diff options
author | Andrei Vagin <avagin@gmail.com> | 2020-06-24 01:33:18 -0700 |
---|---|---|
committer | Catalin Marinas <catalin.marinas@arm.com> | 2020-07-24 13:15:20 +0100 |
commit | 3503d56cc7233ced602e38a4c13caa64f00ab2aa (patch) | |
tree | bc7f29974127abc054e722d88dcd1a3c51750140 /arch/arm64/kernel | |
parent | 1b6867d2916bb91e94ddcc9c709e4779419fe391 (diff) | |
download | linux-3503d56cc7233ced602e38a4c13caa64f00ab2aa.tar.bz2 |
arm64/vdso: Add time namespace page
Allocate the time namespace page among VVAR pages. Provide
__arch_get_timens_vdso_data() helper for VDSO code to get the
code-relative position of VVARs on that special page.
If a task belongs to a time namespace then the VVAR page which contains
the system wide VDSO data is replaced with a namespace specific page
which has the same layout as the VVAR page. That page has vdso_data->seq
set to 1 to enforce the slow path and vdso_data->clock_mode set to
VCLOCK_TIMENS to enforce the time namespace handling path.
The extra check in the case that vdso_data->seq is odd, e.g. a concurrent
update of the VDSO data is in progress, is not really affecting regular
tasks which are not part of a time namespace as the task is spin waiting
for the update to finish and vdso_data->seq to become even again.
If a time namespace task hits that code path, it invokes the corresponding
time getter function which retrieves the real VVAR page, reads host time
and then adds the offset for the requested clock which is stored in the
special VVAR page.
The time-namespace page isn't allocated on !CONFIG_TIME_NAMESPACE, but
vma is the same size, which simplifies criu/vdso migration between
different kernel configs.
Signed-off-by: Andrei Vagin <avagin@gmail.com>
Reviewed-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Reviewed-by: Dmitry Safonov <dima@arista.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/20200624083321.144975-4-avagin@gmail.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'arch/arm64/kernel')
-rw-r--r-- | arch/arm64/kernel/vdso.c | 19 | ||||
-rw-r--r-- | arch/arm64/kernel/vdso/vdso.lds.S | 5 | ||||
-rw-r--r-- | arch/arm64/kernel/vdso32/vdso.lds.S | 5 |
3 files changed, 24 insertions, 5 deletions
diff --git a/arch/arm64/kernel/vdso.c b/arch/arm64/kernel/vdso.c index 33ac18060bfc..fcb559726920 100644 --- a/arch/arm64/kernel/vdso.c +++ b/arch/arm64/kernel/vdso.c @@ -40,6 +40,12 @@ enum vdso_abi { #endif /* CONFIG_COMPAT_VDSO */ }; +enum vvar_pages { + VVAR_DATA_PAGE_OFFSET, + VVAR_TIMENS_PAGE_OFFSET, + VVAR_NR_PAGES, +}; + struct vdso_abi_info { const char *name; const char *vdso_code_start; @@ -125,6 +131,11 @@ static int __vdso_init(enum vdso_abi abi) } #ifdef CONFIG_TIME_NS +struct vdso_data *arch_get_vdso_data(void *vvar_page) +{ + return (struct vdso_data *)(vvar_page); +} + /* * The vvar mapping contains data for a specific time namespace, so when a task * changes namespace we must unmap its vvar data for the old namespace. @@ -173,9 +184,11 @@ static int __setup_additional_pages(enum vdso_abi abi, unsigned long gp_flags = 0; void *ret; + BUILD_BUG_ON(VVAR_NR_PAGES != __VVAR_PAGES); + vdso_text_len = vdso_info[abi].vdso_pages << PAGE_SHIFT; /* Be sure to map the data page */ - vdso_mapping_len = vdso_text_len + PAGE_SIZE; + vdso_mapping_len = vdso_text_len + VVAR_NR_PAGES * PAGE_SIZE; vdso_base = get_unmapped_area(NULL, 0, vdso_mapping_len, 0, 0); if (IS_ERR_VALUE(vdso_base)) { @@ -183,7 +196,7 @@ static int __setup_additional_pages(enum vdso_abi abi, goto up_fail; } - ret = _install_special_mapping(mm, vdso_base, PAGE_SIZE, + ret = _install_special_mapping(mm, vdso_base, VVAR_NR_PAGES * PAGE_SIZE, VM_READ|VM_MAYREAD|VM_PFNMAP, vdso_info[abi].dm); if (IS_ERR(ret)) @@ -192,7 +205,7 @@ static int __setup_additional_pages(enum vdso_abi abi, if (IS_ENABLED(CONFIG_ARM64_BTI_KERNEL) && system_supports_bti()) gp_flags = VM_ARM64_BTI; - vdso_base += PAGE_SIZE; + vdso_base += VVAR_NR_PAGES * PAGE_SIZE; mm->context.vdso = (void *)vdso_base; ret = _install_special_mapping(mm, vdso_base, vdso_text_len, VM_READ|VM_EXEC|gp_flags| diff --git a/arch/arm64/kernel/vdso/vdso.lds.S b/arch/arm64/kernel/vdso/vdso.lds.S index 7ad2d3a0cd48..d808ad31e01f 100644 --- a/arch/arm64/kernel/vdso/vdso.lds.S +++ b/arch/arm64/kernel/vdso/vdso.lds.S @@ -17,7 +17,10 @@ OUTPUT_ARCH(aarch64) SECTIONS { - PROVIDE(_vdso_data = . - PAGE_SIZE); + PROVIDE(_vdso_data = . - __VVAR_PAGES * PAGE_SIZE); +#ifdef CONFIG_TIME_NS + PROVIDE(_timens_data = _vdso_data + PAGE_SIZE); +#endif . = VDSO_LBASE + SIZEOF_HEADERS; .hash : { *(.hash) } :text diff --git a/arch/arm64/kernel/vdso32/vdso.lds.S b/arch/arm64/kernel/vdso32/vdso.lds.S index 337d03522048..3348ce5ea306 100644 --- a/arch/arm64/kernel/vdso32/vdso.lds.S +++ b/arch/arm64/kernel/vdso32/vdso.lds.S @@ -17,7 +17,10 @@ OUTPUT_ARCH(arm) SECTIONS { - PROVIDE_HIDDEN(_vdso_data = . - PAGE_SIZE); + PROVIDE_HIDDEN(_vdso_data = . - __VVAR_PAGES * PAGE_SIZE); +#ifdef CONFIG_TIME_NS + PROVIDE_HIDDEN(_timens_data = _vdso_data + PAGE_SIZE); +#endif . = VDSO_LBASE + SIZEOF_HEADERS; .hash : { *(.hash) } :text |