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target/i386: Do not re-compute new pc with CF_PCREL #50

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dfaggioli merged 2 commits from v8.2.0-factory-fix into factory 2024-02-06 01:38:57 +01:00
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dfaggioli commented 2024-02-05 23:06:01 +01:00 (Migrated from github.com)
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With PCREL, we have a page-relative view of EIP, and an approximation of PC = EIP+CSBASE that is good enough to detect page crossings. If we try to recompute PC after masking EIP, we will mess up that approximation and write a corrupt value to EIP.

We already handled masking properly for PCREL, so the fix in b5e0d5d2 was only needed for the !PCREL path.

Cc: qemu-stable@nongnu.org
Fixes: b5e0d5d22f ("target/i386: Fix 32-bit wrapping of pc/eip computation")
Reported-by: Michael Tokarev mjt@tls.msk.ru

Message-ID: 20240101230617.129349-1-richard.henderson@linaro.org

(cherry picked from commit a58506b748)

With PCREL, we have a page-relative view of EIP, and an approximation of PC = EIP+CSBASE that is good enough to detect page crossings. If we try to recompute PC after masking EIP, we will mess up that approximation and write a corrupt value to EIP. We already handled masking properly for PCREL, so the fix in b5e0d5d2 was only needed for the !PCREL path. Cc: qemu-stable@nongnu.org Fixes: b5e0d5d22fbf ("target/i386: Fix 32-bit wrapping of pc/eip computation") Reported-by: Michael Tokarev <mjt@tls.msk.ru> Message-ID: <20240101230617.129349-1-richard.henderson@linaro.org> (cherry picked from commit a58506b748b8988a95f4fa1a2420ac5c17038b30)
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Reference: dfaggioli/qemu#50
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