aarch64: vdso symbols #1292

chl337 · 2024-05-26T18:12:51Z

TODO:

~~replace hard-coded vdso-symbol value with query~~
~~refactor~~
~~rebase~~
~~test on x86 machine for sanity~~

shrik3 · 2024-05-26T18:56:11Z

x86 and aarch64 have different function (symbol) names, and not necessarily the same ones, e.g. the x86 build has

Symbol table '.symtab' contains 17 entries:
Num:    Value          Size Type    Bind   Vis      Ndx Name
 0: 0000000000000000     0 NOTYPE  LOCAL  DEFAULT  UND 
 1: 0000000000000000     0 FILE    LOCAL  DEFAULT  ABS vdso.cc
 2: 0000000000000000     0 FILE    LOCAL  DEFAULT  ABS vdso_time.cc
 3: ffffffffff701110   168 FUNC    LOCAL  DEFAULT   11 _ZN4vdso13ClockR[...]
 4: ffffffffff7011c0   168 FUNC    LOCAL  DEFAULT   11 _ZN4vdso14ClockM[...]
 5: ffffffffff7004a8   272 OBJECT  LOCAL  HIDDEN     9 _DYNAMIC
 6: ffffffffff700000     0 NOTYPE  LOCAL  DEFAULT  ABS VDSO_PRELINK
 7: ffffffffff6ff000     0 NOTYPE  LOCAL  DEFAULT  ABS _params
 8: 0000000000000000     0 OBJECT  GLOBAL DEFAULT  ABS LINUX_2.6
 9: ffffffffff701100    10 FUNC    WEAK   DEFAULT   11 getcpu
10: ffffffffff701100    10 FUNC    GLOBAL DEFAULT   11 __vdso_getcpu
11: ffffffffff7010d0    34 FUNC    WEAK   DEFAULT   11 time
12: ffffffffff7010d0    34 FUNC    GLOBAL DEFAULT   11 __vdso_time
13: ffffffffff701060    97 FUNC    WEAK   DEFAULT   11 gettimeofday
14: ffffffffff701060    97 FUNC    GLOBAL DEFAULT   11 __vdso_gettimeofday
15: ffffffffff701020    56 FUNC    WEAK   DEFAULT   11 clock_gettime
16: ffffffffff701020    56 FUNC    GLOBAL DEFAULT   11 __vdso_clock_gettime

since aarch64 mandates vdso for signals to work, consider using panic if the symbols are not found.

qlib/kernel/loader/vdso.rs

chl337 · 2024-05-26T19:01:03Z

x86 and aarch64 have different function (symbol) names, and not necessarily the same ones, e.g. the x86 build has
Symbol table '.symtab' contains 17 entries: Num: Value Size Type Bind Vis Ndx Name 0: 0000000000000000 0 NOTYPE LOCAL DEFAULT UND 1: 0000000000000000 0 FILE LOCAL DEFAULT ABS vdso.cc 2: 0000000000000000 0 FILE LOCAL DEFAULT ABS vdso_time.cc 3: ffffffffff701110 168 FUNC LOCAL DEFAULT 11 _ZN4vdso13ClockR[...] 4: ffffffffff7011c0 168 FUNC LOCAL DEFAULT 11 _ZN4vdso14ClockM[...] 5: ffffffffff7004a8 272 OBJECT LOCAL HIDDEN 9 _DYNAMIC 6: ffffffffff700000 0 NOTYPE LOCAL DEFAULT ABS VDSO_PRELINK 7: ffffffffff6ff000 0 NOTYPE LOCAL DEFAULT ABS _params 8: 0000000000000000 0 OBJECT GLOBAL DEFAULT ABS LINUX_2.6 9: ffffffffff701100 10 FUNC WEAK DEFAULT 11 getcpu 10: ffffffffff701100 10 FUNC GLOBAL DEFAULT 11 __vdso_getcpu 11: ffffffffff7010d0 34 FUNC WEAK DEFAULT 11 time 12: ffffffffff7010d0 34 FUNC GLOBAL DEFAULT 11 __vdso_time 13: ffffffffff701060 97 FUNC WEAK DEFAULT 11 gettimeofday 14: ffffffffff701060 97 FUNC GLOBAL DEFAULT 11 __vdso_gettimeofday 15: ffffffffff701020 56 FUNC WEAK DEFAULT 11 clock_gettime 16: ffffffffff701020 56 FUNC GLOBAL DEFAULT 11 __vdso_clock_gettime

since aarch64 mandates vdso for signals to work, consider using panic if the symbols are not found.

I am aware, please note this is not the final version:

TODO:
     refactor

qlib/kernel/loader/vdso.rs

shrik3 · 2024-06-04T00:07:08Z

qlib/kernel/loader/vdso.rs

+
+#[cfg(target_arch = "x86_64")]
+impl VdsoArchSymbols {
+    pub fn set_symbols_page_offset(&mut self, elf_file: &ElfFile, symbol_table: &[Entry64]) {


The code is assuming that vdso is one single page right? Perhaps add a memory limit in the linker script to make sure of that?

ping. could you also do this? perhaps in another PR.
if the vdso object goes beyond (not likely but not impossible) one page, the parser code may go wrong.

e.g. https://sourceware.org/binutils/docs/ld/MEMORY.html

qlib/kernel/loader/vdso.rs

qlib/kernel/threadmgr/task_signals.rs

qlib/kernel/loader/vdso.rs

shrik3 · 2024-06-04T00:36:04Z

qlib/kernel/loader/vdso.rs

+
+    pub fn set_symbols_page_offset(&mut self, elf_file: &ElfFile, symbol_table: &[Entry64]) {
+        let mut found_symbols = 0;
+        for sym in 0..Self::TOTAL_SYMBOLS {


qkernel already uses the hashbrown, a KV store would make life easier here

IMO, too much underling complexity for such a minimal case...

I don't see the complexity of using a hashmap, when the alternative is a nested for loop with strcmp

Because it is done only once, for an unnoticeable small number of elements, with unnoticeable short names as keys and very simple logic for to mess it up.

nit: not just once. Every time a signal happens the kernel for loop through the list and strcmp up to 4 times to find the sigreturn symbol. Not a big difference with only 4 elements though.

nit: not just once.

Sorry, I didn't specify that I meant storing.

up to 4 times to find the sigreturn symbol.

As we are (for now) only concerned with sigreturn,
it could be placed at [0].

... but again:

Not a big difference with only 4 elements though.

P.S. I just learned what 'nit' means :)

* Definition for vdso symbol * New struct for aarch64 * Dummy struct for x86_64

clear warnings for x86_64 build

qlib/kernel/loader/vdso.rs

shrik3 · 2024-06-04T12:27:49Z

qlib/kernel/loader/vdso.rs

+                let mut _vdso_symbols: VdsoArchSymbols = Default::default();
+                _vdso_symbols.set_symbols_page_offset(&elf_file, symbols);
+                self.vdso_symbols = Some(_vdso_symbols);
+            } else if cfg!(target_arch = "aarch64") {


is cfg! macro compile time?

No, and it was not meant so.

shrik3

from a distance perhaps some commits could be squashed, otherwise looks fine to me.

QuarkContainer · 2024-07-06T00:45:36Z

@chl337 what's the current status for the PR and could we merge this?

chl337 · 2024-07-08T13:02:29Z

@chl337 what's the current status for the PR and could we merge this?

Just for sanity, please test it on your machine first. Then it can be merged.

QuarkContainer · 2024-07-08T18:52:49Z

@chl337 it is tested in my side. No issue. Can you merge it or I can do?

chl337 · 2024-07-08T18:54:38Z

@chl337 it is tested in my side. No issue. Can you merge it or I can do?

Then please proceed.

shrik3 reviewed May 26, 2024

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shrik3 mentioned this pull request Jun 2, 2024

aarch64: vvar or vdso being modified after executing a command. #1305

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chl337 force-pushed the aarch64_vdso_symbols branch from 47179e1 to 607d20d Compare June 3, 2024 22:41

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chl337 force-pushed the aarch64_vdso_symbols branch from 607d20d to 2e823f1 Compare June 4, 2024 09:02

chBitta added 5 commits June 4, 2024 12:17

vdso: add field in VdsoInternal to save arch.-specific symbols

5f42da0

* Definition for vdso symbol * New struct for aarch64 * Dummy struct for x86_64

x86_64: vdso: dummy foo()s to store and query arch.-specific symbols

a8c33b8

aarch64: vdso: definitions to store and query arch.-specific symbols

e351742

aarch64: vdso: save arch.-specific symbols when vdso gets loaded

e615990

vdso: extend VDSO to query for arch.-specific symbols by name

e148d04

chl337 force-pushed the aarch64_vdso_symbols branch from 2e823f1 to ee6f075 Compare June 4, 2024 10:17

aarch64: signals: remove hardcoded SIGRETURN address; query VDSO

836f7c2

clear warnings for x86_64 build

chl337 force-pushed the aarch64_vdso_symbols branch from ee6f075 to 836f7c2 Compare June 4, 2024 10:45

chl337 changed the title ~~[WIP]aarch64: vdso symbols~~ aarch64: vdso symbols Jun 4, 2024

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shrik3 mentioned this pull request Jun 10, 2024

Stable version for ARM processors #1313

Closed

QuarkContainer merged commit 44e7fdf into QuarkContainer:main Jul 9, 2024

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aarch64: vdso symbols #1292

aarch64: vdso symbols #1292

chl337 commented May 26, 2024 •

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aarch64: vdso symbols #1292

aarch64: vdso symbols #1292

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chl337 commented May 26, 2024 •

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