[0/1] plugins: add API to read guest CPU memory from hwaddr

Message

Rowan Hart Aug. 28, 2024, 6:32 a.m. UTC

This patch adds a single API function which allows reading from a guest
CPU physical address.

I don't know of a good way to add a self-contained test for this feature
to tests/tcg/plugins, but I did come up with a small test case to
demonstrate the functionality using peiyuanix/riscv-os:

First, grab and build the firmware code:

curl -o firmware.S https://raw.githubusercontent.com/peiyuanix/riscv-os/main/03-Bare-Metal-Hello-RISC-V/firmware.s
curl -o firmware.x https://raw.githubusercontent.com/peiyuanix/riscv-os/main/03-Bare-Metal-Hello-RISC-V/firmware.ld
riscv64-linux-gnu-as firmware.S -o firmware.o
riscv64-linux-gnu-ld -T firmware.x -o firmare firmware.o
riscv64-linux-gnu-objcopy -O binary -S firmware firmware.bin

Next, grab and build the plugin (just dumps from phys address on first
instruction executed):

curl -o dump-riscv-firmware.c https://gist.githubusercontent.com/novafacing/5abc08052fab671a0fb26547810b4c55/raw/33772d614d6e36eae30e3405af34f149d7cc608b/dump-riscv-firmware.c
gcc -rdynamic -shared -fPIC -Iinclude/qemu $(pkg-config --cflags --libs glib-2.0) -o libdump-riscv-firmware.so dump-riscv-firmware.c

Finally, run the plugin:

qemu-system-riscv64 -display none -machine virt -serial stdio -bios firmware.bin -plugin $(pwd)libdump-riscv-firmware.so -d plugin

This outputs as expected -- the hexdump of the running firmware:

b7 01 00 10 a3 80 01 00 93 02 00 08 a3 81 51 00  | ..............Q.
93 02 50 00 23 80 51 00 93 02 00 00 a3 80 51 00  | ..P.#.Q.......Q.
93 02 30 00 a3 81 51 00 93 02 10 00 23 81 51 00  | ..0...Q.....#.Q.
23 82 01 00 83 82 51 00 83 82 01 00 a3 83 01 00  | #.....Q.........
93 02 80 04 23 80 51 00 93 02 50 06 23 80 51 00  | ....#.Q...P.#.Q.
93 02 c0 06 23 80 51 00 93 02 c0 06 23 80 51 00  | ....#.Q.....#.Q.
93 02 f0 06 23 80 51 00 93 02 c0 02 23 80 51 00  | ....#.Q.....#.Q.
93 02 00 02 23 80 51 00 93 02 20 05 23 80 51 00  | ....#.Q.....#.Q.
93 02 90 04 23 80 51 00 93 02 30 05 23 80 51 00  | ....#.Q...0.#.Q.
93 02 30 04 23 80 51 00 93 02 d0 02 23 80 51 00  | ..0.#.Q.....#.Q.
93 02 60 05 23 80 51 00 93 02 10 02 23 80 51 00  | ..`.#.Q.....#.Q.
93 02 a0 00 23 80 51 00 6f 00 00 00 00 00 00 00  | ....#.Q.o.......
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  | ................
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  | ................
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  | ................
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  | ................
Hello, RISC-V!

Rowan Hart (1):
  plugins: add API to read guest CPU memory from hwaddr

 include/qemu/qemu-plugin.h   | 22 ++++++++++++++++++++++
 plugins/api.c                | 17 +++++++++++++++++
 plugins/qemu-plugins.symbols |  2 ++
 3 files changed, 41 insertions(+)

Comments

Alex Bennée Sept. 5, 2024, 3:26 p.m. UTC | #1

Rowan Hart <[e-mail]> writes:

> This patch adds a single API function which allows reading from a guest
> CPU physical address.
>
> I don't know of a good way to add a self-contained test for this feature
> to tests/tcg/plugins, but I did come up with a small test case to
> demonstrate the functionality using peiyuanix/riscv-os:

We have bare metal system tests (hello and memory) for i386, alpha,
loongarch64, aarch64 and arm. If you fancy having a go at implementing a
boot.S for riscv64 that would be super helpful for the check-tcg tests
as a whole.

See:

  tests/tcg/i386/system/boot.S
  tests/tcg/alpha/system/boot.S
  tests/tcg/loongarch64/system/boot.S
  tests/tcg/aarch64/system/boot.S
  tests/tcg/x86_64/system/boot.S
  tests/tcg/arm/system/boot.S

for what is needed (basically a MMU-enabled flat memory map and some
sort of emit char helper, probably using semihosting in this case)

>
> First, grab and build the firmware code:
>
> curl -o firmware.S https://raw.githubusercontent.com/peiyuanix/riscv-os/main/03-Bare-Metal-Hello-RISC-V/firmware.s
> curl -o firmware.x https://raw.githubusercontent.com/peiyuanix/riscv-os/main/03-Bare-Metal-Hello-RISC-V/firmware.ld
> riscv64-linux-gnu-as firmware.S -o firmware.o
> riscv64-linux-gnu-ld -T firmware.x -o firmare firmware.o
> riscv64-linux-gnu-objcopy -O binary -S firmware firmware.bin
>
> Next, grab and build the plugin (just dumps from phys address on first
> instruction executed):
>
> curl -o dump-riscv-firmware.c https://gist.githubusercontent.com/novafacing/5abc08052fab671a0fb26547810b4c55/raw/33772d614d6e36eae30e3405af34f149d7cc608b/dump-riscv-firmware.c
> gcc -rdynamic -shared -fPIC -Iinclude/qemu $(pkg-config --cflags --libs glib-2.0) -o libdump-riscv-firmware.so dump-riscv-firmware.c
>
<snip>

Rowan Hart Sept. 18, 2024, 5:23 a.m. UTC | #2

> 
> See:
> 
>   tests/tcg/i386/system/boot.S
>   tests/tcg/alpha/system/boot.S
>   tests/tcg/loongarch64/system/boot.S
>   tests/tcg/aarch64/system/boot.S
>   tests/tcg/x86_64/system/boot.S
>   tests/tcg/arm/system/boot.S
> 
> for what is needed (basically a MMU-enabled flat memory map and some
> sort of emit char helper, probably using semihosting in this case)

Sounds good! Sorry for the long pause, had some stuff going on :)

Investigating this now! I've never messed with semihosting, should be fun.