Re: [PATCH 1/2] alpha/ptrace: Record and handle the absence of switch_stack
From: Al Viro <viro@zeniv.linux.org.uk>
Date: 2021-06-16 20:17:24
Also in:
linux-arch, linux-m68k, lkml
Possibly related (same subject, not in this thread)
- 2021-06-16 · Re: [PATCH 1/2] alpha/ptrace: Record and handle the absence of switch_stack · Linus Torvalds <torvalds@linux-foundation.org>
- 2021-06-16 · Re: [PATCH 1/2] alpha/ptrace: Record and handle the absence of switch_stack · Al Viro <viro@zeniv.linux.org.uk>
- 2021-06-16 · Re: [PATCH 1/2] alpha/ptrace: Record and handle the absence of switch_stack · Eric W. Biederman <hidden>
- 2021-06-16 · Re: [PATCH 1/2] alpha/ptrace: Record and handle the absence of switch_stack · Eric W. Biederman <hidden>
On Wed, Jun 16, 2021 at 01:31:52PM -0500, Eric W. Biederman wrote:
+.macro SAVE_SWITCH_STACK + DO_SWITCH_STACK +1: ldl_l $1, TI_FLAGS($8) + bis $1, _TIF_ALLREGS_SAVED, $1 + stl_c $1, TI_FLAGS($8) + beq $1, 2f +.subsection 2 +2: br 1b +.previous +.endm
What the hell? *IF* you are going to go that way, at least put it into ->status, not ->flag - those are thread-synchronous and do not require that kind of masturbation.
+.macro RESTORE_SWITCH_STACK +1: ldl_l $1, TI_FLAGS($8) + bic $1, _TIF_ALLREGS_SAVED, $1 + stl_c $1, TI_FLAGS($8) + beq $1, 2f +.subsection 2 +2: br 1b +.previous + UNDO_SWITCH_STACK +.endm
Ditto. What do you need that flag for, anyway?
quoted hunk ↗ jump to hunk
@@ -117,7 +117,13 @@ get_reg_addr(struct task_struct * task, unsigned long regno) zero = 0; addr = &zero; } else { - addr = task_stack_page(task) + regoff[regno]; + int off = regoff[regno]; + if (WARN_ON_ONCE((off < PT_REG(r0)) && + !test_ti_thread_flag(task_thread_info(task), + TIF_ALLREGS_SAVED))) + addr = &zero; + else + addr = task_stack_page(task) + off;
A sanity check in slow path, buggering the hell out of a fast path?