALIGN(PAGE_SIZE);
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_etext = .; /* End of text section */
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NOTES :text :note
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.dummy : { *(.dummy) } :data
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RO_DATA_SECTION(PAGE_SIZE)
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#ifdef CONFIG_SHARED_KERNEL
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. = ALIGN(0x100000); /* VM shared segments are 1MB aligned */
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#endif
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. = ALIGN(PAGE_SIZE);
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_eshared = .; /* End of shareable data */
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_sdata = .; /* Start of data section */
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. = ALIGN(PAGE_SIZE);
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__start_ro_after_init = .;
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.data..ro_after_init : {
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*(.data..ro_after_init)
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}
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EXCEPTION_TABLE(16)
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. = ALIGN(PAGE_SIZE);
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__end_ro_after_init = .;
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RW_DATA_SECTION(0x100, PAGE_SIZE, THREAD_SIZE)
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_edata = .; /* End of data section */
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/* will be freed after init */
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. = ALIGN(PAGE_SIZE); /* Init code and data */
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__init_begin = .;
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. = ALIGN(PAGE_SIZE);
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.init.text : AT(ADDR(.init.text) - LOAD_OFFSET) {
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VMLINUX_SYMBOL(_sinittext) = . ;
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INIT_TEXT
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. = ALIGN(PAGE_SIZE);
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VMLINUX_SYMBOL(_einittext) = . ;
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}
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/*
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* .exit.text is discarded at runtime, not link time,
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* to deal with references from __bug_table
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*/
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.exit.text : {
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EXIT_TEXT
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}
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.exit.data : {
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EXIT_DATA
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}
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/* early.c uses stsi, which requires page aligned data. */
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. = ALIGN(PAGE_SIZE);
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INIT_DATA_SECTION(0x100)
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PERCPU_SECTION(0x100)
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. = ALIGN(PAGE_SIZE);
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__init_end = .; /* freed after init ends here */
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BSS_SECTION(PAGE_SIZE, 4 * PAGE_SIZE, PAGE_SIZE)
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_end = . ;
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/* Debugging sections. */
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STABS_DEBUG
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DWARF_DEBUG
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/* Sections to be discarded */
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DISCARDS
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}
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