x86_64,signal: Fix the set of saved segment registers
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- v1 Latest2 patches 13 repliesIn review
Patches in v1 No applies recorded yet
| # | Subject and files | Size | Replies | Applied |
|---|---|---|---|---|
| 1/2 | x86_64,signal: Save and restore SS in signal framesarch/ arch/ arch/ | +3 | 1 reply | |
| 2/2 | x86_64,signal: Remove 'fs' and 'gs' from sigcontextarch/ arch/ arch/ | +6 | 12 replies |
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Cover letter [PATCH 0/2] x86_64,signal: Fix the set of saved segment registers
The x86_64 signal code claims to save and restore CS, FS, and GS, and it further claims that this is the minimal set that's needed.
Neither of these claims is true. The code does not, and AFAICT never has, saved or restored FS and GS, nor does it need to. On the other hand, all 64-bit syscalls (and rt_sigreturn in particular) clobber SS, making it impossible for signal handlers to correctly restore SS without using a trampoline or ptracing themselves.
This patchset saves and restores SS in the __pad0 slot and renames the FS and GS slots __pad1 and __pad2 to more accurately document their purpose.
I discovered this while writing a test for espfix64.
Andy Lutomirski (2):
x86_64,signal: Save and restore SS in signal frames x86_64,signal: Remove 'fs' and 'gs' from sigcontext
arch/x86/include/asm/sigcontext.h | 6 +++--- arch/x86/include/uapi/asm/sigcontext.h | 6 +++--- arch/x86/kernel/signal.c | 12 +++--------- 3 files changed, 9 insertions(+), 15 deletions(-)
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