Skip to content

tools: Prevent invalid mem access when reading PAGE_OFFSET on s390 #5434

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
jeromemarchand wants to merge 1 commit into
base: master
Choose a base branch
from
Open

tools: Prevent invalid mem access when reading PAGE_OFFSET on s390 #5434

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
7 changes: 6 additions & 1 deletion tools/funcslower.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -172,9 +172,14 @@
#else
page_offset = __PAGE_OFFSET_BASE_L4;
#endif
#elif defined(__identity_base)
// s390 6.10 and later PAGE_OFFSET is not a constant and need
// to be read from the kernel adress space
bpf_probe_read_kernel(&page_offset, sizeof(PAGE_OFFSET), &PAGE_OFFSET);
#else
// earlier x86_64 kernels, e.g., 4.6, comes here
// arm64, s390, powerpc, x86_32
// s390 before 6.10
// arm64, powerpc, x86_32
page_offset = PAGE_OFFSET;
#endif

Expand Down
7 changes: 6 additions & 1 deletion tools/profile.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -212,9 +212,14 @@ def stack_id_err(stack_id):
#else
page_offset = __PAGE_OFFSET_BASE_L4;
#endif
#elif defined(__identity_base)
Copy link
Collaborator

@ekyooo ekyooo Jan 9, 2026

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

How about #elif defined(CONFIG_S390) && defined(__identity_base) ?

Copy link
Contributor Author

@jeromemarchand jeromemarchand Jan 9, 2026

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Currently __identity_base is only defined on s390 so they're equivalent.
I remember hesitating between the two and my reason to chose the former is that if __identity_base is ever defined on an other arch, it would most likely be for the same purpose.
On the other hand, PAGE_OFFSET seems to be very arch specific and I don't how likely my scenario is likely to happen.

// s390 6.10 and later PAGE_OFFSET is not a constant and need
// to be read from the kernel adress space
Copy link
Collaborator

@ekyooo ekyooo Jan 9, 2026

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

address, please.

Copy link
Contributor Author

@jeromemarchand jeromemarchand Jan 9, 2026

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Will fix.

bpf_probe_read_kernel(&page_offset, sizeof(PAGE_OFFSET), &PAGE_OFFSET);
#else
// earlier x86_64 kernels, e.g., 4.6, comes here
// arm64, s390, powerpc, x86_32
// s390 before 6.10
// arm64, powerpc, x86_32
page_offset = PAGE_OFFSET;
#endif
Expand Down
Loading