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Make sure that VDSO patch code is properly aligned #22

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Make sure that VDSO patch code is properly aligned #22

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61 changes: 43 additions & 18 deletions reverie-ptrace/src/vdso.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -21,41 +21,56 @@ use reverie::Guest;
use reverie::Tool;
use tracing::debug;

#[repr(align(64))]
struct BufferAligned<const N: usize>([u8;N]);

// Byte code for the new pseudo vdso functions which do the actual syscalls.
// Note: the byte code must be 8 bytes aligned
#[cfg(target_arch = "x86_64")]
mod vdso_syms {
#![allow(non_upper_case_globals)]

pub const time: &[u8; 8] = &[
use crate::vdso::BufferAligned;

const time_code: BufferAligned::<8> = BufferAligned::<8>([
0xb8, 0xc9, 0x00, 0x00, 0x00, // mov %SYS_time, %eax
0x0f, 0x05, // syscall
0xc3, // retq
];
]);

pub const time: &[u8; 8] = &time_code.0;

pub const clock_gettime: &[u8; 8] = &[
const clock_gettime_code: BufferAligned::<8> = BufferAligned::<8>([
0xb8, 0xe4, 0x00, 0x00, 0x00, // mov SYS_clock_gettime, %eax
0x0f, 0x05, // syscall
0xc3, // retq
];
]);

pub const getcpu: &[u8; 8] = &[
pub const clock_gettime: &[u8; 8] = &clock_gettime_code.0;

const getcpu_code: BufferAligned::<8> = BufferAligned::<8>([
0xb8, 0x35, 0x01, 0x00, 0x00, // mov SYS_getcpu, %eax
0x0f, 0x05, // syscall
0xc3, // retq
];
]);

pub const getcpu: &[u8; 8] = &getcpu_code.0;

pub const gettimeofday: &[u8; 8] = &[
const gettimeofday_code: BufferAligned::<8> = BufferAligned::<8>([
0xb8, 0x60, 0x00, 0x00, 0x00, // mov SYS_gettimeofday, %eax
0x0f, 0x05, // syscall
0xc3, // retq
];
]);

pub const gettimeofday: &[u8; 8] = &gettimeofday_code.0;

pub const clock_getres: &[u8; 8] = &[
const clock_getres_code: BufferAligned::<8> = BufferAligned::<8>([
0xb8, 0xe5, 0x00, 0x00, 0x00, // mov SYS_clock_getres, %eax
0x0f, 0x05, // syscall
0xc3, // retq
];
]);

pub const clock_getres: &[u8; 8] = &clock_getres_code.0;
}

#[cfg(target_arch = "aarch64")]
Expand Down Expand Up @@ -87,26 +102,34 @@ mod vdso_syms {
// See also
// https://developer.arm.com/documentation/ddi0596/2021-06/Base-Instructions/BTI--Branch-Target-Identification-

pub const clock_getres: &[u8; 16] = &[
use crate::vdso::BufferAligned;

const clock_getres_code : BufferAligned::<16> = BufferAligned::<16>([
0x5f, 0x24, 0x03, 0xd5, // bti c
0x48, 0x0e, 0x80, 0xd2, // mov x8, 114 (#__NR_clock_getres)
0x01, 0x00, 0x00, 0xd4, // svc 0
0xc0, 0x03, 0x5f, 0xd6, // ret
];
]);

pub const clock_getres: &[u8; 16] = &clock_getres_code.0;

pub const clock_gettime: &[u8; 16] = &[
const clock_gettime_code : BufferAligned::<16> = BufferAligned::<16>([
0x5f, 0x24, 0x03, 0xd5, // bti c
0x28, 0x0e, 0x80, 0xd2, // mov x8, 113 (#__NR_clock_gettime)
0x01, 0x00, 0x00, 0xd4, // svc 0
0xc0, 0x03, 0x5f, 0xd6, // ret
];
]);

pub const gettimeofday: &[u8; 16] = &[
pub const clock_gettime: &[u8; 16] = &clock_gettime_code.0;

const gettimeofday_code : BufferAligned::<16> = BufferAligned::<16>([
0x5f, 0x24, 0x03, 0xd5, // bti c
0x28, 0x15, 0x80, 0xd2, // mov x8, 169 (#__NR_gettimeofday)
0x01, 0x00, 0x00, 0xd4, // svc 0
0xc0, 0x03, 0x5f, 0xd6, // ret
];
]);

pub const gettimeofday: &[u8; 16] = &gettimeofday_code.0;

// On aarch64, the vdso version of rt_sigreturn is only 8 bytes, so our
// patch can't exceed that size. However, since this syscall doesn't return,
Expand All @@ -115,10 +138,12 @@ mod vdso_syms {
// NOTE: This is currently *exactly* how the kernel implements the
// rt_sigreturn vdso, so we could probably get away with not even patching
// it. See also `linux/arch/arm64/kernel/vdso/sigreturn.S`.
pub const rt_sigreturn: &[u8; 8] = &[
const rt_sigreturn_code : BufferAligned::<8> = BufferAligned::<8>([
0x68, 0x11, 0x80, 0xd2, // mov x8, 139 (#__NR_rt_sigreturn)
0x01, 0x00, 0x00, 0xd4, // svc 0
];
]);

pub const rt_sigreturn: &[u8; 8] = &rt_sigreturn_code.0;
}

#[cfg(target_arch = "x86_64")]
Expand Down
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